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Sample records for surrounding rock mass

  1. Zonal disintegration phenomenon in rock mass surrounding deep tunnels

    Institute of Scientific and Technical Information of China (English)

    WU Hao; FANG Qin; GUO Zhi-kun

    2008-01-01

    Zonal disintegration is a typical static phenomenon of deep rock masses. It has been defined as alternating regions of fractured and relatively intact rock mass that appear around or in front of the working stope during excavation of a deep tunnel. Zonal disintegration phenomenon was successfully demonstrated in the laboratory with 3D tests on analogous gypsum models, two circular cracked zones were observed in the test. The linear Mohr-Coulomb yield criterion was used with a constitutive model that showed linear softening and ideal residual plastic to analyze the elasto-plastic field of the enclosing rock mass around a deep tunnel. The results show that tunneling causes a maximum stress zone to appear between an elastic and plastic zone in the surrounding rock. The zonal disintegration phenomenon is analyzed by considering the stress-strain state of the rock mass in the vicinity of the maximum stress zone. Creep instability failure of the rock due to the development of the plastic zone, and transfer of the maximum stress zone into the rock mass, are the cause of zonal disintegration. An analytical criterion for the critical depth at which zonal disintegration can occur is derived. This depth depends mainly on the character and stress concentration coefficient of the rock mass.

  2. Mechanism of zonal disintegration in surrounding rock mass around deep rock engineering and its application

    Institute of Scientific and Technical Information of China (English)

    2011-01-01

    The mechanical behaviors of deep rock mass are different from those of shallow rock mass.Through cases of Jinping II Hydropower Station,the special phenomenon of zonal disintegration in the surrounding rock mass around the diversion tunnels,is analyzed.On the basis of fracture mechanics,a new strength criterion for deep rock mass is derived.The new nonlinear strength criterion that is relative to the rock mass rating classification can be applied to the study of the tensile failure of deep rock mass.Subsequently,zonal disintegration model is established,and the radius of fractured zone and none-fractured zone of deep surrounding rock mass around cylindrical tunnel are obtained,their exact positions and the evolution law of zonal disintegration of surrounding rock mass is determined.To validate the present model,comparison between calculation results and the experiment observation on facture and failure around underground openings is carried out.It is found that the numerical simulation result is in good agreement with the experimental one on failure modes around the hole.Through sensitivity analysis,the effects of stress condition,cohesion and the angle of internal friction on the phenomenon of zonal disintegration are determined.Finally,the present model is adopted in the analysis of the zonal disintegration in the surrounding rock mass around the diversion tunnels in Jinping II Hydropower Station.Meanwhile,the magnitude and distributions of fractured zones are determined by numerical simulation.

  3. Zonal disintegration phenomenon in enclosing rock mass surrounding deep tunnels Elasto-plastic analysis of stress field of enclosing rock mass

    Institute of Scientific and Technical Information of China (English)

    WU Hao; FANG Qin; ZHANG Ya-dong; GONG Zi-ming

    2009-01-01

    The zonal disintegration phenomenon (ZDP) is a typical phenomenon in deep block rock masses. In order to investigate the mechanism of ZDP, an improved non-linear Hock-Brown strength criterion and a bi-linear constitutive model of rock mass were used to analyze the elasto-plastic stress field of the enclosing rock mass around a deep round tunnel. The radius of the plastic region and stress of the enclosing rock mass were obtained by introducing dimensionless parameters of radial distance. The results show that tunneling in deep rock mass causes a maximum stress zone to appear in the vicinity of the boundary of the elastic and the plas-tic zone in the surrounding rock mass. Under the compression of a large tangential force and a small radial force, the rock mass in the maximum stress zone was in an approximate uniaxial loading state, which could lead to a split failure in the rock mass.

  4. Simulation of coupled THM process in surrounding rock mass of nuclear waste repository in argillaceous formation

    Institute of Scientific and Technical Information of China (English)

    蒋中明; 陈永贵

    2015-01-01

    To investigate and analyze the thermo-hydro-mechanical (THM) coupling phenomena of a surrounding rock mass in an argillaceous formation, a nuclear waste disposal concept in drifts was represented physically in an in-situ test way. A transversely isotropic model was employed to reproduce the whole test process numerically. Parameters of the rock mass were determined by laboratory and in-situ experiments. Based on the numerical simulation results and in-situ test data, the variation processes of pore water pressure, temperature and deformation of surrounding rock were analyzed. Both the measured data and numerical results reveal that the thermal perturbation is the principal driving force which leads to the variation of pore water pressure and deformations in the surrounding rock. The temperature, pore pressure and deformation of rock mass change rapidly at each initial heating stage with a constant heating power. The temperature field near the heater borehole is relatively steady in the subsequent stages of the heating phase. However, the pore pressure and deformation fields decrease gradually with temperature remaining unchanged condition. It also shows that a transversely isotropic model can reproduce the THM coupling effects generating in the near-field of a nuclear waste repository in an argillaceous formation.

  5. Modification of rock mass permeability in the zone surrounding a shaft in fractured, welded tuff

    Energy Technology Data Exchange (ETDEWEB)

    Case, J.B.; Kelsall, P.C.

    1987-03-01

    The excavation of a nuclear waste repository at Yucca Mountain, Nevada requires access through shafts and ramps from the ground surface to the repository horizon. To evaluate the need and performance of the sealing subsystem, it is necessary to predict the modifications in the rock immediately surrounding the shaft. The purpose of this study is to develop a model of permeability changes as a function of radial distance from a shaft. The model is based upon analyses which consider modification in rock mass permeability resulting from stress redistribution and blast damage due to excavation around a shaft. Elastic and elastoplastic stress analyses are performed to estimate the stress distribution for a wide range of rock properties and in situ stress conditions. Changes in stress are related to changes in rock mass permeability using stress-permeability relations for fractures obtained from laboratory and field testing. The effects of blast damage are estimated from case histories. The analyses indicate that rock mass permeability is expected to decline rapidly to the undisturbed value with greater permeability changes occurring at or near the shaft wall. For several conditions evaluated, the equivalent permeability of the modified permeability zone, averaged over an annulus one radius wide around the shaft, ranges from 15 to 80 times the undisturbed rock mass permeability. 61 refs., 24 figs., 6 tabs.

  6. An Index for Estimating the Stability of Brittle Surrounding Rock Mass: FAI and its Engineering Application

    Science.gov (United States)

    Zhang, C. Q.; Zhou, H.; Feng, X. T.

    2011-07-01

    Based on the geometric analysis of the relationship between the stress state at a point and the yield surface defined in the principal stress space, a coefficient ω is set up as an estimation index to describe the stress-induced yield risk. After yield, the equivalent plastic shear strains is usually used to characterize the failure degree (FD) of the material and adopted here as an index of the damage degree for the surrounding rock masses. Then, a unified variable combining ω and FD, named failure approaching index (FAI), is constructed to estimate the stability of rock mass which may be at different deformation stages. The formulas of FAI are derived for some popular yield criteria in geomechanics. Details for such development are addressed in the paper. Its rationality is verified by numerical simulation and comparative analysis of the conventional triaxial compression tests and typical tunnel projects. In addition, the method for applying FAI to the stability estimation of surrounding rock mass is proposed. As examples, the stability of the underground powerhouse, access tunnels and headrace tunnels at the Jinping II hydropower station are estimated by making use of the method we presented. The results indicate that not only is the index rational in mechanics, but the theory also has good expansibility, and the estimation methods are simple and practical as well. It is easier for field engineers to analyze and understand the numerical results.

  7. Model test of anchoring effect on zonal disintegration in deep surrounding rock masses.

    Science.gov (United States)

    Chen, Xu-Guang; Zhang, Qiang-Yong; Wang, Yuan; Liu, De-Jun; Zhang, Ning

    2013-01-01

    The deep rock masses show a different mechanical behavior compared with the shallow rock masses. They are classified into alternating fractured and intact zones during the excavation, which is known as zonal disintegration. Such phenomenon is a great disaster and will induce the different excavation and anchoring methodology. In this study, a 3D geomechanics model test was conducted to research the anchoring effect of zonal disintegration. The model was constructed with anchoring in a half and nonanchoring in the other half, to compare with each other. The optical extensometer and optical sensor were adopted to measure the displacement and strain changing law in the model test. The displacement laws of the deep surrounding rocks were obtained and found to be nonmonotonic versus the distance to the periphery. Zonal disintegration occurs in the area without anchoring and did not occur in the model under anchoring condition. By contrasting the phenomenon, the anchor effect of restraining zonal disintegration was revealed. And the formation condition of zonal disintegration was decided. In the procedure of tunnel excavation, the anchor strain was found to be alternation in tension and compression. It indicates that anchor will show the nonmonotonic law during suppressing the zonal disintegration.

  8. Model Test of Anchoring Effect on Zonal Disintegration in Deep Surrounding Rock Masses

    Directory of Open Access Journals (Sweden)

    Xu-Guang Chen

    2013-01-01

    Full Text Available The deep rock masses show a different mechanical behavior compared with the shallow rock masses. They are classified into alternating fractured and intact zones during the excavation, which is known as zonal disintegration. Such phenomenon is a great disaster and will induce the different excavation and anchoring methodology. In this study, a 3D geomechanics model test was conducted to research the anchoring effect of zonal disintegration. The model was constructed with anchoring in a half and nonanchoring in the other half, to compare with each other. The optical extensometer and optical sensor were adopted to measure the displacement and strain changing law in the model test. The displacement laws of the deep surrounding rocks were obtained and found to be nonmonotonic versus the distance to the periphery. Zonal disintegration occurs in the area without anchoring and did not occur in the model under anchoring condition. By contrasting the phenomenon, the anchor effect of restraining zonal disintegration was revealed. And the formation condition of zonal disintegration was decided. In the procedure of tunnel excavation, the anchor strain was found to be alternation in tension and compression. It indicates that anchor will show the nonmonotonic law during suppressing the zonal disintegration.

  9. Elasto-plastic analysis of the surrounding rock mass in circular tunnel based on the generalized nonlinear unified strength theory

    Institute of Scientific and Technical Information of China (English)

    Huang Xiujie; Zhang Jixun; Yang Ling; Yang Shikou; Wang Xingli

    2016-01-01

    The present paper aims to establish a versatile strength theory suitable for elasto-plastic analysis of underground tunnel surrounding rock. In order to analyze the effects of intermediate principal stress and the rock properties on its deformation and failure of rock mass, the generalized nonlinear unified strength theory and elasto-plastic mechanics are used to deduce analytic solution of the radius and stress of tunnel plastic zone and the periphery displacement of tunnel under uniform ground stress field. The results show that: intermediate principal stress coefficient b has significant effect on the plastic range, the magnitude of stress and surrounding rock pressure. Then, the results are compared with the unified strength criterion solution and Mohr–Coulomb criterion solution, and concluded that the generalized nonlinear unified strength criterion is more applicable to elasto-plastic analysis of underground tunnel surrounding rock.

  10. Numerical simulation on deformation character of surrounding rock masses of Changjiashan tunnel through the gob of coalmine

    Institute of Scientific and Technical Information of China (English)

    ZHANG Zhi-pei

    2006-01-01

    Based on the construction project of the Changjiashan tunnel of the freeway,the variety rule of surrounding rock masses of the tunnel through the gob of coalmine was studied by using of finite element methed(FEM). The status of the stress and strain, the variety of the plastic area were simulated in the whole rock mass before and after the tunnel was excavated. The characters of stress and deformation of surrounding rock masses were analyzed when the tunnel was built. It concluded from the numerical simulation that the influence on the tunneling is great when the tunnel passing through the gob of coalmine is excavated, and the relative measures should be taken.

  11. The instability mechanics of surrounding rock-coal mass system in longwall face and the prevention of pressure bumps

    Institute of Scientific and Technical Information of China (English)

    李新元; 李英明

    2003-01-01

    According to the movement and change rules of mechanical structure of surrounding rock-coal mass system during coal excavation, the mechanism of sudden instability and damage was found out. The criterions that distinguishing the occurring of the pressure bump were put forward. This criteria have been applied successfully in the comprehensive prevent of pressure bumps in Tangshan colliery.

  12. Study of Block Stability of Surrounding Rock Mass of Main Transformer Chamber Based on VATS Program

    Directory of Open Access Journals (Sweden)

    Zhongchang Wang

    2012-11-01

    Full Text Available The fracture of rock mass for main transformer chamber in HuangGou hydropower station is very developed. The blocks slide along the discontinuous face or free face with the excavation of cavern. It leads to the failure of normal construction. In the study, according to geology of disclosed discontinuous face in detecting cavern and local three-dimensional coordinate of underground caverns, the vector analysis program for tunnel stability VATS is compiled by using the method of vector analysis of the block theory which is applicable to analyze the discontinuous rock mass and numerical software MATLAB. The occurrence of joints, the coordinate of measuring point, the radius and vertical wall height of underground caverns and other relevant engineering datum is required to input the program. The combination of discontinuous face, boundary condition, geometric parameter, the mode of failure and stability factor of existent unstable blocks is obtained. The geometry distributing characteristic of block and key discontinuous faces in different position is figured by the AUTOCAD software. The guidance for construction of underground caverns is provided.

  13. Macro mechanical parameters' size effect of surrounding rock of Shuibuya project's underground power station

    Institute of Scientific and Technical Information of China (English)

    GUO Zhi-hua; ZHOU Chuang-bing; ZHOU Huo-ming; SHENG Qian; LENG Xian-lun

    2005-01-01

    Scale effect is one of the important aspects in the macro mechanical parameters' research of rock mass, from a new point of view, by means of lab and field rock mechanics test, establishment of E~Vp relation, classification of engineering rock mass, numerical simulation test and back analysis based on surrounding rock's displacement monitoring results of Shuibuya Project's underground power station, rock mass deformation module's size effect of surrounding rock of Shuibuya Project's undegroud power station was studied. It's shown that rock mass deformation module's scale effect of surrounding rock of Shuibuya Project's undeground power station is obvious, the rock mass deformation module to tranquilization is 20% of intact rock's. Finally the relation between rock mass deformation modules and the scale of research was established.

  14. Rheological properties of surrounding rock in deep hard rock tunnels and its reasonable support form

    Institute of Scientific and Technical Information of China (English)

    王辉; 陈卫忠; 王清标; 郑朋强

    2016-01-01

    Second lining stability, which is the last protection in tunnel engineering, is critically important. The rheological properties of the surrounding rock heavily affect second lining stability. In this work, we used laboratory triaxial compressive rheological limestone tests to study nonlinear creep damage characteristics of surrounding rock mass in construction projects. We established a nonlinear creep damage constitutive model for the rock mass, as well as a constitutive model numerical implementation made by programming. Second, we introduced a new foam concrete with higher compression performance and good ductility and studied its mechanical properties through uniaxial and triaxial tests. This concrete was used as the filling material for the reserved deformation layer between the primary support and second lining. Finally, we proposed a high efficiency and accuracy staged optimization method. The minimum reserved deformation layer thickness was established as the optimization goal, and the presence of plastic strain in the second lining after 100 years of surrounding rock creep was used as an evaluation index. Reserved deformation layer thickness optimization analysis reveals no plastic strain in the second lining when the reserved deformation minimum thickness layer is 28.50 cm. The results show that the new foam concrete used as a reserved deformation layer filling material can absorb creep deformation of surrounding rock mass, reduce second lining deformation that leads to plastic strain, and ensure long-term second lining stability.

  15. 等效数值法在围岩稳定性评价中的应用%Evaluation on Stability of Surrounding Rock Mass Based on Equivalent Numerical Method

    Institute of Scientific and Technical Information of China (English)

    高科; 李夕兵

    2009-01-01

    提出了一种新的围岩的稳定性评价方法--等效数值法,建立了基于等效数值方法的围岩稳定性评价新模型.该方法将样本指标值与围岩稳定性各指标分类标准对比来确定权重,客观性强,计算简捷.对5个典型的围岩作为评价样本进行了评价研究,并将得到的评价结果与模糊识别法、可拓方法与模糊可变集合工程方法结果进行比较.研究结果表明,等效数值法成功率高、客观性强,为围岩稳定性的评价研究提供了一条新思路.%In this paper,a new stability evaluation method on surrounding rock mass by using equivalent numerical method is presented.The stability assessment model for the Surrounding Rock Mass based on an equivalent numerical method is established.5 actual samples were used to verify the effectiveness of this method.Compared with Furry Pattern Reeoginition,extension method and engineering method of variable fuzzy set,equivalent numerical method has a practical performance in evaluating the stability of surrounding rock mass.This paper provides a new way for evaluation on stability of surrounding rock mass.

  16. Numerical simulation study of the failure evolution process and failure mode of surrounding rock in deep soft rock roadways

    Institute of Scientific and Technical Information of China (English)

    Meng Qingbin; Han Lijun; Xiao Yu; Li Hao; Wen Shengyong; Zhang Jian

    2016-01-01

    Based on the safety coefficient method, which assigns rock failure criteria to calculate the rock mass unit, the safety coefficient contour of surrounding rock is plotted to judge the distribution form of the frac-tured zone in the roadway. This will provide the basis numerical simulation to calculate the surrounding rock fractured zone in a roadway. Using the single factor and multi-factor orthogonal test method, the evolution law of roadway surrounding rock displacements, plastic zone and stress distribution under different conditions is studied. It reveals the roadway surrounding rock burst evolution process, and obtains five kinds of failure modes in deep soft rock roadway. Using the fuzzy mathematics clustering analysis method, the deep soft surrounding rock failure model in Zhujixi mine can be classified and pat-terns recognized. Compared to the identification results and the results detected by geological radar of surrounding rock loose circle, the reliability of the results of the pattern recognition is verified and lays the foundations for the support design of deep soft rock roadways.

  17. Review of roadway control in soft surrounding rock under dynamic pressure

    Institute of Scientific and Technical Information of China (English)

    侯朝炯

    2003-01-01

    The basic characteristics of the soft rock roadway under the dynamic pressure are analyzed. At the same time, the three fundamental approaches for controlling the surrounding rock are proposed, which are improving the surrounding rock strength, lowering the rock mass stress and selecting the reasonable supporting technology. The research results are elucidated, including the distribution of the surrounding rock plastic zone, the movement and damage of the surrounding rock under the dynamic pressure, controlling the floor heave through reinforcing the roadway walls and corners, the new route to develop the roadway metal supporting technique, the key theory and technique for the bolt supporting in the coal roadway, the performance and prospect of the ZKD high-water-content quick-setting material, and so on. Finally, some personally views are put forward about the roadway metal supporting, bolt supporting, new material and the stress-relief under the high stress condition.

  18. Numerical Analysis of Advanced Displacement in Construction Progress of Tunnel Excavation with Weak Surrounding Rock

    Directory of Open Access Journals (Sweden)

    Qian Zhang

    2013-07-01

    Full Text Available Analysis of advanced displacement in construction progress of tunnel excavation with weak surrounding rock is carried out by numerical method and comparison of model test result. In allusion to the problems of regional landslides and extruded large-deformation seriously impacting the stability of rock mass in construction process of large-section tunnel with weak surrounding rock, the elastic-plastic numerical simulation relying on Liangshui tunnel of Lan-Yu railroad is conducted on mechanical behaviors and deformation steric effect of tunnel construction and the calculation results are compared with the modeling data. The research results show that: the steric effect of excavation face is the dominant factor in the incidence of working face and the stress of surrounding rocks gradually releases from excavation face; the range of 0.5~1 times the cave diameter around rock mass in front of working face is the disturbance range and the key area of stabilization and reinforcement for wake surrounding rock. According to the analysis and construction practice, the supporting structure of large-section tunnel with weak surrounding rock should be established as soon as possible to control the displacement change of surrounding rock in the range of load-bearing ring, reduce disturbance and improve the self-bearing capability of surrounding rock. Because of the distinct excavation steric effect of weak surrounding rock, the secondary lining structure must be established in time to bear the later pressure and restrict the large displacement of surrounding rock. The research results can provide reliable basis for engineering stability control of analogous tunnels.

  19. Research on characters of surrounding rock in complex geology conditions and supporting time

    Institute of Scientific and Technical Information of China (English)

    Yu Weijian; Gao Qian; Zhai Shuhua; Zhang Meihua

    2008-01-01

    The methods combined by test, field monitoring and theoretical analysis were adopted to do the systemic re- search on the rock mass from micro-structure to macro-deformation, and rheological model of Jinchuan rock mass was es-tablished to discuss the reasonable supporting time. Results show that supporting after suitable stress and displacement release can benefit for the long-term stability of surrounding rock.

  20. FAST CLASSIFICATION METHOD FOR ROCK MASS SURROUNDING HIGHWAY TUNNEL DURING CONSTRUCTION%公路隧道施工期围岩快速分级的一种新方法

    Institute of Scientific and Technical Information of China (English)

    方昱; 刘开云; 刘保国

    2013-01-01

    施工期围岩快速分级是保证隧道施工安全和工程质量的关键措施.结合绩黄、宁绩高速公路隧道群施工期围岩分级实践,在大量现场测试和室内试验的基础上,提出了一种基于国标BQ分级的新分级体系,并给出了每个分级指标的现场快速测试方法.用新分级体系进行隧道施工期围岩的快速分级工作,并以分级结果作为进化支持向量回归算法分级的训练样本,建立了隧道围岩分级的进化支持向量回归智能模型.为了方便现场使用,依据支持向量回归理论,将智能模型进一步转化为初等函数数学模型,经隧道围岩分级实例验证了该初等函数数学模型的准确性,为隧道施工期围岩快速分级提供了一种简便的新方法.%Fast classification of surrounding rock mass during construction period is the key measure for construction security and engineering quality. This paper combines the surrounding rock mass classification work during tunnel group construction in Jihuang and Ningji expressway. It proposes a new classification system as a kind of improved national standard BQ classification method. The system is based on many field tests and indoor experiments. The quick field testing method of each classification index is presented. Furthermore, the new classification system is used to cope with the surrounding rock classification in-situ. The classification results are served as the training samples of the evolutionary support vector regression ( SVR) algorithm in order to establish the intelligent classification model. Finally, the intelligent model is transferred to an elementary function mathematical model according to SVR theory for the purpose of convenience application. The accuracy of this mathematical classification model is verified by classification examples of tunnel group. Thus, the system offers a new simple fast classification method for surrounding rock mass during tunnel construction period.

  1. Catastrophe mechanism and disaster countermeasure for soft rock roadway surrounding rock in Meihe mine

    Institute of Scientific and Technical Information of China (English)

    Yu Yang⇑; Zhu Caikun; Chong Deyu; Liu Yang; Li Sichao

    2015-01-01

    The soft rock’s heterogeneity and nonlinear mechanical behavior cause extremely difficult maintenance on the soft rock roadway. Aiming at the asymmetric deformation and destruction phenomenon appearing after excavating and supporting the 7101 air return way in Meihe mine, this paper comprehensively adopted a variety of methods to analyze the roadway surrounding rock deformation rule, obtaining the roadway surrounding rock stress and plastic zone distribution rule under no supporting condition and the roadway surrounding rock deformation features under original symmetric supporting condition. Furthermore, this paper revealed the catastrophe mechanism, and proposed the concept of‘weak struc-ture’ and the disaster countermeasure of‘overall stabilizing the roadway and strengthening the support of weak structure’ . The industrial test shows that the disaster control technology can realize the coordination deformation of the supporting structure and roadway surrounding rock, thus significantly controlling the deformation of roadway surrounding rock.

  2. Stresses and Shear Fracture Zone of Jinshazhou Tunnel Surrounding Rock in Rich Water Region

    Institute of Scientific and Technical Information of China (English)

    ZHENG Jun-jie; LOU Xiao-ming

    2008-01-01

    Field evidence has shown that large-scale and unstable discontinuous planes in the rock mass surrounding tunnels in rich water region are probably generated after excavation. The tunnel surrounding rock was divided into three zones, including elastic zone, plastic damage zone and shear fracture zone fof assessing the stability of the tunnel surrounding rock. By local hydrogeology, the stresses of surrounding rock of Jinshazhou circular tunnel was analyzed and the stress solutions on the elastic and plastic damage zones were obtained by applying the theories of fluid-solid coupling and elasto-plastic damage mechanics. The shear fracture zone generated by joints was studied and its range was determined by using Mohr-Coulomb strength criterion. Finally, the correctness of the theoretical results was validated by comparing the scopes of shear fracture zones calculated in this paper with those from literature.

  3. Damage Characteristics of Surrounding Rock Subjected to VCR Mining Blasting Shock

    Directory of Open Access Journals (Sweden)

    Nan Jiang

    2015-01-01

    Full Text Available For limiting the damage range caused by explosive shock loads in vertical crater retreat (VCR mining, the blasting damage characteristics of surrounding rock were studied by two methods: numerical simulation and ultrasonic testing. Combined with the mining blasting in Dongguashan Copper Mine of China, the VCR blasting shock characteristics under different conditions are obtained by using LSDYNA. Based on statistical fracture mechanics and damage mechanics theories, a damage constitutive model for rock mass subjected to blasting shock load was established. Then by using the fast Lagrange analysis codes (FLAC3D, the blasting damage characteristics of surrounding rock were analyzed by applying the blasting shock loads obtained from the VCR mining and the damage zone is obtained. At last, the relationship between the amount of explosives and the radius of damaged surrounding rock mass was discussed, and its formula was also derived. The research provides a theoretical basis for rationally controlling stope boundaries and optimizing mining blasting parameters.

  4. Experimental Study of Deformation of Surrounding Rock with Infrared Radiation

    Institute of Scientific and Technical Information of China (English)

    ZHANG Yong-jun; AN Li-qian; REN Run-hou; FAN Shi-min; MA Nian-jie; LI Jian-hui; JI Yuan-ming

    2005-01-01

    According to the practical conditions of coal roadway in Changcun Coal Mine of Lu'an Mining Group, the deformation of rock surrounding roadway was experimentally studied by means of thermal infrared (TIR) imaging system in the process of confined compressions. It is found that the model surface TIR temperature (TIRT) changes with the increase of load. Furthermore, TIRT changes non-synchronously in different ranges such as the roof, floor, wall, corners and bolted ranges. The TIRT is higher in the location of stress concentration and bolted ranges than that in the location of stress relaxation and broken ranges. The interaction ranges of bolt and rock are determined preliminarily according to the corresponding relationship of TIRT fields and the strain fields of the surrounding rock. The new method of TIR image processing has been proved to be effective for the study of bolt support and observation of roadway stability under mine pressure.

  5. 基于广义粒子动力学的巷道围岩弹塑性分析%Elastoplastic analysis of surrounding rock masses around tunnels using general particle dynamics method

    Institute of Scientific and Technical Information of China (English)

    赵毅; 周小平; 钱七虎

    2016-01-01

    提出了广义粒子动力学数值分析方法,该方法是一种无网格数值分析方法,可以考虑关联塑性流动法则和非关联塑性流动法则对岩石材料塑性变形的影响。将广义粒子动力学数值分析方法应用于巷道围岩的弹塑性分析,确定了巷道围岩的应力场、位移场和塑性区。该数值模拟结果与有限元结果吻合较好,表明将考虑岩石材料剪胀特性的弹塑性本构理论引入到广义粒子动力学数值分析方法,不失为模拟岩石类材料弹塑性破坏的一种有效数值手段,研究结果为更好地理解岩石材料的屈服破坏过程提供重要的参考。%The novel meshless numerical method, which is known as general particle dynamics (GPD) method, is proposed. The non-associated flow law and the associated flow law can be employed to analyze the plastic deformation of the surrounding rock masses around tunnels using the GPD method. The stability of the surrounding rock masses around tunnels are also determined using the GPD method as well as the stress fields, displacement fields and plastic zone. The numerical results by the proposed method are in good agreement with the FEM results. It is proved that the GPD method is efficient to predict the elastic-plastic properties of the surrounding rock masses around tunnels.

  6. The anisotropic properties analysis of the rock mass surrounding the roadway' s in seepage and stress field%巷道围岩渗流场和应力场各向异性特征分析及应用

    Institute of Scientific and Technical Information of China (English)

    杨天鸿; 师文豪; 于庆磊; 李海洲; 郑超; 夏冬

    2012-01-01

    依托范各庄煤矿12号煤层底板的砂岩巷道工程实际,应用岩体结构面非接触测量(Sha-peMetriX3D)系统,对巷道开挖面进行岩体结构面数字摄影测量及识别,得到岩体结构面的几何分布参数;在此基础上,利用Mont-Carlo方法生成裂隙网络,分别利用离散介质渗流方法和几何损伤理论计算岩体的渗透张量和弹性张量,研究了岩体力学参数各向异性和尺度效应;最后,建立了平面应变情况下的巷道围岩各向异性渗流力学模型,采用COMSOL Multiphysics多物理场分析软件,计算得到了可以考虑节理分布特征的巷道围岩应力场和渗流场,并讨论了岩体力学性质主方向对围岩应力场、渗流场及损伤区的影响。研究表明,岩体的各向异性对数值模拟结果影响显著,等效连续介质的各向异性模型能考虑岩体结构面的影响,更符合工程实际。%Depending on the sandstone roadway on the floor of No. 12 coal seam in Fangezhuang Coal Mine,a 3D con- tact-free measuring system, named as ShapeMetriX3D, was employed to capture discontinuities on the face of the road- way and obtain statistical parameters for each set of discontinuities. And then, fracture network was generated by Mont- Carlo method. Permeability tensor of rock mass was calculated by the discrete medium seepage method, and the elastic- ity tensor of rock mass was obtained by geometrical damage theory. Then, scale effect and anisotropic behaviors of rock mass were studied. Finally, an anisotropic percolation mechanics model of surrounding rock mass of the roadway was built under plane strain condition. Using COMSOL multiphysics code, the stress field and seepage field surrounding the roadway were obtained, which can take into account the influence of orientation of discontinuities. Furthermore, the in- fluences of principal direction of rock mass properties on stress, seepage and damage zone were discussed. The results show that the

  7. Control over Surrounding Rocks Deformation of Soft Floor and Whole-Coal Gateways with Trapezoidal Supports

    Institute of Scientific and Technical Information of China (English)

    ZHAI Xin-xian; LI De-Quan; SHAO Qiang; SUN Yu-feng

    2005-01-01

    In Gengcun Colliery, Yima Coal Group Co. Ltd.the characteristics of the gateways of thick coal seam and the coal seam is with fully mechanized sublevel caving mining are that the thickness of roof coal seam of gateways is larger, their surrounding rocks are the whole-coal mass and the coal seam is prone to Spontaneous Combustion. With the natural equilibrium arch theory, the reasonable adjacent distance of No.11 mine-type metal supports was calculated in trapezoidal gateways based on these characteristics. Then, in-situ supporting experiments were carried out. The results indicate that under the action of virgin rock stress, the width of broken rocks zone of surrounding rocks is 1.7-2.0 m in return heading and 1.1-1.3 m in going headway. And their surrounding rocks belong to the Ⅳ-type soften rock and the Ⅲ-type common surrounding rock respectively. Therefore, under the movable abutment pressure, the gateways deformation is serious. It is suggested that the designed gateways have to use pre-broadened cross section to suit their deformation. At the same time, the accumulated water on gateway floor must be drained in time. These measures were taken in the 1302 and 1304 coal faces in Gengcun Colliery, and the satisfactory results have been obtained.

  8. Analysis for interaction of supports and surrounding rock of gateways in Iongwall minging

    Institute of Scientific and Technical Information of China (English)

    伍永平

    2001-01-01

    Gateway supporting in long-wall mining has been a problem that restricts the mine production and safety, the paper sets up an interaction model between support and surrounding rock ( rock mass structure) and probes the elementary t.heory about ground pressure behaviors of gateway. Based on the analysis of supporting theories, some new viewpoints about gateways supporting and ground pressure controlling are put forward.

  9. Analysis for interaction of supports and surrounding rock of gateways in longwall minging

    Institute of Scientific and Technical Information of China (English)

    WU Yong-ping

    2001-01-01

    Gateway supporting in long-wall mining has been a problem that restri cts the mine production and safety, the paper sets up an interaction model betwe en support and surrounding rock (rock mass structure) and probes the elementary theory about ground pressure behaviors of gateway. Based on the analysis of supp orting theories, some new viewpoints about gateways supporting and ground pressu re controlling are put forward.

  10. Study on Temperature Fieldof Surrounding Rock with BEM

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The authors analyzed the characteristic of surrounding rock temperature field around a drifting face, setup its mathematic model, and got its numerical result with the boundary element method(BEM). To calculate in-tra-domain integral, it was transformed into boundary integration with the DRM method. Using the similitude the-ory, the dimensionless differential equation was educed. Finally, the authors calculated two drifting faces of San-hejian Coal Mine using the computer software developed by authors based on the above principium, and got the dis-tribution characteristic of surrounding rock temperature field around a drifting face and the periodic variation intemperature with its periodic moving forward. Comparing the calculated heat dissipating-capacity of surroundingrock with the measured data shows that the computer software is proper.

  11. Deformation characteristics of surrounding rock of broken and soft rock roadway

    Energy Technology Data Exchange (ETDEWEB)

    Jin-xi Wang; Ming-yue Lin; Duan-xin Tian; Cun-liang Zhao [Hebei University of Engineering, Handan (China)

    2009-03-15

    A similar material model and a numerical simulation were constructed and are described. The deformation and failure of surrounding rock of broken and soft roadway are studied by using these models. The deformation of the roof and floor, the relative deformation of the two sides and the deformation of the deep surrounding rock are predicted using the model. Measurements in a working mine are compared to the results of the models. The results show that the surrounding rock shows clear rheological features under high stress conditions. Deformation is unequally distributed across the whole section. The surrounding rock exhibited three deformation stages: displacement caused by stress concentration, rheological displacement after the digging effects had stabilized and displacement caused by supporting pressure of the roadway. Floor heave was serious, accounting for 65% of the total deformation of the roof and floor. Floor heave is the main reason for failure of the surrounding rock. The reasons for deformation of the surrounding rock are discussed based on the similar material and numerical simulations. 12 refs., 4 figs., 3 tabs.

  12. Thermal, Mechanical and Thermo-Mechanical Assessment of the Rock Mass Surrounding SKB's Prototype Repository at Äspö HRL

    Science.gov (United States)

    Lönnqvist, Margareta; Hökmark, Harald

    2016-04-01

    The Prototype Repository (PR) was a field test of six, electrically heated, full-scale waste containers resembling the key component of a KBS-3 nuclear waste repository. The design and heat load was similar to the proposed repository at Forsmark, Sweden. In this paper, the thermal, mechanical and thermo-mechanical response of the PR host rock to excavation and to the subsequent heating is assessed. The assessment is carried out using three-dimensional models (numerical and analytical) in combination with monitoring data and visual observations from the excavations. Certain measurements and observations agree well with results from the models. These include temperature measurements during the heating phase. Additional measurements include patterns of low-magnitude acoustic emission events around the deposition holes tracked during the excavation. The spatial distribution of these events coincide with regions of modelled high compressive stresses. Models with a simple fracture network, consisting of planar disks with laboratory-scale properties, appear to give upper bound estimates of the stress disturbances caused by a real fracture network. The magnitude of the modelled stresses around the deposition hole is typically below the spalling strength. The lack of any significant or systematic occurrence of spalling in the deposition hole walls supports the modelling results. Several instruments installed at different positions to monitor stress change, strain and deformation malfunctioned during the nearly 8-year-long monitoring period. Despite this, there is ample evidence to support the overall conclusion that the modelling results and observations are in sufficient agreement to strengthen the confidence in the modelling approach.

  13. Seismic response of rock joints and jointed rock mass

    Energy Technology Data Exchange (ETDEWEB)

    Ghosh, A.; Hsiung, S.M.; Chowdhury, A.H. [Southwest Research Inst., San Antonio, TX (United States). Center for Nuclear Waste Regulatory Analyses

    1996-06-01

    Long-term stability of emplacement drifts and potential near-field fluid flow resulting from coupled effects are among the concerns for safe disposal of high-level nuclear waste (HLW). A number of factors can induce drift instability or change the near-field flow patterns. Repetitive seismic loads from earthquakes and thermal loads generated by the decay of emplaced waste are two significant factors. One of two key technical uncertainties (KTU) that can potentially pose a high risk of noncompliance with the performance objectives of 10 CFR Part 60 is the prediction of thermal-mechanical (including repetitive seismic load) effects on stability of emplacement drifts and the engineered barrier system. The second KTU of concern is the prediction of thermal-mechanical-hydrological (including repetitive seismic load) effects on the host rock surrounding the engineered barrier system. The Rock Mechanics research project being conducted at the Center for Nuclear Waste Regulatory Analyses (CNWRA) is intended to address certain specific technical issues associated with these two KTUs. This research project has two major components: (i) seismic response of rock joints and a jointed rock mass and (ii) coupled thermal-mechanical-hydrological (TMH) response of a jointed rock mass surrounding the engineered barrier system (EBS). This final report summarizes the research activities concerned with the repetitive seismic load aspect of both these KTUs.

  14. Hydro-mechanically coupled modelling of deep-seated rock slides in the surroundings of reservoirs

    Science.gov (United States)

    Lechner, Heidrun; Preh, Alexander; Zangerl, Christian

    2016-04-01

    In order to enhance the understanding of the behaviour of deep-seated rock slides in the surroundings of large dam reservoirs, this study concentrates on failure mechanisms, deformation processes and the ability of self-stabilisation of rock slides influenced by reservoirs. Particular focus is put on internal rock mass deformations, progressive topographical slope changes due to reservoir impoundment and shear displacements along the basal shear zone in relation to its shear strength properties. In this study, a two-dimensional numerical rock slide model is designed by means of the Universal Distinct Element Code UDEC and investigated concerning different groundwater flow scenarios. These include: (i) a completely drained rock slide model, (ii) a model with fully saturated rock mass below an inclined groundwater table and (iii) a saturated groundwater model with a reservoir at the slope toe. Slope displacements initiate when the shear strength properties of the basal shear zone are at or below the critical parameters for the limit-equilibrium state and continue until a numerical equilibrium is reached due to deformation- and displacement-based geometrical changes. The study focuses on the influence of a reservoir at the toe of a rock slide and tries to evaluate the degree of displacement which is needed for a re-stabilisation in relation to the geometrical characteristics of the rock slide. Besides, challenges and limitations of applied distinct element methods to simulate large strain and displacements of deep-seated rock slides are discussed. The ongoing study will help to understand the deformation behaviour of deep-seated pre-existing rock slides in fractured rock mass during initial impounding and will be part of a hazard assessment for large reservoirs.

  15. Rock Cracking Indices for Improved Tunnel Support Design: A Case Study for Columnar Jointed Rock Masses

    Science.gov (United States)

    Feng, Xia-Ting; Hao, Xian-Jie; Jiang, Quan; Li, Shao-jun; Hudson, John A.

    2016-06-01

    Measurements indicate that the development of cracking is a key feature relating to the strength and collapse of a columnar jointed rock mass. In this context, a new support design method utilising rock cracking indices for columnar jointed rock mass under high stress is proposed to restrain the development of cracking in the surrounding rock mass. The method involves limiting the cracking evolution of the surrounding rock mass by designing the appropriate parameters and time of installation of the support system. Two indices are suggested: the allowable depth of the excavation damaged zone (EDZ); and the allowable damage extent of the rock mass in the EDZ. The method involves limiting the evolution of cracking in the surrounding rock mass by designing the parameters and time of installation of the support system. The support system should have a suitable stiffness and installation time so as to restrain the evolution of the depth and damage extent of the EDZ within the surrounding rock. Therefore, the depth and damage extent of the EDZ, as well as the axial stress in the anchor bolts, are calculated at different distances between the support location and the tunnel working face to find the appropriate stiffness and installation time of the support system. The method has been successfully adopted to determine the thickness of shotcrete, the arrangement and installation time of rockbolts, and other parameters, for five large diversion tunnels at the Baihetan hydropower station, China, which were excavated in columnar jointed rock masses.

  16. Stability Evaluation on Surrounding Rocks of Underground Powerhouse Based on Microseismic Monitoring

    Directory of Open Access Journals (Sweden)

    Feng Dai

    2015-01-01

    Full Text Available To study the stability of underground powerhouse at Houziyan hydropower station during excavation, a microseismic monitoring system is adopted. Based on the space-time distribution characteristics of microseismic events during excavation of the main powerhouse, the correlation between microseismic events and blasting construction is established; and the microseismic clustering areas of the underground powerhouse are identified and delineated. The FLAC3D code is used to simulate the deformation of main powerhouse. The simulated deformation characteristics are consistent with that recorded by microseismic monitoring. Finally, the correlation between the macroscopic deformation of surrounding rock mass and microseismic activities is also revealed. The results show that multiple faults between 1# and 3# bus tunnels are activated during excavation of floors V and VI of the main powerhouse. The comprehensive method combining microseismic monitoring with numerical simulation as well as routine monitoring can provide an effective way to evaluate the surrounding rock mass stability of underground caverns.

  17. Reliability analysis of tunnel surrounding rock stability by Monte-Carlo method

    Institute of Scientific and Technical Information of China (English)

    XI Jia-mi; YANG Geng-she

    2008-01-01

    Discussed advantages of improved Monte-Carlo method and feasibility aboutproposed approach applying in reliability analysis for tunnel surrounding rock stability. Onthe basis of deterministic parsing for tunnel surrounding rock, reliability computing methodof surrounding rock stability was derived from improved Monte-Carlo method. The com-puting method considered random of related parameters, and therefore satisfies relativityamong parameters. The proposed method can reasonably determine reliability of sur-rounding rock stability. Calculation results show that this method is a scientific method indiscriminating and checking surrounding rock stability.

  18. Determination and distribution of diesel components in igneous rock surrounding underground diesel storage facilities in Sweden.

    Science.gov (United States)

    Loren, A; Hallbeck, L; Pedersen, K; Abrahamsson, K

    2001-01-15

    In Sweden, a preliminary investigation of the contamination situation of igneous rock surrounding underground storage facilities of diesel showed that the situation was severe. The diesel was believed to have penetrated into the rock as far as 50 m from the walls of the vaults. Consequently, the risk for contamination of groundwater and recipients could not be neglected. To be able to assess the fate of diesel components in rock, both a suitable drilling method and a method for the determination of a wide range of diesel components were needed. The analytical method presented made it possible to quantify a number of hydrocarbons in rock samples collected with triple-tube core drilling. The samples were dissolved in hydrofluoric acid (HF) with hexane in Teflon centrifuge tubes. After digestion of the rock, extraction of the analytes with hexane was performed. Determination of the individual hydrocarbons present was done with gas chromatography-mass spectrometry (GC-MS). The method was used to study the environmental impact of the underground storage of diesel. The drilling method enabled sampling without contamination risks. Our data show that the major transport of diesel components in rock occurs through fracture systems and that diffusion of diesel through the rock is of minor importance. The results have drastically changed the view of the contamination situation of diesel in the vicinity of storage facilities in hard rock in Sweden.

  19. Failure mechanism of Mesozoic soft rock roadway in Shajihai coal mine and its surrounding rock control

    Institute of Scientific and Technical Information of China (English)

    Yuan Yue; Zhu Yongjian; Wang Weijun; Yu Weijian

    2014-01-01

    In view of the buckling failure caused by large deformation of Mesozoic soft rock roadway in Shajihai mining area, such as serious roof fall, rib spalling, floor heave, etc., based on the detail site investigation, theoretical analysis, mineral composition test, microstructure test, water-physical property test and field experiments were carried out. And we revealed the compound failure mechanism of Mesozoic soft rock roadway in Shajihai mining area, namely the molecule expansion-shear slip of weak structural plane-construction disturbance. On this basis, the coupling support technology whose core is constant resistance with large deformation bolt was proposed. The feature of this supporting technology is that a new type of structural composite material was used, which makes the supporting system not only has the ideal deformation characteristics, but also has high supporting resistance. Thus the fully release of plastic energy within surrounding rock and reasonable control of the thickness of the plastic ring were realized. Then the differential deformation between the surrounding rock and support was eliminated by the secondary coupling support of bolt–mesh–cable, and the bolt with high strength was applied in the base angle to control floor. Eventually the collaborative bearing system of surrounding rock–support was formed. Through field tests the validity and rationality of support was also verified.

  20. The principle of stability control of surrounding rock-bearing struc-tures in high stress soft rock roadways

    Institute of Scientific and Technical Information of China (English)

    WANG Wei-jun; ZHU Yong-jian; LI Shu-qing; ZHANG Peng

    2009-01-01

    Through the description of the deformational features of the surrounding rock around high stress engineering soft rock roadways,the coupling stabilization principle of inner and outer structures in surrounding rock was put forward.The supporting principles of high stress engineering soft rock roadway (high resistance and yielding support,timely support,high strength and high stiffness supports) were proposed,which were applied in engineering practices,and obtained better achievements.

  1. The principle of stability control of surrounding rock-bearing structures in high stress soft rock roadways

    Energy Technology Data Exchange (ETDEWEB)

    Wei-jun Wang; Yong-jian Zhu; Shu-qing Li; Peng Zhang [Hunan Key Laboratory of Safe Mining Techniques of Coal Mines, Xiangtan (China)

    2009-03-15

    Through the description of the deformational features of the surrounding rock around high stress engineering soft rock roadways, the coupling stabilization principle of inner and outer structures in surrounding rock was put forward. The supporting principles of high stress engineering soft rock roadway (high resistance and yielding support, timely support, high strength and high stiffness supports) were proposed, which were applied in engineering practices in Shuijingtou colliery, and obtained better achievements. 5 refs., 4 figs.

  2. Numerical analysis of tunnel reinforcing influences on failure process of surrounding rock under explosive stress waves

    Institute of Scientific and Technical Information of China (English)

    ZUO Yu-jun; TANG Chun-an; ZHU Wan-cheng; LI Di-yuan; LI Shu-cai

    2008-01-01

    Based on mesoscopic damage mechanics, numerical code RFPA2D (dynamic edition) was developed to analyze the influence of tunnel reinforcing on failure process of surrounding rock under explosive stress waves. The results show that the propagation phenomenon of stress wave in the surrounding rock of tunnel and the failure process of surrounding rock under explosive stress waves are reproduced realistically by using numerical code RFPAED; from the failure process of surrounding rock,the place at which surrounding rock fractures is transferred because of tunnel reinforcing, and the rockfall and collapse caused by failure of surrounding rock are restrained by tunnel reinforcing; furthermore, the absolute values of peak values of major principal stress, and the minimal principal stress and shear stress at center point of tunnel roof are reduced because of tunnel reinforcing, and the displacement at center point of tunnel roof is reduced as well, consequently the stability of tunnel increases.

  3. Stability classification model of mine-lane surrounding rock based on distance discriminant analysis method

    Institute of Scientific and Technical Information of China (English)

    ZHANG Wei; LI Xi-bing; GONG Feng-qiang

    2008-01-01

    Based on the principle of Mahalanobis distance discriminant analysis (DDA) theory, a stability classification model for mine-lane surrounding rock was established, including six indexes of discriminant factors that reflect the engineering quality of surrounding rock: lane depth below surface, span of lane, ratio of directly top layer thickness to coal thickness, uniaxial comprehensive strength of surrounding rock, development degree coefficient of surrounding rock joint and range of broken surrounding rock zone. A DDA model was obtained through training 15 practical measuring samples. The re-substitution method was introduced to verify the stability of DDA model and the ratio of mis-discrimination is zero. The DDA model was used to discriminate3 new samples and the results are identical with actual rock kind. Compared with the artificial neural network method and support vector mechanic method, the results show that this model has high prediction accuracy and can be used in practical engineering.

  4. Geotechnical Descriptions of Rock and Rock Masses.

    Science.gov (United States)

    1985-04-01

    weathering is presented by Dornbusch (1982). 39. Mechanical, or physical, weathering of rock occurs primarily by (a) freeze expansion (or frost wedging...34Engineering Classifica- tion of In-Situ Rock," Technical Report No. AFWL-TR-67-144, Air Force Weapons Laboratory, Kirtland Air Force Base, N. Mex. Dornbusch , W

  5. Dissipation of Impact Stress Waves within the Artificial Blasting Damage Zone in the Surrounding Rocks of Deep Roadway

    Directory of Open Access Journals (Sweden)

    Jianguo Ning

    2016-01-01

    Full Text Available Artificial explosions are commonly used to prevent rockburst in deep roadways. However, the dissipation of the impact stress wave within the artificial blasting damage zone (ABDZ of the rocks surrounding a deep roadway has not yet been clarified. The surrounding rocks were divided into the elastic zone, blasting damage zone, plastic zone, and anchorage zone in this research. Meanwhile, the ABDZ was divided into the pulverizing area, fractured area, and cracked area from the inside out. Besides, the model of the normal incidence of the impact stress waves in the ABDZ was established; the attenuation coefficient of the amplitude of the impact stress waves was obtained after it passed through the intact rock mass, and ABDZ, to the anchorage zone. In addition, a numerical simulation was used to study the dynamic response of the vertical stress and impact-induced vibration energy in the surrounding rocks. By doing so, the dissipation of the impact stress waves within the ABDZ of the surrounding rocks was revealed. As demonstrated in the field application, the establishment of the ABDZ in the surrounding rocks reduced the effect of the impact-induced vibration energy on the anchorage support system of the roadway.

  6. Effect of longwall length on mechanical characteristics of surrounding rock stress shell in mining face

    Energy Technology Data Exchange (ETDEWEB)

    Guang-Xiang Xie; Lei Wang [Anhui University of Science and Technology, Huainan (China)

    2008-12-15

    The mechanical characteristics of surrounding rock stress shell in longwall mining face were studied, based on the results of in-situ measurement combined with numerical simulation, and the effect of longwall length on mechanical characteristics of surrounding rock stress shell was discovered. The results show that the mechanical characteristics of surrounding rock stress shell are influenced by the length of the face. With an increase of mining face length, the level of concentration of shell stress located in the front face and surrounding rock of roadway is amplified and the three- dimensional stress is focused in the working face. The damage lies in the head entry corner of face and the vertical displacement is reduced but horizontal displacement is enlarged. The dynamic balance of surrounding rock stress shell is improved with rational adjustment of face length. It is effective in protecting the working face and controlling strata behavior. 5 refs., 7 figs.

  7. Analysis of nonlinear dynamic character in the surrounding rock system for deep buried underground engineering

    Institute of Scientific and Technical Information of China (English)

    ZHAO Yu; PENG Hai-you

    2010-01-01

    Combining the field monitoring results of a deep-buried tunnel in Chongqing,the dynamic characteristics of the surrounding rock system under high in situ stress was analyzed by phase space reconstruction, calculating correlation dimension, Kolmogorov entropy and largest Lyapunov exponents. Both the Kolmogorov entropy and largest Lyapunov exponents show that the surrounding rock system is a chaotic one. Based on this, a local model was applied to predict surrounding rock displacement, and a nonlinear dynamic model was derived to forecast the interaction of the surrounding rock and support structure. The local method was found to have an extremely small total error. Also, the nonlinear dynamic model forecasting curves agree with the monitoring ones very well. It is proved that the nonlinear dynamic characteristic study is very important in analyzing rock stability and predicting the evolution of rock systems.

  8. Elastic-plastic model identification for rock surrounding an underground excavation based on immunized genetic algorithm.

    Science.gov (United States)

    Gao, Wei; Chen, Dongliang; Wang, Xu

    2016-01-01

    To compute the stability of underground engineering, a constitutive model of surrounding rock must be identified. Many constitutive models for rock mass have been proposed. In this model identification study, a generalized constitutive law for an elastic-plastic constitutive model is applied. Using the generalized constitutive law, the problem of model identification is transformed to a problem of parameter identification, which is a typical and complicated optimization. To improve the efficiency of the traditional optimization method, an immunized genetic algorithm that is proposed by the author is applied in this study. In this new algorithm, the principle of artificial immune algorithm is combined with the genetic algorithm. Therefore, the entire computation efficiency of model identification will be improved. Using this new model identification method, a numerical example and an engineering example are used to verify the computing ability of the algorithm. The results show that this new model identification algorithm can significantly improve the computation efficiency and the computation effect.

  9. Stress and deformation analysis on deep surrounding rock at different time stages and its application

    Institute of Scientific and Technical Information of China (English)

    Li Ming; Mao Xianbiao; Yu Yuanlin; Li Kai; Ma Chao; Peng Yan

    2012-01-01

    Based on the characteristics of the deep circular tunnel,the surrounding rock was divided into three regions:the cracked region,the plastic region and the viscoelastic region.The process of rock stress deformation and change was divided into three stages after the roadway excavation.By using the elastic-plastic mechanics theory,the analytical solutions of the surrounding stress and displacement at different stages and the radii of cracked and plastic regions were formulated.We additionally explained the surrounding rock stress and displacement which appeared in practical project.Simultaneously,based on the problem which emerged from a mine in Xuzhou during the excavating process of rock roadway's transport,we got the theoretical solutions for the stress and displacement in the process of rock roadway's excavation and considered that the broken area of rock roadway was largely loosing circle.The results indicate that according to the rheological characteristics of surrounding rock,in the primeval excavation of rock roadway,we should increase the length of anchor bolt and cooperate it with anchor nets cable-U steel supporting frame.In addition,when the deformation rate of the surrounding rock is descending after the 15 days' excavation,we should use the "three anchor" supporting method (anchor bolt spray,anchor note and anchor rope) and set aside about 20 cm as the reserved deformation layer.

  10. Chemical Variations in a Granitic Pluton and Its Surrounding Rocks.

    Science.gov (United States)

    Baird, A K; McIntyre, D B; Welday, E E; Madlem, K W

    1964-10-09

    New techniques of x-ray fluorescence spectrography have provided, for the first time, abundant data regarding chemical variability of granitic rocks on different scales. The results suggest that current designs of sampling plans for trend surface analysis should be modified; in particular several specimens, preferably drillcores, may be required at each locality.

  11. A Novel Model of the Ideal Point Method Coupled with Objective and Subjective Weighting Method for Evaluation of Surrounding Rock Stability

    Directory of Open Access Journals (Sweden)

    Yingchao Wang

    2016-01-01

    Full Text Available The classification of surrounding rock stability is the critical problem in tunneling engineering. In order to decrease engineering disasters, the surrounding rock stability should be accurately evaluated. The ideal point method is applied to the classification of surrounding rock stability. Considering the complexity of surrounding rock classification, some factors such as rock uniaxial compressive strengthen, integrality coefficient of rock mass, the angle between tunnel axis and the main joint, joints condition, and seepage measurement of groundwater are selected as evaluation indices. The weight coefficients of these evaluation indices are determined by the objective and subjective weighting method, consisting with the delphi method and the information entropy theory. The objective and subjective weighting method is exact and reliable to determine the weights of evaluation indices, considering not only the expert’s experiences, but also objectivity of the field test data. A new composite model is established for evaluating the surrounding rock stability based on the ideal point method and the objective and subjective weighting method. The present model is applied to Beigu mountain tunnel in Jiangsu province, China. The result is in good agreement with practical situation of surrounding rock, which proves that the ideal point method used to classify the surrounding rock in tunnels is reasonable and effective. The present model is simple and has very strong operability, which possesses a good prospect of engineering application.

  12. Identifying rock blocks based on hierarchical rock-mass structure model

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    Rock-masses are divided into many closed blocks by deterministic and stochastic discontinuities and engineering interfaces in complex rock-mass engineering. Determining the sizes, shapes, and adjacent relations of blocks is important for stability analysis of fractured rock masses. Here we propose an algorithm for identifying spatial blocks based on a hierarchical 3D Rock-mass Structure Model (RSM). First, a model is built composed of deterministic discontinuities, engineering interfaces, and the earth’s surface, and the deterministic blocks surrounded by these interfaces are traced. Then, in each deter-ministic block, a network model of stochastic discontinuities is built and the stochastic blocks are traced. Building a unitary wire frame that connects all interfaces seamlessly is the key for our algorithm to identify the above two kinds of blocks. Using this algorithm, geometric models can be built for block theory, discrete element method, and discontinuous deformation analysis.

  13. Study on visualization simulation of temperature distributions in surrounding rock of tunnels in a deep mine

    Institute of Scientific and Technical Information of China (English)

    SUN Pei-de

    2006-01-01

    Based on the mathematical model for rock temperature distribution in a geothermal field, the properties of rock temperature distribution in geothermal field for four kinds of surrounding rock cross-sections of tunnels in a deep mine were simulated by using finite element method. It is shown that the relationship for rock temperature distribution varied with the geothermal parameters, time and space. Namely, 2-dimensional time-dependent isograms clearly showed the process for rock temperature variation and distribution in a geothermal field which has been redisplayed with visualization numerical simulation.

  14. Settlement behavior of coal mine waste in different surrounding rock conditions

    Institute of Scientific and Technical Information of China (English)

    MA Chun-de; LI Xi-bing; HU Bing-nan; CHEN Feng; XU Ji-cheng; LI Di-yuan

    2008-01-01

    In order to investigate the influence of complex conditions of in-situ surrounding rocks on the settlement behavior of nubbly coal mine waste subjected to high gravity pressure, four kinds of loading chambers made of different similar materials with different elastic moduli in experiments were used to simulate the deformation features of in-site rocks, including soft, moderate hardness, hard and extra-hard rocks. The results show that all the settlement-axial load (or axial strain-stress) curves obtained under four different surrounding rock conditions present power-exponential function feature. The final settlement of coal mine waste under the same axial load is closely related to the lumpiness gradations and the deformation behavior of chamber materials used to simulate behaviors of different in-situ surrounding rocks. In the same surrounding rock condition, the final settlement under the same maximum axial load decreases with the decrease of the proportion of larger gradation of coal mine waste. While for the same lumpiness gradation case, the settlement increases with the decrease of elastic modulus of simulated surrounding rocks and the lateral pressure induced by axial load increases with the increase of elastic modulus of loading chambers that are used to simulate different surrounding rocks. The test results also reveal that both the compaction curve and lateral pressure curve show a three-stage behavior, and the duration of each stage, which is closely related to gradations and the deformation feature of loading chamber materials, decreases with the increase of the proportion of the small size of coal mine waste and elastic modulus of the simulated rock materials.

  15. Development of fractures in soft rock surrounding a roadway and their control

    Institute of Scientific and Technical Information of China (English)

    Li Xuehua; Yao Qiangling; Man Jiankang; Chen Chaoqun; He Lihui

    2011-01-01

    As the excavation of roadway,new fractures will be formed and the pre-existing fractures extend with the redistribution of stress in surrounding rocks.Eventually,fracture zone and bed separation are formed in rocks because of the developed fractures.Therefore,mastering the fracture evolution of surrounding rocks is very important to maintain the stability of roadway.The surrounding rocks of main haulage roadway in a certain coal mine is so broken and loose that the supporting is very difficult.Based on comprehensive analysis of the engineering geological conditions,a sight instrument was used to observe the fractures of internal surrounding rocks.Four indices,i.e.,the width of fracture zone W,the number of fractures n,the width of fractures d and rock fracture designation RFD,are put forward to evaluate the fracture development.According to the evolution rules of the soft rock roadway from this paper,control principles by stages and by regions are presented through the research.At the same time,the best time of grouting reinforcement is determined on the basis of fracture saturation.Field practice shows that the roadway can satisfy normal production during service periods by suitable first support and grouting reinforcement.

  16. Study on calculation of rock pressure for ultra-shallow tunnel in poor surrounding rock and its tunneling procedure

    Institute of Scientific and Technical Information of China (English)

    Xiaojun Zhou; Jinghe Wang; Bentao Lin

    2014-01-01

    A computational method of rock pressure applied to an ultra-shallow tunnel is presented by key block theory, and its mathematical formula is proposed according to a mechanical tunnel model with super-shallow depth. Theoretical analysis shows that the tunnel is subject to asymmetric rock pressure due to oblique topography. The rock pressure applied to the tunnel crown and sidewall is closely related to the surrounding rock bulk density, tunnel size, depth and angle of oblique ground slope. The rock pressure applied to the tunnel crown is much greater than that to the sidewalls, and the load applied to the left side-wall is also greater than that to the right sidewall. Mean-while, the safety of the lining for an ultra-shallow tunnel in strata with inclined surface is affected by rock pressure and tunnel support parameters. Steel pipe grouting from ground surface is used to consolidate the unfavorable surrounding rock before tunnel excavation, and the reinforcing scope is proposed according to the analysis of the asymmetric load induced by tunnel excavation in weak rock with inclined ground surface. The tunneling procedure of bench cut method with pipe roof protection is still discussed and carried out in this paper according to the special geological condition. The method and tunneling procedure have been successfully utilized to design and drive a real expressway tunnel. The practice in building the super-shallow tunnel has proved the feasibility of the calculation method and tunneling procedure presented in this paper.

  17. Motion of rock masses on slope

    Directory of Open Access Journals (Sweden)

    Urška Petje

    2006-12-01

    Full Text Available This paper shows the different ways of how rock masses (stones, rocks, and blocks move along slopes and for each different way of motion (free fall, bouncing, rolling, sliding, slowing down, lubrication, fluidizationadequatedynamicequationsaregiven.Knowingthe kinematics and dynamics of travelling rock masses is necessary for mathematical modeling of motion and by this an assessment of maximal possible rockfall runout distances as an example of a sudden and hazardeous natural phenomenon, threatening man and his property, especially in the natural environment.

  18. Tunnel Design by Rock Mass Classifications

    Science.gov (United States)

    1990-01-01

    fact, rock mass classifications have been successfully applied throughout the world : in the United States,2 - Canada,7 8 Western Europe, 9 -12 South...gneiss. Very high strength >30000 >200 Quartzite, dolerite, gabbro , basalt. Table 10 3 Classification for Discontinuity Spacing Spacing of Rock Mass

  19. ANALYSIS ON INCREMENTAL COHESION OF SURROUNDING ROCK DUE TO PRESTRESSED CABLE ANCHOR

    Institute of Scientific and Technical Information of China (English)

    夏建中; 闫莫明; 滕年保; 李方政

    1998-01-01

    A new method for determining the incremental cohesion △Cm of surrounding rock due toprestressed cable anchor is presented, and the formulas for △Cm are deduced and ACredistributions also are discussed, based on the two anchorage effects, one is the effect with theprestressed value △Q3 of cable anchor improving the stress state of surrounding rock andincreasing the surrounding rock strength, the other is the fully encapsulated effect. Thedetermined incremental cohesion △Cm is subjected to the model test and field measurement in thereferences, and coincides well with those tested results. The formulas for △Cm can be used indesigning supoport parameters and related numerical analyses of prestressed cable anchor.

  20. Research on the stability analysis and design of soil tunnel surrounding rock

    Institute of Scientific and Technical Information of China (English)

    Zheng Yingren; Qiu Chenyu; Xiao Qiang

    2010-01-01

    The paper first analyzes the failure mechanism and mode of tunnel according to model experiments and mechanical calculation and then discusses the deficiency of taking the limit value of displacement around the tunnel and the size of the plastic zone of surrounding rock as the criterion of stability.So the writers put forward the idea that the safety factor of surrounding rock calculated through strength reduction FEM(finit element method)should be regarded as the criterion of stability,which has strict mechanical basis and unified standard and would not be influenced by other factors.The paper also studies the safety factors of tunnel surrounding rock(safety factors of shear and tension failure)and lining and some methods of designing and calculating tunnels.At last,the writers take the loess tunnel for instance and show the design and calculation results of two-lane railway tunnel.

  1. Experimental study on stability control technology of surrounding rock of deep roadways in coal mine

    Institute of Scientific and Technical Information of China (English)

    Luo Yong; Yuan Liang; Yang Yang

    2014-01-01

    In order to solve effectively the problems of deep mining with safety and high efficiency,the multi-ple factors influencing the stability of deep rock roadway and technical problems are analyzed in the light of the severe situation of effective mining for deep coal resource,and the stability control methods for deep rock road-way are provided,which are based on the idea of combined support with separated steps and integral control of surrounding rock of deep rock roadway. The suggested methods were applied to a deep rock roadway with-648 m depth in Gubei coal mine of Huainan area. The field test was carried out and the in-situ monitoring was imple-mented,and the support scheme was optimized and adjusted to improve the stability of the surrounding rock of the roadway based on the feedback analysis. The results showed that the stability can be improved greatly by the provided control methods for deep roadway. The present methods for stability control of deep rock roadway can be used to other deep rock roadways with the similar conditions.

  2. Surrounding rock deformation regularity of roadway under extremely complicated geological conditions in deep mine and its control

    Institute of Scientific and Technical Information of China (English)

    刘长友; 何卓军; 万志军

    2003-01-01

    By combining the practices of deep mine mining in Changguang Mine field and using the Universal Distinct Element Code 3.0(UDEC3.0) numerical computing method, the distribution characteristics of deformation field and stress field as well as the surrounding rock deformation regularity of soft rock roadway are analyzed under extremely complicated geological conditions, a technical principle of bolting to control the surrounding rock of roadway is put forward. And also using a dynamic control for surrounding rocks designing method, the supporting parameters and implement plan are rationally determined. The experimental tests have obtained a good controlling result of surrounding rock.

  3. Study on mechanism and practice of surrounding rock control of high stress coal roadway

    Institute of Scientific and Technical Information of China (English)

    WANG Wei-jun; YANG Lei; OUYANG Guang-bin

    2006-01-01

    The mechanical principle and surrounding rock deformation feature of high stress coal roadway was analyzed. The condition of stress balance of the kind of the roadway was put forward. The surrounding rock control principle and supporting technique of high stress coal roadway were discussed. It was very important to control early days deformation of coal sides. The supporting strength is should increased, so the strength loss of coal sides is decreased. The range of plastic fluid zone is reduced. The above mention-ned principle is applied in industrial test, and the new supporting technique is applied successfully.

  4. Control over surrounding rocks deformation of soft floor and whole-coal gateways with trapezoidal supports

    Energy Technology Data Exchange (ETDEWEB)

    Zhai, X.; Li, D.; Shao, Q.; Sun, Y. [Henan Polytechnic University, Jaozuo (China). Dept. of Resource and Material Engineering

    2005-06-01

    The coal seams of Guengcun Coal mine of Yima Coal Group Co. Ltd. are prone to spontaneous combustion. Fully mechanized longwall mining with sublevel caving is used as the mining method. Based on the characteristics of the gateways of the 1301 coal face and of the roof coal seams, the natural equilibrium arch theory was used to design the parameters of 11 mine-type metal supports. Then, in-situ supporting experiments were carried out. The results indicate that under the action of virgin rock stress, the width of broken rocks zone of surrounding rocks is 1.7-2.0 m in the return heading and 1.1-1.3 m in the outgoing headway and their surrounding rocks belong to the IV-type soft rock and the III-type common surrounding rock respectively. Therefore, under the movable abutment pressure, the gateway deformation is serious. At the same time, the accumulated water on gateway floor must be drained in time. These measures were taken in the 1302 and 1304 coal faces in Gengcun colliery, and satisfactory results have been obtained. 8 refs., 3 figs.

  5. ALTERNATING METHOD STUDY ON STRESS ANALYSIS OF SURROUNDING ROCK FOR TWO RANDOM GEOMETRY TUNNELS

    Institute of Scientific and Technical Information of China (English)

    吕爱钟; 张路青

    1997-01-01

    The stress analysis of surrounding rock for two random geometry tunnels is studied inthis paper by using Schwarz's alternating method. The simple and effective alternating algorithm is found, in which the surplus surface force is approximated by Fourier series, thus the iteration derivation can be conducted according to the precision required, finally, the stress results with high precision are obtained.

  6. Plastic zone distribution laws and its types of surrounding rock in large-span roadway

    Institute of Scientific and Technical Information of China (English)

    Li Chong; Xu Jinhai; Pan Jianzhong; Ma Chao

    2012-01-01

    In order to study the distribution laws and types of plastic zone of surrounding rock in large-span roadway,we analyzed the distribution laws with different spans and lateral pressures using FLAC3D numerical calculation software.Based on the roadway support difficulty and distribution laws of the plastic zone of surrounding rock,we defined the large-span roadway and classified the types of large-span rectangular roadways.As a result,the distribution laws of the plastic zone on surrounding rock in a rectangular roadway with different spans and lateral pressures were obtained.The results show that the area of the plastic zone on surrounding rock increased with the increase of the spans and lateral pressures,and the plastic zone was symmetrical to the center line of roadway.At λ =0.5,1.0,1.5,and 2.0,the plastic zone presented "addleshape" distribution,"ellipse" distribution."thin and high" distribution and "inverse trapezium" distribution,respectively.In addition,we classified the roadways into four types according to the different lateral pressures and spans,including small-span,moderate-span,large-span and extreme-large-span roadways.

  7. Examining the relation between rock mass cuttability index and rock drilling properties

    Science.gov (United States)

    Yetkin, Mustafa E.; Özfırat, M. Kemal; Yenice, Hayati; Şimşir, Ferhan; Kahraman, Bayram

    2016-12-01

    Drilling rate is a substantial index value in drilling and excavation operations at mining. It is not only a help in determining physical and mechanical features of rocks, but also delivers strong estimations about instantaneous cutting rates. By this way, work durations to be finished on time, proper machine/equipment selection and efficient excavation works can be achieved. In this study, physical and mechanical properties of surrounding rocks and ore zones are determined by investigations carried out on specimens taken from an underground ore mine. Later, relationships among rock mass classifications, drillability rates, cuttability, and abrasivity have been investigated using multi regression analysis. As a result, equations having high regression rates have been found out among instantaneous cutting rates and geomechanical properties of rocks. Moreover, excavation machine selection for the study area has been made at the best possible interval.

  8. Mechanic behavior of unloading fractured rock mass

    Institute of Scientific and Technical Information of China (English)

    YIN Ke; ZHANG Yongxing; WU Hanhui

    2003-01-01

    Under tension and shear conditions related to unloading of rock mass, a jointed rock mass model of linear elastic fracture mechanics is established. According to the model, the equations of stresses, strains and displacements of the region influenced by the crack but relatively faraway the crack (the distance between the research point and the center of the crack is longer than the length of crack) are derived. They are important for evaluating the deformation of cracked rock. It is demonstrated by the comparison between computational results of these theoretical equations and the observed data from unloading test that they are applicable for actual engineering.

  9. Improved RMR Rock Mass Classification Using Artificial Intelligence Algorithms

    Science.gov (United States)

    Gholami, Raoof; Rasouli, Vamegh; Alimoradi, Andisheh

    2013-09-01

    Rock mass classification systems such as rock mass rating (RMR) are very reliable means to provide information about the quality of rocks surrounding a structure as well as to propose suitable support systems for unstable regions. Many correlations have been proposed to relate measured quantities such as wave velocity to rock mass classification systems to limit the associated time and cost of conducting the sampling and mechanical tests conventionally used to calculate RMR values. However, these empirical correlations have been found to be unreliable, as they usually overestimate or underestimate the RMR value. The aim of this paper is to compare the results of RMR classification obtained from the use of empirical correlations versus machine-learning methodologies based on artificial intelligence algorithms. The proposed methods were verified based on two case studies located in northern Iran. Relevance vector regression (RVR) and support vector regression (SVR), as two robust machine-learning methodologies, were used to predict the RMR for tunnel host rocks. RMR values already obtained by sampling and site investigation at one tunnel were taken into account as the output of the artificial networks during training and testing phases. The results reveal that use of empirical correlations overestimates the predicted RMR values. RVR and SVR, however, showed more reliable results, and are therefore suggested for use in RMR classification for design purposes of rock structures.

  10. Field investigations of high stress soft surrounding rocks and deformation control

    Directory of Open Access Journals (Sweden)

    Weijian Yu

    2015-08-01

    Full Text Available Field investigations of high stress soft rock deformations show that the high stress soft rock roadway can slide with large deformation. Severe extrusion and floor heave can also be subsequently observed. The supported roadway can be locally damaged or completely fail, where the floor has a large deformation and/or is seriously damaged. The factors inducing large deformation of surrounding rocks in deep roadway are rock strengths, structure face cutting types, stress states, stress release, support patterns, and construction methods. Based on the deformation characteristics of high stress soft rock roadway, a comprehensive support scheme is proposed. The overall support technology of “step-by-step and joint, hierarchical reinforcement” for roadway is presented, and the anchor cable and bolt parameters to check the design methods are also given. Finally, the proposed comprehensive support method “bolt + metal mesh + U-steel arch + shortcrete + grouting and cable” is used in the extension section of east main haulage roadway at −850 m level of Qujiang coal mine. The 173-day monitoring results show that the average convergence of sidewalls reaches 208 mm, and the average relative convergence of roof and floor reaches 448 mm, suggesting that this kind of support technology for controlling large deformation of high stress soft surrounding rock roadway is effective.

  11. Ellipsoidal anisotropy in elasticity for rocks and rock masses

    CERN Document Server

    Pouya, Ahmad

    2011-01-01

    One of the interesting features with the ellipsoidal models of anisotropy presented in this paper is their acceptance of analytical solutions for some of the basic elasticity problems. It was shown by Pouya (2000) and Pouya and Zaoui (2006) that many closed-form solutions for basic problems involving linear isotropic materials could be extended by linear transformation to cover a variety of "ellipsoidal" materials. This paper will describe two main varieties of ellipsoidal elastic models and show how well they fit the in situ data for sedimentary rocks; numerical homogenization results for several varieties of fractured rock masses will also be provided.

  12. MINING INDUCED INFLUENCE ON THE ROADWAYS IN WEAK SURROUNDING ROCK AND ITS CONTROLLING MEASURES

    Institute of Scientific and Technical Information of China (English)

    陆士良; 王悦汉

    1991-01-01

    The application of destressing method can change the distribution patterns of the stress field in the weak rock surrounding openings, locate the openings in the zone of low stress level, thus improve their loading and maintaining conditions. Such method is considered as a new way of opening maintenance in weak rock and has caused extensive interests in mining industry both at home and abroad. The results of theoretic research and lab experiments of utilizing topdestresslng trough to maintain the opening affected by mining activities in weak rock, as well as its practical application in a coal mine are introduced in this paper. The research results indicate that the deformation and floor heaving of the opening in weak rock can be effectively controlled, and long-term stability of the opening can be realized by applying destressing method as long as the destressing plan and concerned parameters are carefully determined.

  13. A Novel Model of Set Pair Analysis Coupled with Extenics for Evaluation of Surrounding Rock Stability

    Directory of Open Access Journals (Sweden)

    Mingwu Wang

    2015-01-01

    Full Text Available The evaluation of surrounding rock stability is a complex problem involving numerous uncertainty factors. Here, based on set pair analysis (SPA coupled with extenics, a novel model, considering incompatibility, certainty, and uncertainty of evaluation indicators, was presented to analyze the surrounding rock stability. In this model, extension set was first utilized to describe the actual problem of surrounding rock stability. Then, the connectional membership degree of the set pair was introduced to compare the measured values with classification standards from three aspects embracing identity, discrepancy, and contrary. Also, according to identity-discrepancy-contrary (IDC analysis in the universe of the extension set, the connection numbers were proposed to specify the connectional membership degree of an evaluation indicator to each class. Combined with the weights of evaluation indicators, integrated connectional membership degrees were calculated to determine their classes of rock stability. Finally, a case study and comparison with variable fuzzy set method, triangular fuzzy number method, and basic quality (BQ grading method were performed to confirm the validity and reliability of the proposed model. The results show that this model can effectively and quantitatively express the differences within a group, transformation of different groups, and uncertainty of complex indicators as a whole.

  14. Field Monitoring of Deformations and Internal Forces of Surrounding Rocks and Lining Structures in the Construction of the Gangkou Double-Arched Tunnel—A Case Study

    Directory of Open Access Journals (Sweden)

    Qixiang Yan

    2017-02-01

    Full Text Available Double-arched tunnel is a special and complex underground structure which needs to be monitored carefully during construction. Taking the Gangkou tunnel as the engineering background, this paper presents a case study of field monitoring of a representative double-arched tunnel. Typical cross sections were chosen in each class of surrounding rock masses in the tunnel area and different types of sensors were embedded in designed locations, and the deformations and forces of both surrounding rocks and lining structures were monitored systematically. The dynamic evolution as well as the spatial distribution characteristics of the monitoring data including the internal displacements of surrounding rocks and the contact pressures between surrounding rocks and primary linings, the axial forces in rock bolts and the internal forces in both steel arches and secondary linings were analyzed. The monitoring and analysis results show that the deformations and forces of both surrounding rocks and lining structures are directly related to the construction procedures, geological conditions and locations in the double-arched tunnel. According to the results, some reasonable suggestions were provided for the improvement of the tunnel construction. This study will provide useful reference and guidance for the design, construction and monitoring of similar engineering projects in future.

  15. Failure mechanism and stability control technology of rock surrounding a roadway in complex stress conditions

    Institute of Scientific and Technical Information of China (English)

    Yu Yang; Bai Jianbiao; Chen Ke; Wang Xiangyu; Xiao Tongqiang; Chen Yong

    2011-01-01

    To solve the problem of supporting three downhill coal structures in the Yongan Coal Mine of Shanxi Jincheng,we studied the regular development of stress and plastic zones and characteristics of deformation of rock surrounding roadway groups after a period of roadway driving,mining one side as well as mining both sides,we used FLAC3D for our numerical and theoretical analyses.Field test were carried out,where we revealed the deformation mechanism of roadways and its coal pillars in complex stress conditions.We proposed a roadway stability control technology using backwall grouting with high-water rapid hardening material and combined support with bolt and cable anchoring after mining both sides.Our field practices showed that deformation of rock surrounding roadways can be controlled with this technology.

  16. Domino instability effect of surrounding rock-coal pillars in a room-and-pillar gob

    Institute of Scientific and Technical Information of China (English)

    Li Chong; Xu Jinhai; Wang Zhongliang; Qin Shuai

    2013-01-01

    To discuss the domino instability effect and large area roof falling and roof accidents of surrounding rock-coal pillars in a room-and-pillar gob, the equilibrium equation for a roof-coal pillar-floor system with the influence of mining floor was developed based on the engineering conditions of the surrounding rock in a room-and-pillar gob in the 3-2 coal seam of Tanggonggou mine. The conditions of system instability and the relationship between system stability and system stiffness were analyzed from an energetic point of view. Numerical simulation using the discrete element software UDEC was also carried out to simulate conditions causing the domino effect on surrounding rock-coal pillars in a 3-2 room-and-pillar gob. The results show that:if we want the system to destabilize, the collective energy in roof-and-floor must be larger than that in the coal pillar. When the stiffness of the coal pillars and the roof-and-floor are both greater than zero, the system is stable. When the stiffness of the coal pillars is negative but the summed stiffness of the coal pillars and roof-and-floor is larger than or equal to zero, the system is statically destroyed. When the sum of the coal pillars and the roof-floor stiffness is negative, the system suffers from severe damages. For equal advance distances of the coal mining face, the wider coal pillars can reduce the probability of domino type instability. Conversely, the smaller width pillars can increase the instability probability. Domino type instability of surrounding rock-coal pillars is predicted to be unli-kely when the width of coal pillars is not less than 8 m.

  17. Damage Characteristics of Surrounding Rock Subjected to VCR Mining Blasting Shock

    OpenAIRE

    Nan Jiang; Chuanbo Zhou; Xuedong Luo; Shiwei Lu

    2015-01-01

    For limiting the damage range caused by explosive shock loads in vertical crater retreat (VCR) mining, the blasting damage characteristics of surrounding rock were studied by two methods: numerical simulation and ultrasonic testing. Combined with the mining blasting in Dongguashan Copper Mine of China, the VCR blasting shock characteristics under different conditions are obtained by using LSDYNA. Based on statistical fracture mechanics and damage mechanics theories, a damage constitutive mode...

  18. Caving thickness effects of surrounding rocks macro stress shell evolving characteristics

    Energy Technology Data Exchange (ETDEWEB)

    Guang-xiang Xie; Ke Yang [Anhui University of Science and Technology, Huainan (China). Key Laboratory of Coal Mine Safety and Efficiently Caving of Ministry of Education

    2009-06-15

    In order to explore the influence of different caving thicknesses on the macro stress shell, (MSS) distribution and evolving characteristics of surrounding rocks in unsymmetrical disposal and fully mechanized top-coal caving (FMTC), based on unsymmetrical disposal characteristics, the analyses of numerical simulation, material simulation and in-situ observation were synthetically applied according to the geological and technical conditions of the 1151(3) working face in Xieqiao Mine. The results show that the stress peak value of the MSS-base and the ratio of MSS-body height to caving thickness are nonlinear and inversely proportional to the caving thickness. The MSS-base width, the MSS-body height, the MSS-base distance to working face wall and the rise distance of MSS-base beside coal pillar are nonlinear and directly proportional to the caving thickness. The characteristics of MSS distribution and its evolving rules of surrounding rocks and the integrated caving thickness effects are obtained. The investigations will provide theoretic references to the surrounding rocks stability control of the working face and roadway, roadway layout, gas extraction and exploitation, and efficiency of caving, etc. 13 refs., 5 figs., 5 tabs.

  19. Caving thickness effects of surrounding rocks macro stress shell evolving characteristics

    Institute of Scientific and Technical Information of China (English)

    XIE Guang-xiang; YANG Ke

    2009-01-01

    In order to explore the influence of different caving thicknesses on the MSS dis-tribution and evolving characteristics of surrounding rocks in unsymmetrical disposal and fully mechanized top-coal caving (FMTC), based on unsymmetrical disposal characteris-tics, the analyses of numerical simulation, material simulation and in-situ observation were synthetically applied according to the geological and technical conditions of the 1151(3) working face in Xieqiao Mine. The results show that the stress peak value of the MSS-base and the ratio of MSS-body height to caving thickness are nonlinear and inversely proportional to the caving thickness. The MSS-base width, the MSS-body height, the MSS-base distance to working face wall and the rise distance of MSS-base beside coal pillar are nonlinear and directly proportional to the caving thickness. The characteristics of MSS distribution and its evolving rules of surrounding rocks and the integrated caving thickness effects are obtained. The investigations will provide lots of theoretic references to the surrounding rocks' stability control of the working face and roadway, roadway layout, gas extraction and exploitation, and efficiency of caving, etc.

  20. Numerical analysis and field monitoring tests on shallow tunnels under weak surrounding rock

    Institute of Scientific and Technical Information of China (English)

    刘建华; 刘晓明; 张永杰; 肖庭

    2015-01-01

    The Jianpudong No. 4 tunnel is a shallow tunnel, which belongs to Shaoshan County scenic highway in Hunan province, China and whose surrounding rock is weak. According to its characteristics, the field monitoring tests and numerical analysis were done. The mechanical characteristics of shallow tunnels under weak surrounding rock and the stress−strain rule of surrounding rock and support were analyzed. The numerical analysis results show that the settlement caused by upper bench excavating accounts for 44% of the total settlement, and the settlement caused by tunnel upper bench supporting accounts for 56% of the total settlement. The maximum axial force of shotcrete lining is 177.2 kN, which locates in hance under the secondary lining. The maximum moment of shotcrete lining is 5.08 kN·m, which locates in the arch foot. The stress curve of steel arch has three obvious stages during the tunnel construction. The maximum axial force of steel arch is 297.4 kN, which locates in tunnel vault. The axial forces of steel arch are respectively 23.5 kN and−21.8 kN, which is influenced by eccentric compression of shallow tunnel and locates in hance. The results show that there is larger earth pressure in tunnel vault which is most unfavorable position of steel arch. Therefore, the advance support should be strengthened in tunnel vault during construction process.

  1. Upper bound analytical solution for surrounding rock pressure of shallow unsymmetrical loading tunnels

    Institute of Scientific and Technical Information of China (English)

    雷明锋; 彭立敏; 施成华; 谢友均; 谭立新

    2015-01-01

    By combining the results of laboratory model tests with relevant flow rules, the failure mode of shallow unsymmetrical loading tunnels and the corresponding velocity field were established. According to the principle of virtual power, the upper bound solution for surrounding rock pressure of shallow unsymmetrical loading tunnel was derived and verified by an example. The results indicate that the calculated results of the derived upper bound method for surrounding rock pressure of shallow unsymmetrical loading tunnels are relatively close to those of the existing “code method” and test results, which means that the proposed method is feasible. The current code method underestimates the unsymmetrical loading feature of surrounding rock pressure of shallow unsymmetrical loading tunnels, so it is unsafe; when the burial depth is less or greater than two times of the tunnel span and the unsymmetrical loading angle is less than 45°, the upper bound method or the average value of the results calculated by the upper bound method and code method respectively, is comparatively reasonable. When the burial depth is greater than two times of the tunnel span and the unsymmetrical loading angle is greater than 45°, the code method is more suitable.

  2. Nonlinear Progressive Failure Analysis of Surrounding Rock System Based on Similarity Theory

    Directory of Open Access Journals (Sweden)

    Zhao Y.

    2016-01-01

    Full Text Available Nonlinear progressive failure study of surrounding rock is important for the stability analysis of underground engineering projects. Taking a deep-buried tunnel in Chongqing as an example, a three dimensional(3-D physical model was established based on similarity theory. To satisfy similarity requirement of physical–mechanical properties, such as elastic modulus, compressive strength and Poisson ratio, physical model materials were developed. Using full inner-spy photograph technology, the deformation and failure process of rock were studied under the situation of independent and combined action of anchor, shotcrete and reinforcing mesh. Based on experimental results, the interaction mechanism between rock and support structure under high stress was investigated.

  3. Rockburst Generation in Discontinuous Rock Masses

    Science.gov (United States)

    He, Ben-Guo; Zelig, Ravit; Hatzor, Yossef H.; Feng, Xia-Ting

    2016-10-01

    We study rockburst generation in discontinuous rock masses using theoretical and numerical approaches. We begin by developing an analytical solution for the energy change due to tunneling in a continuous rock mass using linear elasticity. We show that the affected zone where most of the increase in elastic strain energy takes place is restricted to an annulus that extends to a distance of three diameters from the tunnel center, regardless of initial tunnel diameter, magnitude of in situ stress, and in situ stress ratio. By considering local elastic strain concentrations, we further delineate the Rockbursting Prone Zone found to be concentrated in an annulus that extends to one diameter from the tunnel center, regardless of original stress ratio, magnitude, and the stiffness of the rock mass. We proceed by arguing that in initially discontinuous rock masses shear stress amplification due to tunneling will inevitably trigger block displacements along preexisting discontinuities much before shear failure of intact rock elements will ensue, because of the lower shear strength of discontinuities with respect to intact rock elements, provided of course that the blocks are removable. We employ the numerical discrete element DDA method to obtain, quantitatively, the kinetic energy, the elastic strain energy, and the dissipated energy in the affected zone in a discontinuous rock due to tunneling. We show that the kinetic energy of ejected blocks due to strain relaxation increases with increasing initial stress and with decreasing frictional resistance of preexisting discontinuities. Finally, we demonstrate how controlled strain energy release by means of top heading and bench excavation methodology can assist in mitigating rockburst hazards due to stain relaxation.

  4. Displacement Forecasting Method in Brittle Crack Surrounding Rock Under Excavation Unloading Incorporating Opening Deformation

    Science.gov (United States)

    Li, X. J.; Yang, W. M.; Wang, L. G.; Butler, I. B.

    2014-11-01

    Splitting failure, which is recognized as a special engineering geology phenomenon, occurs continually in the brittle rock mass of caverns during underground excavation. In this paper, a splitting model of linear slippage crack groups is built with fracture mechanics, energy analysis, and crack extension theories. Considering intrinsic cracks in rock mass and change of outer stress, intrinsic cracks propagate into macroscopical splitting cracks that are approximately parallel to the side wall of caverns. The splitting criterion of cavern rock mass and the method for predicting displacement in view of splitting opening displacement are proposed. In the end, the forecasting method is applied to the Jinping-I Hydropower Station, underground caverns engineering in China, the splitting failure zone and forecasting displacement are accordant with the monitoring data. The new forecasting displacement method is proven to contribute to the construction of similar underground caverns.

  5. Gravitational stresses in anisotropic rock masses

    Science.gov (United States)

    Amadei, B.; Savage, W.Z.; Swolfs, H.S.

    1987-01-01

    This paper presents closed-form solutions for the stress field induced by gravity in anisotropic rock masses. These rocks are assumed to be laterally restrained and are modelled as a homogeneous, orthotropic or transversely isotropic, linearly elastic material. The analysis, constrained by the thermodynamic requirement that strain energy be positive definite, gives the following important result: inclusion of anisotropy broadens the range of permissible values of gravity-induced horizontal stresses. In fact, for some ranges of anisotropic rock properties, it is thermodynamically admissible for gravity-induced horizontal stresses to exceed the vertical stress component; this is not possible for the classical isotropic solution. Specific examples are presented to explore the nature of the gravity-induced stress field in anisotropic rocks and its dependence on the type, degree and orientation of anisotropy with respect to the horizontal ground surface. ?? 1987.

  6. Theoretical analysis of a new segmented anchoring style in weakly cemented soft surrounding rock

    Institute of Scientific and Technical Information of China (English)

    Zhao Zenghui; Wang Weiming; Wang Lihua

    2016-01-01

    According to the tensile failure of rock bolt in weakly cemented soft rock, this paper presents a new seg-mented anchoring style in order to weaken the cumulative effect of anchoring force associated with the large deformation. Firstly, a segmented mechanical model was established in which free and anchoring section of rock bolt were respectively arranged in different deformation zones. Then, stress and displace-ment in elastic non-anchoring zone, elastic anchoring zone, elastic sticking zone, softening sticking zone and broken zone were derived respectively based on neural theory and tri-linear strain softening constitutive model of soft rock. Results show that the anchoring effect can be characterized by a supporting parameter β. With its increase, the peak value of tangential stress gradually moves to the roadway wall, and the radial stress significantly increases, which means the decrease of equivalent plastic zone and improvement of confining effect provided by anchorage body. When β increases to 0.72, the equivalent plastic zone disappears, and stresses tend to be the elastic solutions. In addition, the anchoring effect on the displacement of surrounding rock can be quantified by a normalization factorδ.

  7. Mineralogical and microstructural investigations of fractures in Permian z2 potash seam and surrounding salt rocks

    Science.gov (United States)

    Mertineit, Michael; Grewe, Wiebke; Schramm, Michael; Hammer, Jörg; Blanke, Hartmut; Patzschke, Mario

    2017-04-01

    Fractures occur locally in the z2 potash seam (Kaliflöz Staßfurt). Most of them extend several centimeter to meter into the surrounding salt rocks. The fractures are distributed on all levels in an extremely deformed area of the Morsleben salt mine, Northern Germany. The sampling site is located within a NW-SE trending synclinal structure, which was reverse folded (Behlau & Mingerzahn 2001). The samples were taken between the -195 m and - 305 m level at the field of Marie shaft. In this area, more than 200 healed fractures were mapped. Most of them show opening widths of only a few millimeters to rarely 10 cm. The fractures in rock salt are filled with basically polyhalite, halite and carnallite. In the potash seam, the fractures are filled with kainite, halite and minor amounts of carnallite and polyhalite. In some cases the fracture infill changes depending on the type of surrounding rocks. There are two dominant orientations of the fractures, which can be interpreted as a conjugated system. The main orientation is NE-SW trending, the dip angles are steep (ca. 70°, dip direction NW and SE, respectively). Subsequent deformation of the filled fractures is documented by a strong grain shape fabric of kainite, undulatory extinction and subgrain formation in kainite, and several mineral transformations. Subgrain formation in halite occurred in both, the fracture infill and the surrounding salt rocks. The results correlate in parts with investigations which were carried out at the close-by rock salt mine Braunschweig-Lüneburg (Horn et al. 2016). The development of the fractures occurred during compression of clayey salt rocks. However, the results are only partly comparable due to different properties (composition, impurities) of the investigated stratigraphic units. Further investigations will focus on detailed microstructural and geochemical analyses of the fracture infill and surrounding salt rocks. Age dating of suitable minerals, e.g. polyhalite (Leitner et al

  8. Stability assessment of rock surrounding an I-beam supported retreating roadway

    Institute of Scientific and Technical Information of China (English)

    严红; 张吉雄; 李林玥; 冯锐敏

    2015-01-01

    The installation of a back-wall guard-board is the key to successfully supporting underground retreating roadways in coal mines. Based on the coordinate support principle, and using an I-shaped steel support for the surrounding rock, a mechanical model was developed for the stability of the roadway support and surrounding rock. Analysis of the bearing capacity of the roof back-wall guard-board and modelling of the equations for the maximum deflection and the maximum compressive stress of the top and side beams of the I-shaped steel support were undertaken. Simultaneously, the model was used to calculate and analyse the stability of the top and side beams of the I-shaped steel support structure and analyse the criteria for their stability. The results provide a reliable theoretical basis for the judgment of the stability of the surrounding rock and support structure. The theoretical evaluation results are consistent with field data. Finally, the key support parameters of the top and side beams of the I-shaped steel support structure and the variation of the maximum deflection and the maximum compressive stress as affected by the influence of the guard-board length were investigated. It is concluded that, as the back-board length increases, the maximum compressive stress in the top beam of the I-shaped steel support increases while the compressive stress in the side beam decreases. The results show that the accuracy of judgment of the stability of a supported retreating roadway is improved, providing guidance for the design of such typical I-shaped steel support and back-board structures.

  9. Theoretical study of rock mass investigation efficiency

    Energy Technology Data Exchange (ETDEWEB)

    Holmen, Johan G.; Outters, Nils [Golder Associates, Uppsala (Sweden)

    2002-05-01

    The study concerns a mathematical modelling of a fractured rock mass and its investigations by use of theoretical boreholes and rock surfaces, with the purpose of analysing the efficiency (precision) of such investigations and determine the amount of investigations necessary to obtain reliable estimations of the structural-geological parameters of the studied rock mass. The study is not about estimating suitable sample sizes to be used in site investigations.The purpose of the study is to analyse the amount of information necessary for deriving estimates of the geological parameters studied, within defined confidence intervals and confidence level In other words, how the confidence in models of the rock mass (considering a selected number of parameters) will change with amount of information collected form boreholes and surfaces. The study is limited to a selected number of geometrical structural-geological parameters: Fracture orientation: mean direction and dispersion (Fisher Kappa and SRI). Different measures of fracture density (P10, P21 and P32). Fracture trace-length and strike distributions as seen on horizontal windows. A numerical Discrete Fracture Network (DFN) was used for representation of a fractured rock mass. The DFN-model was primarily based on the properties of an actual fracture network investigated at the Aespoe Hard Rock Laboratory. The rock mass studied (DFN-model) contained three different fracture sets with different orientations and fracture densities. The rock unit studied was statistically homogeneous. The study includes a limited sensitivity analysis of the properties of the DFN-model. The study is a theoretical and computer-based comparison between samples of fracture properties of a theoretical rock unit and the known true properties of the same unit. The samples are derived from numerically generated boreholes and surfaces that intersect the DFN-network. Two different boreholes are analysed; a vertical borehole and a borehole that is

  10. Influence Mechanism of Grouting on Mechanical Characteristics of Rock Mass

    Directory of Open Access Journals (Sweden)

    Zhang Jixun

    2013-01-01

    Full Text Available Grouting technology has been widely used in all fields of geotechnical and civil engineering. Prospective engineering objectives including reinforcement of rock mass and groundwater leakage treatment can be achieved by grouting which will change the mechanical parameters of rock mass such as strength, elastic modulus, and coefficient of permeability. In this paper, rock mass is assumed as a composite material consisting of rock particles and random microcracks initially. Since part or all of the cracks will be filled with cement slurry after grouting, rock mass consists of rock particles, grout condensate, and some or no random microcracks after grouting. The damage constitutional law of the mesoscopic element is established based on the theory of mesoscopic damage mechanics. With the heterogeneity of the components of rock mass considered, the variation of mechanical characteristics of rock mass is studied before and after grouting. And the influence mechanism of grouting on rock mass is investigated at mesoscale level.

  11. Application of phase space reconstruction and v-SVR algorithm in predicting displacement of underground engineering surrounding rock

    Institute of Scientific and Technical Information of China (English)

    SHI Chao; CHEN Yi-feng; YU Zhi-xiong; YANG Kun

    2006-01-01

    A new method for predicting the trend of displacement evolution of surrounding rock was presented in this paper. According to the nonlinear characteristics of displacement time series of underground engineering surrounding rock, based on phase space reconstruction theory and the powerful nonlinear mapping ability of support vector machines, the information offered by the time series datum sets was fully exploited and the non-linearity of the displacement evolution system of surrounding rock was well described.The example suggests that the methods based on phase space reconstruction and modified v-SVR algorithm are very accurate, and the study can help to build the displacement forecast system to analyze the stability of underground engineering surrounding rock.

  12. Mechanical Behavior of the Near-field Host Rock Surrounding Excavations

    Energy Technology Data Exchange (ETDEWEB)

    Kelkar, Sharad M. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Stauffer, Philip H. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Robinson, Bruce Alan [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2015-01-09

    This report is being prepared under the FY14 activity FT-14LA0818069, Mechanical and Hydrological Behavior of the Near-Field Host Rock Surrounding Excavations, and fulfills the Los Alamos National Laboratory deliverable M4FT-14LA08180610, which in PICS:NE is titled “Draft report, Test Plan for Mechanical and Hydrological Behavior of the Near-field Host Rock Surrounding Excavations.” Since the report is an intermediate deliverable intended as input to the eventual test plan for this test, rather than being an actual test plan, the activity title is used as the title of this document to avoid confusion as to the contents in the report. This report summarizes efforts to simulate mechanical processes occurring within a hypothetical high-level waste (HLW) repository in bedded salt. The report summarizes work completed since the last project deliverable, “Coupled model for heat and water transport in a high level waste repository in salt “, a Level 2 milestone submitted to DOE in September 2013 (Stauffer et al., 2013).

  13. Improved response surface method and its application in stability reliability degree analysis of tunnel surrounding rock

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    An approach of limit state equation for surrounding rock was put forward based on deformation criterion. A method of symmetrical sampling of basic random variables adopted by classical response surface method was mended, and peak value and deflection degree of basic random variables distribution curve were took into account in the mended sampling method. A calculation way of probability moment, based on mended Rosenbluth method, suitable for non-explicit performance function was put forward.The first, second, third and fourth order moments of functional function value were calculated by mended Rosenbluth method through the first, second, third and fourth order moments of basic random variable. A probability density the function(PDF) of functional function was deduced through its first, second, third and fourth moments, the PDF in the new method took the place of the method of quadratic polynomial to approximate real functional function and reliability probability was calculated through integral by the PDF for random variable of functional function value in the new method. The result shows that the improved response surface method can adapt to various statistic distribution types of basic random variables, its calculation process is legible and need not iterative circulation. In addition, a stability probability of surrounding rock for a tunnel was calculated by the improved method,whose workload is only 30% of classical method and its accuracy is comparative.

  14. Study on mechanical parameters of fractured rock masses

    Institute of Scientific and Technical Information of China (English)

    2011-01-01

    The equivalent strength parameters of fractured rock masses are prerequisite for stability analysis of geotechnical engineering projects constructed in fractured rock masses which are encountered frequently in western china.Based on generated mesh of fractured rock masses,combined with statistic damage constitutive model of intact rock and damage model of structural plane,progressive failure of fractured rock masses is studied using finite element method(FEM) .Furthermore,Scale effect and anisotropy of compressive strength of fractured rock masses are studied.Study results show that the strength decreases and tend towards stability rapidly from intact rock to fractured rock masses,and the anisotropy of strength of fractured rock masses is not significant.At last,based on numerical simulation conducted on 10 m scale rock masses under different confining pressures,the equivalent strength parameters of fractured rock masses are gained and the results are compared with Hoek-Brown criteria.The method developed is helpful for determination of strength parameters of fractured rock masses.

  15. A Model of Anisotropic Property of Seepage and Stress for Jointed Rock Mass

    Directory of Open Access Journals (Sweden)

    Pei-tao Wang

    2013-01-01

    Full Text Available Joints often have important effects on seepage and elastic properties of jointed rock mass and therefore on the rock slope stability. In the present paper, a model for discrete jointed network is established using contact-free measurement technique and geometrical statistic method. A coupled mathematical model for characterizing anisotropic permeability tensor and stress tensor was presented and finally introduced to a finite element model. A case study of roadway stability at the Heishan Metal Mine in Hebei Province, China, was performed to investigate the influence of joints orientation on the anisotropic properties of seepage and elasticity of the surrounding rock mass around roadways in underground mining. In this work, the influence of the principal direction of the mechanical properties of the rock mass on associated stress field, seepage field, and damage zone of the surrounding rock mass was numerically studied. The numerical simulations indicate that flow velocity, water pressure, and stress field are greatly dependent on the principal direction of joint planes. It is found that the principal direction of joints is the most important factor controlling the failure mode of the surrounding rock mass around roadways.

  16. Test studies of gas flow in rock and coal surrounding a mined coal seam

    Institute of Scientific and Technical Information of China (English)

    Lv Youchang

    2012-01-01

    An analysis of the variation rule of abutment pressure at the mining working face in a single coal seam and the mechanical behavior of surrounding rock during stoping is presented.Consideration of the elastic and plastic deformation zones that develop during the mining process allowed the determination of a relationship between horizontal stress and vertical stress.Based on this,a confined pressure unloading test was conducted by the use of the "gas-containing coal thermo-fluid-solid coupling 3-axis servo seepage" experimental apparatus.Thus,gas flow patterns in the elastic and plastic zones were derived from an experimental point of view.Darcy's law and the Klinkenberg effect were used to derive a gas flow equation for the elastic and plastic stress fields.The study of gas flow phenomena at the working face during coal mining is of great importance for the study of gas migration and enrichment oatterns.

  17. Stability control of surrounding rocks for a coal roadway in a deep tectonic region

    Institute of Scientific and Technical Information of China (English)

    Xiao Tongqiang; Wang Xiangyu; Zhang Zhigao

    2014-01-01

    In order to effectively control the deformation and failure of surrounding rocks in a coal roadway in a deep tectonic region, the deformation and failure mechanism and stability control mechanism were stud-ied. With such methods as numerical simulation and field testing, the distribution law of the displace-ment, stress and plastic zone in the surrounding rocks was analyzed. The deformation and failure mechanisms of coal roadways in deep tectonic areas were revealed:under high tectonic stress, two sides will slide along the roof or floor;while the plastic zone of the two sides will extend along the roof or floor, leading to more serious deformation and failure in the corner of two sides and the bolt supporting the corners is readily cut off by the shear force or tension force. Aimed at controlling the large slippage defor-mation of the two sides, serious deformation and failure in the corners of the two sides and massive bolt breakage, a ‘controlling and yielding coupling support’ control technology is proposed. Firstly, bolts which do not pass through the bedding plane should be used in the corners of the roadway, allowing the two sides to have some degree of sliding to achieve the purpose of ‘yielding’ support, and which avoid breakage of the bolts in the corner. After yielding support, bolts in the corner of the roadway and which pass through the bedding plane should be used to control the deformation and failure of the coal in the corner. ‘Controlling and yielding coupling support’ technology has been successfully applied in engineering practice, and the stability of deep coal roadway has been greatly improved.

  18. Borehole camera technology for measuring the relaxation zone of surrounding rock: mechanism and application

    Energy Technology Data Exchange (ETDEWEB)

    Jing Hong-wen; Li Yuan-hai; Liang Jun-qi; Yu De-cheng [China University of Mining & Technology, Xuzhou (China). State Key Laboratory for Geomechanics & Deep Underground Engineering

    2009-05-15

    A panoramic borehole camera technology (BCT) and digital image processing method was developed by constructing a system composed of hardware and software. The technology was used for measuring the relaxation zone of surrounding rock with the borehole camera. The hardware consists of a mini CCD camera and a high-pressure sealed magnetic compass that is used for camera positioning. The software includes real-time image monitoring and a processing program that includes the procedure for analysis of the relaxation zone. The roundness of cracks in the boreholes is taken as the index for identifying the relaxation zone. The system was used to measure the relaxation zone of a deep roadway in the Qiwu coal mine of Shandong province. The distribution of the relaxation zone around the roadway was obtained. The results show that the thickness of the broken rock zone varies with the measuring position within a cross section of the roadway. The reliability of the measuring method was tested and verified by comparing the data from BCT with those measured by an ultrasonic method; the difference is less than 3.5%. The system provides a new method for the measurement of the relaxation zone when engineering deep underground. 6 refs., 11 figs., 2 tabs.

  19. 地下水封储油库围岩稳定性数值分析%Numerical analysis on the stability of surrounding rock for underground water-sealing oil storage in rock caverns

    Institute of Scientific and Technical Information of China (English)

    胡谋鹏; 粱久正; 许杰

    2013-01-01

    An underground water-sealing oil storage in rock caverns in Liaoning Province follows a low level of ground stress in the low-stress area. After its excavation, surrounding rock deformation and fracture are controlled under the combination between single structure plane and multi-group structure plane. Therefore, it is required to first analyze whether the surrounding rock suffer stress problems or structure plane problems and equivalent to value selection of surrounding rock parameters on the importance. Geological strength index (GSI) proposed by Hoek and Brown are based on rock quality evaluation. It can reduce subjectivity in determining the shear strength indicator to define rock mass mechanics parameters by the empirical formula. The underground water-sealed oil storage in rock caverns in Liaoning Province is taken as the object of study. Using the surrounding rock parameter value selection method based on GSI system as well as FLAC3D software, numerical analysis on the surrounding rock stability is conducted and its results are interpreted based on displacement criteria and stress criterion to determine the surrounding rock stability, thus having a guiding significance in engineering practice.%辽宁某地下水封储油硐库地应力水平不高,属于低应力区,开挖后围岩变形破坏受单一结构面和多组结构面的组合控制,因此首先需要分析围岩属于应力型问题还是属于结构面型问题,其重要性等同于围岩参数取值的重要性.Hoek和Brown提出的地质强度指标(GSI)法基于岩体质量评价,应用经验公式确定岩体力学参数,可以一定程度上减少确定抗剪强度指标过程中的主观成分.以辽宁某地下水封储油库工程储油硐室为研究对象,采用基于GSI系统的围岩参数取值方法,借助FLAC3D软件对围岩稳定性进行数值分析,利用位移判据和应力判据对数值分析结果进行解释,进而判断围岩的稳定性,对工程实践具有一定的指导意义.

  20. Gravity-induced rock mass damage related to large en masse rockslides: Evidence from Vajont

    Science.gov (United States)

    Paronuzzi, Paolo; Bolla, Alberto

    2015-04-01

    to failure, unstable rock slopes can be affected by diffuse newly formed gravity-driven joints that are absent in the surrounding area and within the underlying bedrock, as the Vajont case history demonstrates (joint sets J9 and J10). These fractures, caused by critical tensile and shear stresses, represent an important mechanical clue to recognizing, on a geological basis, the instability condition of a rock slope under investigation. Owing to its complex geological evolution, the Vajont landslide is an outstanding example to help learn about cumulative GRMD effects that can accumulate over time when an ancient rockslide is further remobilized by a sudden en masse sliding motion.

  1. Stress analysis of single joint rock mass under triaxial compression

    Institute of Scientific and Technical Information of China (English)

    LIU Xin-rong(刘新荣); JIANG Shu-ping(蒋树屏); LI Xiao-hong(李晓红); BAO Tai(包太)

    2004-01-01

    Based on the fundamental principle of rock mechanics, the stresses of single joint rock mass under three-dimensional compression were analyzed. The effect of the intermediate principle stress on the strength of single joint rock mass were discussed in particular. It is found that the strength of single joint rock are affected by the intermediate principal stress, which may be the main factor in some conditions.

  2. Analysis on mechanism and key factors of surrounding rock instability in deeply inclined roadway affected by argillation and water seepage

    Institute of Scientific and Technical Information of China (English)

    Ma Rui; Li Guichen; Zhang Nong; Liu Cong; Wei Yinghao; Zhang Ming

    2015-01-01

    Based on the characteristics of surrounding rocks for deeply inclined roadway affected by argillation and water seepage, a structure model of layer crack plate was established to analyze the shear sliding insta-bility mechanism. Through solid mechanics analysis of anchored surrounding rock with defect from water seepage, combined with numerical analysis for instability mechanism under water seepage in deeply inclined roadway, key factors were proposed. Results show that with increasing height of layer crack plate, lateral buckling critical load value for high wall of the roadway decreases;there is a multi-stage distribution for tensile stress along the anchor bolt with defect under pulling state condition;groundwater seepage seriously affects the strength of surrounding rock of the roadway, to some extent the plastic zone of the high side rises up to 8 m. Finally some support strategies were proposed for the inclined roadway and successfully applied to Haoyuan coal mine in Tiela mining area, western China.

  3. Periodical zonal character of damage near the openings in highly-stressed rock mass conditions

    Directory of Open Access Journals (Sweden)

    Vladimir V. Makarov

    2016-04-01

    Full Text Available Rock mass damage at great depths near underground openings is often of a zonal character. However, the classical elastoplastic theory fails to explain sufficiently all properties of zonal failure structures. A new non-Euclidean mathematical model for highly-stressed rock mass was developed based on the principles of mechanics of defected material and non-equilibrium thermodynamics. Methods were developed to determine model parameters that provide satisfactory correspondence between the experimental findings concerning faulted zonal structures near openings at great depths and mathematical calculations. The mechanism of this phenomenon was discovered which consisted in a periodical character of stresses in the surrounding rock mass and development of tensile macrocracks at zones of maximal tangential stresses. Main relationships between the cracking zone width and rock mass strength were established.

  4. ROCK MASS DAMAGED ZONE CAUSED BY BLASTING DURING TUNNEL EXCAVATION

    OpenAIRE

    Hrvoje Antičević; Mario Dobrilović; Hrvoje Perković

    2012-01-01

    Design of underground spaces, including tunnels, and repositories for radioactive waste include the application of the same or similar technologies. Tunnel excavation by blasting inevitably results in the damage in the rock mass around the excavation profile. The damage in the rock mass immediately next to the tunnel profile emerges as the expanding of the existing cracks and the appearance of new cracks, i.e. as the change of the physical and-mechanical properties of the rock mass. Concernin...

  5. Influence of underground water seepage flow on surrounding rock deformation of multi-arch tunnel

    Institute of Scientific and Technical Information of China (English)

    LI Xi-bing; ZHANG Wei; LI Di-yuan; WANG Qi-sheng

    2008-01-01

    Based on a typical multi-arch tunnel in a freeway, the fast Lagrangian analysis of continua in 3 dimensions(FLAC3D) was used to calculate the surrounding rock deformation of the tunnel under which the effect of underground water seepage flow was taken into account or not. The distribution of displacement field around the multi-arch tunnel, which is influenced by the seepage field, was gained. The result indicates that the settlement values of the vault derived from coupling analysis are bigger when considering the seepage flow effect than that not considering. Through the contrast of arch subsidence quantities calculated by two kinds of computation situations, and the comparison between the calculated and measured value of tunnel vault settlement, it is found that the calculated value(5.7-6.0 mm) derived from considering the seepage effect is more close to the measured value(5.8-6.8 mm).Therefore, it is quite necessary to consider the seepage flow effect of the underground water in aquiferous stratum for multi-arch tunnel design.

  6. Rock mass characterization for Copenhagen Metro using face logs

    DEFF Research Database (Denmark)

    Hansen, Sanne Louise; Galsgaard, Jens; Foged, Niels Nielsen

    2015-01-01

    of relevant rock mass properties for tunnelling in Danian limestone has previously been difficult, as core logging shows a high degree of induced fracturing and core loss due to drilling disturbance, with an underestimation of the RQD values, and other rock mass properties, compared to face logging. However......, describing rock mass characteristics using detailed face logging with geological description and recording of induration and fracturing, giving a field RQD value during excavation, combined with televiewer logs, when available, has shown to be a valuable tool for rock mass characterization compared...

  7. Reinforcing a Dangerous Rock Mass Using the Flexible Network Method

    Institute of Scientific and Technical Information of China (English)

    Yang Wendong; Xie Quanmin; Xia Yuanyou; Li Xinping

    2005-01-01

    Because the main failure type of a dangerous rock mass is collapse, the treatment of such a mass should focus on controlling collapse failure. When treating dangerous rock masses, disturbing the mass (e.g. by blasting) needs to be avoided, as this new damage could cause collapse. So the self-bearing capacity of the mountain mass must be used to treat the dangerous rock mass. This article is based on a practical example of the control of a dangerous rock mass at Banyan Mountain, Huangshi, Hubei Province. On the basis of an analysis of damage mechanism and the stability of the dangerous rock mass, a flexible network reinforcement method was designed to prevent the collapse of the rock mass. The deformations of section Ⅱw of the dangerous rock mass before and after the flexible network reinforcement were calculated using the two-dimensional finite element method. The results show that the maximum deformation reduced by 55 % after the application of the flexible network reinforcement, from 45.99 to 20.75 mm, which demonstrates that the flexible network method is effective, and can provide some scientific basis for the treatment of dangerous rock masses.

  8. Mechanical analysis on deformation of surrounding rock with road-in packing of gob-side entry retaining in fully-mechanized sub-level caving face

    Institute of Scientific and Technical Information of China (English)

    ZHU Chuan-qu; MIAO Xie-xing; LIU Ze

    2008-01-01

    Based on the movement regularity of surrounding rock with road-in packing of gob-side entry retaining in fully-mechanized sub-level caving face (RPGERFCF), the me-chanical model of its surrounding rock was established and the calculating formulas of the deformation of the roof, coal wall and filling body were attained. By the mechanical analy-sis to the deformation of the surrounding rock of RPGERFCF, the major factors influencing the deformation of the surrounding rock were found out and the technologic approaches reduced the deformation and enhanced the stability of the surrounding rock were put for-ward. Consequently, the scientific bases were provided for the stability control of the sur-rounding rock of RPGERFCF.

  9. Natural radioactivity content in groundwater of Mt. Etna’s eastern flank and gamma background of surrounding rocks.

    Directory of Open Access Journals (Sweden)

    Beata Kozłowska

    2016-02-01

    Full Text Available Waters of Mt. Etna are the main source of drinking water for the local population and are also distributed in municipal supply systems to neighbouring areas. Radioactivity in underground waters and surrounding rocks from the eastern flank of Mt.Etnawas investigated on the basis of 9 water and 8 rocks samples from 12 localities altogether. Three samples were from water drainage galleries and six from water wells. All water intakes are used for consumption. Activity concentration of uranium isotopes 234,238U, radium isotopes 226,228Ra and radon 222Rn were determined with the use different nuclear spectrometry techniques. The determination of uranium isotopes was carried out with the use of alpha spectrometry. The measurements of radium and radon activity concentration in water were performed with the use of a liquid scintillation technique. Additionally, rocks surrounding the intakes were examined with gamma spectrometry. All water samples showed uranium concentration above Minimum Detectable Activity (MDA, with the highest total uranium (234U + 238U activity concentration equal to 149.2±6 mBq/L. Conversely, all samples showed radium isotopes activity concentrations below MDA. Radon activity concentration was within the range from 2.91±0.36 to 21.21±1.10 Bq/L, hence these waters can be classified as low – radon waters. Gamma natural background of the rocks surrounding the water sampling sites was found on the same levels as other volcanic rocks of Italy.

  10. Zonal disintegration mechanism of isotropic rock masses around a deep spherical tunnel

    Institute of Scientific and Technical Information of China (English)

    谷新保; 毕靖; 许明

    2015-01-01

    In order to investigate zonal disintegration mechanism of isotropic rock masses around a deep spherical tunnel, a new mechanical model subjected to dynamic unloading under hydrostatic pressure condition is proposed. The total elastic stress-field distributions is determined using the elastodynamic equation. The effects of unloading rate and dynamic mechanical parameters of isotropic deep rock masses on the zonal disintegration phenomenon of the surrounding rock masses around a deep spherical tunnel as well as the total elastic stress field distributions are considered. The number and size of fractured and non-fractured zones are determined by using the Hoek-Brown criterion. Numerical computation is carried out. It is found from numerical results that the number of fractured zones increases with increasing the disturbance coefficient, in-situ stress, unloading time and unloading rate, and it decreases with increasing parameter geological strength index, the strength parameter and the uniaxial compressive strength of intact rock.

  11. Gravity-induced stresses in stratified rock masses

    Science.gov (United States)

    Amadei, B.; Swolfs, H.S.; Savage, W.Z.

    1988-01-01

    This paper presents closed-form solutions for the stress field induced by gravity in anisotropic and stratified rock masses. These rocks are assumed to be laterally restrained. The rock mass consists of finite mechanical units, each unit being modeled as a homogeneous, transversely isotropic or isotropic linearly elastic material. The following results are found. The nature of the gravity induced stress field in a stratified rock mass depends on the elastic properties of each rock unit and how these properties vary with depth. It is thermodynamically admissible for the induced horizontal stress component in a given stratified rock mass to exceed the vertical stress component in certain units and to be smaller in other units; this is not possible for the classical unstratified isotropic solution. Examples are presented to explore the nature of the gravity induced stress field in stratified rock masses. It is found that a decrease in rock mass anisotropy and a stiffening of rock masses with depth can generate stress distributions comparable to empirical hyperbolic distributions previously proposed in the literature. ?? 1988 Springer-Verlag.

  12. Effect of Stresses and Strains of Roadway Surrounding Rocks on Borehole Airtightness

    Directory of Open Access Journals (Sweden)

    WU Wei

    2016-02-01

    Full Text Available At present, many high gas and outburst mines have poor gas drainage effects. An important reason influencing the gas drainage effect is a poor hole-sealing effect. Most studies on gas drainage borehole sealing focus on local and foreign borehole sealing methods, borehole sealing equipment, and borehole sealing materials. Numerical simulations of initial drilling sealing depth are insufficient because studies on this subject are few. However, when the initial sealing depth of the borehole is not chosen reasonably, air can enter the gas drainage drill hole through the circumferential crack of roadway surrounding rocks under the influence of suction pressure of the drainage system. This phenomenon ultimately affects the hole-sealing effect. To improve the drilling hole sealing of gas drainage boring, we deduced the expression formulas of the crushing zone, plastic zone, and elastic zone around the coal-seam floor stone drift and conducted a stress–strain analysis of the coal-seam floor stone drift of the 2145 working surfaces of the Sixth Coal Mine of Hebi Coal Mine Group Company by using theoretical analysis, numerical simulation, and on-scene verification. Finally, we obtain the initial drilling sealing depth, which is a main contribution of this study. The results prove the following. The performed hole-sealing process with an initial drilling sealing depth of 8 m has a gas drainage efficiency of 55%. Compared with the previous 6.8 m initial drilling sealing depth with a gas drainage efficiency of less than 30%, which was adopted by the mine, the initial sealing depth of 8 m chosen in the numerical simulation is reasonable and conforms to the actual situation on the spot. Therefore, the initial drilling sealing depth chosen in the numerical simulation will produce practical and effective guidance to study the field hole-sealing depth.

  13. 2D DEM analyses for T-M coupling effects of extreme temperatures on surrounding rock-supporting system of a tunnel in cold region

    Institute of Scientific and Technical Information of China (English)

    张玉军; 杨朝帅; 王永刚

    2013-01-01

    Taking the Kunlunshan Tunnel on Qinghai Tibet Railway as an engineering background, the curved wall-inverted arch lining of the tunnel was simplified into the straight wall-umbrella arch one, and the fractured rock mass with developed joints was treated as a discrete medium in the calculation. Using the UDEC code, the numerical simulations for thermo-mechanical coupling processes in the surrounding rock mass-supporting system were carried out aiming at the conditions of mean temperature, extreme highest temperature and extreme lowest temperature in one year. The distributions and changes of stresses, displacements, plastic zones, temperatures in the rock mass of near field, as well as the loading states in the model-building concrete and bolting were investigated and compared for these three computation cases. The results show that compared with the case of mean temperature, the ranges, where the temperatures of surrounding rock mass change obviously, are 6.0 m and 6.5 m, respectively, for the cases of extreme highest temperature and extreme lowest temperature; the displacements of tunnel are raised by 3.2 9.3 and 5.7 12.7 times, and the thicknesses of plastic zones reach 1.5 2.5 m and 2.0 4.5 m for case 2 and 3, respectively; the extreme temperatures of air have strong effects on the stress, deformation and failure states of supporting structure of tunnel in cold region, and the influence degree of extreme lowest temperature is the highest.

  14. Forecast Jointed Rock Mass Compressive Strength Using a Numerical Model

    Directory of Open Access Journals (Sweden)

    Protosenya Anatoliy

    2016-01-01

    Full Text Available The method of forecasting the strength of the jointed rock mass by numerical modeling of finite element method in ABAQUS was described. The paper presents advantages of this method to solve the problem of determining the mechanical characteristics of jointed rock mass and the basic steps of creating a numerical geomechanical model of jointed rock mass and numerical experiment. Numerical simulation was carried out with jointed rock mass in order to obtain the ratio of strain and stress while loading the numerical model, determining parameters of quantitative assessment of the impact of the discontinuities orientation on the value of the compressive strength, compressive strength anisotropy. The results of the numerical experiment are compared with the data of experimental studies investigations. Innovative materials and structures are analyzed in this paper. The results that were obtained by calculation show qualitative agreement with the results of laboratory experiments of jointed rock mass.

  15. [Characterization of dinosaur fossils and their surrounding rocks by atomic emission spectrometry and X-ray powder diffractometry].

    Science.gov (United States)

    Yang, Qun; Wang, Yi-lin; Li, Chao-zhen; Yuan, Bo

    2005-02-01

    More dinosaur fossils have been found in the Laochangqing valley, Lufeng county than anywhere else in the world, and the dinosaur fossils found here cover the longest time span (including the early and middle Jurassic ages). This excavation offers an ideal experimental base for prehistoric biology studies. This paper presents an elementary analysis of the components and structure of the dinosaur fossils in three different geologic-layers and their surrounding rocks in the above mentioned area. Atomic emission spectrum shows that the fossils are rich in the contents of calcium (>5%) and phosphor, but low in the content of silicon (3%-8%), while the surrounding rocks are high in the content of silicon (>10%). Furthermore, XRD results show that the major compound of the fossils is CaCO3 (66%), followed by SiO2 (17%); while that of the surrounding rocks is SiO2 (>80%), followed by CaCO3 (dinosaur fossils from other rocks. This paper provides valuable data for further zoological studies on the living conditions and evolution of the dinosaurs in the Laochangqing valley, Lufeng county.

  16. Sensitivity analysis of GSI based mechanical characterization of rock mass

    CERN Document Server

    Ván, P

    2012-01-01

    Recently, the rock mechanical and rock engineering designs and calculations are frequently based on Geological Strength Index (GSI) method, because it is the only system that provides a complete set of mechanical properties for design purpose. Both the failure criteria and the deformation moduli of the rock mass can be calculated with GSI based equations, which consists of the disturbance factor, as well. The aim of this paper is the sensitivity analysis of GSI and disturbance factor dependent equations that characterize the mechanical properties of rock masses. The survey of the GSI system is not our purpose. The results show that the rock mass strength calculated by the Hoek-Brown failure criteria and both the Hoek-Diederichs and modified Hoek-Diederichs deformation moduli are highly sensitive to changes of both the GSI and the D factor, hence their exact determination is important for the rock engineering design.

  17. Acoustic and physiological effects of the surroundings in rock cutting process

    Directory of Open Access Journals (Sweden)

    Lucia Ivaničová

    2010-03-01

    Full Text Available A noise effect arising in the rock cutting process is gaining a large attention as to the identification and optimization of the cuttingprocess. The sense experience acquired during the experiments in the process of rotary rock drilling related to the determination of rock typeor to the optimal drilling regime determination is formed due to sense perception, mainly hearing, and its further evaluation by the humanbrain from the information exempted from the environment.

  18. Numerical Analysis of Effect of Water on Explosive Wave Propagation in Tunnels and Surrounding Rock

    Institute of Scientific and Technical Information of China (English)

    XIA Chang-jing; SONG Zhen-duo; TIAN Lu-lu; LIU Hong-bin; WANG Lu; WU Xiao-fang

    2007-01-01

    Based on the application of practical engineering, propagation processes of explosive waves in rock with water well and tunnel are simulated by ANSYS/LS-DYNA software. The evolution of damage in rock is presented. The effect of water on the damage of the concrete slab in a tunnel is compared with damage inflicted without water. The numerical simulation illustrates that water plays an important role in the evolution of damage of the concrete slab in a mine tunnel. In the presence of water in the rock the concrete slab is damaged more severely than without water in rock. The effect of water location in the rock is also considered. It is found that the concrete slab in the tunnel shows various degrees of damage as a function of the different locations of water. Attenuation laws of stress waves over time-space in rock with water are also obtained. Numerical results indicate that, under blast loading, there are three zones in the rock: a crushed zone nearby the explosive charge, a damaged zone and an elastic zone. The conclusions of numerical analysis may provide references for blasting designs and structure protection.

  19. Thermo-mechanical ratcheting in jointed rock masses

    KAUST Repository

    Pasten, C.

    2015-09-01

    Thermo-mechanical coupling takes place in jointed rock masses subjected to large thermal oscillations. Examples range from exposed surfaces under daily and seasonal thermal fluctuations to subsurface rock masses affected by engineered systems such as geothermal operations. Experimental, numerical and analytical results show that thermo-mechanical coupling can lead to wedging and ratcheting mechanisms that result in deformation accumulation when the rock mass is subjected to a biased static-force condition. Analytical and numerical models help in identifying the parameter domain where thermo-mechanical ratcheting can take place.

  20. Solution of Strain-Softening Surrounding Rock in Deep Tunnel Incorporating 3D Hoek-Brown Failure Criterion and Flow Rule

    Directory of Open Access Journals (Sweden)

    Jin-feng Zou

    2016-01-01

    Full Text Available In order to investigate the influence of the intermediate principal stress on the stress and displacement of surrounding rock, a novel approach based on 3D Hoek-Brown (H-B failure criterion was proposed. Taking the strain-softening characteristic of rock mass into account, the potential plastic zone is subdivided into a finite number of concentric annulus and a numerical procedure for calculating the stress and displacement of each annulus was presented. Strains were obtained based on the nonassociated and associated flow rule and 3D plastic potential function. Stresses were achieved by the stress equilibrium equation and generalized Hoek-Brown failure criterion. Using the proposed approach, we can get the solutions of the stress and displacement of the surrounding rock considering the intermediate principal stress. Moreover, the proposed approach was validated with the published results. Compared with the results based on generalized Hoek-Brown failure criterion, it is shown that the plastic radius calculated by 3D Hoek-Brown failure criterion is smaller than those solved by generalized H-B failure criterion, and the influences of dilatancy effect on the results based on the generalized H-B failure criterion are greater than those based on 3D H-B failure criterion. The displacements considering the nonassociated flow rule are smaller than those considering associated flow rules.

  1. Automated rock mass characterisation using 3-D terrestrial laser scanning

    NARCIS (Netherlands)

    Slob, S.

    2010-01-01

    The research investigates the possibility of using point cloud data from 3-D terrestrial laser scanning as a basis to characterise discontinuities in exposed rock massed in an automated way. Examples of discontinuities in rock are bedding planes, joints, fractures and schistocity. The characterisati

  2. Comparison of Rock Varnish Bacterial Communities with Surrounding Non-Varnished Rock Surfaces: Taxon-Specific Analysis and Morphological Description.

    Science.gov (United States)

    Esposito, Alfonso; Ahmed, Engy; Ciccazzo, Sonia; Sikorski, Johannes; Overmann, Jörg; Holmström, Sara J M; Brusetti, Lorenzo

    2015-10-01

    Rock varnish is a thin layer of Fe and Mn oxyhydroxides with embedded clay minerals that contain an increased Mn/Fe ratio compared to that of the Earth's crust. Even if the study of rock varnish has important implications in several fields, the composition of epilithic bacterial communities and the distribution of taxa on varnish surfaces are still not wholly described. The aim of this study was (i) to identify the bacterial taxa which show the greatest variation between varnish and non-varnish environments, collected from the same rock, and (ii) to describe the morphology of epilithic communities through scanning electron microscopy (SEM). Triplicate samples of rock surfaces with varnish and triplicate samples without varnish were collected from five sites in Matsch Valley (South Tyrol, Italy). The V4 region of 16S rRNA gene was analyzed by Illumina sequencing. Fifty-five ubiquitous taxa have been examined to assess variation between varnish and non-varnish. Cyanobacteria, Chloroflexi, Proteobacteria along with minor taxa such as Solirubrobacterales, Conexibaxter, and Rhodopila showed significant variations of abundance, diversity, or both responding to the ecology (presence/absence of varnish). Other taxa, such as the genus Edaphobacter, showed a more marked spatial variation responding to the sampling site. SEM images showed a multitude of bacterial morphologies and structures involved in the process of attachment and creation of a suitable environment for growth. The features emerging from this analysis suggest that the highly oxidative Fe and Mn-rich varnish environment favors anoxigenic autotrophy and establishment of highly specialized bacteria.

  3. Rock glaciers of the Karakoram Himalaya and surrounding mountains, Inner Asia

    Science.gov (United States)

    Hewitt, Kenneth

    2013-04-01

    The transHimalayan upper Indus Basin contains thousands of rock glaciers. An exceptional diversity of forms and sizes exist, hitherto largely unresearched. They are in a well-defined elevation band across the mountains, usually less than 1400 m vertically, although total relief exceeds 7000 m. The zone varies from north to south, west to east, and with slope orientation. Interfluve elevations are primary constraints. Rock glaciers are absent below the lowest and the highest interfluves. They are uncommon in the highest Mustagh Karakoram, Nanga Parbat, and Hindu Kush where glacier ice blankets the elevations where they could develop. The heaviest concentrations occur in sub-ranges of intermediate elevation. A full spectrum of generative conditions is found; related to periglacial, talus, glacial, avalanche, wind-blown snow, and rock avalanche processes. Forms vary between north and south slopes; arid, rainshadowed and more snowy, humid valleys. Rock glacier complexes, where two or more join to create extensive lobes, may have tributaries with different source conditions. The larger examples are several kilometres in length,usually glacier-derived, evidently affected by Holocene glacial history, trans-glacial processes, and paraglacial instabilities. In lesser ranges, many smaller rock glaciers are associated with glacier-free cirques, glacially sculpted valley walls, and floors with abundant glacial deposits. In general, they are transitional in genesis, process, and spatially relative to glacierization, to the vertical cascade of moisture and debris, and climate change in the vertical. Their landscape roles include extensive fragmentation of drainage systems. Countless inactive rock glaciers occur, typically continuing below active ones.

  4. Numerical Homogenization of Jointed Rock Masses Using Wave Propagation Simulation

    Science.gov (United States)

    Gasmi, Hatem; Hamdi, Essaïeb; Bouden Romdhane, Nejla

    2014-07-01

    Homogenization in fractured rock analyses is essentially based on the calculation of equivalent elastic parameters. In this paper, a new numerical homogenization method that was programmed by means of a MATLAB code, called HLA-Dissim, is presented. The developed approach simulates a discontinuity network of real rock masses based on the International Society of Rock Mechanics (ISRM) scanline field mapping methodology. Then, it evaluates a series of classic joint parameters to characterize density (RQD, specific length of discontinuities). A pulse wave, characterized by its amplitude, central frequency, and duration, is propagated from a source point to a receiver point of the simulated jointed rock mass using a complex recursive method for evaluating the transmission and reflection coefficient for each simulated discontinuity. The seismic parameters, such as delay, velocity, and attenuation, are then calculated. Finally, the equivalent medium model parameters of the rock mass are computed numerically while taking into account the natural discontinuity distribution. This methodology was applied to 17 bench fronts from six aggregate quarries located in Tunisia, Spain, Austria, and Sweden. It allowed characterizing the rock mass discontinuity network, the resulting seismic performance, and the equivalent medium stiffness. The relationship between the equivalent Young's modulus and rock discontinuity parameters was also analyzed. For these different bench fronts, the proposed numerical approach was also compared to several empirical formulas, based on RQD and fracture density values, published in previous research studies, showing its usefulness and efficiency in estimating rapidly the Young's modulus of equivalent medium for wave propagation analysis.

  5. Habitat surrounding patch reefs influences the diet and nutrition of the western rock lobster

    Science.gov (United States)

    In this study the influence of habitat on the diet and nutrition of a common reef-associated generalist consumer, the western rock lobster Panulirus cygnus, was tested. Stable isotopes (13C/12C and 15N/14N) and gut contents were used to assess the diet of lobsters collected from ...

  6. Most Used Rock Mass Classifications for Underground Opening

    Directory of Open Access Journals (Sweden)

    Al-Jbori A’ssim

    2010-01-01

    Full Text Available Problem statement: Rock mass characterization is an integral part of rock engineering practice. The empirical design methods based on rock mass classifications systems provide quick assessments of the support requirements for underground excavations at any stage of a project, even if the available geotechnical data are limited. The underground excavation industry tends to lean on empirical approaches such as rock mass classification methods, which provide a rapid means of assessing rock mass quality and support requirements. Approach: There were several classifications systems used in underground construction design. This study reviewed and summarized the must used classification methods in the mining and tunneling systems. Results: The method of this research was collected of the underground excavations classifications method with its parameters calculations procedures for each one, trying to find the simplest, less costs and more efficient method. Conclusion: The study concluded with reference to errors that may arise in particular conditions and the choice of rock mass classification depend on the sensitivity of the projects, costs and the efficient.

  7. Factor analysis of rock, soil and water geochemical data from Salem magnesite mines and surrounding area, Salem, southern India

    Science.gov (United States)

    Satyanarayanan, M.; Eswaramoorthi, S.; Subramanian, S.; Periakali, P.

    2017-09-01

    Geochemical analytical data of 15 representative rock samples, 34 soil samples and 55 groundwater samples collected from Salem magnesite mines and surrounding area in Salem, southern India, were subjected to R-mode factor analysis. A maximum of three factors account for 93.8 % variance in rock data, six factors for 84 % variance in soil data, five factors for 71.2 % in groundwater data during summer and six factors for 73.7 % during winter. Total dissolved solids are predominantly contributed by Mg, Na, Cl and SO4 ions in both seasons and are derived from the country rock and mining waste by dissolution of minerals like magnesite, gypsum, halite. The results also show that groundwater is enriched in considerable amount of minor and trace elements (Fe, Mn, Ni, Cr and Co). Nickel, chromium and cobalt in groundwater and soil are derived from leaching of huge mine dumps deposited by selective magnesite mining activity. The factor analysis on trivalent, hexavalent and total Cr in groundwater indicates that most of the Cr in summer is trivalent and in winter hexavalent. The gradational decrease in topographical elevation from northern mine area to the southern residential area, combined regional hydrogeological factors and distribution of ultramafic rocks in the northern part of the study area indicate that these toxic trace elements in water were derived from mine dumps.

  8. Factor analysis of rock, soil and water geochemical data from Salem magnesite mines and surrounding area, Salem, southern India

    Science.gov (United States)

    Satyanarayanan, M.; Eswaramoorthi, S.; Subramanian, S.; Periakali, P.

    2016-04-01

    Geochemical analytical data of 15 representative rock samples, 34 soil samples and 55 groundwater samples collected from Salem magnesite mines and surrounding area in Salem, southern India, were subjected to R-mode factor analysis. A maximum of three factors account for 93.8 % variance in rock data, six factors for 84 % variance in soil data, five factors for 71.2 % in groundwater data during summer and six factors for 73.7 % during winter. Total dissolved solids are predominantly contributed by Mg, Na, Cl and SO4 ions in both seasons and are derived from the country rock and mining waste by dissolution of minerals like magnesite, gypsum, halite. The results also show that groundwater is enriched in considerable amount of minor and trace elements (Fe, Mn, Ni, Cr and Co). Nickel, chromium and cobalt in groundwater and soil are derived from leaching of huge mine dumps deposited by selective magnesite mining activity. The factor analysis on trivalent, hexavalent and total Cr in groundwater indicates that most of the Cr in summer is trivalent and in winter hexavalent. The gradational decrease in topographical elevation from northern mine area to the southern residential area, combined regional hydrogeological factors and distribution of ultramafic rocks in the northern part of the study area indicate that these toxic trace elements in water were derived from mine dumps.

  9. Towards a geomechanics classification of folded layered rock masses

    Science.gov (United States)

    Agliardi, Federico; Zanchi, Andrea; Bianchi, Federico; Crosta, Giovanni B.

    2016-04-01

    Several schemes have been proposed in the last decades to account for the effects of structure and alteration of rock masses on their geo-mechanical properties. Among these, the Geological Strength Index (GSI) turned out as the most effective to account for complex geological conditions, including heavily fractured, heterogeneous (e.g. flysch-like) or tectonically disturbed rock masses. It is well known that folding has a direct impact on the type and degree of fracturing. Nevertheless, no classification scheme has been developed to introduce explicitly the effects of folding and associated fracturing on rock mass strength and deformability. In this perspective, we carried out an exploratory study aimed at establishing relationships between outcrop-scale folding and GSI in layered carbonate rock masses, exceptionally well exposed in a quarry near Bergamo (Lombardia, Southern Alps). A N-S trending, 350m long and 115m high benched rock face exposes a complete cross section of a sub-horizontal inclined fold involving Lower Jurassic cherty mudstones (Moltrasio Lms.) and marly limestones successions (Domaro Lms.). The main fold has an axial surface moderately dipping to the north and is characterised by polyharmonic folds at scales of metres to tens of metres. The site was documented by producing a digital outcrop through a high-resolution terrestrial photogrammetric survey from distances ranging from 70 to 130 m (18 camera stations, 395 pictures), using RTK GNSS measurements for camera station geo-referencing. Data processing by Structure-from-Motion (SfM) techniques resulted in detailed point clouds covering the entire slope with a cm-scale accuracy. In order to establish relationships between lithology, folding styles, and geomechanical properties of folded rock masses we performed a detailed structural analysis at 25 survey stations spread over all the different fold sectors. These surveys include: lithology, bedding attitude and thickness, brittle structures (e

  10. Theoretical relation between water flow rate in a vertical fracture and rock temperature in the surrounding massif

    CERN Document Server

    Maréchal, Jean-Christophe

    2010-01-01

    A steady-state analytical solution is given describing the temperature distribution in a homogeneous massif perturbed by cold water flow through a discrete vertical fracture. A relation is derived to express the flow rate in the fracture as a function of the temperature measured in the surrounding rock. These mathematical results can be useful for tunnel drilling as it approaches a vertical cold water bearing structure that induces a thermal anomaly in the surrounding massif. During the tunnel drilling, by monitoring this anomaly along the tunnel axis one can quantify the flow rate in the discontinuity ahead before intersecting the fracture. The cases of the Simplon, Mont Blanc and Gotthard tunnels (Alps) are handled with this approach which shows very good agreement between observed temperatures and the theoretical trend. The flow rates before drilling of the tunnel predicted with the theoretical solution are similar in the Mont Blanc and Simplon cases, as well as the flow rates observed during the drilling....

  11. Tensile rock mass strength estimated using InSAR

    KAUST Repository

    Jonsson, Sigurjon

    2012-11-01

    The large-scale strength of rock is known to be lower than the strength determined from small-scale samples in the laboratory. However, it is not well known how strength scales with sample size. I estimate kilometer-scale tensional rock mass strength by measuring offsets across new tensional fractures (joints), formed above a shallow magmatic dike intrusion in western Arabia in 2009. I use satellite radar observations to derive 3D ground displacements and by quantifying the extension accommodated by the joints and the maximum extension that did not result in a fracture, I put bounds on the joint initiation threshold of the surface rocks. The results indicate that the kilometer-scale tensile strength of the granitic rock mass is 1–3 MPa, almost an order of magnitude lower than typical laboratory values.

  12. Engineering rock mass classification of the Olkiluoto investigation site

    Energy Technology Data Exchange (ETDEWEB)

    Aeikaes, K. [ed.; Hagros, A.; Johansson, E. [Saanio and Riekkola Consulting Engineers, Helsinki (Finland)] [and others

    2000-06-01

    Olkiluoto in Eurajoki is being investigated as a possible site for the final disposal of spent nuclear fuel from the Finnish nuclear power plants. The selection of the depth, placement and layout of the repository is affected by the constructability of the bedrock. The constructability, in turn, is influenced by several properties of the host rock, such as its Ethology, the extent of fracturing, its hydrogeological properties and rock engineering characteristics and also by the magnitude and orientation of the in situ stresses and the chemistry of the groundwater. The constructability can be evaluated by the application of a rock classification system in which the properties of the host rock are assessed against common rock engineering judgements associated with underground construction. These judgements are based partly on measurements of in situ stresses and the properties of the bedrock determined from rock samples, but an important aspect is also the practical experience which has been gained during underground excavation in similar conditions and rock types. The aim of the engineering rock mass classification was to determine suitable bedrock volumes for the construction of the repository and has used data from the site characterisation programme carried out at Olkiluoto, which consisted of both surface studies and borehole investigations. The classification specifies three categories of constructability - normal, demanding and very demanding. In addition, rock mass quality has also been classified according to the empirical Q-system to enable a comparison to be made. The rock mass parameters that determine the constructability of the bedrock at Olkiluoto depend primarily on the depth and the Ethology, as well as on whether construction takes place in intact or in fractured rock. The differences in the characteristics of intact rock within a single rock type have been shown to be small. The major lithological unit at Olkiluoto, the mica gneiss, lies in the

  13. Deformation mechanism of surrounding rocks and key control technology for a roadway driven along goaf in fully mechanized top-coal caving face

    Institute of Scientific and Technical Information of China (English)

    李学华

    2003-01-01

    The variation of the stress in the bolted surrounding rocks structure of the roadway driven along goaf in a fully mechanized top-coal caving face with moderate stable conditions are studied by using numerical calculation. The essential deformation characteristics of the surrounding rocks in this kind of roadway are obtained and the key technology of bolting support used under these conditions is put forward.

  14. Deformation mechanism of surrounding rocks and key control technology for a roadway driven along goaf in fully mechanized top-coal caving face

    Energy Technology Data Exchange (ETDEWEB)

    Li, X. [China University of Mining and Technology, Xuzhou (China). School of Energy Science and Engineering

    2003-06-01

    The variation of the stress in the bolted surrounding rocks structure of the roadway driven along the goaf in a fully mechanized top-coal caving face with moderate stable conditions are studied by using numerical calculation. The essential deformation characteristics of the surrounding rocks in this kind of roadway are obtained and the key technology of bolting support used under these conditions is put forward. 3 refs., 2 figs., 1 tab.

  15. Intelligent direct analysis of physical and mechanical parameters of tunnel surrounding rock based on adaptive immunity algorithm and BP neural network

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    Because of complexity and non-predictability of the tunnel surrounding rock, the problem with the determination of the physical and mechanical parameters of the surrounding rock has become a main obstacle to theoretical research and numerical analysis in tunnel engineering. During design, it is a frequent practice, therefore, to give recommended values by analog based on experience. It is a key point in current research to make use of the displacement back analytic method to comparatively accurately determi...

  16. Integrated analysis of rock mass deformation within shaft protective pillar

    Directory of Open Access Journals (Sweden)

    Ewa Warchala

    2016-01-01

    Full Text Available The paper presents an analysis of the rock mass deformation resulting from mining in the vicinity of the shaft protection pillar. A methodology of deformation prediction is based on a deterministic method using Finite Element Method (FEM. The FEM solution is based on the knowledge of the geomechanical properties of the various geological formations, tectonic faults, types of mining systems, and the complexity of the behaviour of the rock mass. The analysis gave the stress and displacement fields in the rock mass. Results of the analysis will allow for design of an optimal mining system. The analysis is illustrated by an example of the shaft R-VIII Rudna Mine KGHM Polish Copper SA.

  17. Rock mass characterisation and stability analyses of excavated slopes

    Science.gov (United States)

    Zangerl, Christian; Lechner, Heidrun

    2016-04-01

    Excavated slopes in fractured rock masses are frequently designed for open pit mining, quarries, buildings, highways, railway lines, and canals. These slopes can reach heights of several hundreds of metres and in cases concerning open pit mines slopes larger than 1000 m are not uncommon. Given that deep-seated slope failures can cause large damage or even loss of life, the slope design needs to incorporate sufficient stability. Thus, slope design methods based on comprehensive approaches need to be applied. Excavation changes slope angle, groundwater flow, and blasting increases the degree of rock mass fracturing as well as rock mass disturbance. As such, excavation leads to considerable stress changes in the slopes. Generally, slope design rely on the concept of factor of safety (FOS), often a requirement by international or national standards. A limitation of the factor of safety is that time dependent failure processes, stress-strain relationships, and the impact of rock mass strain and displacement are not considered. Usually, there is a difficulty to estimate the strength of the rock mass, which in turn is controlled by an interaction of intact rock and discontinuity strength. In addition, knowledge about in-situ stresses for the failure criterion is essential. Thus, the estimation of the state of stress of the slope and the strength parameters of the rock mass is still challenging. Given that, large-scale in-situ testing is difficult and costly, back-calculations of case studies in similar rock types or rock mass classification systems are usually the methods of choice. Concerning back-calculations, often a detailed and standardised documentation is missing, and a direct applicability to new projects is not always given. Concerning rock mass classification systems, it is difficult to consider rock mass anisotropy and thus the empirical estimation of the strength properties possesses high uncertainty. In the framework of this study an approach based on

  18. ROCK MASS DAMAGED ZONE CAUSED BY BLASTING DURING TUNNEL EXCAVATION

    Directory of Open Access Journals (Sweden)

    Hrvoje Antičević

    2012-07-01

    Full Text Available Design of underground spaces, including tunnels, and repositories for radioactive waste include the application of the same or similar technologies. Tunnel excavation by blasting inevitably results in the damage in the rock mass around the excavation profile. The damage in the rock mass immediately next to the tunnel profile emerges as the expanding of the existing cracks and the appearance of new cracks, i.e. as the change of the physical and-mechanical properties of the rock mass. Concerning the design of deep geological repositories, requirements in terms of damaged rock are the same or more rigorous than for the design of tunnel. The aforementioned research is directed towards determining the depth of damage zone caused by blasting. The depth of the damage zone is determined by measuring the changes of physical and-mechanical properties of the rock mass around the tunnel excavation profile. By this research the drilling and blasting parameters were correlated with the depth and size of the damage zone (the paper is published in Croatian.

  19. Deformation and Failure Characteristics of the Rock Masses around Deep Underground Caverns

    Directory of Open Access Journals (Sweden)

    Chong Zhang

    2015-01-01

    Full Text Available The deformation and failure characteristics of deep rock masses are the focus of this study on deep rock mass engineering. The study identifies the deformation and failure characteristics of a deep cavern under different ground stress conditions using model test and theoretical analysis methods. First, the similarity theory for model tests is introduced, and then the scale factors used in the present study are calculated according to the Froude criterion. Based on the study objectives, the details of the study methods (the similarity coefficient, the loading conditions, the test steps, etc. are introduced. Finally, the failure characteristics of the deep cavern and the strain distribution characteristics surrounding the caverns under different ground stress conditions are identified using the model test. It was found that compared with shallow rock masses the rock masses of the deep cavern have a much greater tensile range, which reaches 1.5 times the diameter of the cavern under the conditions established in the present study. Under different ground stress conditions, there are differences in failure characteristics and the reasons of the differences were analyzed. The implication of the test results on the design of support system for deep caverns was presented.

  20. Mass exchange between stratosphere and trotosphere over the Tibetan Plateau and its surroundings

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Using NCEP dataset we calculate the exchange of mass across the thermal tropopause by the Wei's method from 1978 to 1997 over the Tibetan Plateau and its surroundings. We also calculate the annual variation of aerosol and ozone of 100 hPa level with the monthly SAGE dataset from July 1988 to December 1993. Results indicate that ( i ) the mass from troposphere to stratosphere is magistral station in summer over the Tibetan Plateau and its surroundings. The air transport reaches the summit in midsummer with two large value centers, which lie in the north of Bengal Bay and southeastern Tibetan Plateau, respectively. A large value center, which lies over the Tibetan Plateau, is smaller than that aforementioned. In winter, the mass transport is from stratosphere to troposphere, and reaches the minimum in January. ( ii ) As far as the 19-year mean cross-tropopause mass exchange from June to September is concerned, the net mass transport is 14.84x1018 kg from troposphere to stratosphere. So the area from the Tibetan Plateau to the Bengal Bay is a channel through which the mass of lower atmosphere layer gets into upper troposphere and lower stratosphere. (iii) The cross-tropopause mass may take the lower level aerosol to the tropopause. Then, the concentration of aerosol near the tropopause becomes larger, which may cause the content of ozone to reduce.

  1. 公路隧道围岩变形破坏理论研究%Deformation Damage Theory of Highway Tunnel Surrounding Rock

    Institute of Scientific and Technical Information of China (English)

    尚峰利

    2014-01-01

    this paper uses the methods of theoretic analysis, simulation, field monitoring and measuring to deeply study deformation damage theory of highway tunnel surrounding rock. This paper gets the relation-ship between damage variable and surrounding material parameter by analyzing the evolution of surround-ing damage in the course of excavation and proposes the method of predicting mechanical parameters of surrounding rocks;by studying rock damage mechanism, the influence scope of surrounding rock damage stress and all of the factors influencing surrounding rock stability, this paper establishes constitutive rela-tionship of surrounding rock damage in unloading condition and damage constitutive model based on ener-gy dissipation. Based on the elastoplastic numerical analysis mechanism, this paper establishes the analy-sis method of tunnel surrounding rock damage evolution in consideration of deterioration course of sur-rounding rock parameters and analyzes the elastoplastic damage evolution mechanism of tunnel surround-ing rock in excavation stress condition;establishes the model of highway tunnel surrounding rock pressure evolution trend and prediction based on experience formula and progressive surrounding rock damage the-ory, and proposes the predicting method of highway tunnel surrounding rock pressure evolution trend.%采用理论分析、数值模拟以及现场监控量测等手段对公路隧道围岩变形破坏理论进行较深入的研究。通过分析开挖过程中围岩损伤演化,获得了损伤变量与围岩材料参数之间的关系,提出了围岩力学参数的预测方法。通过岩体破坏机理、围岩损伤应力影响范围以及影响围岩稳定性的各个因素综合研究,建立了卸荷状态下的围岩损伤本构关系和基于能量耗散的损伤本构模型。基于一般弹塑性数值分析原理,建立了考虑围岩参数劣化过程的隧道围岩损伤演化分析方法,分析了开挖应力状态下隧道围

  2. Image resolution influence on determination of resin injection rock mass

    Science.gov (United States)

    Wang, Weixing; Hakami, Eva

    2006-01-01

    In the context of nuclear waste repositories, an important approach to understanding brittle rock mass behavior to integrate new and powerful observational and numerical methods with multi-functional 3-D imaging and visualization techniques. Since 1994, Swedish Nuclear Fuel and Waste Management Company (SKB) have identified the need for a better understanding of radionuclide transport and retention processes in fractured rock. As a cooperation project between Sweden and China, we sampled a number of rock specimens for analyze rock fracture network by optical image technique. The samples are resin injected, in which way; opened fractures can be seen clearly by means of UV (Ultraviolet) light illumination. In the study period, we used different optical focuses to obtain the images from the same samples; we found that Image resolution influences on porosity determination of resin injected rock mass. This paper presents and discusses the six issues based on our research results: (1) Fracture porosity increases as camera focus distance decreases; (2) Porosity increases as illumination increases in resin injected fracture images; (3) To roughly estimate the porosity, the low resolution image can be used; (4) To collect more details of fracture information, the high resolution image is needed; (5) The resolution of image should be determined based on the aim of fracture analysis; (6) To acquire high resolution image, constructing a special illumination (standard) box maybe helpful to avoid light reflection and diffusion.

  3. Ground reaction curves for circular excavations in non-homogeneous, axisymmetric strain-softening rock masses

    Institute of Scientific and Technical Information of China (English)

    J. González-Cao; F. Varas; F.G. Bastante; L.R. Alejano

    2013-01-01

    Fast methods to solve the unloading problem of a cylindrical cavity or tunnel excavated in elasto-perfectly plastic, elasto-brittle or strain-softening materials under a hydrostatic stress field can be derived based on the self-similarity of the solution. As a consequence, they only apply when the rock mass is homoge-neous and so exclude many cases of practical interest. We describe a robust and fast numerical technique that solves the tunnel unloading problem and estimates the ground reaction curve for a cylindrical cavity excavated in a rock mass with properties depending on the radial coordinate, where the solution is no longer self-similar. The solution is based on a continuation-like approach (associated with the unloading and with the incremental formulation of the elasto-plastic behavior), finite element spatial discretization and a combination of explicit sub-stepping schemes and implicit techniques to integrate the constitutive law, so as to tackle the difficulties associated with both strong strain-softening and elasto-brittle behav-iors. The developed algorithm is used for two practical ground reaction curve computation applications. The first application refers to a tunnel surrounded by an aureole of material damaged by blasting and the second to a tunnel surrounded by a ring-like zone of reinforced (rock-bolted) material.

  4. Time-Dependent Damage Investigation of Rock Mass in an In Situ Experimental Tunnel

    Directory of Open Access Journals (Sweden)

    Jing Chen

    2012-08-01

    Full Text Available In underground tunnels or caverns, time-dependent deformation or failure of rock mass, such as extending cracks, gradual rock falls, etc., are a costly irritant and a major safety concern if the time-dependent damage of surrounding rock is serious. To understand the damage evolution of rock mass in underground engineering, an in situ experimental testing was carried out in a large belowground tunnel with a scale of 28.5 m in width, 21 m in height and 352 m in length. The time-dependent damage of rock mass was detected in succession by an ultrasonic wave test after excavation. The testing results showed that the time-dependent damage of rock mass could last a long time, i.e., nearly 30 days. Regression analysis of damage factors defined by wave velocity, resulted in the time-dependent evolutional damage equation of rock mass, which corresponded with logarithmic format. A damage viscoelastic-plastic model was developed to describe the exposed time-dependent deterioration of rock mass by field test, such as convergence of time-dependent damage, deterioration of elastic modules and logarithmic format of damage factor. Furthermore, the remedial measures for damaged surrounding rock were discussed based on the measured results and the conception of damage compensation, which provides new clues for underground engineering design.

  5. Permeability tensor and representative elementary volume of fractured rock masses

    Science.gov (United States)

    Rong, Guan; Peng, Jun; Wang, Xiaojiang; Liu, Guang; Hou, Di

    2013-11-01

    Based on a simulation of three-dimensional fracture networks and a superposition principle of liquid dissipation energy for fractured rock masses, a model of the fracture permeability tensor is proposed. An elastic constitutive model of rock fractures, considering fracture closure and dilation during shearing, is also proposed, based on the dilation angle of the fracture. Algorithms of flow-path searching and calculation of the effective flow coefficients for fracture networks are presented, together with a discussion on the influence of geometric parameters of the fractures (trace length, spacing, aperture, orientation and the number of fracture sets) on magnitude, anisotropy of hydraulic permeability and the size of a representative elementary volume (REV). The anisotropy of hydraulic permeability of fractured rock masses is mainly affected by orientation and the number of fracture sets, and the REV size is mainly influenced by trace length, spacing and the number of fracture sets. The results of studies on REV size and the influence of in-situ stress on hydraulic conductivity of the rock mass on the slope of Jinping-I hydropower station, China, are presented using the developed models and methods. The simulation results agreed well with the results obtained from field water-pressure measurements, with an error of less than 10 %.

  6. Numerical method to determine mechanical parameters of engineering design in rock masses

    Institute of Scientific and Technical Information of China (English)

    薛廷河; 项贻强; 郭发忠

    2004-01-01

    This paper proposes a new continuity model for engineering in rock masses and a new schematic method for reporting the engineering of rock continuity. This method can be used to evaluate the mechanics of every kind of medium;and is a new way to determine the mechanical parameters used in engineering design in rock masses. In the numerical simulation, the experimental parameters of intact rock were combined with the structural properties of field rock. Theexperimental results for orthogonally-jointed rock are given. The results included the curves of the stress-strain relationship of some rock masses, the curve of the relationship between the dimension Δ and the uniaxial pressure-resistant strength σc of these rock masses, and pictures of the destructive procedure of some rock masses in uniaxial or triaxial tests, etc. Application of the method to engineering design in rock masses showed the potential of its application to engineering practice.

  7. Numerical method to determine mechanical parameters of engineering design in rock masses.

    Science.gov (United States)

    Xue, Ting-He; Xiang, Yi-Qiang; Guo, Fa-Zhong

    2004-07-01

    This paper proposes a new continuity model for engineering in rock masses and a new schematic method for reporting the engineering of rock continuity. This method can be used to evaluate the mechanics of every kind of medium; and is a new way to determine the mechanical parameters used in engineering design in rock masses. In the numerical simulation, the experimental parameters of intact rock were combined with the structural properties of field rock. The experimental results for orthogonally-jointed rock are given. The results included the curves of the stress-strain relationship of some rock masses, the curve of the relationship between the dimension Delta and the uniaxial pressure-resistant strength sc of these rock masses, and pictures of the destructive procedure of some rock masses in uniaxial or triaxial tests, etc. Application of the method to engineering design in rock masses showed the potential of its application to engineering practice.

  8. Effect of blasting on the strength of a rock mass

    Energy Technology Data Exchange (ETDEWEB)

    Muller, L.

    1964-01-01

    Although the fact that blasting concussions tend to loosen a rock mass has always been known, the enormous reduction in strength associated with such loosening is not generally recognized. Recent investigations of the effect of blasting on a rock mass have shown that even slight loosening may markedly reduce the strength. This factor introduces a new slant on modern blasting methods, some of which will have to be considered more critically. The sensitivity of the mass to impacts depends on stress concentrations at the end of joints (Kerbspannungen) and on tensile stresses developed in the immediate vicinity of a joint, even in regions where the field stresses are not tensile. Thus, the sensitivity depends on the shape and orientation of the joints and particularly on the degree of separation of the individual joint families. The orientation of the joint families to the strains produced by blasting is just as important as the reduction in overall strength arising from the drop in friction due to the effects of the ''knocking out'' process (Foppl) on the joint body complex. Concussions may critically increase the degree of separation of the joint network thus reducing the tensile and shear strengths of the rock mass. (19 refs.)

  9. Deep Fracturing of the Hard Rock Surrounding a Large Underground Cavern Subjected to High Geostress: In Situ Observation and Mechanism Analysis

    Science.gov (United States)

    Feng, Xia-Ting; Pei, Shu-Feng; Jiang, Quan; Zhou, Yang-Yi; Li, Shao-Jun; Yao, Zhi-Bin

    2017-08-01

    Rocks that are far removed from caverns or tunnels peripheries and subjected to high geostress may undergo `deep fracturing'. Deep fracturing of hard rock can cause serious hazards that cause delays and increase the cost of construction of underground caverns with high sidewalls and large spans (especially when subjected to high geostress). To extensively investigate the mechanism responsible for deep fracturing, and the relationship between fracturing and the excavation & support of caverns, this paper presents a basic procedure for making in situ observations on the deep fracturing process in hard rock. The basic procedure involves predicting the stress concentration zones in the surrounding rocks of caverns induced by excavation using geomechanical techniques. Boreholes are then drilled through these stress concentration zones from pre-existing tunnels (such as auxiliary galleries) toward the caverns before its excavation. Continuous observations of the fracturing of the surrounding rocks are performed during excavation using a borehole camera in the boreholes in order to analyze the evolution of the fracturing process. The deep fracturing observed in a large underground cavern (high sidewalls and large span) in southwest China excavated in basalt under high geostress is also discussed. By continuously observing the hard rock surrounding the arch on the upstream side of the cavern during the excavation of the first three layers, it was observed that the fracturing developed into the surrounding rocks with downward excavation of the cavern. Fracturing was found at distances up to 8-9 m from the cavern periphery during the excavation of Layer III. Also, the cracks propagated along pre-existing joints or at the interfaces between quartz porphyry and the rock matrix. The relationship between deep fracturing of the surrounding rocks and the advance of the cavern working faces was analyzed during excavation of Layer Ib. The results indicate that the extent of the

  10. Applications of Terrestrial Remote Sensing to Volcanic Rock Masses

    Science.gov (United States)

    Dewit, M.; Williams-Jones, G.; Stead, D.; Kremsater, R.; So, M.; Francioni, M.

    2015-12-01

    Remote sensing methods are widely used in geological applications today. The physical properties of rock such as composition, texture and structure have previously been difficult to accurately quantify through remote sensing, however, new research in the fields of terrestrial LiDAR and infrared thermography has proven useful in the differentiation of lithology in sedimentary outcrops. This study focuses on the application of these methods, in conjunction with digital photogrammetry, to a number of volcanic rock masses in the Garibaldi Volcanic Belt (GVB) and Chilcotin Group (CG) of British Columbia. The GVB is a chain of volcanoes and related features extending through southwestern British Columbia and is the northern extension of the Cascade Volcanic Arc. The CG is an assemblage of Neogene-aged lavas covering nearly 36,500 km2 in central British Columbia. We integrate infrared chronothermography, which enables the characterization of temporal change in the thermal signature, laser waveform attributes such as amplitude and intensity, and digital photogrammetry, in order to distinguish between a range of rock types, lithologies and structures. This data is compared to laboratory experiments on field samples and ground-truth information collected by classical geological and geotechnical methods. Our research clearly shows that it is possible to remotely map, in 3D, otherwise inaccessible volcanic rock masses.

  11. Rock mass characterization for tunnels in the Copenhagen limestone

    DEFF Research Database (Denmark)

    Foged, Niels Nielsen; Jakobsen, Lisa; Jackson, Peter

    2007-01-01

    Tunnels in Copenhagen are drilled through highly anisotropic limestone comprising alternating strongly lithified and less lithified parts. The mass quality of the limestone is usually defined from fracture spacing registered in core samples. The deposit is, however, affected destructively by dril...... by drilling activity yielding a low Rock Quality Designation RQD. In-situ observations of the limestone in excavations or televiewer logs reveal only few natural discontinuities compared to core logging, indicating a very good suitability for tunneling....

  12. Engineering and Design: Rock Mass Classification Data Requirements for Rippability

    Science.gov (United States)

    2007-11-02

    geomechanics classification system (reference ~a(l))~ Bieniawski proposed the geomechanics classification system (RMR) to rate a rock mass by assigning...Weaver (bibliography 3b(l)) proposed a rippability rating chart based upon a modification of the geomechanics rating system; a similar chart is...as used in the geomechanics rating system. 9. Correlation with Tractor Size. Rippability for a given tractor selectlon 1s correlated with he total

  13. Rock mass characterization for tunnels in the Copenhagen limestone

    DEFF Research Database (Denmark)

    Foged, Niels Nielsen; Jakobsen, Lisa; Jackson, Peter;

    2007-01-01

    Tunnels in Copenhagen are drilled through highly anisotropic limestone comprising alternating strongly lithified and less lithified parts. The mass quality of the limestone is usually defined from fracture spacing registered in core samples. The deposit is, however, affected destructively by dril...... by drilling activity yielding a low Rock Quality Designation RQD. In-situ observations of the limestone in excavations or televiewer logs reveal only few natural discontinuities compared to core logging, indicating a very good suitability for tunneling....

  14. THE PETROLOGY CHARACTERISTIC OF GRANITOID ROCK BASED ON GEOCHEMICAL ANALYSIS OF BAJAU CAPE COAST AND ITS SURROUNDING, WEST KALIMANTAN

    Directory of Open Access Journals (Sweden)

    Noor C.D. Aryanto

    2017-07-01

    Full Text Available The aim of this study is to identify of petrology characteristic based on geochemical analysis in order to know the granitoid rock type. Administratively, the study area is in the City and District of Singkawang, West Kalimantan Province, at coordinate 108°48'30” - 109°1'30” E and 0°40'30” - 0°54'30” N and, situated ± 145 km to the north of Pontianak City. The outcrop of granitoid along Bajau Cape coast and its surrounding, had been analyzed petrographically and geochemically using AAS method. Based on analysis of five samples show that the ratio mole of Al2O3/(CaO+Na2O +K2O > 1 ranged between 1.12 and 1.7, while the rest of three samples are moderately aluminous, with a ratio value between 0.5 and 1.0. The ratio between K2O and (K2O+Na2O+CaO ranges 0.07 to 0.55 (moderate that forms alkali feldspar normative ranges from 3.8 to 15.89 wt%. This ratio shows that granite alkali feldspar is classified to be calc-alkaline series. Petrographically, this rock is porfiritic texture, hollocrystalline, granular hypodiomorphic and biotite present as phenocryst, yellowish brown, euhedral, thin and platy. The content of oxides element (Na2O and MgO tend to decrease, whereas of other oxides elements, namely Al2O3, TiO2, K2O, FeO and CaO increased, parallel with the raising of SiO2. Therefore, the Singkawang Granitoid can be grouped as alkali feldspar granite, syeno-granite and quartz monzonite.

  15. Three-dimensional modeling of borehole data cored from engineering rock mass

    Institute of Scientific and Technical Information of China (English)

    HE Manchao; LI Xueyuan; LIU Bin; XU Nengxiong

    2007-01-01

    Vast data from the drilling and geophysical prospecting are reliable original information to describe the space state of engineering rock mass,and one of the main difficulties in three-dimensional (3D) modeling of engineering rock mass is the processing of the primary data.From the viewpoint of 3D modeling,the engineering rock masses are classified as four basic types according to their geometric characteristics of geologic structure:(1) continuum rock mass;(2) discontinuous rock mass;(3) overturned fold rock mass and (4) intrusive rock mass.Because drilling data are very important to describe the characters of multi-scale of the spatial data for rock mass,the rule of how to process drilling data is developed to help appropriately display them in the viewpoint of 3D space.According to the characteristics of rock mass layers,the processing method of drilling data for 3D modeling of engineering rock masses,along with the layer thicknesses,is also proposed,including the evaluation rules and the extensive direction for original borehole data.By this method,the typical 3D data modeled is completed and the model form of the engineering rock mass is developed.By this example,it is finally verified that the method presented is successful and feasible to process 3D engineering rock mass.

  16. Applicability of geomechanical classifications for estimation of strength properties in Brazilian rock masses.

    Science.gov (United States)

    Santos, Tatiana B; Lana, Milene S; Santos, Allan E M; Silveira, Larissa R C

    2017-01-01

    Many authors have been proposed several correlation equations between geomechanical classifications and strength parameters. However, these correlation equations have been based in rock masses with different characteristics when compared to Brazilian rock masses. This paper aims to study the applicability of the geomechanical classifications to obtain strength parameters of three Brazilian rock masses. Four classification systems have been used; the Rock Mass Rating (RMR), the Rock Mass Quality (Q), the Geological Strength Index (GSI) and the Rock Mass Index (RMi). A strong rock mass and two soft rock masses with different degrees of weathering located in the cities of Ouro Preto and Mariana, Brazil; were selected for the study. Correlation equations were used to estimate the strength properties of these rock masses. However, such correlations do not always provide compatible results with the rock mass behavior. For the calibration of the strength values obtained through the use of classification systems, ​​stability analyses of failures in these rock masses have been done. After calibration of these parameters, the applicability of the various correlation equations found in the literature have been discussed. According to the results presented in this paper, some of these equations are not suitable for the studied rock masses.

  17. Quantitative geophysical log interpretation for rock mass characterisation

    Energy Technology Data Exchange (ETDEWEB)

    Peter Hatherly; Renate Sliwa; Roland Turner; Terry Medhurst

    2004-04-01

    Geophysical borehole logging is routinely employed as part of exploration drilling in open pit and underground mining operations. Analysis of results is often empirical or based on theoretical considerations that need not relate to the actual properties of the rocks under consideration. The objectives of this project are to develop techniques for quantitative geophysical log interpretation techniques to enable: better estimation of coal and rock properties such as strength and permeability; better lithological interpretation and strata correlation between boreholes; a rock mass rating scheme for mine design purposes which is based on geophysical logging. This study has placed the techniques for quantitative geophysical log assessment on a firm footing. The authors have demonstrated an approach for log assessment that can be routinely applied. Many of the mineralogical and physical rock properties that impact on the assessments have been investigated and discussed. They have also demonstrated the benefits of quantitative geophysical log assessment. The major recommendation made is that geologists and engineers in the coal mining industry take the time to study this report and begin to put the approach described into practice. The collective understanding that this experience will provide can only help fuel the drive to take the benefits of geophysical logging to greater levels.

  18. Creep in jointed rock masses. State of knowledge

    Energy Technology Data Exchange (ETDEWEB)

    Glamheden, Rune (Golder Associates AB (Sweden)); Hoekmark, Harald (Clay Technology AB, Lund (Sweden))

    2010-06-15

    To describe creep behaviour in hard rock masses in a physically realistic way, elaborate models including various combinations of dash pots, spring elements and sliders would be needed. According to our knowledge, there are at present no numerical tools available that can handle such a creep model. In addition, there are no records over sufficient long time periods of tunnel convergence in crystalline rock that could be used to determine or calibrate values for the model parameters. A possible method to perform bounding estimates of creep movements around openings in a repository may be to use distinct element codes with standard built-in elasto-plastic models. By locally reducing the fracture shear strength near the underground openings a relaxation of fracture shear loads is reached. The accumulated displacements may then represent the maximum possible effects of creep that can take place in a jointed rock mass without reference to the actual time it takes to reach the displacements. Estimates based on results from analyses where all shear stresses are allowed to disappear completely will, however, be over-conservative. To be able to set up and analyse reasonably realistic numerical models with the proposed method, further assumptions regarding the creep movements and the creep region around the opening have to be made. The purpose of this report is to present support for such assumptions as found in the literature.

  19. Lithophysal Rock Mass Mechanical Properties of the Repository Host Horizon

    Energy Technology Data Exchange (ETDEWEB)

    D. Rigby

    2004-11-10

    The purpose of this calculation is to develop estimates of key mechanical properties for the lithophysal rock masses of the Topopah Spring Tuff (Tpt) within the repository host horizon, including their uncertainties and spatial variability. The mechanical properties to be characterized include an elastic parameter, Young's modulus, and a strength parameter, uniaxial compressive strength. Since lithophysal porosity is used as a surrogate property to develop the distributions of the mechanical properties, an estimate of the distribution of lithophysal porosity is also developed. The resulting characterizations of rock parameters are important for supporting the subsurface design, developing the preclosure safety analysis, and assessing the postclosure performance of the repository (e.g., drift degradation and modeling of rockfall impacts on engineered barrier system components).

  20. An overview of the thermography-based experimental studies on roadway excavation in stratified rock masses at CUMTB

    Institute of Scientific and Technical Information of China (English)

    Gong Weili; Peng Yanyan; He Manchao; Xie Tian; Zhao Shijiao

    2015-01-01

    This paper presents an overview of experimental investigations conducted at China University of Mining and Technology Beijing (CUMTB) on roadway excavation using large-scale geomechanical model tests. The simulated sedimentary rocks are composed by alternating layers of sandstone, mudstone and coal seam inclined at varied angles with respect to the horizontal including 0?, 45?, 60?, and 90?. During the excavation, infrared thermography was employed to detect the thermal response of the surrounding rocks under excavation. The obtained raw thermograms were processed using denoising algorithm, data reduction procedure and Fourier analysis. The infrared temperature (IRT) characterizes the overall rock response; the processed thermal images represent the structural behavior, and the Fourier spectrum describes damage development in the frequency domain. Deeper understanding was achieved by the comparative analyses of excavation in differently inclined rock masses using the image features of IRTs, thermal images and Fourier spectra.

  1. Stability principle of big and small structures of rock surrounding roadway driven along goaf in fully mechanized top coal caving face

    Energy Technology Data Exchange (ETDEWEB)

    Hou, C.; Li, X. [China University of Mining and Technology, Xuzhou (China)

    2001-02-01

    Based on the characteristics of the surrounding rock of roadway driven along the goaf in a fully mechanised top coal caving face, the stability principle of big and small structures is put forward, which provides the theoretical basis to the application of bolting. The mechanical characteristics of the arc-triangle key block in the main roof and the stability of the roadway during drivage and extraction and the effect on the roadway driven along the next goaf are analysed. The main factors which affect the stability of the small structure of the surrounding rock are discussed. The bolting surrounding strength reinforcement theory is applied to study the important significance of improving the pre-tension of bolting and the support strength. 4 refs., 7 figs., 2 tabs.

  2. Correlation of the Rock Mass Rating (RMR) System with the Unified Soil Classification System (USCS): Introduction of the Weak Rock Mass Rating System (W-RMR)

    Science.gov (United States)

    Warren, Sean N.; Kallu, Raj R.; Barnard, Chase K.

    2016-11-01

    Underground gold mines in Nevada are exploiting increasingly deeper ore bodies comprised of weak to very weak rock masses. The Rock Mass Rating (RMR) classification system is widely used at underground gold mines in Nevada and is applicable in fair to good-quality rock masses, but is difficult to apply and loses reliability in very weak rock mass to soil-like material. Because very weak rock masses are transition materials that border engineering rock mass and soil classification systems, soil classification may sometimes be easier and more appropriate to provide insight into material behavior and properties. The Unified Soil Classification System (USCS) is the most likely choice for the classification of very weak rock mass to soil-like material because of its accepted use in tunnel engineering projects and its ability to predict soil-like material behavior underground. A correlation between the RMR and USCS systems was developed by comparing underground geotechnical RMR mapping to laboratory testing of bulk samples from the same locations, thereby assigning a numeric RMR value to the USCS classification that can be used in spreadsheet calculations and geostatistical analyses. The geotechnical classification system presented in this paper including a USCS-RMR correlation, RMR rating equations, and the Geo-Pick Strike Index is collectively introduced as the Weak Rock Mass Rating System (W-RMR). It is the authors' hope that this system will aid in the classification of weak rock masses and more usable design tools based on the RMR system. More broadly, the RMR-USCS correlation and the W-RMR system help define the transition between engineering soil and rock mass classification systems and may provide insight for geotechnical design in very weak rock masses.

  3. Normal dynamic deformation characteristics of non-consecutive jointed rock masses under impact loads

    Science.gov (United States)

    Zeng, Sheng; Jiang, Bowei; Sun, Bing

    2017-08-01

    In order to study deformation characteristics of non-consecutive single jointed rock masses under impact loads, we used the cement mortar materials to make simulative jointed rock mass samples, and tested the samples under impact loads by the drop hammer. Through analyzing the time-history signal of the force and the displacement, first we find that the dynamic compression displacement of the jointed rock mass is significantly larger than that of the intact jointless rock mass, the compression displacement is positively correlated with the joint length and the impact height. Secondly, the vertical compressive displacement of the jointed rock mass is mainly due to the closure of opening joints under small impact loads. Finally, the peak intensity of the intact rock mass is larger than that of the non-consecutive jointed rock mass and negatively correlated with the joint length under the same impact energy.

  4. Research on Mechanism of Rock Burst Generation and Development for High Stress Rock Tunnels

    Institute of Scientific and Technical Information of China (English)

    高全臣; 赫建明; 王代华

    2001-01-01

    Through the investigation and analysis of high stress distribution in surrounding rock during the excavation of rock tunnels,the key factors to cause rock burst and the mechanism of rock burst generation and development are researched. The result shows that the scale and range of rock burst are related with elastic deformation energy storied in rock mass and the characteristics of unloading stress waves. The measures of preventing from rock burst for high stress rock tunnels are put forward.

  5. Study on the Characteristic Energy Factor of the Deep Rock Mass Under Weak Disturbance

    Science.gov (United States)

    Wang, Mingyang; Li, Jie; Ma, Linjian; Huang, Houxu

    2016-08-01

    This study aims to investigate the characteristic energy factor of the deep rock mass deformation subjected to the disturbance induced by excavation or explosion. Based on the well-known rock hierarchical structure, the equivalent average kinetic energy of the deep rock mass under weak disturbance is first introduced. The characteristic energy factor that reflects the instable deformation of the deep rock mass is derived using the principle of variation. The relationship between the characteristic energy factor and the energy hierarchical sequence of the deep rock mass deformation and failure has also been illustrated. We believe that the characteristic energy factor is closely related to the characteristic scientific phenomena of deep rock mass in essence, which can provide a new approach for the study of deep rock mass in the fields of nonlinear mechanics, statistic physical mechanics, and mechanics of explosion and geophysics.

  6. Updating of the hierarchical rock mass rating (HRMR) system and a new subsystem developed for weathered granite formations

    Institute of Scientific and Technical Information of China (English)

    Miranda Tiago; e Sousa L. Ribeiro; Tinoco Joaquim

    2014-01-01

    The RMR system is still very much applied in rock mechanics engineering context. It is based on the eval-uation of six weights to obtain a final rating. To obtain the final rating a considerable amount of informa-tion is needed concerning the rock mass which can be difficult to obtain in some projects or project stages at least with accuracy. In 2007 an alternative classification scheme based on the RMR, the Hierarchical Rock Mass Rating (HRMR) was presented. The main feature of this system was the adaptation to the level of knowledge existent about the rock mass to obtain the classification of the rock mass since it followed a decision tree approach. However, the HRMR was only valid for hard rock granites with low fracturing degrees. In this work, the database was enlarged with approximately 40%more cases considering other types of granite rock masses including weathered granites and based on this increased database the sys-tem was updated. Granite formations existent in the north of Portugal including Porto city are predom-inantly granites. Some years ago a light rail infrastructure was built in the city of Porto and surrounding municipalities which involved considerable challenges due to the high heterogeneity levels of the granite formations and the difficulties involved in their geomechanical characterization. In this work it is intended to provide also a contribution to improve the characterization of these formations with special emphasis to the weathered horizons. A specific subsystem applicable to the weathered formations was developed. The results of the validation of these systems are presented and show acceptable perfor-mances in identifying the correct class using less information than with the RMR system.

  7. Climatology of cross-tropopause mass exchange over the Tibetan Plateau and its surroundings

    Science.gov (United States)

    Tian, Hongying; Tian, Wenshou; Luo, Jiali; Zhang, Jiankai; Zhang, Min

    2017-04-01

    The cross-tropopause mass flux (CTMF) and long-term trends in stratosphere-troposphere exchange (STE) over the Tibetan Plateau(TP) and its surroundings were analyzed using European Centre for Medium-Range Weather Forecasts reanalysis data. The gross CTMF (the sum of upward and downward mass flux) shows an evident wave train structure over the TP, which is mainly related to the horizontal exchange of air masses along the tropopause associated with the sharp meridional gradient in tropopause pressure or vertical discontinuity of the thermal tropopause in winter. The seasonal cycle of the STE over the TP shows that the gross mass flux is downwards in Northern Hemisphere (NH) winter and upwards in NH summer. The gross CTMF over the TP accounts for 2.96% of the global total CTMF arising from STE processes resolved by Wei method. Both the upward and downward CTMF over the TP exhibit statistically significant positive trends in winter during the period 1979-2009. The strong positive trends of STE in winter over the TP are resulted from the combined effects of the rising tropopause height, enhanced westerlies and decreasing plateau winter monsoon. In summer, both the upward and downward CTMF exhibit statistically significant negative trends over the northern TP, while the trend in upward CTMF is positive over the southern TP, in accordance with the increasing intensity of Asian summer monsoon in recent decades. The sensitivity simulations with a climate model confirm that changes in the Asian monsoon can significantly affect the tropopause and the CTMF over the TP.

  8. The IC 5146 star forming complex and its surroundings with 2MASS, WISE and Spitzer

    Science.gov (United States)

    Nunes, N. A.; Bonatto, C.; Bica, E.

    2016-02-01

    Throughout the last decade sensitive infrared observations obtained by the Spitzer Space Telescope significantly increased the known population of YSOs associated with nearby molecular clouds. With such a census recent studies have characterized pre-main sequence stars (PMS) and determined parameters from different wavelengths. Given the restricted Spitzer coverage of some of these clouds, relative to their extended regions, these YSO populations may represent a limited view of star formation in these regions. We are taking advantage of mid-infrared observations from the NASA Wide Field Infrared Survey Explorer (WISE), which provides an all sky view and therefore full coverage of the nearby clouds, to assess the degree to which their currently known YSO population may be representative of a more complete population. We extend the well established classification method of the Spitzer Legacy teams to archived WISE observations. We have adopted 2MASS photometry as a "standard catalogue" for comparisons. Besides the massive embedded cluster IC 5146 we provide a multiband view of five new embedded clusters in its surroundings that we discovered with WISE. In short, the analysis involves the following for the presently studied cluster sample: (i) extraction of 2MASS/WISE/Spitzer photometry in a wide circular region; (ii) field-star decontamination to enhance the intrinsic Colour-magnitude diagram (CMD) morphology (essential for a proper derivation of reddening, age, and distance from the Sun); and (iii) construction of Colour-magnitude filters, for more contrasted stellar radial density profiles (RDPs).

  9. Effects of statistical distribution of joint trace length on the stability of tunnel excavated in jointed rock mass

    Directory of Open Access Journals (Sweden)

    Kayvan Ghorbani

    2015-12-01

    Full Text Available The rock masses in a construction site of underground cavern are generally not continuous, due to the presence of discontinuities, such as bedding, joints, faults, and fractures. The performance of an underground cavern is principally ruled by the mechanical behaviors of the discontinuities in the vicinity of the cavern. During underground excavation, many surrounding rock failures have close relationship with joints. The stability study on tunnel in jointed rock mass is of importance to rock engineering, especially tunneling and underground space development. In this study, using the probability density distribution functions of negative exponential, log-normal and normal, we investigated the effect of joint trace length on the stability parameters such as stress and displacement of tunnel constructed in rock mass using UDEC (Universal Distinct Element Code. It was obtained that normal distribution function of joint trace length is more critical on the stability of tunnel, and exponential distribution function has less effect on the tunnel stability compared to the two other distribution functions.

  10. Intelligent direct analysis of physical and mechanical parameters of tunnel surrounding rock based on adaptive immunity algorithm and BP neural network

    Institute of Scientific and Technical Information of China (English)

    Xiao-rui Wang; Yuan-han Wang; Xiao-feng Jia

    2009-01-01

    Because of complexity and non-predictability of the tunnel surrounding rock, the problem with the determination of the physical and, mechanical parameters of the surrounding rock has become a main obstacle to theoretical research and numerical analysis in tunnel engineering. During design, it is a frequent practice, therefore, to give recommended values by analog based on experience. It is a key point in current research to make use of the displacement back analytic method to comparatively accurately determine the parameters of the surrounding rock whereas artificial intelligence possesses an exceptionally strong capability of identifying, expressing and coping with such complex non-linear relationships. The parameters can be verified by searching the optimal network structure, using back analysis on measured data to search optimal parameters and performing direct computation of the obtained results. In the current paper, the direct analysis is performed with the biological emulation system and the software of Fast Lagrangian Analysis of Continua (FLAC3D. The high non-linearity, network reasoning and coupling ability of the neural network are employed. The output vector required of the training of the neural network is obtained with the numerical analysis software. And the overall space search is conducted by employing the Adaptive Immunity Algorithm. As a result, we are able to avoid the shortcoming that multiple parameters and optimized parameters are easy to fall into a local extremum. At the same time, the computing speed and efficiency are increased as well. Further, in the paper satisfactory conclusions are arrived at through the intelligent direct-back analysis on the monitored and measured data at the Erdaoya tunneling project. The results show that the physical and mechanical parameters obtained by the intelligent direct-back analysis proposed in the current paper have effectively unproved the recommended values in the original prospecting data. This is of

  11. Study on the Reinforcement Measures and Control Effect of the Surrounding Rock Stability Based on the Shield Tunneling Under Overpass Structure

    Directory of Open Access Journals (Sweden)

    Qian-cheng Fang

    2016-04-01

    Full Text Available To study the stability of surrounding rocks for shield tunneling under overpass structures and the safety of existing bridge structures, a practical example of the method was cited through a shield tunneling project under the overpass structure between K1+110 and K1+700 on Line 2 of Shenyang Subway, China. The sub-area reinforcement was proposed according to surrounding rock deformation characteristics during shield tunnel excavation. The bridge foundation (i.e., the clear spacing to the shield tunnel is less than 2 m was reinforced by steel support, the bridge foundation (the clear spacing is about 2~7m used “jet grouting pile” reinforcement, whereas the bridge foundation (the clear spacing is greater than 7 m did not adopt any reinforcement measures for the moment. For this study, the mean value and material heterogeneity models were established to evaluate the reinforcement effect from several aspects, such as surrounding rock deformation, plastic zone development, and safety factor. The simulation results were consistent with those of field monitoring. After reinforcement, the maximum deformation values of the surrounding rock were reduced by 4.9%, 12.2%, and 48.46%, and the maximum values of surface subsidence were decreased by 5.6%, 72.2%, and 88.64%. By contrast, the overall safety factor was increased by 4.1%, 55.46%, and 55.46%. This study posited that this reinforcement method can be adopted to solve tunnel construction problems in engineering-geological conditions effectively. References for evaluating similar projects are provided.

  12. Application of AOSVR on Surrounding Rock Displacement Forecasting of Underground Powerhouse%AOSVR在地下厂房围岩变形预测中的应用

    Institute of Scientific and Technical Information of China (English)

    金长宇; 马震岳; 张运良

    2006-01-01

    针对目前广泛使用的模糊系统和神经网络预测方法在地下结构围岩变形预测中的缺陷,提出一种精确在线支持向量机(AOSVR)并将其应用到水电站地下厂房开挖过程中顶拱围岩的变形预测.通过与其他预测方法的比较,可以发现精确在线支持向量机有很强的学习能力和很高的预测精度.%Because the prediction accuracy of ANN and Fuzzy system algorithm is insufficient for underground powerhouse rock surrounding stability, the method of Accurate Online Support Vector Regression(AOSVR) was applied to study the evolution law for underground powerhouse rock surrounding displacement. Comparison of the forecasting results of ANN and Fuzzy System with the monitoring result for rock surrounding displacement of underground powerhouse show that the learning efficiency and prediction accuracy of AOSVR is superior to ANN and Fuzzy System obviously.

  13. Classification and assessment of rock mass parameters in Choghart iron mine using P-wave velocity

    Directory of Open Access Journals (Sweden)

    Mohammadreza Hemmati Nourani

    2017-04-01

    Full Text Available Engineering rock mass classification, based on empirical relations between rock mass parameters and engineering applications, is commonly used in rock engineering and forms the basis for designing rock structures. The basic data required may be obtained from visual observation and laboratory or field tests. However, owing to the discontinuous and variable nature of rock masses, it is difficult for rock engineers to directly obtain the specific design parameters needed. As an alternative, the use of geophysical methods in geomechanics such as seismography may largely address this problem. In this study, 25 seismic profiles with the total length of 543 m have been scanned to determine the geomechanical properties of the rock mass in blocks I, III and IV-2 of the Choghart iron mine. Moreover, rock joint measurements and sampling for laboratory tests were conducted. The results show that the rock mass rating (RMR and Q values have a close relation with P-wave velocity parameters, including P-wave velocity in field (VPF, P-wave velocity in the laboratory (VPL and the ratio of VPF to VPL (i.e. KP = VPF/VPL. However, Q value, totally, has greater correlation coefficient and less error than the RMR. In addition, rock mass parameters including rock quality designation (RQD, uniaxial compressive strength (UCS, joint roughness coefficient (JRC and Schmidt number (RN show close relationship with P-wave velocity. An equation based on these parameters was obtained to estimate the P-wave velocity in the rock mass with a correlation coefficient of 91%. The velocities in two orthogonal directions and the results of joint study show that the wave velocity anisotropy in rock mass may be used as an efficient tool to assess the strong and weak directions in rock mass.

  14. Reactive loading function on tunnel excavation contour in rock mass

    Directory of Open Access Journals (Sweden)

    Lukić Dragan

    2003-01-01

    Full Text Available Investigation of the stress field around the cavity that is loaded or partially loaded at the inner surface by the rotationally symmetric loading is still the contemporary problem in the theory of elasticity. As the contribution to the similar investigations, the paper introduces the new function of loading in the form of the infinite sine series. Besides the definition of the mentioned loading function as the boundary condition on inner surface of the cavity, the paper presents the comparative analysis of the new function with the previously used ones. The said loading function at the inner surface of a cavity is internal loading between rock mass and supporting structure, for the case of homogeneous isotropic elastic medium as the first approximation of the real situation.

  15. Mass transfer controlled by fracturing in micritic carbonate rocks

    Science.gov (United States)

    Richard, James; Coulon, Michel; Gaviglio, Patrick

    2002-05-01

    The fractured Coniacian chalk from the Omey area (Paris Basin, France) displays strong evidence of modifications controlled by brittle deformation. Fracturing is associated with important changes in pore space (decrease in total porosity and pore interconnection, change in distribution of pore access diameters and capillary characteristics), nannofacies (gradual evolution from a point-contact fabric to a welded, interlocked or coalescent fabric) and chemical composition (Sr concentration decrease). These modifications result from fluid-rock interaction that control significant mass transfer (percentage of secondary calcite >50%). Sr is a remarkable indicator of these mass transfers. Sr analyses allowed us to prove that the deformed zone (26.7 m) is wider than the fractured zone (11.3 m). They also indicate that the footwall block is less affected than the hanging wall block. A physicochemical model of the deformation mechanism is proposed. It shows that a cyclic process of fracturing controls the temporal evolution of the fluid saturation and fluid pressure and, consequently, the mass transfer.

  16. Mechanics analysis on the conditions of rock burst occurrence in the coal mass of roadway rib

    Institute of Scientific and Technical Information of China (English)

    CHEN Xue-hua; DENG Xiao-lin; LI Zhong-hua

    2008-01-01

    According to the rock burst features occurred in the coal mass of roadway rib in one mine, the mechanics model of coal mass and roof structure system along the edge of goaf was founded to analyze the stress of roof rock layer, so the subside curve of roof rock layer was deduced. Furthermore, the stability of coal and rock system were analyzed, the critical load and critical resistance zone were used to judge the danger degree of rock burst occurrence. The influence of coal mass strength, brittleness degree, coal seam thickness, roof thickness, suspending length, equivalent shear module on the critical load,critical resistance zone was confirmed. So the rock burst occurrence conditions of coal mass in roadway rib mainly depend on mining depth, coal seam thickness and hard roof and floor, which are decided by the above studies, and successfully applied in prediction and prevention of rock burst in this mine.

  17. Rock mass structure analysis based on seismic velocity and attenuation images

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Seismic traveltime, amplitude and pulse-width can be used to reconstruct seismic velocity and attenuation coefficient images for a rock mass. This study discusses the appearance differences of velocity and attenuation coefficient in the ore vein and rock mass in the images. The location of the rock vein and the characteristic of the rock mass are discussed according to the difference responses of velocity and attenuation from the ore vein and mixed rock vein, fracture and rock body. The effect and limitation of the seismic tomography method for investigating ore body and rock mass is suggested on the basis of a field test result. The special observation method in this study gives a good reference for obtaining full position and directional observation in seismic tomography.

  18. Experimental Study on Mechanical Characteristics of Cracked Rock Mass Reinforced by Bolting and Grouting

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    The stress hardening characteristics of the reinforced rock mass in uniaxial compression tests were revealed by means of the experimental study on mechanical characteristics of cracked rock mass reinforced by bolting and grouting. And the load-bearing mechanism of the reinforced rock mass was perfectly reflected by the experiment. The results can offer some useful advice for support design and stability analysis of deep drifts in unstable strata.

  19. Small impact of surrounding oceanic conditions on 2007-2012 Greenland Ice Sheet surface mass balance

    Science.gov (United States)

    Noël, B.; Fettweis, X.; van de Berg, W. J.; van den Broeke, M. R.; Erpicum, M.

    2014-03-01

    During recent summers (2007-2012), several surface melt records were broken over the Greenland Ice Sheet (GrIS). The extreme summer melt resulted in part from a persistent negative phase of the North-Atlantic Oscillation (NAO), favouring warmer than normal conditions over the GrIS. In addition, it has been suggested that significant anomalies in sea ice cover (SIC) and sea surface temperature (SST) may partially explain recent anomalous GrIS surface melt. To assess the impact of 2007-2012 SIC and SST anomalies on GrIS surface mass balance (SMB), a set of sensitivity experiments was carried out with the regional climate model MAR. These simulations suggest that changes in SST and SIC in the seas surrounding Greenland do not significantly impact GrIS SMB, due to the katabatic winds blocking effect. These winds are strong enough to prevent oceanic near-surface air, influenced by SIC and SST variability, from penetrating far inland. Therefore, the ice sheet SMB response is restricted to coastal regions, where katabatic winds are weaker. However, anomalies in SIC and SST could have indirectly affected the surface melt by changing the general circulation in the North Atlantic region, favouring more frequent warm air advection to the GrIS.

  20. Numerical Simulation of Rock Mass Damage Evolution During Deep-Buried Tunnel Excavation by Drill and Blast

    Science.gov (United States)

    Yang, Jianhua; Lu, Wenbo; Hu, Yingguo; Chen, Ming; Yan, Peng

    2015-09-01

    Presence of an excavation damage zone (EDZ) around a tunnel perimeter is of significant concern with regard to safety, stability, costs and overall performance of the tunnel. For deep-buried tunnel excavation by drill and blast, it is generally accepted that a combination of effects of stress redistribution and blasting is mainly responsible for development of the EDZ. However, few open literatures can be found to use numerical methods to investigate the behavior of rock damage induced by the combined effects, and it is still far from full understanding how, when and to what degree the blasting affects the behavior of the EDZ during excavation. By implementing a statistical damage evolution law based on stress criterion into the commercial software LS-DYNA through its user-subroutines, this paper presents a 3D numerical simulation of the rock damage evolution of a deep-buried tunnel excavation, with a special emphasis on the combined effects of the stress redistribution of surrounding rock masses and the blasting-induced damage. Influence of repeated blast loadings on the damage extension for practical millisecond delay blasting is investigated in the present analysis. Accompanying explosive detonation and secession of rock fragments from their initial locations, in situ stress in the immediate vicinity of the excavation face is suddenly released. The transient characteristics of the in situ stress release and induced dynamic responses in the surrounding rock masses are also highlighted. From the simulation results, some instructive conclusions are drawn with respect to the rock damage mechanism and evolution during deep-buried tunnel excavation by drill and blast.

  1. A review of discrete modeling techniques for fracturing processes in discontinuous rock masses

    Institute of Scientific and Technical Information of China (English)

    A.Lisjak; G.Grasselli

    2014-01-01

    The goal of this review paper is to provide a summary of selected discrete element and hybrid finitee discrete element modeling techniques that have emerged in the field of rock mechanics as simulation tools for fracturing processes in rocks and rock masses. The fundamental principles of each computer code are illustrated with particular emphasis on the approach specifically adopted to simulate fracture nucleation and propagation and to account for the presence of rock mass discontinuities. This description is accom-panied by a brief review of application studies focusing on laboratory-scale models of rock failure processes and on the simulation of damage development around underground excavations.

  2. A review of discrete modeling techniques for fracturing processes in discontinuous rock masses

    Directory of Open Access Journals (Sweden)

    A. Lisjak

    2014-08-01

    Full Text Available The goal of this review paper is to provide a summary of selected discrete element and hybrid finite–discrete element modeling techniques that have emerged in the field of rock mechanics as simulation tools for fracturing processes in rocks and rock masses. The fundamental principles of each computer code are illustrated with particular emphasis on the approach specifically adopted to simulate fracture nucleation and propagation and to account for the presence of rock mass discontinuities. This description is accompanied by a brief review of application studies focusing on laboratory-scale models of rock failure processes and on the simulation of damage development around underground excavations.

  3. System dynamics model of the support-surrounding rock system in fully mechanized mining with large mining height face and its application

    Institute of Scientific and Technical Information of China (English)

    Yuan Yong; Tu Shihao; Zhang Xiaogang; Li Bo

    2013-01-01

    Fully mechanized mining with large mining height (FMMLMH) is widely used in thick coal seam mining face for its higher recovery ratio, especially where the thickness is less than 7.0 m. However, because of the great mining height and intense rock pressure, the coal wall rib spalling, roof falling and the instabil-ity of support occur more likely in FMMLMH working face, and the above three types of disasters interact with each other with complicated relationships. In order to get the relationship between each two of coal wall, roof, floor and support, and reduce the occurrence probability of the three types of disasters, we established the system dynamics (SD) model of the support-surrounding rock system which is composed of‘coal wall-roof-floor-support’ (CW-R-F-S) in a FMMLMH working face based on the condition of No. 15104 working face in Sijiazhuang coal mine. With the software of Vensim, we also simulated the inter-action process between each two factors of roof, floor, coal wall and the support. The results show that the SD model of ‘CW-R-F-S’ system can reveal the complicated and interactive relationship clearly between the support and surrounding rock in the FMMLMH working face. By increasing the advancing speed of working face, the support resistance or the length of support guard, or by decreasing the tip-to-face distance, the stability of ‘CW-R-F-S’ system will be higher and the happening probability of the disasters such as coal wall rib spalling, roof falling or the instability of support will be lower. These research findings have been testified in field application in No. 15104 working face, which can provide a new approach for researching the interaction relationship of support and surrounding rock.

  4. Geomechanical parameters of intact rocks and rock masses from the Canary Islands: Implications on their flank stability

    Science.gov (United States)

    Rodríguez-Losada, J. A.; Hernández-Gutiérrez, L. E.; Olalla, C.; Perucho, A.; Serrano, A.; Eff-Darwich, A.

    2009-05-01

    New data on the geomechanical properties of the highly cohesive volcanic rocks of the Canary Archipelago and their role in the flank stability on oceanic islands are provided in this work. On the basis of the textural and petrological features, a preliminary classification of rocks, grouped into lithotypes, was carried out. This classification includes vesicular and non vesicular basalts, trachybasalts, trachytes, phonolites, welded and non welded ignimbrites. Strength and strain-related features are summarized here for each distinctive lithotype. Taking into account the results of the uniaxial and triaxial compressive tests, the geological strength index of rock masses and their textural-structural features, an estimate of the rock mass parameters and Mohr-Coulomb fit has been carried out. A final discussion on the impact of those geomechanical parameters as factors governing the stability of steep slopes in volcanic islands is then made here as a contribution in volcanic risk.

  5. A study on excavation of rock mass by lasers. Researching the possibility of utilizing low-power lasers

    Energy Technology Data Exchange (ETDEWEB)

    Ito, Fumio [Taisei Corporation, Technology Research Center, Yokohama, Kanagawa (Japan)

    2000-03-01

    The object of this research is to develop the techniques of rock-mass excavation by laser irradiation. This rock-mass excavation technique by lasers has a characteristic of extremely little effect to the surroundings of an excavation site no matter how the target rock mass is with regard to geological aspects and given physical property. Moreover, it could be utilized in excavation of waste dump facilities, which need to be re-buried, and applied to excavation of long piles and tunnels, which are drilled through different kinds of strata, and to improvement of rock mass and ground. Lasers have a characteristic of concentrating the energy into a limited point and not only discontinue or cut a large area with a small output like sharp scissors but also block up the cracks deep inside the rock mass by fusing vitrification for its improvement. It leads to restrain the loss of energy, minimization of the effected environment, effective utilization of resources and energy, environmental restoration, and improvement of the working environment. In the field of nuclear fuel, which includes excavating dump pits, dismantling a furnace, and taking appropriate steps of mine remains, excavating, cutting, and fusing could be required to do within a limited space of rock mass or concrete. Up to the present, those things have been done mainly by large machines, but it is too scarce in possibility for them to improve their large size, heavy weight, difficulty in unmanned operation, limited shapes of cutting, and stabilization of waste. In this research the concrete system images have been examined, doing the fundamental researches about higher-power lasers, smaller sizing, transmitting by fibers to find our the breakthrough to realization of laser excavation, This year, as the summary of examining the laser excavation techniques, utilizing a low-power laser, which is thought to be highly effective in rock-mass improvement, will be examined, considering application of the technique

  6. Rheological numerical simulation for thermo-hydro-mechanical coupling analysis for rock mass

    Institute of Scientific and Technical Information of China (English)

    WANG Zhi-yin; XU Jie; LI Yun-peng; GUO Shu-tai; AI Chuan-zhi

    2007-01-01

    Under the environment of seepage field, stress field and temperature field interaction and influence, the three fields will not only produce coupling effect, but also have deformation with time due to the rheological behavior of rock mass. In the paper, based on the fundamental theories of rock mass coupling theory and rheological mechanics, the rheological model for fully coupled thermo-hydro-mechanical analysis for rock mass was set up, and the corresponding constitutive relationship, the conservation equation of mass and the conservation equation of energy were given, and the finite element formulas were derived for coupling analysis of rock mass. During establishing governing equations, rock mass was assumed approximately as macro-equivalent continuum medium. The obtained rheological numerical model for fully coupled thermo-hydro-mechanical analysis can be used for analyzing and predicting the long-term stability of underground caverns and slope engineering under the condition of thermo-hydro-mechanical coupling with rheological deformation.

  7. THE EFFECT OF FISSURES IN DOLOMITE ROCK MASS ON BLASTING PROJECTS

    Directory of Open Access Journals (Sweden)

    Branko Božić

    1989-12-01

    Full Text Available Rock fractures in the form of fissures are one of more important geological features of a tectonic system. They have an effect on mechanical behaviour of rook masses exposed to the actions of surface forces. For exploitation in dolomite quarries carried out by blasting of deep shot holes it is important to know the system of fissures within a rock mass for the rock brakes along already weakened planes (the paper is published in Croatian.

  8. Study on the Safety of the Rock Mass in the Tongling Bank of Taipinghu Bridge

    Institute of Scientific and Technical Information of China (English)

    2004-01-01

    The Taipinghu Bridge is an important engineering construction, and the safety of rock mass of its foundation is very crucial. This article adopts FLAC 3D to analysis the geologic model. The simulating process shows that no mater the excavating process or the loading process the rock mass are safe. The modeling and analyzing process can be used for reference.

  9. Evaluation of rock mass classification schemes: a case study from the Bowen Basin, Australia

    Science.gov (United States)

    Brook, Martin; Hebblewhite, Bruce; Mitra, Rudrajit

    2016-04-01

    The development of an accurate engineering geological model and adequate knowledge of spatial variation in rock mass conditions are important prerequisites for slope stability analyses, tunnel design, mine planning and risk management. Rock mass classification schemes such as Rock Mass Rating (RMR), Coal Mine Roof Rating (CMRR), Q-system and Roof Strength Index (RSI) have been used for a range of engineering geological applications, including transport tunnels, "hard rock" mining and underground and open-cut coal mines. Often, rock mass classification schemes have been evaluated on subaerial exposures, where weathering has affected joint characteristics and intact strength. In contrast, the focus of this evaluation of the above classification schemes is an underground coal mine in the Bowen Basin, central Queensland, Australia, 15 km east of the town of Moranbah. Rock mass classification was undertaken at 68 sites across the mine. Both the target coal seam and overlying rock show marked spatial variability in terms of RMR, CMRR and Q, but RSI showed limited sensitivity to changes in rock mass condition. Relationships were developed between different parameters with varying degrees of success. A mine-wide analysis of faulting was undertaken, and compared with in situ stress field and local-scale measurements of joint and cleat. While there are no unequivocal relationships between rock mass classification parameters and faulting, a central graben zone shows heterogeneous rock mass properties. The corollary is that if geological features can be accurately defined by remote sensing technologies, then this can assist in predicting rock mass conditions and risk management ahead of development and construction.

  10. Development of a multivariate empirical model for predicting weak rock mass modulus

    Institute of Scientific and Technical Information of China (English)

    Kallu Raj R.; Keffeler Evan R.; Watters Robert J.; Agharazi Alireza

    2015-01-01

    Estimating weak rock mass modulus has historically proven difficult although this mechanical property is an important input to many types of geotechnical analyses. An empirical database of weak rock mass modulus with associated detailed geotechnical parameters was assembled from plate loading tests per-formed at underground mines in Nevada, the Bakhtiary Dam project, and Portugues Dam project. The database was used to assess the accuracy of published single-variate models and to develop a multivari-ate model for predicting in-situ weak rock mass modulus when limited geotechnical data are available. Only two of the published models were adequate for predicting modulus of weak rock masses over lim-ited ranges of alteration intensities, and none of the models provided good estimates of modulus over a range of geotechnical properties. In light of this shortcoming, a multivariate model was developed from the weak rock mass modulus dataset, and the new model is exponential in form and has the following independent variables:(1) average block size or joint spacing, (2) field estimated rock strength, (3) dis-continuity roughness, and (4) discontinuity infilling hardness. The multivariate model provided better estimates of modulus for both hard-blocky rock masses and intensely-altered rock masses.

  11. 大松动圈破碎围岩二次注浆加固试验研究%Experiment Study on Secondary Grouting Reinforcement of Broken Surrounding Rock in Large Loose Circle

    Institute of Scientific and Technical Information of China (English)

    李云; 韩立军; 孙昌兴; 董叶茂

    2012-01-01

    为解决赵庄煤矿高地应力条件下松软破碎围岩巷道持续变形的问题,通过理论分析、试验模拟和现场观测的手段对二次注浆加固进行研究,基于松动圈理论,采用地质雷达探测技术、深浅孔原位复注浆技术及锚注加固技术,在西翼南回风巷原有的锚网索支护基础上进行了全断面二次注浆加固试验。采用数值模拟以及巷道变形量观测的方法对支护效果进行检验。结果表明:二次注浆加固提高了围岩的整体强度,塑性区大幅减小,形成了复合承载结构,实现了锚固体与破碎围岩共同承载和自承载,可有效解决破碎围岩的持续变形问题。%In order to solve the continued deformation problem of the gateway with broken surrounding rock under the high geostress conditions in Zhaozhuang Mine, a study was conducted on the secondary grouting reinforcement with the theoretical analysis, test simulation and site observation means. Based on the loose circle theory, the geological radar detection technology, the in-situ re-grouting technology with shallow borehole and the boh and grouting reinforcement technology were applied to the full section secondary grouting reinforcement test based on the previous bolt/steel mesh/anchor support of the south air returning gateway in the west wing of the mine. The numerical software similar simulation and the gateway deformation observation were applied to the inspection of the support effect. The results showed that the secondary grouting reinforcement had improved the integrated strength of the surrounding rock, high reduced the plastic zone, formed a complex loading structure, released the joint loading and self loading of the anchoring mass and the broken surrounding rock and could effectively solve the continued deformation problem of the broken surrounding rock.

  12. Empirical Assessment of the Mean Block Volume of Rock Masses Intersected by Four Joint Sets

    Science.gov (United States)

    Morelli, Gian Luca

    2016-05-01

    The estimation of a representative value for the rock block volume ( V b) is of huge interest in rock engineering in regards to rock mass characterization purposes. However, while mathematical relationships to precisely estimate this parameter from the spacing of joints can be found in literature for rock masses intersected by three dominant joint sets, corresponding relationships do not actually exist when more than three sets occur. In these cases, a consistent assessment of V b can only be achieved by directly measuring the dimensions of several representative natural rock blocks in the field or by means of more sophisticated 3D numerical modeling approaches. However, Palmström's empirical relationship based on the volumetric joint count J v and on a block shape factor β is commonly used in the practice, although strictly valid only for rock masses intersected by three joint sets. Starting from these considerations, the present paper is primarily intended to investigate the reliability of a set of empirical relationships linking the block volume with the indexes most commonly used to characterize the degree of jointing in a rock mass (i.e. the J v and the mean value of the joint set spacings) specifically applicable to rock masses intersected by four sets of persistent discontinuities. Based on the analysis of artificial 3D block assemblies generated using the software AutoCAD, the most accurate best-fit regression has been found between the mean block volume (V_{{{{b}}_{{m}} }}) of tested rock mass samples and the geometric mean value of the spacings of the joint sets delimiting blocks; thus, indicating this mean value as a promising parameter for the preliminary characterization of the block size. Tests on field outcrops have demonstrated that the proposed empirical methodology has the potential of predicting the mean block volume of multiple-set jointed rock masses with an acceptable accuracy for common uses in most practical rock engineering applications.

  13. Masses of Fluid for Cylindrical Tanks in Rock With Partial Uplift of Bottom Plate.

    Science.gov (United States)

    Taniguchi, Tomoyo; Katayama, Yukihiro

    2016-10-01

    This study proposes the use of a slice model consisting of a set of thin rectangular tanks for evaluating the masses of fluid contributing to the rocking motion of cylindrical tanks; the effective mass of fluid for rocking motion, that for rocking-bulging interaction, effective moment inertia of fluid for rocking motion and its centroid. They are mathematically or numerically quantified, normalized, tabulated, and depicted as functions of the aspect of tanks for different values of the ratio of the uplift width of the tank bottom plate to the diameter of tank for the designer's convenience.

  14. Comparison of laboratory, in situ, and rock mass measurements of the hydraulic conductivity of metamorphic rock at the Savannah River Plant near Aiken, South Carolina

    Energy Technology Data Exchange (ETDEWEB)

    Marine, I W

    1980-01-01

    In situ testing of exploratory wells in metamorphic rock indicates that two types of fracturing occur in the rock mass. Rock containing small openings that permit only extremely slow movement of water is termed virtually impermeable rock. Rock containing openings of sufficient size to permit transmission of water at a significantly faster rate is termed hydraulically transmissive rock. Laboratory methods are unsuitable for measuring hydraulic conductivity in hydraulically transmissive rock; however, for the virtually impermeable rock, values comparable to the in situ tests are obtained. The hydraulic conductivity of the rock mass over a large region is calculated by using the hydraulic gradient, porosity, and regional velocity. This velocity is determined by dividing the inferred travel distance by the age of water which is determined by the helium content of the water. This rock mass hydraulic conductivity value is between the values measured for the two types of fractures, but is closer to the measured value for the virtually impermeable rock. This relationship is attributed to the control of the regional flow rate by the virtually impermeable rock where the discrete fractures do not form a continuous open connection through the entire rock mass. Thus, laboratory methods of measuring permeability in metamorphic rock are of value if they are properly applied.

  15. Comparison of Laboratory, in Situ, and Rock Mass Measurements of the Hydraulic Conductivity of Metamorphic Rock at the Savannah River Plant Near Aiken, South Carolina

    Science.gov (United States)

    Marine, I. Wendell

    1981-06-01

    In situ testing of exploratory wells in metamorphic rock indicates that two types of fracturing occur in the rock mass. Rock containing small openings that permit only extremely slow movement of water is termed virtually impermeable rock. Rock containing openings of sufficient size to permit transmission of water at a significantly faster rate is termed hydraulically transmissive rock. Laboratory methods are unsuitable for measuring hydraulic conductivity in hydraulically transmissive rock; however, for the virtually impermeable rock, values comparable to those of the in situ tests are obtained. The hydraulic conductivity of the rock mass over a large region is calculated by using the hydraulic gradient, porosity, and regional velocity. This velocity is determined by dividing the inferred travel distance by the age of water, which is determined by the helium content of the water. This rock mass hydraulic conductivity value is between the values measured for the two types of fractures but is closer to the measured value for the virtually impermeable rock. This relationship is attributed to the control of the regional flow rate by the virtually impermeable rock where the discrete fractures do not form a continuous open connection through the entire rock mass. Thus laboratory methods of measuring permeability in metamorphic rock are of value if they are properly applied.

  16. Numerical Simulation of Creep Characteristic for Composite Rock Mass with Weak Interlayer

    Science.gov (United States)

    Li, Jian-guang; Zhang, Zuo-liang; Zhang, Yu-biao; Shi, Xiu-wen; Wei, Jian

    2017-06-01

    The composite rock mass with weak interlayer is widely exist in engineering, and it’s essential to research the creep behavior which could cause stability problems of rock engineering and production accidents. However, due to it is difficult to take samples, the losses and damages in delivery and machining process, we always cannot get enough natural layered composite rock mass samples, so the indirect test method has been widely used. In this paper, we used ANSYS software (a General Finite Element software produced by American ANSYS, Inc) to carry out the numerical simulation based on the uniaxial compression creep experiments of artificial composite rock mass with weak interlayer, after experimental data fitted. The results show that the laws obtained by numerical simulations and experiments are consistent. Thus confirmed that carry out numerical simulation for the creep characteristics of rock mass with ANSYS software is feasible, and this method can also be extended to other underground engineering of simulate the weak intercalations.

  17. Comprehensive assessment on dynamic roof instability under fractured rock mass conditions in the excavation disturbed zone

    Institute of Scientific and Technical Information of China (English)

    Xing-ping Lai; Fen-hua Ren; Yong-ping Wu; Mei-feng Cai

    2009-01-01

    The damage process of fractured rock mass showed that the fracture in rocks induced roof collapse in Yangchangwan Coal Mine,China.The rock mass was particularly weak and fractured.There occurred 6 large-scale dynamical roof falls in the excavation disturbed zone (EDZ) with the collapsing volume of 216 m3.First,the field detailed geological environment,regional seismic dy-namics,and dynamic instability of roadways were generally investigated.Second,the field multiple-index monitoring measurements for detecting the deep delamination of the roof,convergence deformation,bolt-cable load,acoustic emission (AE) characteristic pa-rameters,total AE events,AE energy-releasing rate,rock mass fracture,and damage were arranged.Finally,according to the time-space-strength relations,a quantitative assessment of the influence of rock-mass damage on the dynamic roof instability was accomplished.

  18. Earthquake triggering of landslides in highly jointed rock masses: Reconstruction of the 1783 Scilla rock avalanche (Italy)

    Science.gov (United States)

    Bozzano, Francesca; Lenti, Luca; Martino, Salvatore; Montagna, Alfredo; Paciello, Antonella

    2011-06-01

    The Scilla rock avalanche occurred on 6 February 1783 along the coast of the Calabria region (southern Italy), close to the Messina Strait. It was triggered by a mainshock of the “Terremoto delle Calabrie” seismic sequence, and it induced a tsunami wave responsible for more than 1500 casualties along the neighbouring Marina Grande beach. Based on subaerial and submarine surveys, a 5 × 106 m3 subaerial landslide was identified together with a 3 × 106 m3 submarine scar area, whereas block deposits are present in both the subaerial and submerged regions. A detailed geological reconstruction of the slope was obtained and a geomechanical characterisation of the metamorphic rocks involved in the landslide was performed. Based on this reconstruction, intense jointing conditions of the rock mass can be related to main fault zones parallel and normally oriented to the actual coastline. An engineering geology model of the landslide was devised according to an equivalent continuum approach to evaluate both stiffness and strength of the rock mass within the slope. A finite difference stress-strain numerical modelling of the Scilla landslide was performed under dynamic conditions to back-analyse the landslide trigger as well as local seismic amplifications. This modelling gave new insights into the physical interactions between seismic inputs and slopes, as it demonstrated the fundamental role played by i) the interaction between the seismic input and geological setting of unsheared rock slopes (i.e., without preexisting landslide masses), ii) cumulated strain effects due to seismic sequences, and iii) jointing conditions of the involved rock masses responsible for the seismic amplification of the landslide-prone volume, driving it toward failure conditions.

  19. Mass balance of a highly active rock glacier during the period 1954 and 2016

    Science.gov (United States)

    Kellerer-Pirklbauer, Andreas; Kaufmann, Viktor; Rieckh, Matthias

    2017-04-01

    Active rock glaciers are creep phenomena of permafrost in high-relief terrain moving slowly downwards and are often characterised by distinct flow structures with ridges and furrows. Active rock glaciers consist of ice and rock material. The ice component might be either congelation (refreezing of liquid water) or sedimentary ('glacier') ice whereas the rock material might be either of periglacial or glacial origin. The formation period of rock glaciers lasts for centuries to millennia as judged from relative or absolute dating approaches. The input of ice and debris onto the rock glacier mass transport system over such long periods might change substantially over time. Long-term monitoring of mass transport, mass changes and nourishment processes of rock glaciers are rare. In this study we analysed on a decadal-scale mass transport (based on photogrammetric and geodetic data; series 1969-2016), mass changes (geodetically-based mass balance quantification; series 1954-2012), and mass input (based on optical data from an automatic digital camera; series 2006-2016) onto the Hinteres Langtal Rock Glacier. This rock glacier is 900 m long, up to 300 m wide, covers an area of 0.17 km2 and is one of the most active ones in the Eastern European Alps. Mass transport rates at the surface indicate relatively low mean annual surface velocities until the beginning of this millennium. A first peak in the horizontal surface velocity was reached in 2003/04 followed by a period of deceleration until 2007/08. Afterwards the rates increased again substantially from year to year with maximum values in 2014/15 (exceeding 6 m/a). This increase in surface velocities during the last decades was accompanied by crevasse formation and landslide activities at its front. Mass changes show for all six analysed periods between 1954 and 2012 a clear negative surface elevation change with mean annual values ranging from -0.016 to -0.058 m/a. This implies a total volume decrease of -435,895 m3

  20. Heterogeneity in friction strength of an active fault by incorporation of fragments of the surrounding host rock

    Science.gov (United States)

    Kato, Naoki; Hirono, Tetsuro

    2016-07-01

    To understand the correlation between the mesoscale structure and the frictional strength of an active fault, we performed a field investigation of the Atera fault at Tase, central Japan, and made laboratory-based determinations of its mineral assemblages and friction coefficients. The fault zone contains a light gray fault gouge, a brown fault gouge, and a black fault breccia. Samples of the two gouges contained large amounts of clay minerals such as smectite and had low friction coefficients of approximately 0.2-0.4 under the condition of 0.01 m s-1 slip velocity and 0.5-2.5 MP confining pressure, whereas the breccia contained large amounts of angular quartz and feldspar and had a friction coefficient of 0.7 under the same condition. Because the fault breccia closely resembles the granitic rock of the hangingwall in composition, texture, and friction coefficient, we interpret the breccia as having originated from this protolith. If the mechanical incorporation of wall rocks of high friction coefficient into fault zones is widespread at the mesoscale, it causes the heterogeneity in friction strength of fault zones and might contribute to the evolution of fault-zone architectures.

  1. The influence of normal fault on initial state of stress in rock mass

    Directory of Open Access Journals (Sweden)

    Tajduś Antoni

    2016-03-01

    Full Text Available Determination of original state of stress in rock mass is a very difficult task for rock mechanics. Yet, original state of stress in rock mass has fundamental influence on secondary state of stress, which occurs in the vicinity of mining headings. This, in turn, is the cause of the occurrence of a number of mining hazards, i.e., seismic events, rock bursts, gas and rock outbursts, falls of roof. From experience, it is known that original state of stress depends a lot on tectonic disturbances, i.e., faults and folds. In the area of faults, a great number of seismic events occur, often of high energies. These seismic events, in many cases, are the cause of rock bursts and damage to the constructions located inside the rock mass and on the surface of the ground. To estimate the influence of fault existence on the disturbance of original state of stress in rock mass, numerical calculations were done by means of Finite Element Method. In the calculations, it was tried to determine the influence of different factors on state of stress, which occurs in the vicinity of a normal fault, i.e., the influence of normal fault inclination, deformability of rock mass, values of friction coefficient on the fault contact. Critical value of friction coefficient was also determined, when mutual dislocation of rock mass part separated by a fault is impossible. The obtained results enabled formulation of a number of conclusions, which are important in the context of seismic events and rock bursts in the area of faults.

  2. Comparison of input parameters regarding rock mass in analytical solution and numerical modelling

    Science.gov (United States)

    Yasitli, N. E.

    2016-12-01

    Characteristics of stress redistribution around a tunnel excavated in rock are of prime importance for an efficient tunnelling operation and maintaining stability. As it is a well known fact that rock mass properties are the most important factors affecting stability together with in-situ stress field and tunnel geometry. Induced stresses and resultant deformation around a tunnel can be approximated by means of analytical solutions and application of numerical modelling. However, success of these methods depends on assumptions and input parameters which must be representative for the rock mass. However, mechanical properties of intact rock can be found by laboratory testing. The aim of this paper is to demonstrate the importance of proper representation of rock mass properties as input data for analytical solution and numerical modelling. For this purpose, intact rock data were converted into rock mass data by using the Hoek-Brown failure criterion and empirical relations. Stress-deformation analyses together with yield zone thickness determination have been carried out by using analytical solutions and numerical analyses by using FLAC3D programme. Analyses results have indicated that incomplete and incorrect design causes stability and economic problems in the tunnel. For this reason during the tunnel design analytical data and rock mass data should be used together. In addition, this study was carried out to prove theoretically that numerical modelling results should be applied to the tunnel design for the stability and for the economy of the support.

  3. 大断面破碎硐室围岩蠕变模拟及控制技术%Creep simulation on fractured surrounding rock of large section chamber and its control technology

    Institute of Scientific and Technical Information of China (English)

    2013-01-01

    phase of surrounding rock appears with repairing method. Cables are anchored in intact rock mass, but most bolts are in plastic zone. Density of stress contour lines is very intensive outside of grouting range, whose peak value is increasing and moving gradually to deep surrounding rock with the extension of time. The field experiment shows that maximum displacement of chamber is 18 mm, and convergence ratio is less than 0.5 mm/d after 224 days. So the repair scheme of the chamber is successful.

  4. Dynamic Instability of Tunnel in Blocky Rock Mass

    Institute of Scientific and Technical Information of China (English)

    QI Chengzhi; CHEN Canshou; QIAN Qihu; LUO Jian

    2008-01-01

    The displacements and geometry of the rock blocks and the properties of the rock structure play an important role in the stability of tunnels.Based on the key block model, the dynamic instability analysis of underground tunnel subjected to intensive short-time compressional wave was conducted.The instability of the tunnel caused by the spallation and the inertial effect was distinguished.And the influence of the roof contour curvature of tunnel was also determined.

  5. Geoengineering Characterization of the Rock Masses of Northern Face of Jabal Sabir, Taiz City, Yemen

    Directory of Open Access Journals (Sweden)

    Abdul-Aleam Ahmed A. D. Al-Qadhi

    2017-04-01

    Full Text Available This paper is aimed at the description and the geotechnical characterization of the Tertiary granitic rock masses of the northern face of Sabir Mountain, Taiz city, Yemen, for the first time. For accomplishing this task, direct and indirect approaches are adopted. The direct approach is represented by field and laboratory investigations. Field investigations include discontinuity (joints measurements/evaluation, applied Rock Mass Rating (RMR system and Geological Strength Index (GSI system, in addition to field tests, while laboratory investigations encompass physico-mechanical tests carried out on granitic rock materials. Indirect approach for the estimation of shear strength parameters (c, φ, compressive strength (σcm, tensile strength (σtm and deformation modulus (Erm of these rock masses was made by applying the generalized Hoek–Brown failure criterion using geotechnical Roc-Lab software. The laboratory results indicate that the Tertiary granitic rock masses show wide range of variations in their physico-mechanical characteristics owing to degree of weathering /alteration and microfractures. The intact samples of Sabir granitic (Tg rocks show “Moderate” to “High” density, “Low” to "Medium" porosity, “Good" to "Marginal” water absorption capacity and “Weak” to “Very Strong” strength. Stereographically, three main sets of discontinuities (joints are identified at each station; however, the fourth joint set occurs, in addition to random joint sets. The discontinuities (joints trend predominately in NE-SW and NW-SE directions in conformity with the regional structures or faults. According to Jv j/m³ values, the degree of jointing of these rock masses are varied from “Moderate” to “High” jointing. These rocks are categorized as “Fair” to “Excellent” quality, “Fair” to “Good/Very Good” quality and “Poor” to “Very Good” quality classes according to RQD, RMR89 and GSI respectively. Values

  6. Relationship between the rock mass deformation and places of occurrence of seismological events

    Institute of Scientific and Technical Information of China (English)

    MAKOWKA Janusz; KABIESZ Jozef; DOU Lin-ming

    2009-01-01

    Static effort of rock mass very rarely causes of rock burst in polish coal mines. Rock bursts with source in the seismic tremor within the roof rock layers are prevailing. A seismic tremor is an effect of rupture or sliding in roof layers above the exploited panel in coal seam, sometime in a distance from actual exploitation. Sliding, as a rule occurs in fault zone and tremors in it are expected, but monolithic layer rupture is very hard to predict. In a past few years a practice of analyzing state of deformation in high energy seismic tremors zones has been employed. It let gathering experience thanks to witch determination of dangerous shape of reformatted roof is possible. In the paper some typical forms of roof rocks deformations leading to seismic tremor occurrence will be presented. In general these are various types of multidirectional rock layers bending. Real examples of seismic events and rock bursts will be shown.

  7. Numerical simulations of water flow and contaminants transport near mining wastes disposed in a fractured rock mass

    Institute of Scientific and Technical Information of China (English)

    Ben Abdelghani Farouk; Aubertin Michel; Simon Richard; Therrien René

    2015-01-01

    A numerical tool, called Hydro-Geosphere, was used to simulate unsaturated water flow and contami-nants migration around an open pit filled with mining wastes. Numerical simulations had been carried out to assess the influence of various factors on water flow and solute transport in and around the surface openings including recharge, properties of the waste material and presence of fractures in the surround-ing rock mass. The effect of the regional hydraulic gradient was also investigated. The analyses were con-ducted by simulating various 2D cases using experimentally obtained material properties and controlled boundary conditions. The effects of the hydrogeological properties of the filling material (i.e., water reten-tion curve and hydraulic conductivity function), fracture network characteristics and conductivity of the joints were assessed. The results illustrate that fractures control water flow and contaminants transport around the waste disposal area. A fracture network can desaturate the system and improve the regional gradient effect.

  8. Determination of hydraulic conductivity of fractured rock masses:A case study for a rock cavern project in Singapore

    Institute of Scientific and Technical Information of China (English)

    Zhipeng Xu; Zhiye Zhao; Jianping Sun; Ming Lu

    2015-01-01

    In order to reduce the risk associated with water seepage in an underground rock cavern project in Singapore, a reliable hydro-geological model should be established based on the in situ investigation data. The key challenging issue in the hydro-geological model building is how to integrate limited geological and hydro-geological data to determine the hydraulic conductivity of the fractured rock masses. Based on the data obtained from different stages (feasibility investigation stage, construction stage, and post-construction stage), suitable models and methods are proposed to determine the hy-draulic conductivities at different locations and depths, which will be used at other locations in the future.

  9. Simulation of rock mass balance of two typical altered rocks in Wulong gold deposit of Liaoning, China

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Wulong gold deposit hosted in granite and fine-grained diorite dikes, is a typical gold deposit of quartz vein type. Granite and fine-grained diorite dikes in the ore deposit were altered by metallogenic fluid.Based on the altered zoning, the samples of petrochemistry were collected and major and trace elements were analyzed systematically. Calculation of rock mass balance shows that the major elements (SiO2, K2 O, P2O5,Fe2 O3) in the two typical altered rocks are clearly added into the altered system, and that trace elements (V,Y, Zr, Ni, Co, Sr) assume an increasing and decreasing tendencies in the altered granite and altered diorite dike, respectively. The fluid/rock ratios are 30.17-181.00 and 115.44-692.67 respectively for altered granite and altered diorite dike, they have profoundly effects on metallogenesis.

  10. A new model to predict roadheader performance using rock mass properties

    Institute of Scientific and Technical Information of China (English)

    Yazdani-Chamzini ABDOLREZA; SIAMAK Haji Yakhchali

    2013-01-01

    Prediction of roadheader performance plays a significant role in the plan of tunnel construction,which is influenced by different key parameters,including rock strength,discontinuity in rock mass,type and specifications of roadheader machine,and brittleness.The main aim of this study is to build a robust empirical equation based on rock mass properties for the roadheader performance prediction.For achieving the aim,a dataset composed of roadheader performance rate and rock properties is established using the dataset compiled from an underground coal mine located in a remote rugged desert environment some 85 km south of Tabas City in mid east Iran.By using gathered data,the statistical analyses are conducted between rock mass properties and roadheader performance to find whether there is a significant relationship between input variables and roadheader performance.The results show that rock mass properties have a considerable impact on the rate of the roadheader performance.It is demonstrated that the proposed model can accurately predict the roadheader performance as a function of rock mass properties.

  11. Degradation of potassium rock by earthworms and responses of bacterial communities in its gut and surrounding substrates after being fed with mineral.

    Directory of Open Access Journals (Sweden)

    Dianfeng Liu

    Full Text Available BACKGROUND: Earthworms are an ecosystem's engineers, contributing to a wide range of nutrient cycling and geochemical processes in the ecosystem. Their activities can increase rates of silicate mineral weathering. Their intestinal microbes usually are thought to be one of the key drivers of mineral degradation mediated by earthworms,but the diversities of the intestinal microorganisms which were relevant with mineral weathering are unclear. METHODOLOGY/PRINCIPAL FINDINGS: In this report, we show earthworms' effect on silicate mineral weathering and the responses of bacterial communities in their gut and surrounding substrates after being fed with potassium-bearing rock powder (PBRP. Determination of water-soluble and HNO(3-extractable elements indicated some elements such as Al, Fe and Ca were significantly released from mineral upon the digestion of earthworms. The microbial communities in earthworms' gut and the surrounding substrates were investigated by amplified ribosomal DNA restriction analysis (ARDRA and the results showed a higher bacterial diversity in the guts of the earthworms fed with PBRP and the PBRP after being fed to earthworms. UPGMA dendrogram with unweighted UniFrac analysis, considering only taxa that are present, revealed that earthworms' gut and their surrounding substrate shared similar microbiota. UPGMA dendrogram with weighted UniFrac, considering the relative abundance of microbial lineages, showed the two samples from surrounding substrate and the two samples from earthworms' gut had similarity in microbial community, respectively. CONCLUSIONS/SIGNIFICANCE: Our results indicated earthworms can accelerate degradation of silicate mineral. Earthworms play an important role in ecosystem processe since they not only have some positive effects on soil structure, but also promote nutrient cycling of ecosystem by enhancing the weathering of minerals.

  12. Integrated geophysical and geological investigations applied to sedimentary rock mass characterization

    Directory of Open Access Journals (Sweden)

    S. Negri

    2008-06-01

    Full Text Available The Salento Peninsula (south-eastern Italy is characterized by sedimentary rocks. The carbonatic nature of the rocks means they are affected by karst phenomena, forming such features as sinkholes, collapsed dolines and caverns, as a result of chemical leaching of carbonates by percolating water. The instability of these phenomena often produces land subsidence problems. The importance of these events is increasing due to growing urbanization, numerous quarries affecting both the subsoil and the surface, and an important coastline characterized by cliffs. This paper focuses on geological and geophysical methods for the characterization of soft sedimentary rock, and presents the results of a study carried out in an urban area of Salento. Taking the Q system derived by Barton (2002 as the starting point for the rock mass classification, a new approach and a modification of the Barton method are proposed. The new equation proposed for the classification of sedimentary rock mass (Qsrm takes account of the permeability of the rock masses, the geometry of the exposed rock face and their types (for example, quarry face, coastal cliff or cavity, the nature of the lithotypes that constitute the exposed sequence, and their structure and texture. This study revises the correlation between Vp and Q derived by Barton (2002, deriving a new empirical equation correlating P-wave velocities and Qsrm values in soft sedimentary rock. We also present a case history in which stratigraphical surveys, Electrical Resistivity Tomography (ERT, and seismic surveys were applied to in situ investigations of subsidence phenomena in an urban area to estimate rock mass quality. Our work shows that in the analysis of ground safety it is important to establish the rock mass quality of the subsurface structures; geophysical exploration can thus play a key role in the assessment of subsidence risk.

  13. Deformation analysis of transversely isotropic coal-rock mass with porous and cracks

    Institute of Scientific and Technical Information of China (English)

    Xue Dongjie; Zhou Hongwei; Kong Lin; Tang Xianli; Zhao Tian; Yi Haiyang; Zhao Yufeng

    2012-01-01

    Coal-rock as a typical sedimentary rock has obvious stratification,namely it has transversely isotropic feature.Meanwhile,deformation leads to coal-rock mass having the characteristics of different porous and crack structures as well as local anisotropy.Equivalent axial and circumferential strain' formulas of the pure coal-rock mass specimen with a single crack were derived through the establishment of equivalent mechanical model of standard cylindrical coal-rock specimen,and have been widely used to a variety of media combined different structures containing multiple cracks.The complete stress strain curve of a real coal-rock specimen was obtained by the CTC test.Additionally,according to the comparison with the theoretical value,the theoretical mechanical model could well explain the deformation characteristics of coal-rock mass and verify its validity.Further,following features were analyzed:strain normalized coefficient and elastic modulus (Poisson's ratio) in vertical and parallel direction to the stratification,stratification angle,porosity,pore radius,normal and tangential stiffness of crack,and the relationship of different crack width with different tangential stiffness of crack.Through the analysis above,it substantiate this claim that the theoretical model with better reliability reflects the transversely isotropic nature of the coal-rock and the local anisotropy caused by the porous and cracks.

  14. Deformation analysis of transversely isotropic coal-rock mass with porous and cracks

    Institute of Scientific and Technical Information of China (English)

    Xue; Dongjie; Zhou; Hongwei; Kong; Lin; Tang; Xianli; Zhao; Tian; Yi; Haiyang; Zhao; Yufeng

    2012-01-01

    Coal-rock as a typical sedimentary rock has obvious stratification,namely it has transversely isotropic feature.Meanwhile,deformation leads to coal-rock mass having the characteristics of different porous and crack structures as well as local anisotropy.Equivalent axial and circumferential strain' formulas of the pure coal-rock mass specimen with a single crack were derived through the establishment of equivalent mechanical model of standard cylindrical coal-rock specimen,and have been widely used to a variety of media combined different structures containing multiple cracks.The complete stress strain curve of a real coal-rock specimen was obtained by the CTC test.Additionally,according to the comparison with the theoretical value,the theoretical mechanical model could well explain the deformation characteristics of coal-rock mass and verify its validity.Further,following features were analyzed:strain normalized coefficient and elastic modulus(Poisson's ratio) in vertical and parallel direction to the stratification,stratification angle,porosity,pore radius,normal and tangential stiffness of crack,and the relationship of different crack width with different tangential stiffness of crack.Through the analysis above,it substantiate this claim that the theoretical model with better reliability reflects the transversely isotropic nature of the coal-rock and the local anisotropy caused by the porous and cracks.

  15. Research on inspection of stability of subsiding area in composite rock-mass roadway

    Institute of Scientific and Technical Information of China (English)

    来兴平

    2002-01-01

    The research concentrates mainly on the development of failure process in composite rock-mass through acoustic emission, convergence inspection, stress measurement, subside area measurement, level measurement in the process of stability and safety monitoring as well as inspecting of subside area in composite hard rock. In terms of the modern signal analysis technology, various aspects are discussed. The monitoring result and the stability of rock mass can be synthetically evaluated and inferred, and the location of acoustic origin according to the acoustic emission regularity can be successfully detected. Finally the key factors of the deformation can be inferred from in subside area.

  16. NUMERICAL MODELLING OF DISCONTINUOUS ROCK MASS IN THE ELASTIC DOMAIN

    Directory of Open Access Journals (Sweden)

    Biljana Kovačević-Zelić

    1995-12-01

    Full Text Available Constitutive relationships of rock materials are an important component of the numerical modelling, it is not possible to find a generally acceptable constitutive law for rock materials, because of their complex nature. In this paper, the applicability of some models within the framework of theory of elasticity are examined. The analyses are carried out using next models: isotropic and transversely isotropic model, and 'equivalent' material approach The parametric study is also made to examine the influence of discontinuities on the parameters of the equivalent materials the comparison of above mentioned models is made through numerical modelling of the direct shear test. The analysis were performed with finite difference code FLAC (the paper is published in Croatian.

  17. 3D Multiscale Integrated Modeling Approach of Complex Rock Mass Structures

    Directory of Open Access Journals (Sweden)

    Mingchao Li

    2014-01-01

    Full Text Available Based on abundant geological data of different regions and different scales in hydraulic engineering, a new approach of 3D engineering-scale and statistical-scale integrated modeling was put forward, considering the complex relationships among geological structures and discontinuities and hydraulic structures. For engineering-scale geological structures, the 3D rock mass model of the study region was built by the exact match modeling method and the reliability analysis technique. For statistical-scale jointed rock mass, the random network simulation modeling method was realized, including Baecher structure plane model, Monte Carlo simulation, and dynamic check of random discontinuities, and the corresponding software program was developed. Finally, the refined model was reconstructed integrating with the engineering-scale model of rock structures, the statistical-scale model of discontinuities network, and the hydraulic structures model. It has been applied to the practical hydraulic project and offers the model basis for the analysis of hydraulic rock mass structures.

  18. 3D Geological Modeling and Visualization of Rock Masses Based on Google Earth: A Case Study

    CERN Document Server

    Mei, Gang; Xu, Nengxiong

    2013-01-01

    Google Earth (GE) has become a powerful tool for geological modeling and visualization. An interesting and useful feature of GE, Google Street View, can allow the GE users to view geological structure such as layers of rock masses at a field site. In this paper, we introduce a practical solution for building 3D geological models for rock masses based on the data acquired by use with GE. A real study case at Haut-Barr, France is presented to demonstrate our solution. We first locate the position of Haut-Barr in GE, and then determine the shape and scale of the rock masses in the study area, and thirdly acquire the layout of layers of rock masses in the Google Street View, and finally create the approximate 3D geological models by extruding and intersecting. The generated 3D geological models can simply reflect the basic structure of the rock masses at Haut-Barr, and can be used for visualizing the rock bodies interactively.

  19. Assessment of rock mass decay in artificial slopes : Beoordeling van de degradatie van gesteentemassa's in kunstmatige hellingen

    NARCIS (Netherlands)

    Huisman, M.

    2006-01-01

    This research investigates the decay of rock masses underlying slopes, and seeks to quantify the relations of such decay with time and geotechnical parameters of the slope and rock mass. Decay can greatly affect the geotechnical properties of rocks within engineering timescales, and may induce a

  20. Particle Discrete Method Based on Manifold Cover for Crack Propagation of Jointed Rock Mass

    Directory of Open Access Journals (Sweden)

    Yang Ping

    2014-01-01

    Full Text Available The rock mass can be assumed to be homogeneous material from a macroscopic view; however, it is the heterogeneous material in mesoscopic scale and its physicomechanical properties are discontinuous in space. The failure of jointed rock mass was usually caused by the initiation, propagation, and coalescence of new wing cracks derived from primary joint. In order to further study the rock fracture instability, we need to study the expansion of rock cracks under external loads from the macro-meso perspective. This paper, based on the manifold cover concept, proposes a new discrete element numerical method, manifold particle discrete (MPD, combined with the particle contact model and the introduced concept of stress boundary. The proposed method can easily simulate the crack generation, propagation, and coalescence of jointed rock mass from the macro-meso perspective. The whole process of rock fragmentation is thereafter reproduced. By analyzing the manifold cover and sphere particle model, this paper constitutes the sphere unit cover function of three-dimensional manifold cover, establishes tetrahedron units, and obtains the equilibrium equation and compatible equation of the MPD model. For rock-like brittle material, crack propagation process can be simulated, and it also verifies the accuracy of the proposed numerical method.

  1. Discrete Fracture Networks Groundwater Modelling at Bedding Control Fractured Sedimentary Rock mass

    Science.gov (United States)

    Pin, Yeh; Yuan-Chieh, Wu

    2017-04-01

    Groundwater flow modelling in fractured rock mass is an important challenging work in predicting the transport of contamination. So far as we know about the numerical analysis method was consider for crystalline rock, which means discontinuous are treated as stochastic distribution in homogeneous rock mass. Based on the understanding of geology in Taiwan in past few decades, we know that the hydraulic conductivities of Quaternary and Tertiary system rock mass are strongly controlled by development of sedimentary structures (bedding plane). The main purpose of this study is to understand how Discrete Fracture Networks (DFN) affects numerical results in terms of hydraulic behavior using different DFN generation methods. Base on surface geology investigation and core drilling work (3 boreholes with a total length of 120m), small scale fracture properties with in Cho-lan formation (muddy sandstone) are defined, including gently dip of bedding and 2 sub-vertical joint sets. Two FracMan/MAFIC numerical modellings are conducted, using ECPM approach (Equivalent Continuum Porous Media); case A considered all fracture were Power law distribution with Poisson fracture center; case B considered all bedding plans penetrate into modelling region, and remove the bedding count to recalculate joint fracture parameters. Modelling results show that Case B gives stronger groundwater pathways than Case A and have impact on flow field. This preliminary modelling result implicates the groundwater flow modelling work in some fractured sedimentary rock mass, might be considerate to rock sedimentary structure development itself, discontinuous maybe not follow the same stochastic DFN parameter.

  2. Determining the REV for Fracture Rock Mass Based on Seepage Theory

    Directory of Open Access Journals (Sweden)

    Lili Zhang

    2017-01-01

    Full Text Available Seepage problems of the fractured rock mass have always been a heated topic within hydrogeology and engineering geology. The equivalent porous medium model method is the main method in the study of the seepage of the fractured rock mass and its engineering application. The key to the method is to determine a representative elementary volume (REV. The FractureToKarst software, that is, discrete element software, is a main analysis tool in this paper and developed by a number of authors. According to the standard of rock classification established by ISRM, this paper aims to discuss the existence and the size of REV of fractured rock masses with medium tractility and provide a general method to determine the existence of REV. It can be gleaned from the study that the existence condition of fractured rock mass with medium tractility features average fracture spacing smaller than 0.6 m. If average fracture spacing is larger than 0.6 m, there is no existence of REV. The rationality of the model is verified by a case study. The present research provides a method for the simulation of seepage field in fissured rocks.

  3. Piezoelectric responses of brittle rock mass containing quartz to static stress and exploding stress wave respectively

    Institute of Scientific and Technical Information of China (English)

    WAN Guo-xiang; LI Xi-bing; HONG Liang

    2008-01-01

    The electromagnetic emission (EME) induced from the rock containing piezoelectric materials was investigated under both static stress and exploding stress wave in the view of piezoelectric effect. The results show that the intensity of the EME induced from the rock under static stress increases with increasing stress level and loading rate; the relationship between the amplitude of theme from the rock under different modes of stress wave and elastic parameters and propagation distance was presented. The intensity of the EME relates not only to the strength and elastic moduli of rock masses, but also to the initial damage of the rock. The intensity of EME induced by stress wave reaches the highest at the explosion-center and attenuates with the propagation distance. The intensity of EME increases with increasing the elastic modulus and decreases with increasing initial damage. The results are in good agreement with the experimental results.

  4. The IC 5146 star forming complex and its surroundings with 2MASS, WISE and Spitzer

    CERN Document Server

    Nunes, N A; Bica, E

    2016-01-01

    Throughout the last decade sensitive infrared observations obtained by the Spitzer Space Telescope significantly increased the known population of YSOs associated with nearby molecular clouds. With such a census recent studies have characterized pre-main sequence stars (PMS) and determined parame- ters from different wavelengths. Given the restricted Spitzer coverage of some of these clouds, relative to their extended regions, these YSO populations may represent a limited view of star formation in these regions. We are taking advantage of mid-infrared observations from the NASA Wide Field Infrared Survey Explorer (WISE), which provides an all sky view and therefore full coverage of the nearby clouds, to assess the degree to which their currently known YSO population may be representative of a more complete population. We extend the well established classification method of the Spitzer Legacy teams to archived WISE observations. We have adopted 2MASS photometry as a standard catalogue for comparisons. Besides ...

  5. Seismic bearing capacity of strip footings on rock masses using the Hoek–Brown failure criterion

    Directory of Open Access Journals (Sweden)

    Amin Keshavarz

    2016-04-01

    Full Text Available In this paper, the bearing capacity of strip footings on rock masses has been studied in the seismic case. The stress characteristics or slip line method was used for analysis. The problem was analyzed in the plane strain condition using the Hoek–Brown failure criterion. First, the equilibrium equations along the stress characteristics were obtained and the rock failure criterion was applied. Then, the equations were solved using the finite difference method. A computer code has been provided for analysis. Given the footing and rock parameters, the code can calculate the stress characteristics network and obtain the stress distribution under the footing. The seismic effects have been applied as the horizontal and vertical pseudo-static coefficients. The results of this paper are very close to those of the other studies. The seismic bearing capacity of weightless rock masses can be obtained using the proposed equations and graphs without calculating the whole stress characteristics network.

  6. Analysis of borehole expansion and gallery tests in anisotropic rock masses

    Science.gov (United States)

    Amadei, B.; Savage, W.Z.

    1991-01-01

    Closed-form solutions are used to show how rock anisotropy affects the variation of the modulus of deformation around the walls of a hole in which expansion tests are conducted. These tests include dilatometer and NX-jack tests in boreholes and gallery tests in tunnels. The effects of rock anisotropy on the modulus of deformation are shown for transversely isotropic and regularly jointed rock masses with planes of transverse isotropy or joint planes parallel or normal to the hole longitudinal axis for plane strain or plane stress condition. The closed-form solutions can also be used when determining the elastic properties of anisotropic rock masses (intact or regularly jointed) in situ. ?? 1991.

  7. Numerical Analysis of Finite Deformation of Overbroken Rock Mass in Gob Area Based on Euler Model of Control Volume

    Institute of Scientific and Technical Information of China (English)

    LIU Wei-qun; MIAO Xie-xing

    2006-01-01

    The overbroken rock mass of gob areas is made up of broken and accumulated rock blocks compressed to some extent by the overlying strata. The bearing pressure of the gob can directly affect the safety of mining fields, formation of road retained along the next goaf and seepage of water and methane through the gob. In this paper, the software RFPA'2000 is used to construct numerical models. Especially the Euler method of control volume is proposed to solve the simulation difficulty arising from plastically finite deformations. The results show that three characteristic regions occurred in the gob area: (1) a naturally accumulated region, 0-10 m away from unbroken surrounding rock walls, where the bearing pressure is nearly zero; (2) an overcompacted region, 10-20 m away from unbroken walls, where the bearing pressure results in the maximum value of the gob area; (3) a stable compaction region, more than 20 m away from unbroken walls and occupying absolutely most of the gob area, where the bearing pressures show basically no differences. Such a characteristic can explain the easy-seepaged "O"-ring phenomena around mining fields very well.

  8. Identification of rock mass characteristics using microtremor in the boring hole

    Science.gov (United States)

    Che, Ailan; Wang, Huan; Feng, Shaokong; Siguyama, Takeshi

    2014-05-01

    An identification analysis method of the rock mass characteristics is proposed using microtremor measurements in the boring hole. The method is based on the assumption that the epicenter of incident waves of each observation point in the same boring hole almost agrees. And the calculations are deconvoluted by the multiple reflection theory. The procedure applicable to the identification of the average elastic characteristics of in situ rock masses is presented. It is based on the minimization of an error function representing the difference between microtremor measurements performed on the rock mass and the corresponding data obtained by a numerical analysis subjected to known external actions. The method requires the formulation of the elasticity inverse problem and is based on the least square minimization procedure. As an example the approach has been applied to the identification of the dynamic properties and the predominant characteristics of the rock mass underlying a deep excavated quarry in west of Shanghai city. The inverted rock mass characteristics are compared with the PS logs at the sites and show consistency, confirming that the proposed inversion is promising.

  9. Analysis of microseismic activity in rock mass controlled by fault in deep metal mine

    Institute of Scientific and Technical Information of China (English)

    Liu Jianpo; Liu Zhaosheng; Wang Shaoquan; Shi Changyan; Li Yuanhui

    2016-01-01

    Aiming at evaluating the stability of a rock mass near a fault, a microseismic (MS) monitoring system was established in Hongtoushan copper mine. The distribution of displacement and log(EI), the relationship between MS activity and the exploitation process, and the stability of the rock mass controlled by a fault were studied. The results obtained from microseismic data showed that MS events were mainly concentrated at the footwall of the fault. When the distance to the fault exceeded 20 m, the rock mass reached a relatively stable state. MS activity is closely related to the mining process. Under the strong disturbance from blasting, the initiation and propagation of cracks is much faster. MS activity belongs in the category of aftershocks after large scale excavation. The displacement and log(EI) obtained from MS events can reflect the difference in physical and mechanical behavior of different areas within the rock mass, which is useful in judging the integrity and degradation of the rock mass.

  10. Simulation of Rock Mass Horizontal Displacements with Usage of Cellular Automata Theory.

    Science.gov (United States)

    Sikora, Paweł

    2016-12-01

    In the article there was presented two dimensional rock mass model as a deterministic finite cellular automata. Used to describe the distribution of subsidence of rock mass inside and on its surface the theory of automata makes it relatively simple way to get a subsidence trough profile consistent with the profile observed by geodetic measurements on the land surface. As a development of an existing concept of the rock mass model, as a finite cellular automaton, there was described distribution function that allows, simultaneously with the simulation of subsidence, to simulate horizontal displacements inside the rock mass model and on its surface in accordance with real observations. On the basis of the results of numerous computer simulations there was presented fundamental mathematical relationship that determines the ratio of maximum horizontal displacement and maximum subsidence, in case of full subsidence trough, in relation to the basic parameters of the rock mass model. The possibilities of presented model were shown on the example of simulation results of deformation distribution caused by extraction of abstract coal panel. Obtained results were consistent with results obtained by geometric-integral theory.

  11. CRITERIA FOR ROCK ENGINEERING FAILURE

    Institute of Scientific and Technical Information of China (English)

    ZHUDeren; ZHANGYuzhuo

    1995-01-01

    A great number of underground rock projects are maintained in the rock mass which is subject to rock damage and failure development. In many cases, the rock. engineering is still under normal working conditions even though rock is already fails to some extent. This paper introduces two different concepts: rock failure and rock engineering failure. Rock failure is defined as a mechanical state under which an applicable characteristic is changed or lost.However, the rock engineering failure is an engineering state under which an applicable function is changed or lost. The failure of surrounding rocks is the major reason of rock engineering failure. The criterion of rock engineering failure depends on the limit of applicable functions. The rock engineering failure state possesses a corresponding point in rock failure state. In this paper, a description of rock engineering failure criterion is given by simply using a mechanical equation or expression. It is expected that the study of rock engineering failure criterion will be an optimal approach that combines research of rock mechanics with rock engineering problems.

  12. New design equations for estimation of ultimate bearing capacity of shallow foundations resting on rock masses

    Institute of Scientific and Technical Information of China (English)

    Amir H Alavi; Ehsan Sadrossadat

    2016-01-01

    Rock masses are commonly used as the underlying layer of important structures such as bridges, dams and transportation constructions. The success of a foundation design for such structures mainly depends on the accuracy of estimating the bearing capacity of rock beneath them. Several traditional numerical approaches are proposed for the estimation of the bearing capacity of foundations resting on rock masses to avoid performing elaborate and expensive experimental studies. Despite this fact, there still exists a serious need to develop more robust predictive models. This paper proposes new nonlinear prediction models for the ultimate bearing capacity of shallow foundations resting on non-fractured rock masses using a novel evolutionary computational approach, called linear genetic programming. A comprehen-sive set of rock socket, centrifuge rock socket, plate load and large-scaled footing load test results is used to develop the models. In order to verify the validity of the models, the sensitivity analysis is conducted and discussed. The results indicate that the proposed models accurately characterize the bearing capacity of shallow foundations. The correlation coefficients between the experimental and predicted bearing capacity values are equal to 0.95 and 0.96 for the best LGP models. Moreover, the derived models reach a notably better prediction performance than the traditional equations.

  13. Effects of fracture distribution and length scale on the equivalent continuum elastic compliance of fractured rock masses

    Institute of Scientific and Technical Information of China (English)

    Marte Gutierrez; Dong-Joon Youn

    2015-01-01

    Fracture systems have strong influence on the overall mechanical behavior of fractured rock masses due to their relatively lower stiffness and shear strength than those of the rock matrix. Understanding the effects of fracture geometrical distribution, such as length, spacing, persistence and orientation, is important for quantifying the mechanical behavior of fractured rock masses. The relation between fracture geometry and the mechanical characteristics of the fractured rock mass is complicated due to the fact that the fracture geometry and mechanical behaviors of fractured rock mass are strongly dependent on the length scale. In this paper, a comprehensive study was conducted to determine the effects of fracture distribution on the equivalent continuum elastic compliance of fractured rock masses over a wide range of fracture lengths. To account for the stochastic nature of fracture distributions, three different simulation techniques involving Oda’s elastic compliance tensor, Monte Carlo simulation (MCS), and suitable probability density functions (PDFs) were employed to represent the elastic compliance of fractured rock masses. To yield geologically realistic results, parameters for defining fracture distribu-tions were obtained from different geological fields. The influence of the key fracture parameters and their relations to the overall elastic behavior of the fractured rock mass were studied and discussed. A detailed study was also carried out to investigate the validity of the use of a representative element volume (REV) in the equivalent continuum representation of fractured rock masses. A criterion was also proposed to determine the appropriate REV given the fracture distribution of the rock mass.

  14. Effects of fracture distribution and length scale on the equivalent continuum elastic compliance of fractured rock masses

    Directory of Open Access Journals (Sweden)

    Marte Gutierrez

    2015-12-01

    Full Text Available Fracture systems have strong influence on the overall mechanical behavior of fractured rock masses due to their relatively lower stiffness and shear strength than those of the rock matrix. Understanding the effects of fracture geometrical distribution, such as length, spacing, persistence and orientation, is important for quantifying the mechanical behavior of fractured rock masses. The relation between fracture geometry and the mechanical characteristics of the fractured rock mass is complicated due to the fact that the fracture geometry and mechanical behaviors of fractured rock mass are strongly dependent on the length scale. In this paper, a comprehensive study was conducted to determine the effects of fracture distribution on the equivalent continuum elastic compliance of fractured rock masses over a wide range of fracture lengths. To account for the stochastic nature of fracture distributions, three different simulation techniques involving Oda's elastic compliance tensor, Monte Carlo simulation (MCS, and suitable probability density functions (PDFs were employed to represent the elastic compliance of fractured rock masses. To yield geologically realistic results, parameters for defining fracture distributions were obtained from different geological fields. The influence of the key fracture parameters and their relations to the overall elastic behavior of the fractured rock mass were studied and discussed. A detailed study was also carried out to investigate the validity of the use of a representative element volume (REV in the equivalent continuum representation of fractured rock masses. A criterion was also proposed to determine the appropriate REV given the fracture distribution of the rock mass.

  15. NUMERICAL ANALYSIS OF SATURATED-UNSATURATED SEEPAGE FLOW IN FRACTURED ROCK MASS DUE TO SURFACE INFILTRATION

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Seepage flow in fractured rock mass due to surface infiltration is a saturated-unsaturated seepage process. Aimed at rock mass with large fracture density, which can be equivalent to continuum, a mathematical model for saturated-unsaturated seepage flow in fractured rock mass due to surface infiltration was established in this paper. The Galerkin finite element method was used in numerical simulation and a finite element program used to calculate saturated-unsaturated seepage flow due to surface infiltration was worked out. A model experiment was employed examine the reasonableness of the program. The results show that the proposed model and program are reasonable. The application of the analysis method in this paper in an engineering project shows that the method is reliable and feasible.

  16. Equivalent elastic compliance tensor for rock mass with multiple persistent joint sets:Exact derivation via modified crack tensor

    Institute of Scientific and Technical Information of China (English)

    崔洁; 江权; 冯夏庭; 李邵军; 高红; 李帅军

    2016-01-01

    Discontinuities constitute an integral part of rock mass and inherently affect its anisotropic deformation behavior. This work focuses on the equivalent elastic deformation of rock mass with multiple persistent joint sets. A new method based on the space geometric and mechanical properties of the modified crack tensor is proposed, providing an analytical solution for the equivalent elastic compliance tensor of rock mass. A series of experiments validate the capability of the compliance tensor to accurately represent the deformation of rock mass with multiple persistent joint sets, based on conditions set by the basic hypothesis. The spatially varying rules of the equivalent elastic parameters of rock mass with a single joint set are analyzed to reveal the universal law of the stratified rock mass.

  17. Influence of discontinuities on the rock mass stress-strain state around excavation

    Directory of Open Access Journals (Sweden)

    V.N. Bukhartsev

    2013-06-01

    Full Text Available Adequate mathematical modeling of selvage zone and natural fracturing as well as assessment of its impact on stress-strain state – urgent problems in calculation of hydraulic tunnels. Modern Russian regulations in fact give dependences only to solve the problems in plane deformation conditions. The specificity of work of the tunnel that crosses the discontinuity, as a space frame are not taken into account. This article presents influence of discontinuities and fracture characteristics on the rock mass stress-strain state around excavation. Fractured rock mass model was analyzed. Formula of modulus of elasticity for fractured rock mass at distance from the fault was deduced. Influence of discontinuities on the stress distribution was estimated with using experiment design method. On the basis of the conducted research it was established, that assessing rock stress-strain state around the fracture is necessary to consider rock mass fracture characteristics; and using principal stresses distribution in combination with Lode parameter we can clearly estimate the type of stress-strain state in each point, therefore, we can use different strength theories for different sections of the tunnel.

  18. Study on engineering geological stability of rock mass at Shanmen silver deposit

    Institute of Scientific and Technical Information of China (English)

    Ming FENG; Li LIU; Yu ZHANG; Xigang REN; Chengke XU

    2006-01-01

    The natural balance conditions will be disturbed and produce a series of problems when mineral deposit has mined. This paper has researched the engineering rock masses have been researched in this study, structural planes, the distribution characteristics of tectonic geological factors and the stability of engineering structures according to the theory and research methods of rock mechanics, it will provide the engineering geological evidence for mining area exploited, meanwhile pledge the safety production. Shanmen silver deposit is a large epithermal deposit,it is controlled by NE to NNE strike faults. The stability of rock mass is acted on the tectonic movement and hot metalliferous brine in long-term. Especially,strength of rock mass becomes softened, muddy and loosed under the action of water,so the lower stability of rock mass is,the easier it can take place for harm of disaster threatening production safe of mining. For this reason,it is very important that drawing up a plan to lower harm for mine and protect.

  19. 基于Hoek-Brown准则的隧洞围岩变形研究%Study of deformations of surrounding rock of tunnel based on Hoek-Brown criterion

    Institute of Scientific and Technical Information of China (English)

    温森; 杨圣奇

    2011-01-01

    In many practical situations, for instance, in jointed rock mass, linear M-C yield criterion may not be justified and a nonlinear Hoek-Brown yield criterion would be more appropriate, so it is necessary to attempt to calculate deformation of tunnel by the criterion.The surrounding rock is divided into three zones: elastic zone, strain softening zone and plastic flow zone.Theoretical derivation on deformation is carried out by Hoek-Brown criterion and non-associated flow rule.Parameters of surrounding rock in strain softening zone are variable and they depend on the plastic deformation of this zone, so it's difficult to derive the analytical solution for stress in this zone.Runge-Kutta method is used to carry out numerical calculation and the radiuses of strain softening zone and plastic flow zone are calculated.Finally, the deformations of tunnel are calculated.It is demonstrated by an example that the results calculated by the method in this paper and Carranza-Torres's method are almost the same when strain softening zone and plastic flow zone are not be considered.Furthermore, it is demonstrated by the other example that dilation angle affects deformation more severely when in-situ stress becomes greater.%由于在许多实际条件下,比如节理岩体中,线性的M-C准则不太适用,非线性的Hoek-Brown比较适用,因此,可以尝试使用这一非线性屈服准则对洞室变形进行研究.研究隧洞变形时,将围岩分为弹性区、应变软化区、塑性流动区.采用Hoek-Brown准则和非关联流动法则对洞室变形进行了理论推导:软化区域围岩参数随着塑性变形增加而变化,解析法难以求得应力,采用龙格一库塔方法进行数值计算,求解得到塑性软化区和流动区半径,并最终求得洞室变形.通过算例计算表明,在不考虑软化区和流动区时,方法和Carranza-Torres计算结果相差甚小;随着原岩应力的增加,膨胀角对洞室变形的影响增大.

  20. Study on the Safety of the Foundation Rock Masses in the Tangkou Bank of the Taipinghu Bridge

    Institute of Scientific and Technical Information of China (English)

    2004-01-01

    The Taipinghu Bridge is an important project, and the safety of rock masses of its foundation is very crucial. This article analyzes the potential causes of the deformation of the rock masses of the bridge foundation, and uses the Fast Lagrangian Analysis of Continua to analyze the geologic model. The simulating process shows that no mater in the excavating process or in the loading process the rock masses are suit for the engineering. The modeling and analyzing process can be used for reference.

  1. De-stressed mining of multi-seams: Surrounding rock control during the mining of a roadway in the overlying protected seam

    Institute of Scientific and Technical Information of China (English)

    Wang Cheng; Zhang Nong; Li Guichen; Zhang Nianchao

    2011-01-01

    Surrounding rock control in the overlying protective coal seam is a challenging topic for de-stressed mining of multi-seamed coal. Current research findings on roadway control were used in the design of a physical model of a complex textured roof having a varying thickness. The model was used to study roadway instability and collapse caused by dynamic pressure. The results show that when the thickness of the roof exceeds the bolted depth the roadway security is least and the roof has the greatest possibility for collapse. Numerical simulations were also carried out to study stress redistribution before and after roadway excavation during underlying protective seam mining. The evolution of roadway displacement and fracture, as affected by support methods, has been well studied. A series of support principles and technologies for mining affected roadways has been proposed after demonstration of successful practical application in the Huainan Mines. These principles and technologies are of extended value to deep coal mining support in China.

  2. The test research on partial relieving pressure for the entry in the deep mine under high stress and friable surrounding rock

    Institute of Scientific and Technical Information of China (English)

    DU Ji-ping; HOU Chao-jiong; ZHU Ya-ping; HAO Ming-kui

    2007-01-01

    Based on the geological condition of Zhangxiaolou deep mine in Xuzhou mining area, under 986 m in depth, 20.6~31.6 MPa in maximum horizontal principal stress, and friable and fractured surrounding rock, test researches on partial relieving pressure were completed for the entry with U-steel arched yielding support. The relieving pressure parameters, technology process and results of springing blasting by boreholes and excavating pockets in the two sides of entry were introduced. It is demonstrated that springing will not be shaped under the condition of single borehole arrangement after exploded, the arrangement by a group, it will make borehole bottom form springing in 0.6~0.8 m in diameter, that convergence of two sides and roof to floor have some increments by using springing blasting for reliving pressure. This kind of method for reliving pressure is not suitable to use in the deep mine, and that the convergence of two sides obviously declined by excavating pocket in two sides, it can be still used in the entry with metal support, while maintenance of entry in deep mines is difficult, and can not be supported by bolt or bolt with wire mesh.

  3. 铁路松散破碎围岩隧道防塌控制技术%Collapse Control Technology in Incompact and Fractured Surrounding Rock Railway Tunnel

    Institute of Scientific and Technical Information of China (English)

    柴跃进

    2013-01-01

    隧道施工中经常遇到破碎围岩而发生塌方及掌子面涌出、坍塌的事故.一旦塌方灾害发生,不仅影响工程进度,而且影响施工企业形象;若处理不当,将遭受更大损失,如塌方频繁发生,或留下隐患.提出一种新型隧道防塌控制技术-“双曲拱”耦合支护技术,支护效果表明该技术可靠性强,能有效控制隧道顶板坍塌,具有很好的经济效益和社会效益.%Often fractured surrounding rock in tunnel construction and face the collapse and gushing, collapse accident.Once the landslide disaster, not only the project, but construction corporate image;If not handled properly, will suffer more losses, such as landslides are frequent, hidden or left.Made a new tunnel collapse prevention control technologies - "double -curved arch" coupling supporting technology, supporting effect indicates that the technical reliability, can effectively control the tunnel roof collapsed, with good economic and social benefits.

  4. Identification of Stress Change Within a Rock Mass Through Apparent Stress of Local Seismic Events

    Science.gov (United States)

    Brown, Laura; Hudyma, Martin

    2017-01-01

    Mine blasting produces excavation geometry changes which induce stress change that can be observed in the seismic source parameter apparent stress calculated for local seismic events. Using high apparent stress as a proxy for increasing stress within a rock mass, areas experiencing increases in the local stress conditions can be determined. This paper presents the use of apparent stress of seismic events to identify areas within a rock mass experiencing local stress change. Examples from a deep Canadian mine, operating in excess of 2900 m below surface, are provided.

  5. The comparative study on analytical solutions and numerical solutions of displacement in transversely isotropic rock mass

    Science.gov (United States)

    Zhang, Zhizeng; Zhao, Zhao; Li, Yongtao

    2016-06-01

    This paper attempts to verify the correctness of the analytical displacement solution in transversely isotropic rock mass, and to determine the scope of its application. The analytical displacement solution of a circular tunnel in transversely isotropic rock mass was derived firstly. The analytical solution was compared with the numerical solution, which was carried out by FLAC3D software. The results show that the expression of the analytical displacement solution is correct, and the allowable engineering range is that the dip angle is less than 15 degrees.

  6. Advective-diffusive mass transfer in fractured porous media with variable rock matrix block size.

    Science.gov (United States)

    Sharifi Haddad, Amin; Hassanzadeh, Hassan; Abedi, Jalal

    2012-05-15

    Traditional dual porosity models do not take into account the effect of matrix block size distribution on the mass transfer between matrix and fracture. In this study, we introduce the matrix block size distributions into an advective-diffusive solute transport model of a divergent radial system to evaluate the mass transfer shape factor, which is considered as a first-order exchange coefficient between the fracture and matrix. The results obtained lead to a better understanding of the advective-diffusive mass transport in fractured porous media by identifying two early and late time periods of mass transfer. Results show that fractured rock matrix block size distribution has a great impact on mass transfer during early time period. In addition, two dimensionless shape factors are obtained for the late time, which depend on the injection flow rate and the distance of the rock matrix from the injection point.

  7. Relationship between the rock mass deformation and places of occurrence of seismological events

    Energy Technology Data Exchange (ETDEWEB)

    Janusz Makowka; Jozef Kabiesz; Lin-ming Ddou [Central Mining Institute, Katowice (Poland)

    2009-09-15

    Static effort of rock mass very rarely causes of rock burst in Polish coal mines. Rock bursts with source in the seismic tremor within the roof rock layers are prevailing. A seismic tremor is an effect of rupture or sliding in roof layers above the exploited panel in coal seam, sometime in a distance from actual exploitation. Sliding, as a rule occurs in fault zone and tremors in it are expected, but monolithic layer rupture is very hard to predict. In a past few years a practice of analyzing state of deformation in high energy seismic tremors zones has been employed. It let gathering experience thanks to witch determination of dangerous shape of reformatted roof is possible. In the paper some typical forms of roof rocks deformations leading to seismic tremor occurrence will be presented. In general these are various types of multidirectional rock layers bending. Real examples of seismic events and rock bursts in the Czech Republic will be shown. 5 refs., 6 figs.

  8. Tunnel behaviour and support associated with the weak rock masses of flysch

    Institute of Scientific and Technical Information of China (English)

    V.Marinos

    2014-01-01

    Flysch formations are generally characterised by evident heterogeneity in the presence of low strength and tectonically disturbed structures. The complexity of these geological materials demands a more specialized geoengineering characterisation. In this regard, the paper tries to discuss the standardization of the engineering geological characteristics, the assessment of the behaviour in underground excava-tions, and the instructionseguidelines for the primary support measures for flysch layer qualitatively. In order to investigate the properties of flysch rock mass, 12 tunnels of Egnatia Highway, constructed in Northern Greece, were examined considering the data obtained from the design and construction records. Flysch formations are classified thereafter in 11 rock mass types (IeXI), according to the siltstone esandstone proportion and their tectonic disturbance. A special geological strength index (GSI) chart for heterogeneous rock masses is used and a range of geotechnical parameters for every flysch type is presented. Standardization tunnel behaviour for every rock mass type of flysch is also presented, based on its site-specific geotechnical characteristics such as structure, intact rock strength, persistence and complexity of discontinuities. Flysch, depending on its types, can be stable even under noticeable overburden depth, and exhibit wedge sliding and wider chimney type failures or cause serious defor-mation even under thin cover. Squeezing can be observed under high overburden depth. The magnitude of squeezing and tunnel support requirements are also discussed for various flysch rock mass types under different overburdens. Detailed principles and guidelines for selecting immediate support mea-sures are proposed based on the principal tunnel behaviour mode and the experiences obtained from these 12 tunnels. Finally, the cost for tunnel support from these experiences is also presented.

  9. Tunnel behaviour and support associated with the weak rock masses of flysch

    Directory of Open Access Journals (Sweden)

    V. Marinos

    2014-06-01

    Full Text Available Flysch formations are generally characterised by evident heterogeneity in the presence of low strength and tectonically disturbed structures. The complexity of these geological materials demands a more specialized geoengineering characterisation. In this regard, the paper tries to discuss the standardization of the engineering geological characteristics, the assessment of the behaviour in underground excavations, and the instructions–guidelines for the primary support measures for flysch layer qualitatively. In order to investigate the properties of flysch rock mass, 12 tunnels of Egnatia Highway, constructed in Northern Greece, were examined considering the data obtained from the design and construction records. Flysch formations are classified thereafter in 11 rock mass types (I–XI, according to the siltstone–sandstone proportion and their tectonic disturbance. A special geological strength index (GSI chart for heterogeneous rock masses is used and a range of geotechnical parameters for every flysch type is presented. Standardization tunnel behaviour for every rock mass type of flysch is also presented, based on its site-specific geotechnical characteristics such as structure, intact rock strength, persistence and complexity of discontinuities. Flysch, depending on its types, can be stable even under noticeable overburden depth, and exhibit wedge sliding and wider chimney type failures or cause serious deformation even under thin cover. Squeezing can be observed under high overburden depth. The magnitude of squeezing and tunnel support requirements are also discussed for various flysch rock mass types under different overburdens. Detailed principles and guidelines for selecting immediate support measures are proposed based on the principal tunnel behaviour mode and the experiences obtained from these 12 tunnels. Finally, the cost for tunnel support from these experiences is also presented.

  10. A new method for automatic discontinuity traces sampling on rock mass 3D model

    Science.gov (United States)

    Umili, G.; Ferrero, A.; Einstein, H. H.

    2013-02-01

    A new automatic method for discontinuity traces mapping and sampling on a rock mass digital model is described in this work. The implemented procedure allows one to automatically identify discontinuity traces on a Digital Surface Model: traces are detected directly as surface breaklines, by means of maximum and minimum principal curvature values of the vertices that constitute the model surface. Color influence and user errors, that usually characterize the trace mapping on images, are eliminated. Also trace sampling procedures based on circular windows and circular scanlines have been implemented: they are used to infer trace data and to calculate values of mean trace length, expected discontinuity diameter and intensity of rock discontinuities. The method is tested on a case study: results obtained applying the automatic procedure on the DSM of a rock face are compared to those obtained performing a manual sampling on the orthophotograph of the same rock face.

  11. Rock mass movements around development workings in various density of standing-and-roof-bolting support

    Institute of Scientific and Technical Information of China (English)

    MAJCHERCZYK Tadeusz; MALKOWSKLI Piotr; NIEDBALSKI Zbighiew

    2008-01-01

    Presented measurement results of roof rocks and wall rock movements of un-derground development workings after their drifting. The research was carried out in thecoal mine workings with standing-and-roof bolting support. There were various density ofthe support, so the aim of the special monitoring programme was to determine movementintensity of rock mass in the premises of the heading area. There were four types of re-search did by the authors. They measured convergence, roof layers separation using tell-tales and sonic probes and load bearing of the headings' roofs by hydraulic dynamometers.Evaluation of fracture zone around the heading and investigation the load zone caused byfailed roof rocks may become a basement for the determination of support parameters ofthe workings. The combined system of standing support and roof bolting seems to be anessential for underground headings protection.

  12. Towards semi-automatic rock mass discontinuity orientation and set analysis from 3D point clouds

    Science.gov (United States)

    Guo, Jiateng; Liu, Shanjun; Zhang, Peina; Wu, Lixin; Zhou, Wenhui; Yu, Yinan

    2017-06-01

    Obtaining accurate information on rock mass discontinuities for deformation analysis and the evaluation of rock mass stability is important. Obtaining measurements for high and steep zones with the traditional compass method is difficult. Photogrammetry, three-dimensional (3D) laser scanning and other remote sensing methods have gradually become mainstream methods. In this study, a method that is based on a 3D point cloud is proposed to semi-automatically extract rock mass structural plane information. The original data are pre-treated prior to segmentation by removing outlier points. The next step is to segment the point cloud into different point subsets. Various parameters, such as the normal, dip/direction and dip, can be calculated for each point subset after obtaining the equation of the best fit plane for the relevant point subset. A cluster analysis (a point subset that satisfies some conditions and thus forms a cluster) is performed based on the normal vectors by introducing the firefly algorithm (FA) and the fuzzy c-means (FCM) algorithm. Finally, clusters that belong to the same discontinuity sets are merged and coloured for visualization purposes. A prototype system is developed based on this method to extract the points of the rock discontinuity from a 3D point cloud. A comparison with existing software shows that this method is feasible. This method can provide a reference for rock mechanics, 3D geological modelling and other related fields.

  13. A Copula-Based Method for Estimating Shear Strength Parameters of Rock Mass

    Directory of Open Access Journals (Sweden)

    Da Huang

    2014-01-01

    Full Text Available The shear strength parameters (i.e., the internal friction coefficient f and cohesion c are very important in rock engineering, especially for the stability analysis and reinforcement design of slopes and underground caverns. In this paper, a probabilistic method, Copula-based method, is proposed for estimating the shear strength parameters of rock mass. The optimal Copula functions between rock mass quality Q and f, Q and c for the marbles are established based on the correlation analyses of the results of 12 sets of in situ tests in the exploration adits of Jinping I-Stage Hydropower Station. Although the Copula functions are derived from the in situ tests for the marbles, they can be extended to be applied to other types of rock mass with similar geological and mechanical properties. For another 9 sets of in situ tests as an extensional application, by comparison with the results from Hoek-Brown criterion, the estimated values of f and c from the Copula-based method achieve better accuracy. Therefore, the proposed Copula-based method is an effective tool in estimating rock strength parameters.

  14. An estimation of the penetration rate of rotary drills using the Specific Rock Mass Drillability index

    Institute of Scientific and Technical Information of China (English)

    Cheniany Alireza; Hasan Khoshrou Seyed; Shahriar Kourosh; Khademi Hamidi Jafar

    2012-01-01

    The main purpose of the present study was to provide a practical,convenient drillability prediction model based on rock mass characteristics,geological sampling from blast holes,and drill operational factors.Empirical equations that predict drill penetration rate have been developed using statistical analyses of data from the Sarcheshmeh Copper Mine.Seven parameters of the rock or rock mass,including uniaxial compressive strength (UCS) of the rock,Schmidt hammer hard hess vatue,quartz content,fragment size (d80),alteration,and joint dip,are included in the model along with two operational parameters of the rotary drill,bit rotational speed and thrust.These parameters were used to predict values of the newly developed Specific Rock Mass Drillability (SRMD) index.Comparing measured SRMD values to those predicted by the multi-parameter linear,or nonlinear,regression models showed good agreement.The correlation coefficients were 0.82 and 0.81,respectively.

  15. 复杂围岩条件下开切眼全锚支护%Full-bolt supporting in open-off cut under complex surrounding rock condition

    Institute of Scientific and Technical Information of China (English)

    刘惠德; 尹根成; 栗兴仁; 李志强

    2001-01-01

    The mine open-off cut should be very safety because it is a wide-spanned place where the mining facilities are located. In the past, the supporting of open-off cut used to be log shed. Since the space is limited, the facilities fixing efficiency and safety are influenced greatly. The rock layer above coal bed of Malan mine 2th coal bed is composed of multiple layers of different rock beds or thin coal beds. So if using log shed to support open-off cut, the deformation of surrounding would be large and the space would be limited, then the facilities fixing efficiency would be low and the log consume would be huge. The method of bolt + stay rope is an effective way. It can improve the facilities fixing environment greatly as well as efficiency and safety reliability. At the same time, the cost and working intensity are lowed geratly.%采煤工作面的开切眼不仅跨度大,而且是采煤设备安装的场所,对于空间的安全有较高的要求。以往开切眼的支护一般为木棚,使开切眼的空间狭小,对于安装设备的效率和安全有很大影响。马兰矿2#煤层的顶板为多层不同性质的岩层和薄煤层组成,属于复杂性顶板,用木棚支护,开切眼围岩变形大,安装空间狭小,使安装效率低下,而且木材消耗量大。用锚杆+锚索支护获得成功,从根本上改善了综采设备安装的环境,提高了安装的效率和安全可靠性,降低了开切眼的支护成本和劳动强度。

  16. Estimate of rock mass stability in surface–borehole mining of high-grade iron ore

    Science.gov (United States)

    Sammal, AS; Antsiferov, SV; Deev, PV; Sergeev, SV

    2017-02-01

    Under consideration is the estimate of rock mass stability around underground openings generated as a result of hydraulic borehole mining of iron ore. The authors use analytical solutions of two plane elasticity problems on stress state of infinite media with the zone of weakening in the form of one or two circular holes, given initial stresses are set in the study domains.

  17. Rock mass condition, behaviour and seismicity in mines of the Bushveld igneous complex.

    CSIR Research Space (South Africa)

    Haile, AT

    1995-12-01

    Full Text Available This project report gives an overall view of the rock mass environment of the Bushveld complex and influence on the mine design practices. The main focus of the project was to survey the currently available data and conduct further analysis in order...

  18. Numerical Modeling of Exploitation Relics and Faults Influence on Rock Mass Deformations

    Science.gov (United States)

    Wesołowski, Marek

    2016-12-01

    This article presents numerical modeling results of fault planes and exploitation relics influenced by the size and distribution of rock mass and surface area deformations. Numerical calculations were performed using the finite difference program FLAC. To assess the changes taking place in a rock mass, an anisotropic elasto-plastic ubiquitous joint model was used, into which the Coulomb-Mohr strength (plasticity) condition was implemented. The article takes as an example the actual exploitation of the longwall 225 area in the seam 502wg of the "Pokój" coal mine. Computer simulations have shown that it is possible to determine the influence of fault planes and exploitation relics on the size and distribution of rock mass and its surface deformation. The main factor causing additional deformations of the area surface are the abandoned workings in the seam 502wd. These abandoned workings are the activation factor that caused additional subsidences and also, due to the significant dip, they are a layer on which the rock mass slides down in the direction of the extracted space. These factors are not taken into account by the geometrical and integral theories.

  19. Elastic-plastic analytical solutions for surrounding rocks of tunnels and its engineering applications%巷道围岩弹塑性解析解及工程应用

    Institute of Scientific and Technical Information of China (English)

    曾开华; 鞠海燕; 盛国君; 张常光

    2011-01-01

    Based on the unified strength theory and a non-associated flow rule, the elastic-plastic analytical solutions of stress and displacement for surrounding rocks of tunnels were presented. The effects of intermediate principal stress,elastic strains in the plastic zone and dilatancy properties were taken into account in the analytical solutions. The resuits show that the influences of intermediate principal stress and dilatancy properties on the ground reaction curve and support pressure are significant. The strength potentials of rock mass are better achieved due to considering the intermediate principal stress effect. The tunnel design with ignoring volume changes in the plastic zone is in danger, in that the corresponding support pressure is smaller. The effect of dilatancy is important for the tunnel support design.%基于统一强度理论和非关联流动法则,合理考虑中间主应力、围岩塑性区弹性应变和剪胀特性等影响,建立了巷道围岩弹塑性应力和位移解析解.研究结果表明:中间主应力和围岩剪胀特性对围岩特征曲线和支护压力的影响显著,考虑中间主应力的影响能充分发挥围岩的强度潜能;不考虑塑性区体积变化所得支护压力较小,设计偏危险;巷道支护设计应考虑围岩剪胀特性的重要影响.

  20. 隧道石膏质围岩溶蚀及溶出特性试验研究%Experimental Research on Corrosion and Leaching Characteristics of Gypsum Rock Surrounding Tunnels

    Institute of Scientific and Technical Information of China (English)

    祝艳波; 吴银亮; 余宏明

    2016-01-01

    rock becomes weaker after corrosion, while at the same time a mass of sulfate ions is leached out into the water. Corrosion of gypsum rock is affected by various complicated factors, and it is intensified by hydrodynamic conditions. The faster the flow of water is, the more obvious the corrosion characteristics are. In addition, the weak acid aqueous solution also promotes corrosion, and temperature affects the corrosion of the gypsum rock in terms of amount and rate by influencing the solubility of gypsum rock in water. The stability of a tunnel′s surrounding rock is reduced after the corrosion of gypsum rock, and the leaching sulfate ions can cause moderate corrosion to a tunnel′s reinforced concrete lining structure. Therefore, corresponding preventive measures should be applied in tunnel construction to avoid the occurrence of engineering problems.

  1. Virtual multi-dimensional internal bonds model and its application in simulation of rock mass

    Institute of Scientific and Technical Information of China (English)

    ZHANG ZhenNan; GE XiuRun

    2008-01-01

    VMIB (virtual multi-dimensional internal bonds) is a multiscale mechanical model developed from the VIB (virtual internal bond) theory. In VIB theory, the solid material is considered to consist of random-distributed material particles in microscale. These particles are connected with normal bonds. The macro constitutive relation is derived from the cohesive law between particles. However, in VMIB, the micro particles are connected with both normal and shear bonds. The macro constitutive relation is derived in terms of bond stiffness coefficients. It has been theoretically certified that there exists a corresponding relationship between the two bond stiffness coefficients and the two macro material constants, i.e. the Young's modulus and Poisson ratio. This corresponding relationship suggests that it should be necessary and sufficient to simultaneously account for the normal and shear interactions between particles. Due to the fact that the fracture criterion is directly incorporated into the constitutive relation, both VIB and VMIB present many advantages in simulating fractures of materials. In the damage model of rock mass, a damage tensor is usually defined to describe the distribution of cracks. The damage value in one direction determines the relative stiffness of rock mass in this direction. In VMIB solid, the relative distribution density of micro bonds in one direction determines the relative macro stiffness of the material in this direction. The effects of the damage value and the relative distribution density of bonds are consistent. To simulate the failure behavior of rock mass with VMIB, the presented paper sets up a quantitative relationship between the damage tensor and the relative distribution density of bonds. Comparison of the theoretical and the experimental results shows that VMIB model can represent the effect of distributed cracks on rock mass with this relationship. The presented work provides a foundation for further simulating fracture

  2. In Situ Geochemical Analysis and Age Dating of Rocks Using Laser Ablation-Miniature Mass Spectrometer

    Science.gov (United States)

    Sinha, Mahadeva P.; Hecht, Michael H.; Hurowitz, Joel A.

    2012-01-01

    A miniaturized instrument for performing chemical and isotopic analysis of rocks has been developed. The rock sample is ablated by a laser and the neutral species produced are analyzed using the JPL-invented miniature mass spectrometer. The direct sampling of neutral ablated material and the simultaneous measurement of all the elemental and isotopic species are the novelties of this method. In this laser ablation-miniature mass spectrometer (LA-MMS) method, the ablated neutral atoms are led into the electron impact ionization source of the MMS, where they are ionized by a 70-eV electron beam. This results in a secondary ion pulse typically 10-100 microsecond wide, compared to the original 5-10-nanosecond laser pulse duration. Ions of different masses are then spatially dispersed along the focal plane of the magnetic sector of the miniature mass spectrometer and measured in parallel by a modified CCD (charge-coupled device) array detector capable of detecting ions directly. Compared to conventional scanning techniques, simultaneous measurement of the ion pulse along the focal plane effectively offers a 100% duty cycle over a wide mass range. LAMMS offers a more quantitative assessment of elemental composition than techniques that detect laser-ionized species produced directly in the ablation process because the latter can be strongly influenced by matrix effects that vary with the structure and geometry of the surface, the laser beam, and the ionization energies of the elements. The measurement of high-precision isotopic ratios and elemental composition of different rock minerals by LAMMS method has been demonstrated. The LA-MMS can be applied for the absolute age determination of rocks. There is no such instrument available presently in a miniaturized version that can be used for NASA space missions. Work is in progress in the laboratory for geochronology of rocks using LA-MMS that is based on K-Ar radiogenic dating technique.

  3. Developing a MatLab code for determine geometry of rock mass blocks and its applications in mining and rock mechanic engineering

    Directory of Open Access Journals (Sweden)

    Yarahmadi R.

    2015-01-01

    Full Text Available Various geological processes such as tectonic activities develop fractures and discontinuities in the rock mass body; these, in turn, form blocks with different shapes and sizes in the rock mass body. Accurate understanding of these blocks' geometry is essential in different domains of rock and mine engineering such as determination of yield in quarries, optimization of fragmentation energy, the design of blasting pattern, block stability in slopes and underground spaces and the prediction of dilution potential in caving methods exploitation. Because of costly operation and uncertainties in the measurement of fractures and discontinuities properties in 3D, 2D simple models are recommended. So far, all investigations have been focused on the problem of finding primary blocks analytically and mathematically, but these problem applications have been neglected slightly. This paper introduces a MATLAB code for geometry determination of rock mass blocks in two dimensional spaces and investigates the applications of it.

  4. Determination of the mechanical parameters of rock mass based on a GSI system and displacement back analysis

    Science.gov (United States)

    Kang, Kwang-Song; Hu, Nai-Lian; Sin, Chung-Sik; Rim, Song-Ho; Han, Eun-Cheol; Kim, Chol-Nam

    2017-08-01

    It is very important to obtain the mechanical paramerters of rock mass for excavation design, support design, slope design and stability analysis of the underground structure. In order to estimate the mechanical parameters of rock mass exactly, a new method of combining a geological strength index (GSI) system with intelligent displacment back analysis is proposed in this paper. Firstly, average spacing of joints (d) and rock mass block rating (RBR, a new quantitative factor), surface condition rating (SCR) and joint condition factor (J c) are obtained on in situ rock masses using the scanline method, and the GSI values of rock masses are obtained from a new quantitative GSI chart. A correction method of GSI value is newly introduced by considering the influence of joint orientation and groundwater on rock mass mechanical properties, and then value ranges of rock mass mechanical parameters are chosen by the Hoek-Brown failure criterion. Secondly, on the basis of the measurement result of vault settlements and horizontal convergence displacements of an in situ tunnel, optimal parameters are estimated by combination of genetic algorithm (GA) and numerical simulation analysis using FLAC3D. This method has been applied in a lead-zinc mine. By utilizing the improved GSI quantization, correction method and displacement back analysis, the mechanical parameters of the ore body, hanging wall and footwall rock mass were determined, so that reliable foundations were provided for mining design and stability analysis.

  5. Rock Mass Characterization by High-Resolution Sonic and GSI Borehole Logging

    Science.gov (United States)

    Agliardi, F.; Sapigni, M.; Crosta, G. B.

    2016-11-01

    We investigate the relationships between the in situ P-wave velocity (Vp) of rock masses, measured by borehole acoustic logging, and their Geological Strength Index (GSI), to support a reliable assessment of equivalent continuum rock mass properties at depth. We quantified both Vp and GSI in three deep boreholes drilled in a crystalline core complex of the central Italian Alps. The boreholes were driven up to 400 m in depth and provided high-quality drill cores in gneiss, schist and metasedimentary rocks with variable lithology. Geological and geomechanical logging was carried out for over 800 m of cores, and acoustic logging was performed for more than 600 m of borehole length. High-resolution core logging in terms of GSI was obtained using an original quantitative approach. Candidate empirical correlation functions linking Vp and GSI were tested by a two-step statistical analysis of the experimental dataset, including outlier removal and nonlinear regression analysis. We propose a sigmoid Vp-GSI equation valid over a depth range between 100 and 400 m. This accounts for extremely variable lithological, weathering and rock mass damage conditions, complementing existing shallow-depth approaches and showing potential for practical applications in different engineering settings.

  6. Assessment of stress state of rock mass with the help of seismic soundings

    Energy Technology Data Exchange (ETDEWEB)

    Blyakhman, A.S.; Proskuryakov, V.M.

    1984-01-01

    Method of measurement using seismic soundings without drilling boreholes is described. A physical basis is provided for the method used and the results are supplied for the assessment of the stress state of rock mass in the Norilsk coal basin. In the last few years, wide use has been made of linear profiling without drilling boreholes in order to determine the stress state of rock needed for predicting outbursts in coal seams. The method can be used to investigate rectilinear sections of mine workings which are over 20 m. However, in order to resolve a variety of mine problems, e.g. predicting and investigating dynamic phenomena, it is necessary to acquire information about the state of rock mass up to 10 to 15 m. With this in mind the VNIMI has developed a new variant of seismic sounding without the need to drill boreholes which, unlike other known methods, makes it possible to determine parameters of the abutment pressure along the whole perimeter of the rock mass in question. The investigations carried out indicate that the increases and decreases in stress as well as the rise and fall in the rate of stress wave propagation in the abutment zone can be approximated with sufficient accuracy by line segments. Results of the investigations obtained with the help of seismic soundings at the Oktyabrskii mine, Norilsk coal basin, are given.

  7. Rock damage caused by underground excavation and meteorite impacts

    OpenAIRE

    Bäckström, Ann

    2008-01-01

    The intent of this thesis is to contribute to the understanding of the origin of fractures in rock. The man-made fracturing from engineering activities in crystalline rock as well as the fracturing induced by the natural process of meteorite impacts is studied by means of various characterization methods. In contrast to engineering induced rock fracturing, where the goal usually is to minimize rock damage, meteorite impacts cause abundant fracturing in the surrounding bedrock. In a rock mass ...

  8. 随机介质理论下隧道围岩渐进破坏过程数值实验研究%Numerical Experiment Research on the Progressive Failure Process of the Surrounding Rock of the Tunnel under the Stochastic Medium Theory

    Institute of Scientific and Technical Information of China (English)

    商拥辉; 李航; 张波; 方前程

    2015-01-01

    The strength subtraction is introduced to safety evaluation of tunnel surrounding rock,combining with “the shallow tunnel rapid construction double small spacing tunnels,wear interchange structure under the shield tunnel and the surface of the structure containing joint,irregular fissure of mountain highway tunnel”engi-neering examples,using real damage of material analysis software RFPA -2D ,the finite element model of each strength reduction factor is set up.Viscoelastic artificial boundary is adopted to eliminate the influence of boundary conditions on the calculation precision in model,and the model achieves the mesoscopic structure unit of surround-ing rock of the mean and the defects of random distribution by means of random medium theory,it also reveals the dynamic gradual damage process of surrounding rock,the primitive phase change damage evolution mechanism and characteristics of rock mass structural plane under different working conditions,the mesoscopic damage of surround-ing rock is thought to be caused by non average of rock nonlinear material macroscopic unit,the calculation results judged in failure of tunnel surrounding rock with different step reduction in crack development trends and the num-ber of cell damage,and calculates safety factor in the sense of the safety reserve.At the same time,combining ABAQUS with RFPA -2D two different finite element models,comparatively analyzing the random medium theory and continuum theory combining strength subtraction in differences of the evaluation of surrounding rock stability.%将强度折减法引入到隧道围岩安全评价中,结合“浅埋暗挖快速施工双线小间距隧道、盾构下穿立交结构隧道和结构面含有节理、不规则裂隙的山体公路隧道”等工程实例,借助材料真实破坏分析软件 RFPA-2D,建立每个强度折减系数下的有限元模型。模型采用了黏弹性人工边界来消除边界条件对计算精度的影响,并借助随机介

  9. Automatic extraction of discontinuity orientation from rock mass surface 3D point cloud

    Science.gov (United States)

    Chen, Jianqin; Zhu, Hehua; Li, Xiaojun

    2016-10-01

    This paper presents a new method for extracting discontinuity orientation automatically from rock mass surface 3D point cloud. The proposed method consists of four steps: (1) automatic grouping of discontinuity sets using an improved K-means clustering method, (2) discontinuity segmentation and optimization, (3) discontinuity plane fitting using Random Sample Consensus (RANSAC) method, and (4) coordinate transformation of discontinuity plane. The method is first validated by the point cloud of a small piece of a rock slope acquired by photogrammetry. The extracted discontinuity orientations are compared with measured ones in the field. Then it is applied to a publicly available LiDAR data of a road cut rock slope at Rockbench repository. The extracted discontinuity orientations are compared with the method proposed by Riquelme et al. (2014). The results show that the presented method is reliable and of high accuracy, and can meet the engineering needs.

  10. Comparison of Two Methods for Determining Rock Mass Parameters%两种岩体参数求解方法比较

    Institute of Scientific and Technical Information of China (English)

    仇圣华; 杨志锡; 徐峰; 杨林德

    2011-01-01

    岩体参数具有结构性和随机性的空间变异特征,其导致岩体参数具有不确定性.本文结合某地下工程的地质勘探资料、试验洞量测资料,一方面通过应用地质统计学理论建立岩体参数变异数学模型,优选出理想实验变差函数参数值,实现岩体参数的普通克立格估计,求得试验洞区域岩体弹性模量值;另一方面,假设初始地应力成线性分布,应用位移反分析方法求得试验洞相邻围岩弹性模量值;且通过应用三元件模型,求出试验洞相邻围岩粘弹性参数值.结果表明两种方法结果相对误差仅1.27%.%Rock mass parameters have the properties of structural and random spatial variance, which result in the uncertainty of the parameters. This paper analyzed the geological exploring data and the measurement data of the experimental cavity in an underground factory. On one hand, geostatistics is applied to establish the mathematical model of variation of rock mass parameters. The ideal parameter values of experimental variance function are determined. The ordinary Kriging estimation of rock mass parameters is realized according to these values, and the rock mass elastic modulus are worked out. On the other hand, it evaluated rock mass elastic modulus of the surroundings in neighboring experimental cavity by having assumed the initial rock stresses to be in linear distribution and applied back analysis method, and get the material visco-elastic parameters of the surroundings in neighboring experimental cavity by applying tri-element model. Results show that the relative error is only 1.27 percent in the two methods.

  11. Effects of pre-existing discontinuities on the residual strength of rock mass - Insight from a discrete element method simulation

    Science.gov (United States)

    Gao, F. Q.; Kang, H. P.

    2016-04-01

    When rock failure is unavoidable, the designer of engineering structures must know and account for the residual strength of the rock mass. This is particularly relevant in underground coal mine openings. Pre-existing discontinuities play an important role in the mechanical behavior of rock masses and thus it is important to understand the effects of such pre-existing discontinuities on the residual strength. For this purpose, the present study demonstrates a numerical analysis using a discrete element method simulation. The numerical results indicate that fracture intensity has no significant influence on the residual strength of jointed rock masses, independent of confining conditions. As confining pressures increase, both peak and residual strengths increase, with residual strength increasing at a faster rate. The finding was further demonstrated by analyzing documented laboratory compressive test data from a variety of rocks along with field data from coal pillars. A comprehensive interpretation of the finding was conducted using a cohesion-weakening-friction-strengthening (CWFS) model. The effect of rock bolts on rock mass strength was also evaluated by using a discrete element method model which suggested that rock bolts can significantly increases residual strength but have limited effect on increasing the peak strength of rock masses.

  12. Development of a Highly Portable Plate Loading Device and In Situ Modulus Measurements in Weak Rock Masses

    Science.gov (United States)

    Kallu, Raj R.; Keffeler, Evan R.; Watters, Robert J.; Warren, Sean N.

    2016-02-01

    In recent years, underground mines in Nevada are increasingly exploiting in weak mineralized zones at greater depths that are intensely fractured and highly altered. The mechanical behavior of these rock masses ranges between weak rock and very stiff soil. A common limitation for design of underground mining excavations in these types of rock masses is absence of in situ geotechnical data. This limitation is generally overcome by estimating in situ mechanical behavior from empirical relationships so that the continuum-based numerical methods can be used to evaluate ground support designs. Because of the cost, time, and specialized equipment involved, historically in situ tests have not been performed in these underground mines. Predictive rock mass modulus relationships that are currently available in the literature are derived from field testing of predominantly good-quality rock masses. Consequently, there is limited confidence in using these models for rock masses with Rock Mass Ratings less than 45. In order to overcome some of these limitations, a portable plate loading device (PPLD) was designed and fabricated. The PPLD allows one to perform low cost and relatively quick in situ deformability tests to be performed on weak rock masses in underground mines. Test procedures and data reduction methods were developed to limit potential sources of error associated with the PPLD test. A total of fourteen plate loading tests were performed in weak rock masses at two different active underground mines in Nevada, USA. The resulting the test data were compared to eight published empirical rock mass modulus relationships to determine which, if any, of these relationships are sufficiently accurate for estimating modulus in similar geotechnical conditions. Only two of these relationships were found to be sufficient for first-order estimations of in situ modulus.

  13. Rock Mass Characteristics Modification Using Back Analysis Method for Isfahan Subway

    Directory of Open Access Journals (Sweden)

    Farzad Habibbeygi

    2015-10-01

    Full Text Available In the recent decades, the construction of tunnels has been increased vastly in all over the world. Despite all the efforts have been put into the geotechnical investigation, determining the precise and reliable design parameters is a difficult task to accomplish. Therefore, using back analysis techniques to modify geotechnical parameters and optimize the design of initial and final supports is more effective and even less expensive nowadays. In this paper, the results of monitoring and instrumentation of Isfahan subway have been investigated. Moreover, two important parameters for stability analysis, the modulus of elasticity of rock mass and the coefficient of the lateral earth pressure, are modified based on the measured convergence by using the direct method. Results show the Young modulus of rock mass and the lateral earth coefficient are less than the initial values from geotechnical investigation.

  14. A Genetic Algorithm for Locating the Multiscale Critical Slip Surface in Jointed Rock Mass Slopes

    Directory of Open Access Journals (Sweden)

    Qiang Xu

    2014-01-01

    Full Text Available The joints have great influence on the strength of jointed rock mass and lead to the multiscale, nonhomogeneous, and anisotropic characteristics. In order to consider these effects, a new model based on a genetic algorithm is proposed for locating the critical slip surface (CSS in jointed rock mass slope (JRMS from its stress field. A finite element method (FEM was employed to analyze the stress field. A method of calculating the mechanical persistence ratio (MPR was used. The calculated multiscale and anisotropic characteristics of the MPR were used in the fitness function of genetic algorithm (GA to calculate the factor of safety. The GA was used to solve optimization problems of JRMS stability. Some numerical examples were given. The results show that the multiscale and anisotropic characteristics of the MPR played an important role in locating the CSS in JRMS. The proposed model calculated the CSS and the factor of safety of the slope with satisfactory precision.

  15. The nature of carbon material in the black shale rock mass of Kazakhstan

    Energy Technology Data Exchange (ETDEWEB)

    Marchenko, L.G.

    1981-01-01

    Carbon material is closely tied to ores of various origin lying in the carbon (black shale) rock masses of Kazakhastan. The nature of the carbon material in several gold fields is closely examined. Shungite, its paragenesis with ore materials and its role in the carbon and ore material processes, is described. The accumulation of shungite in zones determined to consist of ores, is looked at in terms of prospecting criteria.

  16. Determination of Rock Mass Modulus Using the Plate Loading Method at Yucca Mountain, Nevada

    Energy Technology Data Exchange (ETDEWEB)

    Finley, R.E.; George, J.T.; Riggins, M.

    1999-08-02

    A suite of plate loading tests has recently been conducted by Sandia National Laboratories at the Exploratory Studies Facility at Yucca Mountain, Nevada. Fielding of these in situ tests as well as other approaches undertaken for the determination of rock mass modulus are described. The various methodologies are evaluated and their data compared. Calculation by existing empirical methods and numerical modeling are compared to each other as well as to field data.

  17. 高应力松软围岩煤仓失稳分析及联合支护技术%High Stress Soft Surrounding Rock Coal Bunker Instability Analysis and Combined Support Technology

    Institute of Scientific and Technical Information of China (English)

    张鹏

    2015-01-01

    Aiming at the supporting problem of coal bunker instability under high stress soft surrounding rock, studies the mechanism of coal bunker damage under complicated conditions through theory analysis,puts forward the combined supporting technology,which includes first high -strength anchor net spray support and secondary structure reinforcement,and carries out the engineering application and surrounding rock deformation monitoring.The results show that by adopting the recovery technique for support,the surrounding rock deformation of coal bunker is effective-ly controlled,the supporting result is well,and safety and normal use of coal bunker is ensured.It provides an effec-tive support method for coal bunker soft surrounding rock supporting under the similar condition.%针对高应力松软围岩煤仓失稳破坏面临的支护难题,通过理论分析,研究了复杂条件下煤仓破坏的机理,提出了“一次高强锚网喷支护+二次结构补强”的联合支护技术,并进行了工程应用和围岩变形量监测。结果表明,采用该支护修复技术后,煤仓围岩变形得到有效控制,支护效果良好,保障了煤仓正常安全使用。为类似条件下煤仓软弱围岩支护提供了一种有效的支护方法。

  18. Workflow for the fast evaluation of rock mass properties and stability of rock slopes along trafficways in Lower Austria

    Science.gov (United States)

    Straka, Wolfgang; Zangerl, Christian

    2016-04-01

    In Lower Austria there is a total of 17.000 km of provincial and 24.000 km of communal roads, to be maintained by the province and the municipalities. In addition, there are approx. 1.500 km of railroads, and the Danube as a major waterway. A large part of this infrastructure is, or is potentially, affected by various types of instability of adjacent slopes. Due to insufficient knowledge, as well as slope design and management practice in the past, every year, especially in connection to weather extremes, slopes known to be critical become active landslides again, and unexpected new ones arise, causing damage as well as financial stress. Engineering intervention, if possible, should be quick and effective. Geologists and engineers in public service, not having the means for detailed investigation in most cases, are using guidelines to assess the requirements to be met by slope design on traffic ways. But these guidelines don't reflect many of the newer scientific advances. Therefore, scientists at BOKU and backers in the administration want to gain more insight into causative factors, which, if successful, may render maintenance of traffic lines under critical conditions more effective and predictable. The specific project goal is to produce new guidelines to allow quick assessment of the most likely behaviour of rock masses common in the area, especially when cut into shape along infrastructure lines, using readily available information. The scientific investigations include simple and ready tests (like Schmidt hammer), as well as photogrammetry, laserscanning, and other complex geophysical and numerical techniques, but the final product (guidelines) is expected to work without such difficult methods. It is important to note, on the other hand, that the rock mass stability classification inherent in the new guidelines must allow distinction between conclusions which are safe, and conjectures which are in need of validation by contracted experts. It is planned to

  19. Geostatistical methods for rock mass quality prediction using borehole and geophysical survey data

    Science.gov (United States)

    Chen, J.; Rubin, Y.; Sege, J. E.; Li, X.; Hehua, Z.

    2015-12-01

    For long, deep tunnels, the number of geotechnical borehole investigations during the preconstruction stage is generally limited. Yet tunnels are often constructed in geological structures with complex geometries, and in which the rock mass is fragmented from past structural deformations. Tunnel Geology Prediction (TGP) is a geophysical technique widely used during tunnel construction in China to ensure safety during construction and to prevent geological disasters. In this paper, geostatistical techniques were applied in order to integrate seismic velocity from TGP and borehole information into spatial predictions of RMR (Rock Mass Rating) in unexcavated areas. This approach is intended to apply conditional probability methods to transform seismic velocities to directly observed RMR values. The initial spatial distribution of RMR, inferred from the boreholes, was updated by including geophysical survey data in a co-kriging approach. The method applied to a real tunnel project shows significant improvements in rock mass quality predictions after including geophysical survey data, leading to better decision-making for construction safety design.

  20. Rheological Characteristics of Weak Rock Mass and Effects on the Long-Term Stability of Slopes

    Science.gov (United States)

    Yang, Tianhong; Xu, Tao; Liu, Hongyuan; Zhang, Chunming; Wang, Shanyong; Rui, Yongqin; Shen, Li

    2014-11-01

    The creep deformation behavior of the northern slope of an open-pit mine is introduced. Direct shear creep tests are then conducted for the samples taken from the northern slope to study the rheological characteristics of the rock mass. The experimental results are analyzed afterwards using an empirical method to develop a rheological model for the rock mass. The proposed rheological model is finally applied to understand the creep behavior of the northern slope, predict the long-term stability, and guide appropriate measures to be taken at suitable times to increase the factor of safety to ensure stability. Through this study, a failure criterion is proposed to predict the long-term stability of the slope based on the rheological characteristics of the rock mass and a critical deformation rate is adopted to determine when appropriate measures should be taken to ensure slope stability. The method has been successfully applied for stability analysis and engineering management of the toppling and slippage of the northern slope of the open-pit mine. This success in application indicates that it is theoretically accurate, practically feasible, and highly cost-effective.

  1. Evaluation of Rock Mass Responses Using High Resolution Water-level Tiltmeter Arrays

    Science.gov (United States)

    Roberts, J. S.; Wang, H. F.; Fratta, D.; Stetler, L. D.; Volk, J. T.; Geox^Tm

    2010-12-01

    External forces act on the surface of the earth and produce deformation across all spatial and temporal scales. This research study focuses on the deformation evaluation of the rock-mass subjected to tidal, earthquake and surface forces. The events are monitored over horizontal distances of over 100 meters with tilt measurement arrays with a resolution of 10-8 radians. These measurements are obtained from hydrostatic leveling system (HLS) arrays that have been installed in the LaFarge mine in North Aurora, IL by Fermilab. Each sensor in the array is equipped with a water-filled reservoir beneath a capacitor. The amount of water in the reservoir is calculated as a function of the measured capacitance. Individual sensors are connected in a closed system via a water and air line. As the host rock expands and contracts sensors are raised relative to another and water is displaced. The water level in each reservoir is sent to a computer in the mine and recorded. In order to measure the tilt of the rock between two points, the difference in water levels between adjacent sensors is computed. The difference between the end sensors is also calculated to determine the larger-scale tilt of the array. The tiltmeters in LaFarge mine are supported by concrete pedestals installed on the floor of the drift. In the Homestake mine the tiltmeters are placed on similar pedestals, as well as platforms made of artificial wood decking. These platforms are fixed to the wall of the drift with a rock bolt. Time and frequency domain analyses were performed on time series ranging from hours to six months to capture relevant time scales including the response to the 2010 Chile Earthquake (hour-long scale), the stages of the moon (month scale), Fox River floods (flooding week long scales and pressure dissipation month-long scales). By monitoring tiltmeter array responses to different forces, we aim at making predictions about the material properties of rock masses.

  2. SITE-94. Natural elemental mass movement in the vicinity of the Aespoe Hard Rock Laboratory

    Energy Technology Data Exchange (ETDEWEB)

    Miller, W.M.; Smith, G.M.; Towler, P.A.; Savage, D. [QuantiSci, Melton Mowbray (United Kingdom)

    1997-05-01

    The primary objective of this study is to quantify natural elemental fluxes at a location exhibiting typical characteristics of a site for a spent fuel repository in Sweden. The relevant pathways are considered to be: Groundwater transport; Glacial erosion; Non-glacial weathering; River transport. Calculations are made of elemental mass fluxes from a volume of rock equivalent to that which would hold a KBS-3 style repository. In addition, the radioactive flux associated with the natural series radionuclide mass fluxes from the repository are also calculated. These can be compared directly to performance assessment predictions of the releases from a repository. 88 refs, 13 figs, 24 tabs.

  3. SITE-94. Natural elemental mass movement in the vicinity of the Aespoe Hard Rock Laboratory

    Energy Technology Data Exchange (ETDEWEB)

    Miller, W.M.; Smith, G.M.; Towler, P.A.; Savage, D. [QuantiSci, Melton Mowbray (United Kingdom)

    1997-05-01

    The primary objective of this study is to quantify natural elemental fluxes at a location exhibiting typical characteristics of a site for a spent fuel repository in Sweden. The relevant pathways are considered to be: Groundwater transport; Glacial erosion; Non-glacial weathering; River transport. Calculations are made of elemental mass fluxes from a volume of rock equivalent to that which would hold a KBS-3 style repository. In addition, the radioactive flux associated with the natural series radionuclide mass fluxes from the repository are also calculated. These can be compared directly to performance assessment predictions of the releases from a repository. 88 refs, 13 figs, 24 tabs.

  4. 隧道爆破开挖围岩动力损伤效应数值模拟%Numerical simulation of dynamic damage effect of surrounding rocks for tunnels by blasting excavation

    Institute of Scientific and Technical Information of China (English)

    左双英; 肖明; 续建科; 史文兵

    2011-01-01

    采用数值模拟技术预估岩体开裂深度及爆破损伤影响范围对工程设计可以起到事先指导作用,对施工安全具有重大意义,其中科学的、合理的损伤模型及迭代计算方法是关键.基于FLAC3D程序的用户自定义本构模块,将考虑累积应变和荷载作用时间的Yang-Liu率相关动力损伤模型与Mohr-Coulomb弹塑性本构进行耦合,将围岩破坏过程中的损伤特性反映在荷载增量迭代计算中,形成了弹塑性动力损伤本构模型,详细推导了损伤应力修正迭代计算方法.对一圆形隧道爆破开挖进行模拟,探讨了爆破诱发的质点振动衰减特征及围岩损伤分布规律.分析结果表明,爆破产生的质点振动速度峰值与其所造成的损伤具有很好的相关性.该爆破损伤模型及模拟方法可以为类似工程提供一定参考.%It can not only play a guiding role in engineering design in advance predicting the cracking depth and damaged range of surrounding rocks by blasting excavation in use of numerical simulation method, but also is of great significance to construction safety; in which, a scientific and reasonable damage model and iterative calculation method are most important key technique. Based on the user-defined constitutive modules of the fast Lagrangian analysis of continua in three dimensions (FLAC3D) procedure, Yang-Liu dynamic damage model dependent on strain rate considering cumulative strain and load time is embedded in Mohr-Coulomb elastoplastic model. The rock damage characteristic is reflected in the iteration calculation process of a incremental load; thus an elastoplastic dynamic damage constitutive model is formed. Subsequently, iterative format of damaged and modified stresses is derived in detail. In simulating a circular tunnel by blasting excavation, a discussion and analysis for characteristics of vibration attenuation and distribution rules of damage in surrounding rock mass induced by blasting are carried

  5. Structural Characteristics and Mechanical Properties of Rock Mass in the Field of Tianwan Nuclear Power Plant, China

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    The structural characteristics and mechanical properties of the rock mass are important parts of the feasibility study on the nuclear power engineering field. In this study, by means of in situ investigation and statistics,the structural plane and joint fissure features of the rock mass were analyzed and discussed at different plots and different depth scopes in the Tianwan Nuclear Power engineering field, the rock mass integrality and its weathered degree were evaluated respectively, and especially, the unfavorable geological phenomena of strongly-weathered cystid existing in the field were studied. According to the results of indoor rock mechanical tests, in combination with drilling, the shallow seismic prospecting, sonic logging and point load tests, the statistical results of physical and mechanical indices of rocks at key plots of the field were analyzed, and the design parameters of the field were calculated. It provided scientific basis for the foundation design of the nuclear power plant.

  6. Virtual multi-dimensional internal bonds model and its application in simulation of rock mass

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    VMIB (virtual multi-dimensional internal bonds) is a multiscale mechanical model developed from the VIB (virtual internal bond) theory. In VIB theory,the solid mate-rial is considered to consist of random-distributed material particles in microscale. These particles are connected with normal bonds. The macro constitutive relation is derived from the cohesive law between particles. However,in VMIB,the micro particles are connected with both normal and shear bonds. The macro constitutive relation is derived in terms of bond stiffness coefficients. It has been theoretically certified that there exists a corresponding relationship between the two bond stiffness coefficients and the two macro material constants,i.e. the Young’s modulus and Poisson ratio. This corresponding relationship suggests that it should be necessary and sufficient to simultaneously account for the normal and shear interactions between particles. Due to the fact that the fracture criterion is directly incorporated into the constitutive relation,both VIB and VMIB present many advantages in simulating fractures of materials. In the damage model of rock mass,a damage tensor is usually defined to describe the distribution of cracks. The damage value in one direction determines the relative stiffness of rock mass in this direction. In VMIB solid,the relative distribution density of micro bonds in one direction determines the relative macro stiffness of the material in this direction. The effects of the damage value and the relative distribution density of bonds are consistent. To simulate the failure behavior of rock mass with VMIB,the presented paper sets up a quantitative relationship between the damage tensor and the rela-tive distribution density of bonds. Comparison of the theoretical and the experi-mental results shows that VMIB model can represent the effect of distributed cracks on rock mass with this relationship. The presented work provides a founda-tion for further simulating fracture

  7. Hydromechanical Rock Mass Fatigue in Deep-Seated Landslides Accompanying Seasonal Variations in Pore Pressures

    Science.gov (United States)

    Preisig, Giona; Eberhardt, Erik; Smithyman, Megan; Preh, Alexander; Bonzanigo, Luca

    2016-06-01

    The episodic movement of deep-seated landslides is often governed by the presence of high pore pressures and reduced effective stresses along active shear surfaces. Pore pressures are subject to cyclic fluctuation under seasonal variations of groundwater recharge, resulting in an intermittent movement characterized by acceleration-deceleration phases. However, it is not always clear why certain acceleration phases reach alarming levels without a clear trigger (i.e., in the absence of an exceptional pore pressure event). This paper presents a conceptual framework linking hydromechanical cycling, progressive failure and fatigue to investigate and explain the episodic behavior of deep-seated landslides using the Campo Vallemaggia landslide in Switzerland as a case study. A combination of monitoring data and advanced numerical modeling is used. The principal processes forcing the slope into a critical disequilibrium state are analyzed as a function of rock mass damage and fatigue. Modeling results suggest that during periods of slope acceleration, the rock slope experiences localized fatigue and gradual weakening through slip along pre-existing natural fractures and yield of critically stressed intact rock bridges. At certain intervals, pockets of critically weakened rock may produce a period of enhanced slope movement in response to a small pore pressure increase similar to those routinely experienced each year. Accordingly, the distribution and connectivity of pre-existing permeable planes of weakness play a central role. These structures are often related to the rock mass's tectonic history or initiate (and dilate) in response to stress changes that disturb the entire slope, such as glacial unloading or seismic loading via large earthquakes. The latter is discussed in detail in a companion paper to this (Gischig et al., Rock Mech Rock Eng, 2015). The results and framework presented further demonstrate that episodic movement and progressive failure of deep

  8. Rock Mass Strength Assessment and Significance to Edifice Stability, Mount Rainier and Mount Hood, Cascade Range Volcanoes

    Science.gov (United States)

    Watters, R. J.; Zimbelman, D. R.; Bowman, S. D.; Crowley, J. K.

    Catastrophic edifice and sector failure occur commonly on stratovolcanoes worldwide and in some cases leave telltale horseshoe-shaped calderas. Many of these failures are now recognised as having resulted from large-scale landsliding. These slides often transform into debris avalanches and lahars that can devastate populations downstream of the volcano. Research on these phenomena has been directed mainly at understanding avalanche mechanics and travel distances and related socioeconomic impacts. Few investigations have examined volcanic avalanche source characteristics. The focus of this paper is to 1) describe a methodology for obtaining rock strengths that control initial failure and 2) report results of rock mass strength testing from Mount Rainier and Mount Hood. Rock mass and shear strength for fresh and hydrothermally altered rocks were obtained by 1) utilizing rock strength and structural information obtained from field studies and 2) applying rock mechanics techniques common in mining and civil engineering to the edifice region. Rock mass and intact rock strength differences greatly in excess of one order of magnitude were obtained when comparing strength behavior of fresh and completely altered volcanic rock. The recognition and determination of marked strength differences existing on the volcano edifice and flank, when combined with detailed geologic mapping, can be used to quantify volcano stability assessment and improve hazard mitigation efforts.

  9. Mass Rock Fall Prediction in Zhezkazgan Mines at the Basis of Seismic Regime Analyzing.

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    @@Zhezkazgan copper deposit is strongly exploited since 1942. Its typical feature is multilevel mineralization. Mine′s thickness of sedimentary rock. Primary copper supply is from 150 to 450meters in depth. Capacity of ore body is 1,5~30 m; suddenly 30 - 60 meters. High capacity parts of deposit is mined oUt by room -pillar system. Stress state of rock mass of the deposit is characterized by that, what horizontal stresses is higher in 4~ 10 times than vertical stresses, which is caused by weight of straining thickness of sedimentary rock and submeridianally oriented. At present over than 50 thousands of pillars is formed as the result of deposit mining. Mined oUt area is divided on separate parts by over than 400 barrier and chain pillars. Spread of primary traderground tunnels exceeds 1200 kilometers, 540kilometers of the spread is operating mines. Tens of any purposes shafts are exploited with general spread of 45 kilometers. Some its decreasing at last time is caused by filling of emptiness by loosened rock as the result of happening falls at mines (Fig. 1).

  10. STRESSES AND DEFORMABILITY OF ROCK MASS UPON OPEN PIT EXPLOITATION OF DIMENSION STONE

    Directory of Open Access Journals (Sweden)

    Siniša Dunda

    2003-12-01

    Full Text Available The appearance of increased stresses and deformability of rock mass in the quarry of Zečevo (exploitation field of Selca – island of Brač has caused a considerable decrease of usability of mineral raw materials, which put into question the survival of the pit. Therefore the research and measurements of the state of stresses and deformability of rock mass within the pit were carried out. Besides detailed laboratory testings (testings on small samples performed were trial in-situ testings on large samples including the corresponding numerical analyses. The exploitation of dimension stone by sowing regularly shaped rectangular blocks has been proved to be appropriate for in-situ testing of bending strength. The paper presents the results of carried out laboratory testings, in-situ testings of bending strength including measuring of deformations after sowing cuts and numerical analyses by which the possible range of horizontal stresses was determined. Since for the case of massive rocks, for which the continuum concept is applied, there are no specifically defined methods of corrections, presented is a possible relation for correction of input size values based on the carried out laboratory and in-situ testings.

  11. Shear Creep Simulation of Structural Plane of Rock Mass Based on Discontinuous Deformation Analysis

    Directory of Open Access Journals (Sweden)

    Guoxin Zhang

    2017-01-01

    Full Text Available Numerical simulations of the creep characteristics of the structural plane of rock mass are very useful. However, most existing simulation methods are based on continuum mechanics and hence are unsuitable in the case of large displacements and deformations. The discontinuous deformation analysis method proposed by Genhua is a discrete one and has a significant advantage when simulating the contacting problem of blocks. In this study, we combined the viscoelastic rheological model of Burgers with the discontinuous deformation analysis (DDA method. We also derived the recurrence formula for the creep deformation increment with the time step during numerical simulations. Based on the minimum potential energy principle, the general equilibrium equation was derived, and the shear creep deformation in the structural plane was considered. A numerical program was also developed and its effectiveness was confirmed based on the curves obtained by the creep test of the structural plane of a rock mass under different stress levels. Finally, the program was used to analyze the mechanism responsible for the creep features of the structural plane in the case of the toppling deformation of the rock slope. The results showed that the extended DDA method is an effective one.

  12. Cranny density parameters and porosity measured by elastic wave method in quasi-isotropic cranny rock masses

    Institute of Scientific and Technical Information of China (English)

    WANG Hong-tu; JIA Jian-qing; LI Xiao-hong; XIAN Xue-fu; HU Guo-zhong

    2006-01-01

    According to the characteristic of elastic waves propagation in medium and the application of elastic waves method in rock mass engineering, the cranny mass with random crannies was regarded as quasi-isotropic cranny mass. In accordance with the rock rupture mechanics, principle of energy balance and Castiglano's theorem, the relationship of effective dynamic parameters of elasticity ((E),(v),(G)) and cranny density parameters or porosity was put forward. On this basis, through the theory of elastic waves propagation in isotropic medium, the relationship between the elastic wave velocity and cranny density parameters and porosity was set up. The theoretical research results show that, in this kind of cranny rock masses, there is nonlinear relationships between the effective dynamic parameters of elasticity and wave velocities and the cranny density parameter or porosity; and with the increase of cranny density parameter or porosity of cranny rock masses, the effective dynamic modulus and the elastic wave velocities of cranny rock masses will decrease; and at the same time, when the cranny density parameter or porosity is very small, the effective dynamic modulus of elasticity and the elastic wave velocities change with the cranny density parameter, which can explain the sensitivity of effective elastic parameters and elastic wave velocities to cranny rock masses.

  13. 不衬砌水工隧洞围岩稳定性数值模拟分析%Numerical simulation analysis for surrounding rock stability of unlined high pressure hydraulic tunnels

    Institute of Scientific and Technical Information of China (English)

    刘新颖; 曹平; 刘涛影; 梅慧浩; 宁果果

    2012-01-01

    Aiming at the phenomena that hyperosmolar role will not only change the stress state of rock and soil, but also cause the rock splitting , destroy the original structure of the rock. Based on the coupled fluid - solid theorem, numerical analysis for the stability of tunnel surrounding rock was done with fast Lagrangian analysis of continua in three - dimension (FLAC3D). Based on the surrounding rock stability considering percolation and the surrounding rock characteristics with the internal water fluid as main research aspects, the stress field and displacement field feature after rock excavation, feedback of excavation on seepage field, evolution trend of failure characteristics and hydraulic characteristics of the tunnel under the role of internal water was achieved. The research results can provide a theoretical basis for corresponding safety measurement in construction process and waterproofing of tunnel in aquifer condition.%针对高渗压作用不仅会改变岩土体的应力状态,同时可能会使岩体劈裂、破坏岩体的原有结构的现象,基于流固耦合分析理论,利用快速拉格朗日有限差分法对隧洞围岩稳定性进行分析.从考虑渗流效应时围岩开挖稳定性、内水作用下围岩力学特性方面开展研究,得到围岩开挖后应力场、位移场分布特征,开挖卸载对渗流场的反馈,内水作用下隧洞的破坏特征和水力特性演变趋势.研究结果表明:对隧洞施工过程中采取安全措施,富水条件下的隧洞工程防排水提供一定的理论参考.

  14. Geochemistry and spatial distribution of late-Paleozoic mafic volcanic rocks in the surrounding areas of the Gonghe Basin: Implications for Majixueshan triple-junction and east Paleotethyan archipelagic ocean

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The late-Paleozoic mafic volcanic rocks occurring in the surrounding areas of the Gonghe basin are distributed in the A'nyêmaqên ophiolite zone, Zongwulong tectonic zone and Kuhai-Saishitang volcanic zone. The mafic volcanics in the A'nyêmaqên zone formed an ancient ridge-centered hotspot around the Majixueshan OIB, the Kuhai-Saishitang mafic rocks consist of E-MORB and continental rift basalts and the Zongwulong volcanic rocks are enriched N-MORB. The regionally low Nb/U and Ce/Pb ratios reflect the influence of the OIB material on the mafic magma source. From geochemistry, spatial distribution and tectonic relationship of the mafic rocks, an ancient triple-junction centered at the Majixueshan can be inferred. The existence of the Kuhai-Saishitang aulacogen may have provided a tectonic channel for the Majixueshan OIB materials metasomatizing the magma source for the Zongwulong rocks. The formation of the triple-junction and the rifting of the Zongwulong zone have separated the orogens and massifs in the region.

  15. Multi-scale characterization of rock mass discontinuities and rock slope geometry using terrestrial remote sensing techniques

    Science.gov (United States)

    Sturzenegger, Matthieu

    Terrestrial remote sensing techniques including both digital photogrammetry and laser scanning, represent useful complements to conventional field mapping and rock mass discontinuity characterization. Several studies have highlighted practical advantages at close-range (design projects has grown substantially over recent years. As these techniques are increasingly applied by geologists and geological engineers, it is important that their use be properly evaluated. Furthermore, guidelines to optimize their application are required in a similar manner to standardization of conventional discontinuity mapping techniques. An important thesis objective is to develop recommendations for optimal applications of terrestrial remote sensing techniques for discontinuity characterization, based on a quantitative evaluation of various registration approaches, sampling bias and extended manual mapping of 3D digital models. It is shown that simple registration networks can provide adequate measurement of discontinuity geometry for engineering purposes. The bias associated with remote sensing mapping is described. The advantages of these techniques over conventional mapping are demonstrated, including reliable discontinuity orientation measurements. Persistence can be precisely quantified instead of approximately estimated, resulting in a new class for extremely persistent discontinuities being suggested. Secondary roughness and curvature can also be considered at larger scales. The techniques are suitable for the definition of discontinuity sets, and the estimation of both trace intensity and block size/shape, if sampling bias is correctly accounted for. A new type of sampling window, suitable for the incorporation of remote sensing data into discrete fracture network models is presented. Another significant thesis objective is the extension of terrestrial digital photogrammetric methods to greater distances (> 1 km), using f = 200-400 mm lenses. This has required a careful

  16. Support loss and Q factor enhancement for a rocking mass microgyroscope.

    Science.gov (United States)

    Wang, Xiong; Xiao, Dingbang; Zhou, Zelong; Wu, Xuezhong; Chen, Zhihua; Li, Shengyi

    2011-01-01

    A rocking mass gyroscope (RMG) is a kind of vibrating mass gyroscope with high sensitivity, whose driving mode and sensing mode are completely uniform. MEMS RMG devices are a research hotspot now because they have the potential to be used in space applications. Support loss is the dominant energy loss mechanism influencing their high sensitivity. An accurate analytical model of support loss for RMGs is presented to enhance their Q factors. The anchor type and support loss mechanism of an RMG are analyzed. Firstly, the support loads, powers flowing into support structure, and vibration energy of an RMG are all developed. Then the analytical model of support loss for the RMG is developed, and its sensitivities to the main structural parameters are also analyzed. High-Q design guidelines for rocking mass microgyroscopes are deduced. Finally, the analytical model is validated by the experimental data and the data from the existing literature. The thicknesses of the prototypes are reduced from 240 μm to 60 μm, while Q factors increase from less than 150 to more than 800. The derived model is general and applicable to various beam resonators, providing significant insight to the design of high-Q MEMS devices.

  17. Support Loss and Q Factor Enhancement for a Rocking Mass Microgyroscope

    Directory of Open Access Journals (Sweden)

    Zhihua Chen

    2011-10-01

    Full Text Available A rocking mass gyroscope (RMG is a kind of vibrating mass gyroscope with high sensitivity, whose driving mode and sensing mode are completely uniform. MEMS RMG devices are a research hotspot now because they have the potential to be used in space applications. Support loss is the dominant energy loss mechanism influencing their high sensitivity. An accurate analytical model of support loss for RMGs is presented to enhance their Q factors. The anchor type and support loss mechanism of an RMG are analyzed. Firstly, the support loads, powers flowing into support structure, and vibration energy of an RMG are all developed. Then the analytical model of support loss for the RMG is developed, and its sensitivities to the main structural parameters are also analyzed. High-Q design guidelines for rocking mass microgyroscopes are deduced. Finally, the analytical model is validated by the experimental data and the data from the existing literature. The thicknesses of the prototypes are reduced from 240 µm to 60 µm, while Q factors increase from less than 150 to more than 800. The derived model is general and applicable to various beam resonators, providing significant insight to the design of high-Q MEMS devices.

  18. 某水工隧洞围岩稳定及支护结构分析%ANALYSIS ON SURROUNDING ROCK STABILITY AND SUPPORTING STRUCTURE OF DIVERSION SPILLWAY TUNNEL

    Institute of Scientific and Technical Information of China (English)

    秦雷; 郭德发; 王庆

    2012-01-01

    隧洞的围岩稳定及支护结构安全是保证隧洞安全、实现隧洞功能的关键因素.由围岩加固圈承担主要的外水压力是优化支护结构设计、保证围岩稳定的一种有效方法.建立肯斯瓦特导流泄洪洞三维有限元模型,并进行非线性有限元分析.分析结果表明,设计的支护措施能明显减少围岩变形、改善应力分布,为类似工程设计提供参考.%The stability of surrounding rock tunnel and the safe of support structure is the key factor to ensure tunnels safe and to achieve tunnel function. It is a optimized design to exert major external water pressure at reinforce circle also it is an effective method for the stability of surrounding rock. The author did the nonlinear finite element analysis by creating three-dimensional finite element model of Kensi-wate diversion spillway tunnel. The results show that the designed support measures can significantly reduce the rock deformation and improve the stress distribution,and it can provide a reference for the design of similar projects.

  19. 围岩松动圈锚注联合支护技术研究与应用%Research and Application of Surrounding Rock Loosen Zone Bolting Grouting United Support Technology

    Institute of Scientific and Technical Information of China (English)

    李飞鹏; 郜建明

    2014-01-01

    为解决赵庄煤业西翼胶带巷极破碎软岩的变形控制技术问题,对西翼胶带巷两帮和底板进行了探地雷达松动圈测试,得出了巷道围岩松动圈范围和破碎情况,基于松动圈测试及分析,提出了由预留变形量让压、初次全锚索网喷支护、深浅孔注浆加固、底角锚注加固组成的锚注联合支护体系,并在西翼胶带巷进行了应用。数值模拟和现场围岩变形监测结果表明,全锚索及深浅孔注浆加固下,巷道围岩强度提高,整体性较好,围岩破坏范围大幅减小,巷道表面变形得到有效控制,能够较好地满足巷道的使用,成功地解决了胶带巷大松动圈极破碎软岩条件下的巷道稳定控制问题。%In order to solve the problem of the deformation control technology in the Zhao Zhuang coal mine west wing belt roadway with bro-ken soft surrounding rock , the GPR loose circle testing was carried on two sides wall and bottom of the roadway surrounding rock and got the loose circle range and broken rock conditions. Based on the analysis of the loose circle testing , a combined support system was proposed with a reserved deformation pressure first, the anchor net spray support, deep-shallow hole grouting reinforcement and bottom anchor grouting re-inforcement, which were applied in the West Wing belt roadway. Deformation monitoring and the numerical simulation results show that under the deep-shallow hole grouting reinforcement, the surrounding rock strength is improved, integrity is better, rock damage range is greatly re-duced, the roadway surface deformation is effectively controlled, which means the scheme can better meet the roadway operating requirement, successfully resolved the conveyor broken roadway stability control problem of soft rock conditions.

  20. Mechanism of Pendulum-type wave phenomenon in deep block rock mass

    Institute of Scientific and Technical Information of China (English)

    WU Hao; FANG Qin; ZHANG Ya-dong; LIU Jin-chun; GONG Zi-ming

    2009-01-01

    Pendulum-type (μ wave) wave is a new type of elastic wave propagated with low frequency and low velocity in deep block rock masses. The μ wave is sharply different from the traditional longitudinal and transverse waves propagated in continuum media and is also a phenomenon of the sign-variable reaction of deep block rock masses to dynamic actions, besides the Anomalous Low Friction (ALF) phenomenon. In order to confirm the existence of the μ wave and study the rule of variation of this μ wave experimentally and theoretically, we first carried out one-dimensional low-speed impact experiments on granite and cement mortar blocks and continuum block models with different characteristic dimensions, based on the multipurpose testing system developed by us independently, The effects of model material and dimensions of models on the propagation properties of 1D stress wave in blocks medium are discussed. Based on a comparison and analysis of the propagation properties (acceleration amplitudes and Fou-rier spectra) of stress wave in these models, we conclude that the fractures in rock mass have considerable effect on the attenuation of the stress wave and retardarce of high frequency waves. We compared our model test data with the data of in-situ measurements from deep mines in Russia and their conclusions. The low-frequency waves occurring in blocks models were validated as Pendu-lum-type wave. The frequencies corresponding to local maxima of spectral density curves of three-directional acceleration satisfied several canonical sequences with the multiple of (√2),most of those frequencies satisfied the quantitative expression(√2)iVP/2△.

  1. Effect Blasting Excavation of Yujiapeng Tunnel on Stability of Nearby Giant Dangerous Rock Masses (DRM)

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    On the basis of the interpretation of engineering geology of the tunnel and of its adjacent dangerous rock masses (DRM), this paper presents the energy and vibration parameters of the explosion that propagates in different blasting modes according to the experimental formulas now usually employed. Then the stability checking computation of T8-T12 area, the most dangerous area of DRM, is conducted under the limited blasting condition and with the limited equilibrium method. The result shows that the effect on the stability is only 5.5 % and that this area also contains certain safety reserves.

  2. Bolt-Grout Interactions in Elastoplastic Rock Mass Using Coupled FEM-FDM Techniques

    Directory of Open Access Journals (Sweden)

    Debasis Deb

    2010-01-01

    Full Text Available Numerical procedure based on finite element method (FEM and finite difference method (FDM for the analysis of bolt-grout interactions are introduced in this paper. The finite element procedure incorporates elasto-plastic concepts with Hoek and Brown yield criterion and has been applied for rock mass. Bolt-grout interactions are evaluated based on finite difference method and are embedded in the elasto-plastic procedures of FEM. The experimental validation of the proposed FEM-FDM procedures and numerical examples of a bolted tunnel are provided to demonstrate the efficacy of the proposed method for practical applications.

  3. Spontaneous rupture of pedunculate gastric gastrointestinal stromal tumor into the gastrocelic ligament presenting as a stalked mass surrounded by loculated hematoma

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Hyun Soo; Ahn, Sung Eun; Park, Seong Jin; Moon, Sung Kyoung; Lim, Joo Won; Lee, Dong Ho; Kim, Yong Ho [Kyung Hee University Medical Center, Kyung Hee University School of Medicine, Seoul (Korea, Republic of)

    2015-04-15

    Gastric gastrointestinal stromal tumor (GIST) is one of the most common mesenchymal tumors of the stomach, which may be asymptomatic or cause symptoms such as pain, gastrointestinal bleeding, and obstruction. Hemoperitoneum due to spontaneous rupture of the tumor is an extremely rare complication. We described a case of a 52-year-old man with a large pedunculated GIST causing loculated hematoma within the gastrocolic ligament. The patient visited our hospital due to a 3 week history of epigastric pain. A computed tomography scan revealed a 10.3 x 7.5 x 9.4 cm sized mass that was growing exophytically from the greater curvature of the stomach and was surrounded by loculated hematoma within the gastrocolic ligament. Laparotomy revealed a large stalked gastric mass surrounded by loculated hematoma within the gastrocolic ligament and blood fluid in the peritoneal cavity. Pathologic examination confirmed a GIST, of the high risk group.

  4. Systematic study of the effects of mass and time scaling techniques applied in numerical rock mechanics simulations

    Science.gov (United States)

    Heinze, Thomas; Jansen, Gunnar; Galvan, Boris; Miller, Stephen A.

    2016-08-01

    Numerical modeling is a well established tool in rock mechanics studies investigating a wide range of problems. Implicit methods for solving linear equations have the advantage of being unconditionally stable, while explicit methods, although limited by the time step, are often used because of their limited memory demand, their scalability in parallel computing, and simple implementation of complex boundary conditions. In numerical modeling of explicit elastoplastic dynamics where the time step is limited by the material density, mass scaling techniques can be used to overcome this limit and significantly reduce computation time. While often used, the effect of mass and time scaling and how it may influence the numerical results is rarely-mentioned in publications, and choosing the right scaling technique is typically performed by trial and error. To our knowledge, no systematic studies have addressed how mass scaling might affect the numerical results. In this paper, we present results from an extensive and systematic study of the influence of mass and time scaling on the behavior of a variety of rock-mechanical models. We employ a finite difference scheme to model uniaxial and biaxial compression experiments using different mass and time scaling factors, and with physical models of increasing complexity up to a cohesion-weakening frictional-strengthening model (CWFS). We also introduce a normalized energy ratio to assist analyzing mass scaling effects. We find the tested models to be less sensitive to time scaling than to mass scaling, so mass scaling has higher potential for decreasing computational costs. However, we also demonstrate that mass scaling may lead to quantitatively wrong results, so care must be taken in interpreting stress values when mass scaling is used in complicated rock mechanics simulations. Mass scaling significantly influences the stress-strain response of numerical rocks because mass scaling acts as an artificial hardening agent on rock

  5. Parameter analysis of anchor bolt support for large-span and jointed rock mass

    Institute of Scientific and Technical Information of China (English)

    LI Xi-bing; ZHOU Zi-long; LI Qi-yue; HU Liu-qing

    2005-01-01

    In order to obtain the optimal parameters of anchor bolt supporting system for large-span and jointed rock mass in Kaiyang Phosphor Mine, it is expensive and unavailable with the method of in-situ experiments. This paper describes a numerical modeling with discrete element method for the supporting effects of different type of anchor bolts. The anchor bolts with variant length of 0.5 m, 0.8 m, 1.0 m, diameter of 10 mm, 15 mm, 20 mm, setting spacing of 3.0 m, 2.5 m, 2.0 m, and setting angle of 10°, 20°, 30°, are simulated respectively. The results show that there exist optimal parameters of anchor bolt support for large-span and jointed rock mass. For the bolt support of the concerning, the optimal length is 2.5-3.5 m, the diameter is 25-35 mm, the spacing is 0.5-0.6 m, and the setting angle is 105°.

  6. Water flow in fractured rock masses: numerical modeling for tunnel inflow assessment

    Science.gov (United States)

    Gattinoni, P.; Scesi, L.; Terrana, S.

    2009-04-01

    Water circulation in rocks represents a very important element to solve many problems linked with civil, environmental and mining engineering. In particular, the interaction of tunnelling with groundwater has become a very relevant problem not only due to the need to safeguard water resources from impoverishment and from the pollution risk, but also to guarantee the safety of workers and to assure the efficiency of the tunnel drainage systems. The evaluation of the hydrogeological risk linked to the underground excavation is very complex, either for the large number of variables involved or for the lack of data available during the planning stage. The study is aimed to quantify the influence of some geo-structural parameters (i.e. discontinuities dip and dip direction) on the tunnel drainage process, comparing the traditional analytical method to the modeling approach, with specific reference to the case of anisotropic rock masses. To forecast the tunnel inflows, a few Authors suggest analytic formulations (Goodman et al., 1965; Knutsson et al., 1996; Ribacchi et al., 2002; Park et al., 2008; Perrochet et al., 2007; Cesano et al., 2003; Hwang et al., 2007), valid for infinite, homogeneous and isotropic aquifer, in which the permeability value is given as a modulus of equivalent hydraulic conductivity Keq. On the contrary, in discontinuous rock masses the water flow is strongly controlled by joints orientation, by their hydraulic characteristics and by rocks fracturing conditions. The analytic equations found in the technical literature could be very useful, but often they don't reflect the real phenomena of the tunnel inflow in rock masses. Actually, these equations are based on the hypothesis of homogeneous aquifer, and then they don't give good agreement for an heterogeneous fractured medium. In this latter case, the numerical modelling could provide the best results, but only with a detailed conceptual model of the water circulation, high costs and long

  7. Effect of rock mass structure and block size on the slope stability--Physical modeling and discrete element simulation

    Institute of Scientific and Technical Information of China (English)

    LI; Shihai; LIAN; Zhenzhong; J.; G.; Wang

    2005-01-01

    This paper studies the stability of jointed rock slopes by using our improved three-dimensional discrete element methods (DEM) and physical modeling. Results show that the DEM can simulate all failure modes of rock slopes with different joint configurations. The stress in each rock block is not homogeneous and blocks rotate in failure development. Failure modes depend on the configuration of joints. Toppling failure is observed for the slope with straight joints and sliding failure is observed for the slope with staged joints. The DEM results are also compared with those of limit equilibrium method (LEM). Without considering the joints in rock masses, the LEM predicts much higher factor of safety than physical modeling and DEM. The failure mode and factor of safety predicted by the DEM are in good agreement with laboratory tests for any jointed rock slope.

  8. Estimation of fluid flow and mass transport properties in a natural fracture using laboratory testing system on mass transport in fractured rock (LABROCK)

    Energy Technology Data Exchange (ETDEWEB)

    Yoshino, Naoto; Uchida, Masahiro [Japan Nuclear Cycle Development Inst., Tokai Works, Tokai, Ibaraki (Japan); Satou, Hisashi [Inspection Development Company Ltd., Tokai, Ibaraki (Japan)

    2003-03-01

    The understanding of mass transport and fluid flow properties in natural rock fractures is important for safety assessment of geological disposal of high level nuclear waste. The authors developed advanced tracer test equipment in which a 50-cm cubic scale rock sample was feasible. The mass transport and fluid flow properties in a single fracture were also examined. The relation among hydraulic, transport and mass balance apertures of a natural single fracture were obtained. Heterogeneity of the aperture distribution was evident, as was the possibility of some major flow line perpendicular to the flow direction. Additionally, the relation between normal stress and each aperture was also obtained by loading normal stress on the fracture. In future, measuring the aperture distribution and establishing the model considering fluid flow and mass transport properties in natural rock fractures will be conducted. (author)

  9. Inflatable rock bolt bond strength versus rock mass rating (RMR):A comparative analysis of pull-out testing data from underground mines in Nevada

    Institute of Scientific and Technical Information of China (English)

    Barnard Chase; Kallu Raj R.; Warren Sean; Thareja Rahul

    2016-01-01

    The purpose of this paper is to establish confidence in anticipated minimum bond strength for inflatable rock bolts by comparing the bond strength to variable geotechnical conditions using the rock mass rating (RMR) system. To investigate a correlation between these parameters, the minimum bond strength of pull-out tested inflatable rock bolts was compared to the RMR of the rock in which these bolts were placed. Bond strength vs. RMR plots indicate that expected minimum bond strength is positively corre-lated with RMR;however, the correlation is not strong. Cumulative percent graphs indicate that 97%of pull-out tests result in a minimum bond strength of 3.3 and 1.7 ton/m in RMR P 45 and<45, respectively. Although lower bond strengths are more commonly encountered in low RMR ground, high bond strengths are possible as well, yielding higher variability in bond strengths in low RMR ground. Bond strength of friction bolts relies on contact between the rock bolt and drill hole. Experience in Nevada indicates that RMR is known to affect both the quality and consistency of drill holes which likely affects bond strength. Drilling and bolting in low RMR ground is more sensitive to drilling and bolting practices, and strategies for maximizing bond strength in these conditions are discussed.

  10. Mass wasting process at the surface of the Sangun metamorphic rocks in Kaminishigawa area, Asahi-machi, Okayama Prefecture.

    OpenAIRE

    新宮原, 秀和; 平山, 恭之; 津島, 淳; 於保, 幸正

    1999-01-01

    The relation among microstructures, weathering and mass wasting of the Sangun metamorphic rocks in the Kaminishigawa area, Asahi-machi, Okayama Prefecture, was studied. Three stages of penetrative planar structures are recognized; S1 schistosity, S2 crenulation cleavage and S3 crenulation cleavage. The S2 cleavage is the most commonly observed structure. The deree of weathering is divided into two classes on the base of appearance; slightly weathered and highly weathered rock. The three types...

  11. Development of Helium-Mass-Spectrometry-Permeameter for the Measurement of Permeability of Near-Impermeable Rock

    Science.gov (United States)

    Lee, Moo Y.; Bauer, Stephen J.

    2016-12-01

    A helium leakage detection system was modified to measure gas permeability on extracted cores of nearly impermeable rock. The Helium-Mass-Spectrometry-Permeameter (HMSP) is duplicating the classic Darcy's experiment with a constant pressure differential and steady-state flow through a sample using helium gas. Under triaxial stress condition, the newly developed HMSP can measure hydraulic permeability of rocks and geomaterials down to the nanoDarcy scale (10-21 m2). The extension of measuring the lower end of the permeability scale may help answer important questions regarding the permeability of rock at great depth where fractures may close completely under high lithostatic stress.

  12. Evaluation of models for estimating changes in fracture permeability due to thermo-mechanical stresses in host rock surrounding a potential repository

    Energy Technology Data Exchange (ETDEWEB)

    Berge, P A; Blair, S C; Shaffer, R J; Wang, H F

    1997-02-18

    We provide in this report a methodology to estimate bounds on the changes in fracture permeability due to thermal-mechanical processes associated with excavation of drifts and emplacement of waste. This report is the first milestone associated with Task A of the LLNL initiative to evaluate available methods for estimating chamges in fracture permeability surrounding drifts in the Exploratory Studies Facility (ESF) and the potential repository at Yucca Mountain in response to (1) construction-induced stress changes and (2) subsequent thermal pulse effects due to waste emplacement. These results are needed for modeling changes in repository-level moisture movement and seepage.

  13. Determination of Stability and Reinforcement Range of Horse-head under Condition of Weak Surrounding Rock%软弱围岩条件下马头门稳定性及加固范围确定

    Institute of Scientific and Technical Information of China (English)

    张兆军

    2012-01-01

    以国内某大型矿井副井马头门的高埋深、高应力、高破碎、大断面等复杂条件为工程背景,采用理论分析,研究了马头门附近围岩破坏区分布规律及应力场分布规律,并通过建立三维立体数值计算模型予以验证。据此确定了马头门围岩的不稳定区域,提出了支护建议。%Taking complex conditions of auxiliary shaft horse-head of high burial depth, high stress, high crushing and large section, the author researched distribution law of breakdown area of surrounding rock and stress field by using theoretical analysis. Through verification of building three-dimensional numeric calculation model, the author determined unstable area of surrounding rock of horse-head, and put forward suggestions of support.

  14. Research on The Surrounding Rock Deformation Law of Carbon Shale Small Interval Tunnel%炭质页岩小净距隧道围岩变形规律研究

    Institute of Scientific and Technical Information of China (English)

    段宝福; 翁现合

    2012-01-01

    以湖北宴家隧道工程为例,结合现场施工监测,采用有限元程序对节理围岩隧道施工进行模拟,对节理围岩隧道的开挖对地层扰动的范围进行定量确定.对小间距双线隧道在炭质页岩条件下节理面上游隧道先行施工进行数值模拟,将实测数据与数值模拟进行对比,总结出炭质页岩小间距隧道左右洞有施工差别时围岩变形规律.%Taking the Hubei Yanjia tunnel project as an example, the construction of jointed surrounding rock tunnels was simulated using finite element software and the range of disturbance caused by the excavation was quantatively determined. Numerical simulations were also performed for the upper tunnel under carbonaceous shale in small interval tunnel and simulation results were compared against site measurement.Conclusions were drawn regarding the principles of tunnel surrounding rock deformation when the two holes are constructed differently.

  15. Stability Analysis on Recovery Goaf Surrounding Rock of the Pillar-9 in Dongshengmiao Mine%东升庙矿9号矿柱回收采空区围岩稳定性分析

    Institute of Scientific and Technical Information of China (English)

    张飞; 王滨; 菅玉荣; 刘文刚; 冀杰

    2012-01-01

    This topic is based on the project of Pillar recovery and goaf processing at Dongshengmiao mine#2 and #11 ore deposit, with the purpose that in the goaf processing field to form a relatively perfect key technical model for empty area processing, by means of the treatment of goaf and the indoor test, using the new version of FLAC3D 4. 0 numerical simulation software to simulate and analyse the stability of surrounding rock after goaf processing, combined with the natural equilibrium arch theory to forecast scope of the surrounding rock of goaf which may inbreak, so as to effectively control groud pressure and to prevent the roof rock burst which may cause a major accident. We mainly study the Pillar-9 recovery process at above the midpiece of 900 m, in Pillar-9 recovery process, the major damage form of the surrounding rocks of the goafs upper plate was plastic damage due to that the tensile stress and shear stress exceeded the yield limit, the plastic damage area was mainly distributed in the surrounding areas of the plate under angle, footwall upper corner of surrounding rock and in the Pillar-32 position within the area of the strata.%以东升庙矿2#和11#矿床矿柱回收及空区处理项目为基石展开,目的是想在空区处理研究领域形成一套相对完善的空区处理关键性技术模式,通过开展东矿现场和室内试验研究,采用FLAC3D 4.0新版本数值模拟软件对空区围岩稳定性进行模拟分析,结合极限自然平衡拱理论对空区围岩可能冒落的范围进行预测,以便有效地控制地压,预防空区顶板围岩突然冒落造成矿山重大安全事故.我们对900 m中段以上9号矿柱回收过程进行了详尽的模拟研究,在9号矿柱回收过程中,空区上盘围岩的主要破坏形式主要为拉应力及剪应力超过屈服极限引发的塑性破坏,塑性破坏区域主要分布在空区上、下盘围岩隅角及32号矿柱上覆岩层内的部分区域.

  16. Study of dynamic damage of surrounding rocks for tunnels under high in-situ stress%高地应力下隧道围岩动力损伤分析

    Institute of Scientific and Technical Information of China (English)

    杨栋; 李海波; 夏祥; 罗超文; 李卫兵

    2013-01-01

    为预估和控制爆破荷载作用下围岩损伤范围,在赣龙铁路梅花山隧道工程现场进行岩体声波测试,得到围岩的损伤范围。根据爆破荷载作用下岩体损伤发展规律,采用基于概率形式的损伤变量定义,运用三维有限差分软件对不同地应力状态下爆破产生的围岩损伤范围进行数值模拟,并与现场岩体声波测试结果进行比较。计算结果表明,数值计算与实测结果有较好的一致性,随着地应力大小增大,围岩损伤范围呈现先减小后增大的趋势,且增大幅度较大,地应力较高时,局部部位如顶板、底板损伤更为明显,说明地应力大小对围岩损伤分布有着显著影响;随着侧压力系数增大,损伤范围先减小后增大,但增速逐渐减小。所得到的结论可为高地应力下隧道稳定性分析和支护设计提供依据。%In order to forecast and control the damage zone of surrounding rock under blasting load, sound wave tests have been conducted in the construction site of Meihuashan Tunnel in Jiangxi province dragon railway. Based on the change rate of sound wave speed, damage zone size of surrounding rock are obtained. On this basis, a statistics-based damage variable of rockmass has been proposed based on micromechanics. Damage zone size of surrounding rock under blasting load at different in-situ stresses is thus studied by using three-dimensional finite difference software. Calculations show that the numerical simulation results agree well with the site monitoring results. With the in-situ stress increasing, the size of damage zone decreases first, then increases, and increases by a large margin;when the in-situ stress is high, local parts such as tunnel roof, floor damage is more obvious; it is shown that the in-situ stress has significant impact on surrounding rock damage distribution. With the lateral pressure coefficient increasing, the size of damage zone decreases first

  17. Natural radioactivity levels in soils, rocks and water at a mining concession of Perseus gold mine and surrounding towns in Central Region of Ghana.

    Science.gov (United States)

    Faanu, A; Adukpo, O K; Tettey-Larbi, L; Lawluvi, H; Kpeglo, D O; Darko, E O; Emi-Reynolds, G; Awudu, R A; Kansaana, C; Amoah, P A; Efa, A O; Ibrahim, A D; Agyeman, B; Kpodzro, R; Agyeman, L

    2016-01-01

    Levels of naturally occurring radioactive materials prior to processing of gold ore within and around the new eastern concession area of Perseus Mining (Ghana) Limited were carried out to ascertain the baseline radioactivity levels. The study was based on situ measurements of external gamma dose rate at 1 m above ground level as well as laboratory analysis by direct gamma spectrometry to quantify the radionuclides of interest namely; (238)U, (232)Th and (40)K in soil, rock, ore samples and gross alpha/beta analysis in water samples. The average absorbed dose rate in air at 1 m above sampling point using a radiation survey metre was determined to be 0.08 ± 0.02 μGyh(-1) with a corresponding average annual effective dose calculated to be 0.093 ± 0.028 mSv. The average activity concentrations of (238)U, (232)Th, and (40)K in the soil, rock, and ore samples were 65.1 ± 2.2, 71.8 ± 2.2 and 1168.3 Bqkg(-1) respectively resulting in an average annual effective dose of 0.91 ± 0.32 mSv. The average Radium equivalent activity value was 257.8 ± 62.4 Bqkg(-1) in the range of 136.6-340.2 Bqkg(-1). The average values of external and internal indices were 0.7 ± 0.2 and 0.9 ± 0.2 respectively. The average gross alpha and gross beta activity concentrations in the water samples were determined to be 0.0032 ± 0.0024 and 0.0338 ± 0.0083 Bql(-1) respectively. The total annual effective dose from the pathways considered for this study (gamma ray from the soil, rock and ore samples as well as doses determined from the gross alpha/beta activity concentration in water samples) was calculated to be 0.918 mSv. The results obtained in this study shows that the radiation levels are within the natural background radiation levels found in literature and compare well with similar studies for other countries and the total annual effective dose is below the ICRP recommended level of 1 mSv for public exposure control.

  18. Engineering rock mechanics practices in the underground powerhouse at Jinping I hydropower station

    Directory of Open Access Journals (Sweden)

    Aiqing Wu

    2016-10-01

    Full Text Available Based on the analyses of data obtained from the underground powerhouse at Jinping I hydropower station, a comprehensive review of engineering rock mechanics practice in the underground powerhouse is first conducted. The distribution of strata, lithology, and initial geo-stress, the excavation process and corresponding rock mass support measures, the deformation and failure characteristics of the surrounding rock mass, the stress characteristics of anchorage structures in the cavern complex, and numerical simulations of surrounding rock mass stability and anchor support performance are presented. The results indicate that the underground powerhouse of Jinping I hydropower station is characterized by high to extremely high geo-stresses during rock excavation. Excessive surrounding rock mass deformation and high stress of anchorage structures, surrounding rock mass unloading damage, and local cracking failure of surrounding rock masses, etc., are mainly caused by rock mass excavation. Deformations of surrounding rock masses and stresses in anchorage structures here are larger than those found elsewhere: 20% of extensometers in the main powerhouse record more than 50 mm with the maximum at around 250 mm observed in the downstream sidewall of the transformer hall. There are about 25% of the anchor bolts having recorded stresses of more than 200 MPa. Jinping I hydropower plant is the first to have an underground powerhouse construction conducted in host rocks under extremely high geo-stress conditions, with the ratio of rock mass strength to geo-stress of less than 2.0. The results can provide a reference to underground powerhouse construction in similar geological conditions.

  19. 考虑围岩蠕变特性的轴对称有限元非线性分析%The nonlinear axisymmetric finite element method for anlaysis of surrounding rock in consideration of creeping

    Institute of Scientific and Technical Information of China (English)

    杜丽惠; 黄丽清

    2001-01-01

    本文采用轴对称非线性有限元方法分析竖洞开挖与混凝土的衬砌施工过程中围岩的应力应变,计算中引入破坏接近度的概念以判定材料的非线性及其破坏问题,分析了围岩的软化及其破坏形态,并进行了实际竖洞的蠕变分析.%In this paper, the nonlinear axisymmetric finite element method is adopted to analyze the stree-strain of surrounding rock of vertical tunnel in the process of excavation and lining. The failure approach concept is introduced in the discrimination of the non-linearity and failure of the rock. The softening of the rock and the types of failure are simulated and the creeping of the tunnel is analyzed.

  20. Probing the cosmic ray mass composition in the knee region through TeV secondary particle fluxes from solar surroundings

    Science.gov (United States)

    Banik, Prabir; Bijay, Biplab; Sarkar, Samir K.; Bhadra, Arunava

    2017-03-01

    The possibility of estimating the mass composition of primary cosmic rays above the knee of their energy spectrum through the study of high-energy gamma rays, muons, and neutrinos produced in the interactions of cosmic rays with solar ambient matter and radiation is explored. It is found that the theoretical fluxes of TeV gamma rays, muons, and neutrinos from a region around 15° of the Sun are sensitive to a mass composition of cosmic rays in the PeV energy range. The experimental prospects for the detection of such TeV gamma rays/neutrinos by future experiments are discussed.

  1. Use of an Integrated Discrete Fracture Network Code for Stochastic Stability Analyses of Fractured Rock Masses

    Science.gov (United States)

    Merrien-Soukatchoff, V.; Korini, T.; Thoraval, A.

    2012-03-01

    The paper presents the Discrete Fracture Network code RESOBLOK, which couples geometrical block system construction and a quick iterative stability analysis in the same package. The deterministic or stochastic geometry of a fractured rock mass can be represented and interactively displayed in 3D using two different fracture generators: one mainly used for hydraulic purposes and another designed to allow block stability evaluation. RESOBLOK has downstream modules that can quickly compute stability (based on limit equilibrium or energy-based analysis), display geometric information and create links to other discrete software. The advantage of the code is that it couples stochastic geometrical representation and a quick iterative stability analysis to allow risk-analysis with or without reinforcement and, for the worst cases, more accurate analysis using stress-strain analysis computer codes. These different aspects are detailed for embankment and underground works.

  2. Self-oscillation acoustic system destined to measurement of stresses in mass rocks

    CERN Document Server

    Kwasniewski, Janusz; Dominik, Ireneusz; Dorobczynski, Lech

    2011-01-01

    The paper presents an electronic self-oscillation acoustic system (SAS) destined to measure of stresses variations in the elastic media. The system consists of piezoelectric detector, amplifier-limiter, pass-band filter, piezoelectric exciter and the frequency meter. The mass rock plays a role of delaying element, in which variations in stresses causing the variations of acoustic wave velocity of propagation, and successive variation in frequency of oscillations generated by system. The laboratory test permitted to estimate variations in frequency caused by variations in stresses of elastic medium. The principles of selection of frequency and other parameters of the electronic system in application to stresses measurement in condition of the mine were presented.

  3. Collaborative Research: failure of RockMasses from Nucleation and Growth of Microscopic Defects and Disorder

    Energy Technology Data Exchange (ETDEWEB)

    Klein, William [Boston Univ., MA (United States)

    2016-09-12

    Over the 21 years of funding we have pursued several projects related to earthquakes, damage and nucleation. We developed simple models of earthquake faults which we studied to understand Gutenburg-Richter scaling, foreshocks and aftershocks, the effect of spatial structure of the faults and its interaction with underlying self organization and phase transitions. In addition we studied the formation of amorphous solids via the glass transition. We have also studied nucleation with a particular concentration on transitions in systems with a spatial symmetry change. In addition we investigated the nucleation process in models that mimic rock masses. We obtained the structure of the droplet in both homogeneous and heterogeneous nucleation. We also investigated the effect of defects or asperities on the nucleation of failure in simple models of earthquake faults.

  4. Strength properties of the jointed rock mass medium under dynamic cyclic loading *

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The dynamic strength properties of the intermittently jointed mediums are studied using model test to investigate the jointed rock mass behavior under dynamic cyclic load. The model test results demonstrate that (i) the dynamic strength of the jointed samples increases with the loading frequency and decreases with the loading loops; (ii) the dynamic residual strength will not be zero like the static residual strength under one-axle loading condition; (iii) the dynamic strength changes greatly with the joint density and joint angle, and it differs from that of the static strength which reaches the lowest at an angle of 45° + ψ/2, while in the dynamic case, the lowest strength is at the angle of 45°.

  5. Example Building Damage Caused by Mining Exploitation in Disturbed Rock Mass

    Science.gov (United States)

    Florkowska, Lucyna

    2013-06-01

    Issues concerning protection of buildings against the impact of underground coal mining pose significant scientific and engineering challenges. In Poland, where mining is a potent and prominent industry assuring domestic energy security, regions within reach of mining influences are plenty. Moreover, due to their industrial character they are also densely built-up areas. Because minerals have been extracted on an industrial scale in majority of those areas for many years, the rock mass structure has been significantly disturbed. Hence, exploitation of successive layers of multi-seam deposits might cause considerable damage - both in terms of surface and existing infrastructure networks. In the light of those facts, the means of mining and building prevention have to be improved on a regular basis. Moreover, they have to be underpinned by reliable analyses holistically capturing the comprehensive picture of the mining, geotechnical and constructional situation of structures. Scientific research conducted based on observations and measurements of mining-induced strain in buildings is deployed to do just that. Presented in this paper examples of damage sustained by buildings armed with protection against mining influences give an account of impact the mining exploitation in disturbed rock mass can have. This paper is based on analyses of mining damage to church and Nursing Home owned by Evangelical Augsburg Parish in Bytom-Miechowice. Neighbouring buildings differ in the date they were built, construction, building technology, geometry of the building body and fitted protection against mining damage. Both the buildings, however, have sustained lately significant deformation and damage caused by repeated mining exploitation. Selected damage has been discussed hereunder. The structures have been characterised, their current situation and mining history have been outlined, which have taken their toll on character and magnitude of damage. Description has been supplemented

  6. A convection-conduction model for analysis of the freeze-thaw conditions in the surrounding rock wall of a tunnel in permafrost regions

    Institute of Scientific and Technical Information of China (English)

    何春雄; 吴紫汪; 朱林楠

    1999-01-01

    Based on the analyses of fundamental meteorological and hydrogeological conditions at the site of a tunnel in the cold regions, a combined convection-conduction model for air flow in the tunnel and temperature field in the surrounding has been constructed. Using the model, the air temperature distribution in the Xiluoqi No. 2 Tunnel has been simulated numerically. The simulated results are in agreement with the data observed. Then, based on the in situ conditions of air temperature, atmospheric pressure, wind force, hydrogeology and engineering geology, the air-temperature relationship between the temperature on the surface of the tunnel wall and the air temperature at the entry and exit of the tunnel has been obtained, and the freeze-thaw conditions at the Dabanshan Tunnel which is now under construction is predicted.

  7. The North Water Polynya and Velocity, Calving Front and Mass Change in Surrounding Glaciers in Greenland and Canada Over the Last 30 Years

    Science.gov (United States)

    Edwards, L.

    2015-12-01

    Major uncertainties surround future estimates of sea level rise attributable to mass loss from Greenland and the surrounding ice caps in Canada. Understanding changes across these regions is vital as their glaciers have experienced dramatic changes in recent times. Attention has focused on the periphery of these regions where land ice meets the ocean and where ice acceleration, thinning and increased calving have been observed. Polynyas are areas of open water within sea ice which remain unfrozen for much of the year. They vary significantly in size (~3 km2 to > ~85,000 km2 in the Arctic), recurrence rates and duration. Despite their relatively small size, polynyas strongly impact regional oceanography and play a vital role in heat and moisture exchange between the polar oceans and atmosphere. Where polynyas are present adjacent to tidewater glaciers their influence on ocean circulation and water temperatures has the potential to play a major part in controlling subsurface ice melt rates by impacting on the water masses reaching the calving front. They also have the potential to influence air masses reaching nearby glaciers and ice caps by creating a maritime climate which may impact on the glaciers' accumulation and surface melt and hence their thickness and mass balance. Polynya presence and size also have implications for sea ice extent and therefore may influence the buttressing effect on neighbouring tidewater glaciers. The work presented uses remote sensing and mass balance model data to study changes in the North Water polynya (extent, ice concentration, duration) and neighbouring glaciers and ice caps (velocities, calving front positions and mass balance) in Canada and Greenland over a period of approximately 30 years from the mid-1980s through to 2015.

  8. 强采动下近距离硐室群围岩应力演化及加固对策%Stress Development and Reinforcement Countermeasure of Surrounding Rock of Close-distance Caverns Influenced by Strong Mining

    Institute of Scientific and Technical Information of China (English)

    姜鹏飞; 郭相平

    2014-01-01

    Stress development rule of close-distance caverns influenced by 2322 face's strong mining was researched with FLAC3D , and the mechanism of grouting reinforcement for close-distance caverns was researched by applying UDEC software. Corresponding reinforce-ment countermeasure was put forward. Results showed that after close-distance caverns including water sumps and substation were exca-vated, superimposition effect of vertical stress of surrounding rock between caverns was more obvious than that of horizontal stress, but horizontal stress concentration degree was larger. Mining of 2322 face result into abutment pressure of coal-pillar moving to floor. Influenced by high stress superimposition of coal and floor, strong floor heave occurred in caverns. Under the condition of the same grouting pressure and ratio of water-to-ash, slurry diffusion radius along tangential direction of hole was larger than that along radial di-rection. Bearing capacity of caverns' shallow surrounding rock largely increased by reinforcing with grouting anchored-cable. High mining stress was transferred from deep to shallow location, which prevented further failure of deep rock. Underground test showed that after ap-plying grouting anchored-cable, surrounding rock of every cavern could keep stability and deformation of surrounding rock of close-dis-tance caverns influenced by strong mining was effectively controlled.%以成庄煤矿井下甲、乙水仓及变电所等近距离硐室群为背景,采用FLAC3D 有限差分程序计算分析了2322工作面强采动下近距离硐室群围岩应力演化规律,采用UDEC离散元软件研究了近距离硐室群注浆加固机理,并提出了相应的加固对策。研究结果表明:成庄煤矿甲、乙水仓及变电所等近距离硐室群开挖后,围岩间垂直应力叠加效应较水平应力更为明显,但水平应力集中程度更高;2322工作面回采引起煤柱支承压力向底板传递,受煤柱高应力与底

  9. Salinity minima, water masses and surface circulation in the Eastern Tropical Pacific off Mexico and surrounding areas

    Science.gov (United States)

    Portela, Esther; Beier, Emilio; Godínez, Victor; Castro, Rubén; Desmond Barton, Eric

    2016-04-01

    The seasonal variations of the water masses and their interactions are analyzed in the Tropical Pacific off Mexico (TPOM) and four contiguous areas of on the basis of new extensive hydrographic database. The regional water masses intervals are redefined in terms of Absolute Salinity (SA) in g kg-1 and Conservative Temperature (Θ) according to TEOS - 10. The California Current System Water (CCSW) mass is introduced as an improved description of the former California Current Water (CCW) together with the Subarctic Water (SAW) to describe better the characteristics of the components of the California Current System. Hydrographic data, Precipitation-Evaporation balance and geostrophic currents were used to investigate the origin and seasonality of two salinity minima in the area. The shallow salinity minimum of around 33.5 g kg-1 originated in the California Current System and became saltier but less dense water as it traveled to the southeast. It can be identified as a mixture of CCSW and tropical waters. The surface salinity minimum of 32 - 33 g kg-1 was seen as a sharp surface feature in the TPOM from August to November. It was produced by the arrival of tropical waters from the south in combination with the net precipitation in the area during these months. This result provides new evidence of the presence of the poleward-flowing Mexican Coastal Current and, for the first time, of its seasonal pattern of variation.

  10. Mass Transport Modelling in low permeability Fractured Rock: Eulerian versus Lagrangian approaches.

    Science.gov (United States)

    Capilla, J. E.; Rodrigo, J.; Llopis, C.; Grisales, C.; Gomez-Hernandez, J. J.

    2003-04-01

    Modeling flow and mass transport in fractured rocks can not be always successfully addressed by means of discrete fracture models which can fail due to the difficulty to be calibrated to experimental measurements. This is due to the need of having an accurate knowledge of fractures geometry and of the bidimensional distribution of hydrodynamic parameters on them. Besides, these models tend to be too rigid in the sense of not being able to re-adapt themselves correcting deficiencies or errors in the fracture definition. An alternative approach is assuming a pseudo-continuum media in which fractures are represented by the introduction of discretization blocks of very high hydraulic conductivity (K). This kind of model has been successfully tested in some real cases where the stochastic inversion of the flow equation has been performed to obtain equally likely K fields. However, in this framework, Eulerian mass transport modeling yields numerical dispersion and oscillations that make very difficult the analysis of tracer tests and the inversion of concentration data to identify K fields. In this contribution we present flow and mass transport modelling results in a fractured medium approached by a pseudo-continuum. The case study considered is based on data from a low permeability formation and both Eulerian and Lagrangian approaches have been applied. K fields in fractures are modeled as realizations of a stochastic process conditional to piezometric head data. Both a MultiGaussian and a non-multiGaussian approches are evaluated. The final goal of this research is obtaining K fields able to reproduce field tracer tests. Results show the important numerical problems found when applying an Eurelian approach and the possibilities of avoiding them with a 3D implementation of the Lagrangian random walk method. Besides, we see how different can be mass transport predictions when Gaussian and non-Gaussian models are assumed for K fields in fractures.

  11. Stability and Control Technology of Surrounding Rock under Permanent Coal Pillar%永久煤柱下巷道围岩稳定性及控制技术分析

    Institute of Scientific and Technical Information of China (English)

    孙明磊; 李佳丽

    2016-01-01

    Broken influence elements and mechanism of special return air entry of Daihe coal mine were analyzed, which included supporting pressure of coal pillar, surrounding rock strength and supporting way. Detailed numerical modeling of FLAC2D was conducted to evaluate surrounding rock stress distribution that influence by horizontal distance of roadway to coal pillar edge and supporting way. These papers studied the characters of roadway moment distribution and surrounding rock displacement that influenced by three different supporting way, which included U style steel supporting, grouting reinforcement and compensate supporting with cable, put forward grouting and compensate supporting with cable should be used on the basis of U style steel supporting in roadway under the per-manent coal pillar, then stability supporting body would formed, and roadway deformation could be controlled effectively.%以岱河煤矿Ⅳ1专用回风巷变形破坏为研究对象,从煤柱支承压力、围岩强度、现有支护措施3个方面分析了其破坏影响因素和机理,通过建立FLAC2D 模拟模型明确了巷道与煤柱边缘水平距离、巷道支护方式对围岩应力分布的影响。研究了U型钢、注浆及锚索结构补偿支护3种作用下的巷道弯矩分布、围岩位移等特点,提出了永久煤柱下的巷道在U型钢基础上应进行注浆加固,再用锚索进行针对性支护结构补偿,形成稳定的共同承载体,有效地控制巷道变形。

  12. 黄土连拱隧道动态施工围岩损伤局部化研究%Study of damage localization of loess multi-arch tunnel's surrounding rock under dynamic construction

    Institute of Scientific and Technical Information of China (English)

    钟祖良; 刘新荣; 刘元雪; 李鹏; 王吉明

    2012-01-01

    In order to study the damage distribution of tunnel's surrounding rock, firstly, an elastoplastic damage constitutive model of Q2 loess is deduced based on triaxial shear tests and compiled as a user-defined damage model( UDM ) of FLAC3D. Then the conception of surrounding rock damage degree (SRDD) is put forward and compiled into a post-processing module. Based on the first loess multi-arch tunnel of road-Lishi tunnel, the damage position of tunnel's surrounding rock of two construction schemes is numerically simulated. The research results show that the SRDD and damage localization rules can be simulated well at every excavation step; and it also provides reference for the optimization of tunnel construction scheme. The research results provide a new method for the optimization of tunnel construction scheme and choice of construction scheme.%为了研究黄土连拱隧道动态施工时围岩的损伤情况和损伤分布规律,在室内试验的基础上推导了Q2黄土的弹塑性损伤本构模型,并基于FLAC3D平台编制了自定义本构模型,提出了损伤度概念并编制了损伤度后处理模块.以国内首条高速公路黄土连拱隧道-离石隧道为依托工程,对两种开挖方案施工时围岩损伤情况进行数值分析.研究表明,该成果可以较好地掌握隧道每一开挖步后围岩损伤度的分布情况和损伤区的演化规律,为施工方案优化选择提供依据.该研究成果为地下工程支护参数优化和方案的选择开辟了一个新的方向.

  13. Displacement Monitoring and Analysis Platform for Highway Tunnel Surrounding Rock Based on Internet Technology%基于互联网技术的公路隧道围岩常规位移监测分析平台

    Institute of Scientific and Technical Information of China (English)

    姜锡宸; 孟陆波; 李天斌; 刘家民

    2015-01-01

    Informationization of tunnel construction management is a trend nowadays.A displacement monitoring and analysis platform for highway tunnel surrounding rocks based on internet technology is developed by using PHP (Personal Home Page)programming language and in conjunction with Mysql data storage function and analysis principles of the least square method and regression model,so as to meet the informationization requirement of highway tunnel monitoring.By using the mentioned platform,the recording and regression analysis of the monitoring data of the highway tunnel,the assessment of the stability of the surrounding rock and the estimation of the final displacement of the surrounding rock and the secondary lining time can be realized.Furthermore,by using the mentioned platform,the technical staffs that are not at the site can obtain the monitoring data and analysis results of the tunnel so that they can make timely adjustment on the lining structure.%信息化是当前隧道施工管理的必然趋势,针对公路隧道监控量测信息化建设要求,采用 PHP 编程语言,结合 Mysql 的数据存储功能、最小二乘法及回归模型的分析原理,研发基于互联网技术的公路隧道围岩常规位移监测分析平台。该平台实现了在网络上对公路隧道监测断面数据的录入存储、回归分析、围岩稳定性判别及隧道围岩最终位移变形量与二次衬砌时间预估等功能。通过网络访问该平台,可使不在现场的参建人员及时掌握隧道监测数据及分析结果,可为支护结构的调整和变更提供更有效率的依据,进而提高公路隧道的管理效率。

  14. The Attenuation Law of Vibrations in Highway Tunnel Surrounding Rocks Caused by Smooth Blasting%公路隧道光面爆破围岩振动衰减规律

    Institute of Scientific and Technical Information of China (English)

    陆瑜; 李超

    2014-01-01

    为了获得隧道围岩在爆破荷载作用下的振动效应,运用有限元软件 ADINA 建立隧道计算模型,通过加载简化的三角形等效爆破荷载,模拟了青山隧道Ⅲ类围岩段在单循环进尺为2 m 、2.5 m 和3 m 三种情况下的爆破振动效应,得到了隧道拱顶、拱脚和边墙部位围岩的振动衰减规律。计算结果表明:围岩质点的峰值振速随着与开挖轮廓面距离的增大先急剧衰减后平缓衰减,开挖进尺越大,围岩受到的扰动越大。最后通过满足规范的安全质点振动速度来确定三种开挖进尺条件下的最大段药量大小,为类似隧道钻爆设计的合理性提供参考。%In order to obtain vibration effect of tunnel surrounding rocks under blasting load ,the tunnel calculation model was established by using the finite element software ADINA .Under simplified triangle equivalent blast loading ,the blast-ing vibration effect of class Ⅲ surrounding rock section of Qingshan tunnel with the single footage driving cycle being 2 m ,2 .5 m and 3 m was simulated .And then the vibration attenuation law for adjacent rocks at the arch vault ,spring and side walls of the tunnel under blasting load action was obtained .As shown by the calculation results ,the peak particle velocity showed abrupt attenuation first and then flat attenuation with the increase of excavation profile distance .The larg-er the footage ,the more vibrations the rock was subject to .Lastly ,safety particle vibration velocity in compliance with specifications was used to determine the maximum charge under these three excavation footage conditions .This study will provide reference to the rationality of blasting and drilling design of similar tunnels .

  15. 渗水泥化巷道锚杆支护围岩稳定性控制研究%Surrounding rock stability control with bolt support in seepage argillaceous roadway

    Institute of Scientific and Technical Information of China (English)

    王成; 韩亚峰; 张念超; 钱德雨

    2014-01-01

    Because of the poor reliability of bolt support in seepage argillaceous roadway, roof fall accidents occur frequently. In this paper, typical rock disintegration and weathering experiments, field tests of roadway deformation rules and bolt anchorage performance in water seepage roadways were studied. The results indicate that once the clay mineral in roadway surrounding rock meet water, the rock will become sliming and weathering embrittlement, which will cause a sharply decrease in the load bearing capability. In addition, the deformation of seepage argillaceous roadway has obvious stage cha-racteristics, which shows whole process of “decelerated deformation-weak argillization-accelerated deformation-strong argillization-instability”. Thus, the key point of stability control in such roadway is to control the argillaceous process effectively. Meanwhile, the surrounding rock control technology in seepage argillaceous roadway was proposed, which is composed of “there-high” bolt enhancement technology and lag grouting strengthening technology. Moreover, the best grouting time which is 10 to 30 days after the roadway drivage was given, engineering practice was then conducted, and good results were obtained.%渗水泥化巷道锚杆支护可靠性差,导致此类巷道冒顶事故频发。通过典型岩样崩解和风化实验、渗水泥质巷道变形规律及锚杆锚固性能实测开展研究。结果表明:煤系地层含有黏土类矿物,使得巷道围岩遇水崩解,发生泥化现象,且风化脆裂,导致自身承载力急剧降低;渗水泥质巷道围岩变形破坏具有明显阶段性,演绎“减速变形-弱泥化-加速变形-强泥化-失稳”全过程,有效控制泥化进程是该类巷道稳定性控制的关键;提出了渗水泥化巷道围岩的控制技术,即新型“三高”锚杆强化控制技术和滞后注浆加固技术,给出巷道掘进后10~30 d最佳注浆时机,开展了典型的工程实践

  16. Discovery of a low-mass companion inside the debris ring surrounding the F5V star HD206893

    CERN Document Server

    Milli, Julien; Christiaens, Valentin; Choquet, Elodie; Bonnefoy, Mickael; Kennedy, Grant M; Wyatt, Mark C; Absil, Olivier; Gonzalez, Carlos A Gomez; del Burgo, Carlos; Matra, Luca; Augereau, Jean-Charles; Boccaletti, Anthony; Delacroix, Christian; Ertel, Steve; Dent, William R F; Forsberg, Pontus; Fusco, Thierry; Girard, Julien H; Habraken, Serge; Huby, Elsa; Karlsson, Mikael; Lagrange, Anne-Marie; Mawet, Dimitri; Mouillet, David; Perrin, Marshall; Pinte, Christophe; Pueyo, Laurent; Reyes, Claudia; Soummer, Remi; Surdej, Jean; Tarricq, Yoann; Wahhaj, Zahed

    2016-01-01

    Uncovering the ingredients and the architecture of planetary systems is a very active field of research that has fuelled many new theories on giant planet formation, migration, composition, and interaction with the circumstellar environment. We aim at discovering and studying new such systems, to further expand our knowledge of how low-mass companions form and evolve. We obtained high-contrast H-band images of the circumstellar environment of the F5V star HD206893, known to host a debris disc never detected in scattered light. These observations are part of the SPHERE High Angular Resolution Debris Disc Survey (SHARDDS) using the InfraRed Dual-band Imager and Spectrograph (IRDIS) installed on VLT/SPHERE. We report the detection of a source with a contrast of 3.6x10^{-5} in the H-band, orbiting at a projected separation of 270 milliarcsecond or 10 au, corresponding to a mass in the range 24 to 73 Mjup for an age of the system in the range 0.2 to 2 Gyr. The detection was confirmed ten months later with VLT/NaCo...

  17. Rock mechanics modelling of rock mass properties - summary of primary data. Preliminary site description Laxemar subarea - version 1.2

    Energy Technology Data Exchange (ETDEWEB)

    Lanaro, Flavio [Berg Bygg Konsult AB, Solna (Sweden); Oehman, Johan; Fredriksson, Anders [Golder Associates AB, Uppsala (Sweden)

    2006-05-15

    The results presented in this report are the summary of the primary data for the Laxemar Site Descriptive Modelling version 1.2. At this stage, laboratory tests on intact rock and fracture samples from borehole KSH01A, KSH02A, KAV01 (already considered in Simpevarp SDM version 1.2) and borehole KLX02 and KLX04 were available. Concerning the mechanical properties of the intact rock, the rock type 'granite to quartz monzodiorite' or 'Aevroe granite' (code 501044) was tested for the first time within the frame of the site descriptive modelling. The average uniaxial compressive strength and Young's modulus of the granite to quartz to monzodiorite are 192 MPa and 72 GPa, respectively. The crack initiation stress is observed to be 0.5 times the uniaxial compressive strength for the same rock type. Non negligible differences are observed between the statistics of the mechanical properties of the granite to quartz monzodiorite in borehole KLX02 and KLX04. The available data on rock fractures were analysed to determine the mechanical properties of the different fracture sets at the site (based on tilt test results) and to determine systematic differences between the results obtained with different sample preparation techniques (based on direct shear tests). The tilt tests show that there are not significant differences of the mechanical properties due to the fracture orientation. Thus, all fracture sets seem to have the same strength and deformability. The average peak friction angle for the Coulomb's Criterion of the fracture sets varies between 33.6 deg and 34.1 deg, while the average cohesion ranges between 0.46 and 0.52 MPa, respectively. The average of the Coulomb's residual cohesion and friction angle vary in the ranges 28.0 deg - 29.2 deg and 0.40-0.45 MPa, respectively. The only significant difference could be observed on the average cohesion between fracture set S{sub A} and S{sub d}. The direct shear tests show that the

  18. Numerical probabilistic analysis for slope stability in fractured rock masses using DFN-DEM approach

    Directory of Open Access Journals (Sweden)

    Alireza Baghbanan

    2017-06-01

    Full Text Available Due to existence of uncertainties in input geometrical properties of fractures, there is not any unique solution for assessing the stability of slopes in jointed rock masses. Therefore, the necessity of applying probabilistic analysis in these cases is inevitable. In this study a probabilistic analysis procedure together with relevant algorithms are developed using Discrete Fracture Network-Distinct Element Method (DFN-DEM approach. In the right abutment of Karun 4 dam and downstream of the dam body, five joint sets and one major joint have been identified. According to the geometrical properties of fractures in Karun river valley, instability situations are probable in this abutment. In order to evaluate the stability of the rock slope, different combinations of joint set geometrical parameters are selected, and a series of numerical DEM simulations are performed on generated and validated DFN models in DFN-DEM approach to measure minimum required support patterns in dry and saturated conditions. Results indicate that the distribution of required bolt length is well fitted with a lognormal distribution in both circumstances. In dry conditions, the calculated mean value is 1125.3 m, and more than 80 percent of models need only 1614.99 m of bolts which is a bolt pattern with 2 m spacing and 12 m length. However, as for the slopes with saturated condition, the calculated mean value is 1821.8 m, and more than 80 percent of models need only 2653.49 m of bolts which is equivalent to a bolt pattern with 15 m length and 1.5 m spacing. Comparison between obtained results with numerical and empirical method show that investigation of a slope stability with different DFN realizations which conducted in different block patterns is more efficient than the empirical methods.

  19. Molecular identification of foreign inclusions in inflammatory tissue surrounding metal implants by Fourier transform laser microprobe mass spectrometry.

    Science.gov (United States)

    De Nollin, S; Poels, K; Van Vaeck, L; De Clerck, N; Bakker, A; Duwel, V; Vandevelde, D; Van Marck, E

    1997-01-01

    Fourier transform laser microprobe mass spectrometry (FT LMMS) is a novel technique for micro-analysis of solids with a lateral resolution in the 5 microns range. One of the major advantages of the technique is the capability to perform characterisation of the molecular composition of both organic and inorganic compounds. The information is directly deduced from the signals without the aid of reference spectra. FT LMMS was applied to the characterisation of black tissue fragments in a biopsy from a patient, in which a constrained condylar nodular knee system was implanted ten years ago. The tissue contained numerous foreign giant cells with a black non-birefringent pigment in their cytoplasm. FT LMMS analysis allowed us to detect directly by means of molecular signals, that the debris consisted primarily of titanium oxide and not metallic titanium, while the implant itself only contained titanium.

  20. In-situ monitoring and modelling of the rock mass response to mining: Japanese-South African collaborative research

    CSIR Research Space (South Africa)

    Ogasawara, H

    2013-09-01

    Full Text Available of seismic hazard in South African gold mines. Some preliminary results of the activities of in-situ monitoring of the rock mass are documented, which include an attempt to constrain stress and strength on a rupture plane accurately delineated by AE...

  1. THEORIES OF ROCK BREAKAGE WITH EXPLOSIVES

    Directory of Open Access Journals (Sweden)

    Vinko Škrlec

    2014-12-01

    Full Text Available The prediction and observation of the nature and dimensions of damaged zones in the surrounding rock mass and understanding the mechanisms of fracturing and crushing of the rock mass with explosives is one of the most important parameters in blasting design in order to obtain preferred granulation and reduce damaging effects of blasting on the environment. An overview of existing rock breakage theories with the energy released by the detonation of explosives is given in this paper (the paper is published in Croatian.

  2. Tunnel large deformation of surrounding rock research based on radar information and monitoring warning%基于雷达信息与监测预警的隧道围岩大变形研究

    Institute of Scientific and Technical Information of China (English)

    董辉; 陈家博; 杨珺博; 侯俊敏

    2012-01-01

    针对公路隧道溶洞和孔洞的存在给围岩的稳定性控制带来不同程度的困难且围岩大变形极易发生而造成工程事故,采用探地雷达超前探测和监控量测,归纳分析隧道围岩大变形的异常特征,并进一步通过贵州省晴兴高速公路登攀隧道出口围岩大变形预警的工程实例进行验算,获得黔西南区强风化多孔玄武岩及下伏灰岩溶洞雷达图像特征:有充填物时反射波振幅在洞腔范围内衰减强烈,强弱相间;无充填物时反射波基本无衰减,存在中断、起伏和错动现象。围岩大变形监测以拱顶下沉为主,21d最大累计沉降值达到89.40mm,变形速率最大波动范围为14.66~0.64mm/d。应用此结论可以在围岩出现大变形时及时预警并采取控制措施,更好地为后续工程服务。%Aiming at the existence of caves and holes in high.way tunnel will cause difficulty for surrounding rock' s stability in varying degrees and it is prone to result in large deformation of surrounding rock, cause accident, the paper summarizes and analyzes the abnormal characteristics of tunnel large deformation of surrounding rock by advanced detection of ground penetrating radar and monitoring. Meanwhile, with the project of Qingxing highway Dengpan tunnel exit surrounding rock' s large deformation and warning, we obtain radar images' characteristics to highly weathered porous basalt and underlying limestone caves in southwest of Guizhou province: reflection amplitude attenuates strongly and strength of the white in filling caves and there is almost no attenuation but with the phenomenon of disruption, ups and downs and dislocation in inanition. On the other side, when large deformation of surrounding rock is mainly vault sedimentation, its maximum cumulative settlement is 89.40mm during 21 days and deformation rate fluctuates from 14.66mm to 0.64mm per day. With the conclusion, it should be warned and take control measures timely

  3. The structure of the protoplanetary disk surrounding three young intermediate mass stars. II. Spatially resolved dust and gas distribution

    CERN Document Server

    Fedele, D; Acke, B; van der Plas, G; Van Boekel, R; Wittkowski, M; Henning, T; Bouwman, J; Meeus, G; Rafanelli, P

    2008-01-01

    [Abridged] We present the first direct comparison of the distribution of the gas, as traced by the [OI] 6300 AA emission, and the dust, as traced by the 10 micron emission, in the protoplanetary disk around three intermediate-mass stars: HD 101412, HD 135344 B and HD 179218. N-band visibilities were obtained with VLTI/MIDI. Simple geometrical models are used to compare the dust emission to high-resolution optical spectra in the 6300 AA [OI] line of the same targets. The disks around HD 101412 and HD 135344 B appear strongly flared in the gas, but self-shadowed in the dust beyond ~ 2 AU. In both systems, the 10 micron emission is rather compact (< 2 AU) while the [OI] brightness profile shows a double peaked structure. The inner peak is strongest and is consistent with the location of the dust, the outer peak is fainter and is located at 5-10 AU. Spatially extended PAH emission is found in both disks. The disk around HD 179218 is flared in the dust. The 10 micron emission emerges from a double ring-like str...

  4. TOF-secondary ion mass spectrometry imaging of polymeric scaffolds with surrounding tissue after in vivo implantation.

    Science.gov (United States)

    Klerk, Leendert A; Dankers, Patricia Y W; Popa, Eliane R; Bosman, Anton W; Sanders, Marjolein E; Reedquist, Kris A; Heeren, Ron M A

    2010-06-01

    Supramolecular polymeric materials are of increasing interest for the use as drug delivery carriers. A thorough insight in the biocompatibility and the degradation of these materials in vivo are of fundamental importance to further their development and application in medical practice. Molecular imaging techniques are powerful tools that enable the elucidation of molecular distributions in and around such polymer implants. A supramolecular polymeric hydrogel was implanted under the renal capsule to study its biocompatibility with TOF-SIMS. This results in a molecular cartography of the polymer implant combined with the cellular signature of the implantation environment. In this experiment, molecular signals are observed from cells that are involved in the biological response to the implant, e.g., macrophages. These molecular signatures are compared with macrophage standards cultured in different polarization environments. On the basis of this comparison, information can be acquired on the various macrophage differentiations that are connected to different stages in the foreign body response. Mass spectrometric imaging techniques offer the opportunity to visualize different histological phenomena in a single experiment without the need for specific immunohistochemical markers. Cellular infiltration into the polymer is visualized, offering a clear view on both biological and polymer features in a single imaging experiment.

  5. The Alteration History of Clovis Class Rocks in Gusev Crater as Determined by Ti-Normalzed Mass Balance Analysis

    Science.gov (United States)

    Sutter, Brat; Ming, Douglas W.; Niles, P. B.; Golden, D. C.

    2012-01-01

    The West Spur Clovis class rocks in Gusev Crater are some of the most altered rocks in Gusev Crater and likely contain a mixed sulfate and phyllosilicate mineralogy [1,2]. The high S and Cl content of the Clovis rocks suggests that acidic vapors or fluids of H2SO4 and HCl reacted with the Clovis parent rock to form Ca, Mg,- sulfates, iron-oxyhydroxides and secondary aluminosilicates (approx.60 wt.%) of a poorly crystalline nature (e.g., allophane) [1]. Up to 14-17 wt.% phyllosilicates (e.g., kaolinite, chlorite, serpentine) are hypothesized to exist in the Clovis materials suggesting that Clovis parent materials while possibly exposed to acidic pHs were likely neutralized by basalt dissolution which resulted in mildly acidic pHs (4-6) [1, 2]. This work proposes that subsequent to the alteration of the Clovis rocks, alteration fluids became concentrated in ions resulting in the addition of silicate and salts. The objective of this work is to utilize Ti-normalized mass balance analysis to evaluate (1) mineral gains and losses and (2) elemental gains and losses in the Clovis rocks. Results of this work will be used evaluate the nature of geochemical conditions that affect phyllosilicate and sulfate formation at Gusev crater.

  6. Coupled gas flow/solid dynamics model for predicting the formation of fracture patterns in gas well simulation experiments. [Propellant mixture used instead of explosives to fracture rock surrounding borehole

    Energy Technology Data Exchange (ETDEWEB)

    Taylor, L.M.; Swenson, D.V.; Cooper, P.W.

    1984-07-01

    A two-dimensional finite element model for predicting fracture patterns obtained in high energy gas fracture experiments is presented. In these experiments, a mixture of propellants is used instead of explosives to fracture the rock surrounding the borehole. The propellant mixture is chosen to tailor the pressure pulse so that multiple fractures emanate from the borehole. The model allows the fracture pattern and pressure pulse to be calculated for different combinations of propellant mixture, in situ stress conditions, and rock properties. The model calculates the amount of gas generated by the burning propellants using a burn rate given by a power law in pressure. By assuming that the gas behaves as a perfect gas and that the flow down the fractures is isothermal, the loss of gas from the borehole due to flow down the cracks is accounted for. The flow of gas down the cracks is included in an approximate manner by assuming self-similar pressure profiles along the fractures. Numerical examples are presented and compared to three different full-scale experiments. Results show a good correlation with the experimental data over a wide variety of test parameters. 9 reference, 10 figures, 3 tables.

  7. Partitioning characteristics of gas channel of coal-rock mass in mining space and gas orientation method

    Institute of Scientific and Technical Information of China (English)

    Zhao Zhiqiang; Ma Nianjie; Jia Housheng; Cheng Yuanping

    2013-01-01

    In order to research the influence of coal-rock mass morphology of mining space on the flow law of gas, the laboratory physical model and numerical computation methods were adopted to simulate coal min-ing activities. The simulation results indicate that, after coal seam mining, the loose rock accumulation body of free caving, ordered rock arrangement body of plate damage rich in longitudinal and transverse fractures and horizontal fissure body formed by rock mass deformation imbalance are formed from bottom to top in the mining space. For these three types of accumulation bodies, there are essential differences in the accumulation state, rock size and gas breakover characteristics. According to this, the coal-rock mass in the mining space is classified into gas turbulence channel area, gas transitional flow channel area and gas seepage channel area. In the turbulence channel area, the gas is distributed trans-versely and longitudinally and gas diffuses in the form of convection with Reynolds number Re more than 100;in the transitional flow channel area, one-way or two-way gas channels are crisscross and gas is of transitional flow regime with Re between 10 and 100. In the seepage channel area, there are a few vertical gas channels with Re less than 10. In this paper, the researches on the gas orientation method in different partitions were further carried out, gas orientation methods of low-level pipe burying, middle-level interception and high-level extraction were determined and an on-site industrial test was conducted, achieving the effective diversion of gas and verifying the reasonableness of gas channel partition.

  8. 砂性地层中盾构隧道掘进围岩变形特性%Deformation characteristics of the shield tunnelling surrounding rock in sandy stratum

    Institute of Scientific and Technical Information of China (English)

    张业炜; 杨新安

    2011-01-01

    Based on the geological conditions and construction data in the sandy stratum of Shiziyang tunnel, the numerical model was established. By the comparison on the displacement of monitoring points in different sections during the excavation, it concluded that; the surrounding rock of the antecedence tunnel shrink to the centre, and the deformation of the top & bottom rock is obviously larger than that of the two sides. The antecedence tunnel has applied external force on the later tunnel; however, it has applied little longitudinal force. By the comparison on the two conditions with seepage and without seepage, it concluded that the early effects of the seepage are limited, but the deformation of the surrounding rock is aggravated to a large extent eventually. The method was put forward to determine the cumulative effects and cumulative effect curves of the soil disturbance in front of the excavation face, and the disturbance scope and extent were determined by the cumulative effects curves. Finally two factors affect the soil displacement rate were obtained, there were the distance between the soil and the excavation face and shield thrust.%以狮子洋隧道砂性地层段地质条件和施工资料为基础,建立有限差分数值计算模型.通过比较不同断面监测点随开挖进程的位移值,结果表明:先掘隧道围岩向中心收缩,上下部围岩变形明显大于两侧;后掘隧道对先掘隧道有横向外挤的作用,但对纵向几乎没有影响.对有、无渗流作用的2种工况的比较分析说明,起初渗流对围岩变形影响不大,但最终加剧了围岩的变形程度.提出了开挖面前方土体扰动的累积效应和累积效应曲线的确定方法,通过该曲线可确定土体扰动范围和程度,经过理论分析,认为影响土体位移速率的2个因素是土体与开挖面间距和盾构推力.

  9. Stress evolution and support mechanism of a bolt anchored in a rock mass with a weak interlayer

    Institute of Scientific and Technical Information of China (English)

    Ding Shuxue; Jing Hongwen; Chen Kunfu; Xu Guo'an; Meng Bo

    2017-01-01

    By applying experimental method, the bolt stress and supporting mechanism is studied during the deformation process of a rock mass containing a weak interlayer. The force measuring bolt is installed manually and instrumented five pairs of symmetrical strain gauges. The experimental results show that the fully grouted bolt suffers tensile, compressive, bending and shear stress at the same time. The bolt stress evolution is closely related to the deformation stages of the rock mass which are very gradually varying stage, gradually varying stage at the pre-peak and suddenly varying stage at the post peak stage.The axial compressive stress in the bolt is mainly induced by the moment. Thus, in most cases the axial compressive stress is distributed on one side of the bolt. For axial stresses, induced by the axial force and the bending moment at the post-peak stage, three types of changing are observed, viz. increasingincreasing type, decreasing-increasing type and increasing-decreasing type. The stress characteristics of the bolt section in the weak interlayer are significantly different from those in the hard rock. The failure models of the anchored bolt are tensile failure and shear failure, respectively. The bolt not only provides constraints on the free surface of the rock mass, but also resists the axial and lateral loading by the bending moment. This study provides valuable guidelines for bolting support design and its safetyssessment.

  10. Demarcation of homogeneous structural domains within a rock mass based on joint orientation and trace length

    Science.gov (United States)

    Song, Shengyuan; Wang, Qing; Chen, Jianping; Cao, Chen; Li, Yanyan; Zhou, Xin

    2015-11-01

    This paper presents a new method for determining the structural domain boundaries within the rock mass. This new method is based on a statistical comparison of data from pairs of sample regions. The stereonet is divided into 100 windows with approximately equal areas. The poles of joints occurring in each corresponding window on the two projection plots of the regions being compared are then merged and arranged in ascending order with respect to their trace lengths. Finally, the Wald-Wolfowitz runs test is used to identify the homogeneity of structural populations by analyzing the joint sequence. Based on a significance level of 0.01, the homogeneity of structural populations collected from four adjacent adits at the Songta dam site is determined using the proposed method. The results show that the boundaries of structural domain change with the sizes of the sampling domains being compared. The initial sampling domains should be selected according to the engineering geological conditions of the studied area. In addition, the clear advantage of the proposed method is that both joint orientation and trace length are considered.

  11. Preliminary evaluation of the rock-mass disturbance resulting from shaft, tunnel, or borehole excavation

    Energy Technology Data Exchange (ETDEWEB)

    Kelsall, P.C.; Case, J.B.; Chabannes, C.R.

    1982-11-01

    The isolation of nuclear wastes in deep, mined repositories will require the sealing of all penetrations such as shafts, tunnels, or boreholes, into or nearby the repository. An important consideration in penetration sealing is the disturbed zone, or zone of increased permeability, which may be created in the rock mass adjacent to the penetration as a result of excavation. Disturbed zone characteristics for shafts, tunnels, and boreholes are evaluated by analysis and by review of previous laboratory and field tests. Consideration is given also to test methods for characterizing the disturbed zone in situ, and to methods for treating the disturbed zone in seal construction. Laboratory tests indicate that the disturbed zone associated with small-diameter boreholes is probably insignificant. In contrast, the disturbed zone is potentially a significant pathway for flow through seals placed in shafts and tunnels. Because a major mechanism for disturbance is believed to be stress relief acting across fractures, much of the disturbance occurs regardless of the excavation method used. Various test methods are proposed for disturbed zone characterization in shafts and tunnels, with seismic refraction identified as a promising index test. A proposed method for treating the disturbed zone uses cutoffs constructed as a series of overlapping boreholes. Each hole is filled with concrete which is allowed to cure before the adjacent holes are drilled.

  12. Dynamic subsidence basins in coal mines based on rock mass theological theory

    Institute of Scientific and Technical Information of China (English)

    Yang Yu; Gong Zhiqiang; Liang Bing

    2011-01-01

    In order to investigate the surface deformation caused by coal mining and to reduce environmental damage,more accurate information of dynamic subsidence basins,caused by coal mining,is needed.Based on rheological theory,we discuss surface deformation mechanism of dynamic subsidence on the assumption that both the roof and the coal seam are visco-elastic media,put forward the idea that the principle of surface deformation is similar to that of roofs,except for their parameters.Therefore,a surface deformation equation can be obtained,given the equation of the roof deformation derived.from using a HM rheological model.In the end,we apply the equation of surface deformation as a practical subsidence prediction in a coal mine.Given the rheologic properties of a rock mass,the results of our research of a dynamic subsidence basin can predict the development of surface deformation as a function of time.which is more important than the ultimate subsidence itself.The results indicate that using rheological theory to calculate the deformation of a dynamic subsidence basin is suitable and provides some reference for surface deformation of dynamic subsidence basins.

  13. A methodology for lining design of circular mine shafts in different rock masses

    Institute of Scientific and Technical Information of China (English)

    Ozturk Hasan⇑; Guler Erdogan

    2016-01-01

    In this study, the finite element numerical modelling of 2D shaft sections in a Hoek–Brown medium are carried out in a non-hydrostatic stress state in an attempt to predict pressures developing around mine shafts. An iterative process of applying support pressure until observing no failure zone around the shaft is used to simulate the required lining support pressure for different shaft models. Later, regression anal-ysis is carried out to find a generic shaft pressure equation representing the rock mass and the stress state. Finally, the developed pressure equation which shows a good agreement with a case study is used in elastic‘thick-walled cylinder”equation to calculate the lining thickness required to prevent the devel-opment of a failure zone around the shaft. At the end of the study, a user-friendly object-oriented com-puter program‘Shaft 2D”is developed to simplify the rigorous shaft lining thickness calculation process.

  14. RESEARCH ON MECHANISM OF LARGE DEFORMATION AND COUNTERMEASURES OF SURROUNDING ROCKS OF TUNNEL THROUGH COAL STRATA%穿越煤系地层隧道围岩大变形机制及处治研究

    Institute of Scientific and Technical Information of China (English)

    李生杰; 谢永利; 吴丹泽; 朱小明

    2013-01-01

    Surrounding rock of Anyuan highway tunnel through coal strata is made of carbonaceous shale,coal line and mudstone weak interlayer. The uniaxial compressive strength of the carbonaceous shale specimens are 3.9-4.8 MPa. The geostress measurement is carried out,and the results show that the maximum horizontal principal stress is 8-10 MPa,and the horizontal principal stress is dominant in the area of tunnel. Based on the on-site monitoring and numerical simulation,the characteristics of surrounding rock deformation are analyzed. The reasons for large deformation are summarized as follows:(1) The strength of surrounding rock is low and the rock swells easily;(2) The level of geostress is high as to the low strength of rockmass;(3) Water effect;(4) Improper construction. The mechanism of large deformation is discussed also. The countermeasures are proposed as follows:the tunnel face should be closed quickly after excavation,then the temporary support is set up,long bolts and grouting pipe are used to control the deformation,the arch is replaced after deformation become stable,the spacing of steel arch is reduced,and finally,invert and inner lining are applied timely. According to the measurement results,it is shown that the treatment measures are effective.%高速公路安远隧道穿越煤系地层,围岩主要由炭质页岩、煤线、泥岩夹层组成,炭质页岩试件单轴抗压强度为3.9~4.8 MPa。开展地应力测量,测量结果表明隧址区最大水平主应力为8~10 MPa,水平应力作用占主导。通过现场监测以及数值模拟分析,分析围岩大变形的特征,总结围岩大变形产生的原因,主要有:(1)围岩强度低且易膨胀;(2)相对岩体强度,地应力较高;(3)水理作用;(4)施工不当。在此基础上探讨变形机制。提出相应的处治措施:开挖后迅速封闭掌子面,设置临时支撑,施作长锚杆和注浆小导管控制变形,待变形稳定后适时进行拱圈

  15. In Situ Observation of Failure Mechanisms Controlled by Rock Masses with Weak Interlayer Zones in Large Underground Cavern Excavations Under High Geostress

    Science.gov (United States)

    Duan, Shu-Qian; Feng, Xia-Ting; Jiang, Quan; Liu, Guo-Feng; Pei, Shu-Feng; Fan, Yi-Lin

    2017-09-01

    A weak interlayer zone (WIZ) is a poor rock mass system with loose structure, weak mechanical properties, variable thickness, random distribution, strong extension, and high risk due to the shear motion of rock masses under the action of tectonism, bringing many stability problems and geological hazards, especially representing a potential threat to the overall stability of rock masses with WIZs in large underground cavern excavations. Focusing on the deformation and failure problems encountered in the process of excavation unloading, this research proposes comprehensive in situ observation schemes for rock masses with WIZs in large underground cavern on the basis of the collection of geological, construction, monitoring, and testing data. The schemes have been fully applied in two valuable project cases of an underground cavern group under construction in the southwest of China, including the plastic squeezing-out tensile failure and the structural stress-induced collapse of rock masses with WIZs. In this way, the development of rock mass failure, affected by the step-by-step excavations along the cavern's axis and the subsequent excavation downward, could be observed thoroughly. Furthermore, this paper reveals the preliminary analyses of failure mechanism of rock masses with WIZs from several aspects, including rock mass structure, strength, high stress, ground water effects, and microfracture mechanisms. Finally, the failure particularities of rock masses with WIZs and rethink on prevention and control of failures are discussed. The research results could provide important guiding reference value for stability analysis, as well as for rethinking the excavation and support optimization of rock masses with WIZs in similar large underground cavern under high geostress.

  16. Study of thermo-mechano-damage coupling behavior of surrounding rock of deep tunnel%热-应力-损伤耦合作用下深埋隧洞围岩稳定性分析

    Institute of Scientific and Technical Information of China (English)

    贾善坡; 吴渤; 陈卫忠; 伍国军; 高敏; 龚俊

    2014-01-01

    以热力学和弹塑性力学理论为基础,分析岩石热-力完全耦合作用及其对力学参数和热特性参数的影响,建立了岩石热-力-损伤耦合模型及其参数演化方程,以ABAQUS软件为平台对其进行二次开发,并通过典型算例验证了岩石热-力完全耦合的重要性。然后以某深埋软岩隧洞为例,研究温度和开挖卸载共同作用下的隧洞围岩力学行为和损伤过程。计算结果表明:温度对岩石的力学性质和损伤演化过程影响显著,开挖损伤和热应力诱发的损伤对围岩热力学参数的影响不可忽略;所提出的力学模型可以有效反映围岩损伤演化、调热圈演化以及热力学参数演化,具有一定的借鉴作用。%Based on the theories of thermo-mechanics and elastoplastic mechanics, the thermo-mechanical coupling effects of rock and their effects on mechanical and thermal parameters are analyzed. By defining the evolution equations of thermo-mechanical coupling parameters under the damage of temperature effects and mechanics, a new coupled thermo-mechanical damage model with improved Mohr-Coulomb criterion is established, and the numerical implementation in ABAQUS is given. Using finite element method, a typical example was given to verify the importance of the thermo-mechanical fully coupling of rock. Taking a deep tunnel of clay stone as background, the evolution and distribution of damage, temperature and coupling parameters of the surrounding rock are simulated in detail. The results show that the temperature has a great influence on rock properties and damage evolution. Also, the damage by excavation and thermal stress has a great influence on conducting and diffusing of heat. The proposed model can depict the excavation damage, control heat circle and coupling parameters evolution, and may provide a new tool for associated applications.

  17. Distinct element modelling of fracture plan control in continuum and jointed rock mass in presplitting method of surface mining

    Institute of Scientific and Technical Information of China (English)

    Sharafisafa Mansour; Aliabadian Zeinab; Alizadeh Rezvan; Mortazavi Ali

    2014-01-01

    Controlled blasting techniques are used to control overbreak and to aid in the stability of the remaining rock formation. Presplitting is one of the most common methods which is used in many open pit mining and surface blast design. The purpose of presplitting is to form a fracture plane across which the radial cracks from the production blast cannot travel. The purpose of this study is to investigate of effect of pre-splitting on the generation of a smooth wall in continuum and jointed rock mass. The 2D distinct element code was used to simulate the presplitting in a rock slope. The blast load history as a function of time was applied to the inner wall of each blasthole. Important parameters that were considered in the analysis were stress tensor and fracturing pattern. The blast loading magnitude and blasthole spacing and jointing pattern were found to be very significant in the final results.

  18. Active and passive seismic methods for characterization and monitoring of unstable rock masses: field surveys, laboratory tests and modeling.

    Science.gov (United States)

    Colombero, Chiara; Baillet, Laurent; Comina, Cesare; Jongmans, Denis; Vinciguerra, Sergio

    2016-04-01

    Appropriate characterization and monitoring of potentially unstable rock masses may provide a better knowledge of the active processes and help to forecast the evolution to failure. Among the available geophysical methods, active seismic surveys are often suitable to infer the internal structure and the fracturing conditions of the unstable body. For monitoring purposes, although remote-sensing techniques and in-situ geotechnical measurements are successfully tested on landslides, they may not be suitable to early forecast sudden rapid rockslides. Passive seismic monitoring can help for this purpose. Detection, classification and localization of microseismic events within the prone-to-fall rock mass can provide information about the incipient failure of internal rock bridges. Acceleration to failure can be detected from an increasing microseismic event rate. The latter can be compared with meteorological data to understand the external factors controlling stability. On the other hand, seismic noise recorded on prone-to-fall rock slopes shows that the temporal variations in spectral content and correlation of ambient vibrations can be related to both reversible and irreversible changes within the rock mass. We present the results of the active and passive seismic data acquired at the potentially unstable granitic cliff of Madonna del Sasso (NW Italy). Down-hole tests, surface refraction and cross-hole tomography were carried out for the characterization of the fracturing state of the site. Field surveys were implemented with laboratory determination of physico-mechanical properties on rock samples and measurements of the ultrasonic pulse velocity. This multi-scale approach led to a lithological interpretation of the seismic velocity field obtained at the site and to a systematic correlation of the measured velocities with physical properties (density and porosity) and macroscopic features of the granitic cliff (fracturing, weathering and anisotropy). Continuous

  19. A New Method to Evaluate Rock Mass Brittleness Based on Stress-Strain Curves of Class I

    Science.gov (United States)

    Xia, Y. J.; Li, L. C.; Tang, C. A.; Li, X. Y.; Ma, S.; Li, M.

    2017-05-01

    Brittleness is a key controlling parameter for rock engineering projects such as hydrocarbon production and other applications. In this paper, commonly used methods based on stress-strain curves of Class I for the calculation of rock brittleness are reviewed. In order to describe the rock brittleness more reasonable, the new index B i was proposed based on the stress drop rate obtained from post-peak stress-strain curve and the ratio of elastic energy released during failure to the total energy stored before the peak strength. Then the validity of B i is verified with experimental tests conducted on rock specimens drilled from the interlayer and oil layer through a well of Shengli Oilfield. Moreover, numerical simulation is performed to analyze the effects of primary mechanical parameters on the brittleness of rock masses. Based on experimental tests and numerical simulation results, the acoustic emission modes influenced by brittleness index B i are summarized. At last, correlation between acoustic emission mechanism and index B i is verified by comparing the acoustic emission modes of limestone under different levels of confining pressure and various types of coal.

  20. Mine geophysics methods in studying the coal bearing rock mass condition in low magnitude tectonic fault zones

    Science.gov (United States)

    Alexeev, A. D.; Zhitlyonok, D. M.; Pitalenko, E. I.

    2003-04-01

    Disjunctive type tectonic faults are quite serious problem at underground coal winning. In the fault adjacent areas both coal seam and coal bearing rocks are usually essentially fractured that makes them less stable in coalfaces at underground mining. Some researchers have pointed out to enhanced stress state in these areas as well provided that loosening zones are absent. Coal seams are mostly inclined to disjunctive faults in Central region of Donets Coal Basin where tectonic processes were very intense. There are a lot of small faults with magnitudes close to seam thickness about 2 m in this region along with large thrust or fault disjunctives with stratigraphic magnitudes over 10 m (Dyleyev, Northern, Brunvald, Bulavin faults and others). Highest disjunctive dislocation is typical for coalfields near mines "Toretskaya" and "Novodzerzhinskaya", Coal Production Co. "Dzerzhinskugol", where dislocation density reaches about 8.5 faults per 1 km across the field. Small disjunctive faults often coincide with sites of sudden coal and gas outbursts, longwall inrushes, and poor support condition in development workings. It is known that affected zones on either side accommodate each disjunctive fault, these zones being distinctive for increased fissuring, higher stresses, coal and rocks differing strength. Affected zone width dependence on the fault parameters was determined using geological approach. Mine electrical survey and acoustical probing methods were used to study rock mass faulted condition in the vicinity of development workings and stopes intercepting low magnitude (below 5 m) disjunctive faults in coal field of mine "Toretskaya". These findings have allowed to establish a new fault magnitude dependence of rupture tectonic dislocation's affected zone width in the form of B = 3.2 H, where B is dislocation's affected zone width (m); H is the dislocation's stratigraphic magnitude (m). It was established as well that stress level in rock mass near disjunctive

  1. Computing in-situ strength of rock masses based upon RQD and modified joint factor: Using pressure and damage sensitive constitutive relationship

    Directory of Open Access Journals (Sweden)

    Ashutosh Trivedi

    2015-10-01

    Full Text Available In this study, a new model was presented for computing strength of rock masses based upon in-situ observations of RQD popularly known as rock quality designation. This model links up the rock mass parameters from in-situ investigations with the strength parameters of jointed rocks obtained from laboratory scale experimental observations. Using the constitutive relation, the author derived a pressure and damage sensitive plastic parameter to determine strength of rock masses for varied extents of discontinuity and pressure induced damage. The test results show that plasticity characterized by hardening and softening inclusive of damage invariably depends upon mean pressure and extent of deformations already experienced by rock masses. The present work explores the test data that reveal the dependence of in-situ strength on incremental joint parameters obtained from the joint number, joint orientation, joint roughness, gouge parameters and water pressure. Substituting the relationship between the RQD and modified joint factor with that between modulus ratio and strength ratio, the model shows successfully that using damage inclusive plastic parameter and RQD provides a relationship for estimating the strength of rock masses. One of the main objectives of this work is to illustrate that the present model is sensitive to plasticity and damage together in estimating in-situ strength of rock masses in foundations, underground excavation and tunnels.

  2. Computing in-situ strength of rock masses based upon RQD and modified joint factor:Using pressure and damage sensitive constitutive relationship

    Institute of Scientific and Technical Information of China (English)

    Ashutosh; Trivedi

    2015-01-01

    In this study, a new model was presented for computing strength of rock masses based upon in-situ observations of RQD popularly known as rock quality designation. This model links up the rock mass parameters from in-situ investigations with the strength parameters of jointed rocks obtained from laboratory scale experimental observations. Using the constitutive relation, the author derived a pressure and damage sensitive plastic parameter to determine strength of rock masses for varied extents of discontinuity and pressure induced damage. The test results show that plasticity characterized by hardening and softening inclusive of damage invariably depends upon mean pressure and extent of deformations already experienced by rock masses. The present work explores the test data that reveal the dependence of in-situ strength on incremental joint parameters obtained from the joint number, joint orientation, joint roughness, gouge parameters and water pressure. Substituting the relationship between the RQD and modified joint factor with that between modulus ratio and strength ratio, the model shows successfully that using damage inclusive plastic parameter and RQD provides a relationship for estimating the strength of rock masses. One of the main objectives of this work is to illustrate that the present model is sensitive to plasticity and damage together in estimating in-situ strength of rock masses in foundations, underground excavation and tunnels.

  3. Site Measurement of Surrounding Rock Pressure and Analysis of Structure Stress of Large-span Bias-pressured Shallow Tunnels%大跨浅埋偏压隧道围压实测及结构受力分析

    Institute of Scientific and Technical Information of China (English)

    江磊; 侯哲生; 吴海卫

    2015-01-01

    大跨浅埋偏压隧道由于其非对称的受力条件,易引发结构变形与开裂等突出问题,近年来越来越受工程技术界的重视。以邢汾高速公路邢台段后偏梁大跨度隧道浅埋偏压段为例,通过实测围岩压力,根据荷载结构法的基本原理,利用 ANSYS 软件对其结构受力特性进行数值分析,得到结论:实测的围岩压力分布和偏压的地形之间具有较为一致的对应性,即围岩压力受地形的影响显著;二衬总应力受轴力引起的应力影响较小,主要受弯矩引起的应力控制,整个拱圈范围内最危险的部位是在受围岩压力最大的左侧拱肩处;随着二衬厚度的变化,二衬总应力在不同的部位均发生相应变化,但变化幅度均不大。相关研究结论为后续类似大跨浅埋偏压隧道的合理设计与施工提供参考依据。%The asymmetrical stress condition of the Large-span bias-pressured shallow tunnels can cause many problems easily ,such as structural deformation and cracking .These problems have attracted more and more attentions from engi-neering and technology research field in recent years .The Houpianliang large-span bias-pressured shallow tunnel in Xing-tai section of Xingtai - Fenyang highway was taken as an example to numerically analyze the mechanical characteristics of the structure by adopting ANSYS ,according to the data of site measurement of surrounding rock pressure and the princi -ple of load structure method .The results indicate that :the actual measured surrounding rock pressure is consistent with the bias terrain ,which means the surrounding rock pressure is influenced by topography significantly ;the total stress of the second lining is mainly controlled by the stress from bending moment and is less influenced by the stress from axial force ,the weakest part within the scope of the arch ring is the left spandrel which is subject to maximum pressure ;with the change of the

  4. Numerical simulation study on hard-thick roof inducing rock burst in coal mine

    Institute of Scientific and Technical Information of China (English)

    何江; 窦林名; 牟宗龙; 曹安业; 巩思园

    2016-01-01

    In order to reveal the dynamic process of hard-thick roof inducing rock burst, one of the most common and strongest dynamic disasters in coal mine, the numerical simulation is conducted to study the dynamic loading effect of roof vibration on roadway surrounding rocks as well as the impact on stability. The results show that, on one hand, hard-thick roof will result in high stress concentration on mining surrounding rocks; on the other hand, the breaking of hard-thick roof will lead to mining seismicity, causing dynamic loading effect on coal and rock mass. High stress concentration and dynamic loading combination reaches to the mechanical conditions for the occurrence of rock burst, which will induce rock burst. The mining induced seismic events occurring in the roof breaking act on the mining surrounding rocks in the form of stress wave. The stress wave then has a reflection on the free surface of roadway and the tensile stress will be generated around the free surface. Horizontal vibration of roadway surrounding particles will cause instant changes of horizontal stress of roadway surrounding rocks; the horizontal displacement is directly related to the horizontal stress but is not significantly correlated with the vertical stress; the increase of horizontal stress of roadway near surface surrounding rocks and the release of elastic deformation energy of deep surrounding coal and rock mass are immanent causes that lead to the impact instability of roadway surrounding rocks. The most significant measures for rock burst prevention are controlling of horizontal stress and vibration strength.

  5. Research on Impact on Plastic Zone of Roadway Surrounding Rock Based on Different Yield Criteria%不同屈服条件对巷道围岩塑性区的影响研究

    Institute of Scientific and Technical Information of China (English)

    王洪涛; 尤春安; 王绪勇

    2011-01-01

    基于Drucker-Prager 准则,推导了巷道围岩塑性区的解析解,以某工程为例分析比较了基于不同屈服准则的巷道围岩塑性区的解答,并结合数值软件分析的计算结果,探究了不同屈服条件对巷道围岩塑性区的影响规律.结果表明,Drucker-Prager系列准则考虑了中间主应力的影响,计算结果更符合实际,外交点圆DP1准则用于工程设计计算稍显危险,内切圆DP5准则用于工程设计计算偏于安全,而MC等面积圆DP3准则与MC准则计算结果较接近,为巷道围岩支护设计计算屈服准则的选取与应用提供了依据.%The analytic solution of plastic zone of roadway surrounding rock is deduced from the Drucker-Prager criterion. Taking a practical project for an example, the solutions are compared and analyzed in terms of the different yield criteria. Then, combination of results with numerical analysis software, the impact rules of plastic zone of roadway surrounding rock is studied in this paper. The results show that the it is more realistic for considering the influence of intermediate principal stress in DP series criteria; the result with DP1 criterion is a little dangerous in project design, DP5 criterion is the most conservative and a little safe in project design; while the result with MC criterion is close to it under its equivalent area circle criterion. Thus, it provides basis for selection and application of yield criteria in supporting design of roadway.

  6. 充填采煤面收作眼围岩变形控制技术研究%Study on surrounding rock deformation control of finishing cut in backfilling mining face

    Institute of Scientific and Technical Information of China (English)

    李猛; 张吉雄; 巨峰; 刘世伟; 曹远威

    2016-01-01

    To solve support dismantling problems caused by big cross-section finishing cut and to con-trol strata movement in solid backfilling mining face,this paper has adopted the theoretical analysis and FLAC3D numerical simulation method to study laws of surrounding rock deformation and failure mechanism of finishing cut. Then the comprehensive support technology of anchor (rope) mesh rein-forcement, temporary support of“#” type wooden cogs filled with grouting and permanent support of finishing cut grouting have been put forward. In addition,the supporting parameters of concrete pier consisting of wooden cogs has been optimized. The results have shown that when the reasonable spac-ing of concrete pier is 2 000 mm, the pier bearing capacity can satisfy the requirement of temporary support. The technology has been applied in Yangzhuang coal mine of Huaibei Coal Mining Group, and the accumulated sink value about 80 m above the working face has been only 60 mm, which has indi-cated that surrounding rock deformation control of finishing cut is well controlled.%为解决充填采煤面收作眼断面大、难支护及撤架困难等难题,采用理论分析和FLAC3D数值模拟方法研究了收作眼围岩变形破坏规律,提出了滑架通道锚(索)网加强支护、“井”字型木垛封闭灌浆的临时支护和收作眼空间注浆永久支护相结合的围岩控制技术方法,优化设计了“井”字型木垛形成的混凝土墩柱支护参数。结果表明:混凝土墩柱间排距均为2000 mm时,墩柱承载能力可满足临时支护的要求。该技术在淮北矿业集团杨庄煤矿进行了应用,通过监测工作面上方垂距约为80 m的巷道变形,其巷道累积下沉量仅为60 mm,表明收作眼围岩变形控制效果显著。

  7. The Geomorphology of the surroundings of the Ría de Arosa (Galicia, NW Spain)

    NARCIS (Netherlands)

    Pannekoek, A.J.

    1966-01-01

    This paper is intended to provide a geomorphological introduction to a series of papers on the sedimentology and weathering phenomena of the Ría de Arosa area. The area contains a large mass of coarse-grained porphyritic granite surrounded by other crystalline rocks. The granite is deeply weathered

  8. The Geomorphology of the surroundings of the Ría de Arosa (Galicia, NW Spain)

    NARCIS (Netherlands)

    Pannekoek, A.J.

    1966-01-01

    This paper is intended to provide a geomorphological introduction to a series of papers on the sedimentology and weathering phenomena of the Ría de Arosa area. The area contains a large mass of coarse-grained porphyritic granite surrounded by other crystalline rocks. The granite is deeply weathered

  9. Coupling analysis of unsteady seepage and stress fields in discrete fractures network of rock mass in dam foundation

    Institute of Scientific and Technical Information of China (English)

    2011-01-01

    The drag force of water flow through single fracture and the coupling characteristics of seepage and stress in single fracture surface are analyzed,and a three dimensional model of coupled unsteady seepage and stress fields is proposed.This model is used to the analysis of foundation rock mass of a high dam.If the coupling effects are considered,the changes of boundary heads have less influence on the inner head of rock mass,and the strong permeability of main fractures appears.If the coupling effects are not considered,the fractures distribution affects the inner head more greatly.When the upstream water head declines,the inner head of dam foundation slightly declines and the hydraulic gradient distribution becomes smoother.A bigger upstream water level declining velocity has a stronger lag effect,meanwhile the values of stress components change more greatly.Therefore the upstream water level declining velocity directly affects the stability of rock mass in dam foundation and we should take into account the above factors to make sure the safety of the dam during reservoir level fluctuation period.

  10. The heater test at the Grimsel Rock Laboratory: The thermo-mechanical response of the rock mass to a heat flux

    Energy Technology Data Exchange (ETDEWEB)

    Schneefuss, J.; Gommlich, G.; Noell, U. (Gesellschaft fuer Strahlen- und Umweltforschung m.b.H. Muenchen, Braunschweig (Germany, F.R.). Inst. fuer Tieflagerung)

    1989-08-01

    The Grimsel Test Site (Felslabor Grimsel - FLG) is situated at a depth of 450 m in the Juchlistock massif of the Bernese Oberland. It is managed by the National Cooperative for the Storage of Radioactive Waste (NAGRA-Switzerland). By means of a heater test, the power output of canisters filled with high-level waste is simulated. This heater test is performed by the German Gesellschaft fuer Strahlen- und Umweltforschung - GSF. Two electrical heaters, with a heatable length of 6 m, a diameter of 0.3 m and an available power of 4 kW/m, are installed in two vertical boreholes. One of them is located in the granite adjacent to a strongly fractured lamprophyre vein, the other one directly within this disturbed zone. They are operating since August 1986. The thermo-mechanical reaction of the rock mass is registered by a large number of measurement devices which are installed in an array of instrument boreholes around the heaters. They record the deformation and the alteration of rock stresses, the pore water pressure and the water conductivity caused by heating. (orig.).

  11. Numerical Simulation of Blast Vibration and Crack Forming Effect of Rock-Anchored Beam Excavation in Deep Underground Caverns

    Directory of Open Access Journals (Sweden)

    XinPing Li

    2017-01-01

    Full Text Available Aiming at surrounding rock damage induced by dynamic disturbance from blasting excavation of rock-anchored beam in rock mass at moderate or far distance in underground cavern, numerical model of different linear charging density and crustal stress in underground cavern is established by adopting dynamic finite element software based on borehole layout, charging, and rock parameter of the actual situation of a certain hydropower station. Through comparison in vibration velocity, contour surface of rock mass excavation, and the crushing extent of excavated rock mass between calculation result and field monitoring, optimum linear charging density of blast hole is determined. Studies are also conducted on rock mass vibration in moderate or far distance to blasting source, the damage of surrounding rock in near-field to blasting source, and crushing degree of excavated rock mass under various in situ stress conditions. Results indicate that, within certain range of in situ stress, the blasting vibration is independent of in situ stress, while when in situ stress is increasing above certain value, the blasting vibration velocity will be increasing and the damage of surrounding rock and the crushing degree of excavated rock mass will be decreasing.

  12. 深部高应力煤巷围岩变形与控制技术研究%Research on Surrounding Rock Deformation of Deep Coal Roadway under High Stress and Its Control Technology

    Institute of Scientific and Technical Information of China (English)

    翟金腾

    2012-01-01

    Using methods of theoretical analysis, physical simulation,industrial test and in - situ measurement, the deformation laws of coal roadway along gob in different depth were researched in Chensilou Coal Mine. The results showed that when the depth is up to 950 m over the deformation velocity of surrounding rock for roadway drivage along goaf increases rapidly, and the deformation of 6 m coal pillar is small er than that of 4 m coal pillar. The researched results provide a theoretical basis for the design of mining roadway support in working face.%采用理论分析、物理模拟、工业性试验与实测方法,对陈四楼煤矿沿空煤巷不同深度的变形规律进行了研究,结果表明,当采深达到950m以上时,沿采空区掘巷的围岩变形速度将会迅速增加,此时6m煤柱比4m煤柱的围岩变形要小,研究结果为工作面回采巷道支护设计等提供了理论依据。

  13. 节理岩体隧道围岩稳定性判定指标合理性研究%A Study of the Criterion for the Stability of a Tunnel in a Jointed Rock Mass

    Institute of Scientific and Technical Information of China (English)

    张志强; 何本国; 关宝树

    2012-01-01

    隧道围岩失稳模式和稳定性判据一直是工程界争论的焦点,迄今没有科学合理的标准,常以洞周位移或塑性区经验值作为稳定性判定指标.洞周位移受围岩弹模、隧道形状等因素影响,而且不同部位变形值差异很大,很难找到统一标准;以塑性区作为稳定性判据优于以位移作为判据,围岩塑性化反映连续介质宏观塑性流动力学动态,而不能用于量化判定由优势结构面控制节理岩体破坏的隧道稳定性.文章结合细观节理形态和变化,通过UDEC离散元程序,研究节理岩体隧道失稳模式及量化的稳定性判定指标,探讨了细观结构机制和宏观力学行为关系.结果表明:(1)结构面极大地削弱岩体力学性质及其稳定性,结构面变形与强度性质对于隧道稳定性起着关键控制性作用;(2)节理岩体隧道扰动区可划分为脱落区、张开区和剪切滑移区,其中脱落区表征围岩失稳模式,张开区围岩处于脱落临界状态,即塌方潜在区域;(3)剪切滑移区是诱发围岩发生渐进性破坏主因,提出将剪切滑移区作为节理岩体隧道稳定性判定指标具有严格力学依据,可以定量化评价围岩稳定程度.最后,以在建兰渝铁路木寨岭隧道为例,对比了锚杆支护前后力学效应,验证了以剪切滑移区作为节理岩体隧道稳定性判定指标的可靠性、合理性和现实性.%The instability model and criterion for the stability of tunnels in jointed rock masses have been a subject of debate, and no scientific and reasonable standard has been reached for the subject so far. The empirical value of the displacement around the tunnel and plastic zone is deemed the criterion for stability of surrounding rock; elastic modulus and the shape of a tunnel have a great influence on the displacement around the tunnel. Additionally, displacements around a tunnel are unequal at different positions. For these reasons, it is difficult to

  14. Numerical simulation for rheological characteristics of alternating distribution of soft and hard rock layers

    Institute of Scientific and Technical Information of China (English)

    HAN Bing; WANG Zhi-yin; DING Xiu-li; XU Ping

    2006-01-01

    The difficulty of selecting appropriate rheological model and parameters for the alternating distribution of soft and hard rock layers was often encountered due to the unhomogeneity, discontinuity and anisotropy of rock mass. The Burgers and generalized Kelvin models were applied to the soft and hard rock respectively and the rheological parameters were obtained based on the method of optimum separation. By using the simulated code FLAC3D, the stability of surrounding rocks of a certain underground plant was analyzed. The effect of surface load and weakening the parameters intensity of argillaceous and bioclastic interlayers between soft and hard rock on rheological behavior of layer composite rock mass was investigated. The results indicate that the rheological characteristics of soft and hard rock layer in composite rock mass can be described well with above two rheological models.

  15. THE APPLICATION OF ACOUSTIC LOGGING METHOD IN THE MODEL AND PARAMETERS IDENTIFICATION OF ROCK MASS

    Institute of Scientific and Technical Information of China (English)

    于师建

    1999-01-01

    This paper describes the new method that is introduced into prediction of subsidence using system engineering method with acoustic logging and density logging. According to the result of acoustic logging, the real and complex rock beds are divided into a set of different bed groups and the equivalent mechanical model is to be built. Based on the modern control theory, according to the input data (convergence or settlement of the roof) and the output data (surface movement and deformation) of the system, the static parameters of equivalent rock beds can be derived from back calculation using the optimum method. Then the regression relationship between the dynamic and static parameters can be built. So the prediction of rock and ground movements for other areas in the same district can be done, when using this relationship with the acoustic logging data and density logging data in situ.

  16. Rock salt mass in the Paleoproterozoic sequence of the Onega trough in Karelia (from the Onega parametric well data)

    Science.gov (United States)

    Morozov, A. F.; Khakhaev, B. N.; Petrov, O. V.; Gorbachev, V. I.; Tarkhanov, G. V.; Tsvetkov, L. D.; Erinchek, Yu. M.; Akhmedov, A. M.; Krupenik, V. A.; Sveshnikova, K. Yu.

    2010-11-01

    A thick (200 m) rock salt mass covering Late Archean granitoids was exposed for the first time in the Early Proterozoic volcanogenic-sedimentary formations in the Onega trough of the east Baltic Shield by the Onega parametric well. The mineral composition of salts, their geochemical features, and the isotopic composition of carbonate carbon and oxygen have been studied. After fluid inclusions present in salts, their metamorphism temperature and isotopic composition of helium and argon were determined. The obtained results give evidence of the fact that rock salts and magnesites associated with them were formed in an evaporate basin with participation of deep crustal processes. The age of the underlying granitoids (2.716 ± 9 Ma) is determined using the Pb—Pb method.

  17. Intelligent Displacement Back Analysis of Surrounding Rock Parameters of the Mined Subway Tunnel in Changchun%长春地铁暗挖隧道围岩参数智能位移反分析

    Institute of Scientific and Technical Information of China (English)

    王志斌; 麻凤海; 张碧雪

    2015-01-01

    为了更加真实的反映岩土体整体特性主要力学参数的取值,以长春地铁某暗挖区间现场监测位移值为依据,通过敏感性分析,确定了该地区对地表变形影响最大的力学参数为弹性模量 E和内摩擦角φ,运用Madis GTS三维正算模型、BP神经网络模型组成的智能位移反分析系统对其进行了反分析。运用反分析得到的参数值进行数值模拟,将得到的监测断面位移值与实测值进行了对比,并根据断面的位移云图对隧道围岩的稳定性进行了评价,验证了反分析结果的合理性和准确性。%In order to determine the value of the main mechanical parameters that could truely reflect the global property of rock and soil ,the mining section of Changchun subway was taken as the engineering background ,and it was confirmed that the mechanical parameters with the greatest impact on the surface deformation were the elasticity modulus E and in-ternal friction angle φ,based on the sensitivity analysis of the field monitoring displacement data .And then the intelli-gent displacement back analysis system formed by the Midas GTS 3D forward solution model and BP neural network was applied for the back analysis of these parameters .The new parameters obtained from the back analysis were used in the simulation analysis ,and the displacement value was calculated and then compared with the monitoring data .According to the displacement cloud picture of the section ,the stability of the tunnel surrounding rock was evaluated ,and the rational-ity and accuracy of the back analysis result was verified .

  18. 大连地下石油储备库洞室群围岩稳定性及渗流场分析%ANALYSES OF SURROUNDING ROCK STABILITY OF CAVERN GROUP AND SEEPAGE FIELD AT DALIAN UNDERGROUND OIL STORAGE

    Institute of Scientific and Technical Information of China (English)

    于崇; 李海波; 周庆生

    2012-01-01

    为分析水封式大连地下石油储备库洞室群围岩稳定性及渗流场特征,首先基于现场地应力实测结果的回归分析,利用Fish语言编写函数,反演初始地应力场.其次,采用三维离散元程序3DEC生成三维节理网络模型,反演库区初始渗流场的各向异性特征.最后,利用应力与渗流耦合模块实施开挖仿真计算,获取围岩应力场、位移场变化特征.考虑平行、垂直层理面不同材料特性,基于带有抗拉的Mohr-Coulomb强度储备型点安全系数,定量评价洞室群的稳定性.借鉴国外水封效果评价标准,分别从地下水位线和垂直水力坡降2个方面,分析渗流场变化特征.研究表明:在洞室周边平行层理面点安全系数为1.02~1.25,垂直层理面点安全系数为1.95~2.00.在补水隧道及注水孔组成的人工水幕系统作用下,建设期内地下水位下降3~5 m,地下水位距洞室顶55 m.开挖洞室附近平均垂直水力坡降大于1.0,满足设计规范及密封性要求.%Aiming at analyses of surrounding rock stability of cavern group and seepage field characteristics at Dalian water-tight underground oil storage, firstly, based on regression analysis of in-situ stress testing data, initial in-situ stress field inversion is conducted with functions defined with program language Fish. Secondly, after three-dimensional random joint networks with different sizes are generated with 3DEC. a new method of calculating the anisotropy permeability is proposed. Finally, stress field and displacement field of surrounding rocks are gained using coupled fluid and mechanical excavation calculations. Based on point safety factor, whose criterion is the Mohr-Coulomb one with the tensile strength, cavern group stability is quantitatively evaluated considering parallel and vertical bedding planes owing to different materials characteristics. Referring to ideas from abroad, seepage field is analyzed by groundwater table and vertical

  19. The role of post-failure brittleness of soft rocks in the assessment of stability of intact masses: FDEM technique applications to ideal problems

    Science.gov (United States)

    Lollino, Piernicola; Andriani, Gioacchino Francesco; Fazio, Nunzio Luciano; Perrotti, Michele

    2016-04-01

    Strain-softening under low confinement stress, i.e. the drop of strength that occurs in the post-failure stage, represents a key factor of the stress-strain behavior of rocks. However, this feature of the rock behavior is generally underestimated or even neglected in the assessment of boundary value problems of intact soft rock masses. This is typically the case when the stability of intact rock masses is treated by means of limit equilibrium or finite element analyses, for which rigid-plastic or elastic perfectly-plastic constitutive models, generally implementing peak strength conditions of the rock, are respectively used. In fact, the aforementioned numerical techniques are characterized by intrinsic limitations that do not allow to account for material brittleness, either for the method assumptions or due to numerical stability problems, as for the case of the finite element method, unless sophisticated regularization techniques are implemented. However, for those problems that concern the stability of intact soft rock masses at low stress levels, as for example the stability of shallow underground caves or that of rock slopes, the brittle stress-strain response of rock in the post-failure stage cannot be disregarded due to the risk of overestimation of the stability factor. This work is aimed at highlighting the role of post-peak brittleness of soft rocks in the analysis of specific ideal problems by means of the use of a hybrid finite-discrete element technique (FDEM) that allows for the simulation of the rock stress-strain brittle behavior in a proper way. In particular, the stability of two ideal cases, represented by a shallow underground rectangular cave and a vertical cliff, has been analyzed by implementing a post-peak brittle behavior of the rock and the comparison with a non-brittle response of the rock mass is also explored. To this purpose, the mechanical behavior of a soft calcarenite belonging to the Calcarenite di Gravina formation, extensively

  20. Green and Fast Laser Fusion Technique for Bulk Silicate Rock Analysis by Laser Ablation-Inductively Coupled Plasma Mass Spectrometry.

    Science.gov (United States)

    Zhang, Chenxi; Hu, Zhaochu; Zhang, Wen; Liu, Yongsheng; Zong, Keqing; Li, Ming; Chen, Haihong; Hu, Shenghong

    2016-10-18

    Sample preparation of whole-rock powders is the major limitation for their accurate and precise elemental analysis by laser ablation inductively-coupled plasma mass spectrometry (ICPMS). In this study, a green, efficient, and simplified fusion technique using a high energy infrared laser was developed for major and trace elemental analysis. Fusion takes only tens of milliseconds for each sample. Compared to the pressed pellet sample preparation, the analytical precision of the developed laser fusion technique is higher by an order of magnitude for most elements in granodiorite GSP-2. Analytical results obtained for five USGS reference materials (ranging from mafic to intermediate to felsic) using the laser fusion technique generally agree with recommended values with discrepancies of less than 10% for most elements. However, high losses (20-70%) of highly volatile elements (Zn and Pb) and the transition metal Cu are observed. The achieved precision is within 5% for major elements and within 15% for most trace elements. Direct laser fusion of rock powders is a green and notably simple method to obtain homogeneous samples, which will significantly accelerate the application of laser ablation ICPMS for whole-rock sample analysis.

  1. High-precision thermal ionization mass spectrometry dating of young volcanic rocks by using U-series method

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    A high precision thermal ionization mass spectrometric (HP-TIMS) technique is used to determine 238U,234U,232Th,230Th concentrations and their ratios in whole rocks and minerals separated from Quaternary Maanshan,Dayingshan and Heikongshan volcanic rocks of Tengchong volcanic field,Yunnan Province,China.The 238U-230Th isochrons are given,yielding four age values (227± 20) ka (D-1,Dayingshan),(79.6± 5.5) ka (D-7,Dayingshan),(21.9± 3.0) ka (h-1,Heikongshan),and (7.5± 1.0) ka (M-1,Maanshan).The result is not only consistent with but also preciser than those measured by the K-Ar method and the alpha spectrometry U-series method,indicating that the HP-TIMS method is reliable and has high precision.Besides,a procedure of HP-TIMS analysis of young volcanic rocks in China is set up preliminarily.

  2. Some Open Issues on Rockfall Hazard Analysis in Fractured Rock Mass: Problems and Prospects

    Science.gov (United States)

    Ferrero, Anna Maria; Migliazza, Maria Rita; Pirulli, Marina; Umili, Gessica

    2016-09-01

    Risk is part of every sector of engineering design. It is a consequence of the uncertainties connected with the cognitive boundaries and with the natural variability of the relevant variables. In soil and rock engineering, in particular, uncertainties are linked to geometrical and mechanical aspects and the model used for the problem schematization. While the uncertainties due to the cognitive gaps could be filled by improving the quality of numerical codes and measuring instruments, nothing can be done to remove the randomness of natural variables, except defining their variability with stochastic approaches. Probabilistic analyses represent a useful tool to run parametric analyses and to identify the more significant aspects of a given phenomenon: They can be used for a rational quantification and mitigation of risk. The connection between the cognitive level and the probability of failure is at the base of the determination of hazard, which is often quantified through the assignment of safety factors. But these factors suffer from conceptual limits, which can be only overcome by adopting mathematical techniques with sound bases, not so used up to now (Einstein et al. in rock mechanics in civil and environmental engineering, CRC Press, London, 3-13, 2010; Brown in J Rock Mech Geotech Eng 4(3):193-204, 2012). The present paper describes the problems and the more reliable techniques used to quantify the uncertainties that characterize the large number of parameters that are involved in rock slope hazard assessment through a real case specifically related to rockfall. Limits of the existing approaches and future developments of the research are also provided.

  3. The Interplay of In Situ Stress Ratio and Transverse Isotropy in the Rock Mass on Prestressed Concrete-Lined Pressure Tunnels

    Science.gov (United States)

    Simanjuntak, T. D. Y. F.; Marence, M.; Schleiss, A. J.; Mynett, A. E.

    2016-11-01

    This paper presents the mechanical and hydraulic behaviour of passively prestressed concrete-lined pressure tunnels embedded in elastic transversely isotropic rocks subjected to non-uniform in situ stresses. Two cases are distinguished based on whether the in situ vertical stress in the rock mass is higher, or lower than the in situ horizontal stress. A two-dimensional finite element model was used to study the influence of dip angle, α, and horizontal-to-vertical stress ratio, k, on the bearing capacity of prestressed concrete-lined pressure tunnels. The study reveals that the in situ stress ratio and the orientation of stratifications in the rock mass significantly affect the load sharing between the rock mass and the lining. The distribution of stresses and deformations as a result of tunnel construction processes exhibits a symmetrical pattern for tunnels embedded in a rock mass with either horizontal or vertical stratification planes, whereas it demonstrates an unsymmetrical pattern for tunnels embedded in a rock mass with inclined stratification planes. The results obtained for a specific value α with coefficient k are identical to that for α + 90° with coefficient 1/ k by rotating the tunnel axis by 90°. The maximum internal water pressure was determined by offsetting the prestress-induced hoop strains at the final lining intrados against the seepage-induced hoop strains. As well as assessing the internal water pressure, this approach is capable of identifying potential locations where longitudinal cracks may occur in the final lining.

  4. Geo-engineering evaluation of Termaber basalt rock mass for crushed stone aggregate and building stone from Central Ethiopia

    Science.gov (United States)

    Engidasew, Tesfaye Asresahagne; Barbieri, Giulio

    2014-11-01

    The geology of the central part of Ethiopia exhibits a variety of rock types that can potentially be developed for construction stone production, of which the most wide spread and important one is the Termaber basalt. Even though some preliminary work is done on these rocks towards construction material application, it remains largely that this resource is untouched and needs further scientific characterization for the use in large scale industrial application. Basaltic rocks have been widely used in many parts of the world as concrete aggregate and dimension stone for various civil structures. The present research study was carried out for Geo-engineering evaluation of Termaber basalt rock mass for crushed stone aggregate and building stone from Central Ethiopia (around Debre Birhan). The main objective of the present research study was to assess the general suitability of the Termaber basalt to be used as coarse aggregate for concrete mix and/or to utilize it as cut stone at industrial level. Only choice made with full knowledge of the basic characteristics of the material, of its performance and durability against the foreseen solicitations will ensure the necessary quality of the stone work and thereby a possibility to reach its intended service life. In order to meet out the objective of the present study, data from both field and laboratory were collected and analyzed. The field data included geological investigations based on different methods and sample collection while the laboratory work included, uniaxial compressive strength, ultrasonic pulse velocity, dynamic elasticity modulus, bulk density, water absorption, specific gravity, open porosity, aggregate impact value, petrographic examination and XRF, aggregate crushing value, Los Angeles abrasion value, sodium sulfate soundness, X-ray diffraction and alkali silica reactivity tests. The field and laboratory data were compiled and compared together to reveal the engineering performance of the rock mass in

  5. A numerical manifold method model for analyzing fully coupled hydro-mechanical processes in porous rock masses with discrete fractures

    Science.gov (United States)

    Hu, Mengsu; Rutqvist, Jonny; Wang, Yuan

    2017-04-01

    In this study, a numerical manifold method (NMM) model was developed for fully coupled analysis of hydro-mechanical (HM) processes in porous rock masses with discrete fractures. Using an NMM two-cover-mesh system of mathematical and physical covers, fractures are conveniently discretized by dividing the mathematical cover along fracture traces to physical cover, resulting in a discontinuous model on a non-conforming mesh. In this model, discrete fracture deformation (e.g. open and slip) and fracture fluid flow within a permeable and deformable porous rock matrix are rigorously considered. For porous rock, direct pore-volume coupling was modeled based on an energy-work scheme. For mechanical analysis of fractures, a fracture constitutive model for mechanically open states was introduced. For fluid flow in fractures, both along-fracture and normal-to-fracture fluid flow are modeled without introducing additional degrees of freedom. When the mechanical aperture of a fracture is changing, its hydraulic aperture and hydraulic conductivity is updated. At the same time, under the effect of coupled deformation and fluid flow, the contact state may dynamically change, and the corresponding contact constraint is updated each time step. Therefore, indirect coupling is realized under stringent considerations of coupled HM effects and fracture constitutive behavior transfer dynamically. To verify the new model, examples involving deformable porous media containing a single and two sets of fractures were designed, showing good accuracy. Last, the model was applied to analyze coupled HM behavior of fractured porous rock domains with complex fracture networks under effects of loading and injection.

  6. Filter property of stratified rock mass%层状岩体滤波特性研究

    Institute of Scientific and Technical Information of China (English)

    王观石; 龙平; 胡世丽

    2015-01-01

    用振幅、相位透射、反射系数描述应力波在结构面的波形变化,充分考虑应力波在层间、层内多重透射、反射条件下建立层状岩体中透射、反射系数计算模型;分别计算的层状岩体透射系数及波形与已有研究结果吻合,表明该模型计算结果合理。讨论结构面刚度、岩层厚度及结构面数量对层状岩体滤波特性影响。结果表明,结构面刚度及岩层厚度是影响弹性层状岩体滤波特性的主要因素,层状岩体具有多尺度梳状滤波器特性,随岩层厚度与波长之比γ增加,振幅透、反射系数成两种尺度周期性变化,由层内多重透、反射形成大尺度周期γ=0.5,并存在一个带通、一个带阻,在带通内又存在多个小尺度周期,由层间多重透、反射形成;层状岩体具有多带通滤波特性,结构面刚度增加,岩体带通上、下限频率同时增加,且上限频率增加幅度较下限大,随频率增加,带通宽度近似成负指数减小;所有岩层厚度相同时带通中心频率约为岩层一阶固有频率的整数倍,各岩层厚度不相等时层状岩体仅在各岩层共同谐振频率处表现为带通。%The waveform change of stress wave propagating across the interfaces can be described by the transmission and reflection coefficients of its amplitude and phase.The calculation model for the transmission and reflection coefficients of stress wave propagating through stratified rock mass was established on the basis of considering fully the conditions of propagating through multiple interlayers as well as the intrastratal transmissions and reflections.The transmission coefficient and transmission waveform through stratified rock mass were calculated using the established model,and the results are of good agreement with the previous research results.The analysis results show that the model is reasonable.The effects of interface stiffness,thickness of

  7. Preliminary study on interaction between plant frictional root and rock-soil mass

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    The interaction between lateral root system of woody plant and soil mass is similar to the one between shrub, herbage and soil mass, and has the effect of frictional reinforcement on slope soil. It plays an important role in reinforcing soil strength in shallow slope. Therefore, slope soil mass can be considered as a composite of soil and plant roots and the soil strength and stability of shallow slope soil mass are improved. However, current researches still remain on the level of qualitatively analyzing the relation between root and soil mass. In this paper, some exploratory researches on quantitative analysis of the interaction mechanism between root and soil mass are conducted. With the study of interaction between herbage root system (lateral root system of woody plants) and soil mass, the mechanical model of interaction between frictional root and soil mass is established. The accuracy of the model is verified by field experiments of Pinus Yunnanensis. The mechanical model provides a crucial theoretical guidance to quantitatively analyzing the interaction between plant root and soil mass; it also has certain values in application.

  8. Numerical analysis ofsandificated rock masses under the disturbance of excavation based on elastoplastic damage model%砂化岩体在开挖干扰下弹塑性损伤数值模拟

    Institute of Scientific and Technical Information of China (English)

    熊清蓉; 肖明; 胡田清

    2013-01-01

    以连续介质力学和不可逆热力学为基础,求解砂化岩体损伤演化方程,并将损伤引入到修正的弹塑性本构方程中,提出了适用于砂化岩体的弹塑性损伤三维有限元计算方法.该方法反映砂化岩体在开挖施工干扰下的岩体破坏过程.应用该方法进行数值模拟计算了坪头水电站引水隧道1#竖并开挖过程,分析成果与实际情况较为吻合,验证了该分析方法的合理性,为砂化岩体计算提供了理论依据.%Based on the irreversible thermodynamics and nonlinear continuum mechanics, the damage e-volution equation of rocks sandification is suggested and a new elastoplastic damage model with elastoplastic constitutive equation is presented. Furthermore, three-dimensional elastoplastic damage finite element numerical modeling iterating method for sandificated rock masses is put forward. Based on this method, the damage process of sandificated rock due to the disturbance of surrounding rock during shaft excavation is considered. The presented method is applied to the excavation of No. 1 shaft of seepage tunnel at Pingtou hydropower station. By making comparison with calculation results and in-situ observations, the rationality of this method is proved and the results are helpful for the design of sandificated rocks in similar projects.

  9. Measurements of I-129 in meteorites and lunar rock by tandem accelerator mass spectrometry

    Science.gov (United States)

    Nizhiizumi, K.; Arnold, J. R.; Elmore, D.; Gove, H. E.; Honda, M.

    1983-01-01

    Precise measurements of the half-life of I-129 in three different meteorites and one lunar surface rock are reported. The meteorite source of I-129 was produced by cosmic ray secondary neutron reactions on Te, while the source in lunar materials in spallation on barium and rare earth elements. The Abee, Allende, and Dhajala meteorites were examined, together with the lunar rock 14310. Details of the process used to extract the iodine are provided. The Abee and Allende samples exhibited a production of 0.5 atom/min per gm of Te from the (n,2n) reaction and 0.05 atom/min/gm for the (n,gamma) reaction. The I-129 is concluded to be a viable tool for long-lived cosmogenic nuclide studies. Further work to extend the data to include the constancy of the cosmic ray flux, the meteorite bombardment history, and the cosmic exposure age dating by means of the I-129 and Xe-129 method is indicated.

  10. Stresses induced by post-tensioned anchor in jointed rock mass

    Institute of Scientific and Technical Information of China (English)

    Alan Showkati; Parviz Maarefvand; Hossein Hassani

    2015-01-01

    A new analytical study on stresses around a post-tensioned anchor in rocks with two perpendicular joint sets is presented. The assumptions of orthotropic elastic rock with plane strain conditions are made in derivation of the formulations. A tri-linear bond-slip constitutive law is used for modeling the tendon-grout interface behavior and debonding of this interface. The bearing plate width is also considered in the analysis. The obtained solutions are in the integral forms and numerical techniques that have been used for evaluation. In the illustrative example given, the major principal stress is compressive in the anchor free zone and compressive stress concentrations of 815 kPa and 727 kPa (for the anchor load of 300 kN) are observed under the bearing plate and the bond length proximal end, respectively. However, large values of tensile stresses with the maximum of−434 kPa are formed at the bond length distal end. The results obtained using the proposed solution are compared very those of numerical method (FEM).

  11. Rules for confidence intervals of permeability coefficients for water flow in over-broken rock mass

    Institute of Scientific and Technical Information of China (English)

    Liu Weiqun; Fei Xiaodong; Fang Jingnian

    2012-01-01

    Based on the steady-state seepage method,we used the Mechanical Testing and Simulation 815.02 System and a self-designed seepage instrument for over-broken stone to measure seepage properties of water flows in three types of crushed rock samples.Three methods of confidence interval in describing permeability coefficients are presented:the secure interval,the calculated interval and the systemic interval.The lower bound of the secure interval can be applied to water-inrush and the upper bound can solve the problem of connectivity.For the calculated interval,as the axial pressure increases,the length of confidence interval is shortened and the upper and lower bounds are reduced.For the systemic interval,the length of its confidence interval,as well as the upper and lower bounds,clearly vary under low axial pressure but are fairly similar under high axial pressure.These three methods provide useful information and references for analyzing the permeability coefficient of over-broken rock.

  12. 新城金矿深部热环境分析及围岩温度测试%Analysis on Deep Thermal Environment and Temperature Measurement of Surrounding Rock in Xincheng Gold Mine

    Institute of Scientific and Technical Information of China (English)

    刘凯; 朱兆文; 朱万成; 刘洪磊; 侯晨

    2016-01-01

    随着开采深度的增加,新城金矿已经进入深部开采阶段,逐步面临高温热害问题。鉴于此,开展地下深部热环境分析,分析矿区主要热源及其形成机理,应用工程热力学手段量测不同开采深度下巷道风流温度、湿度以及风速等环境因素。采用深孔测量法测定不同深度的围岩温度,研究地温梯度变化规律。测试结果表明,巷道风温、水温均随着开采深度的增加而增大,主要生产中段相对湿度在80% RH以上,矿区恒温带温度为23℃,正常地温梯度为0.018℃/m,调热圈半径为17~18 m。该结果为有效控制井下作业场所的热环境状况以及热害防治研究提供了基础数据。%With the increase of mining depth,Xincheng Gold Mine has entered the stage of deep mining,and is gradually facing with the problem of high temperature stress. In this regard,an analysis of deep underground thermal environment was conducted,the main heat sources and the formation mechanism in the mining area were analyzed,environmental factors such as air temperature,humidity and wind speed of different mining depths of roadways were measured by means of Engineering Ther-modynamics. The temperature of surrounding rock in different depths was determined by Deep Hole Measurement Method and the variation regularity of geothermal gradient was studied. Test results show that the air temperature and water temperature of the roadways increase with the increasing of mining depth,the relative humidity of main mining levels are above 80% RH,the temperature of underground constant temperature zone in the mine area is 23 ℃, the normal geothermal gradient is 0. 018 ℃/m,and the radius of heat adjustment circle is 17~18 m,all these will provide basic data for the effective control of thermal environment conditions in underground workplaces and the prevention and treatment of thermal hazard.

  13. Equilizing of the Primary Stress State in the Rock Mass, Simulated by a Model of Layer in an Elastic-Viscous Medium

    Science.gov (United States)

    Kortas, Grzegorz

    2016-12-01

    This paper is devoted to the analysis of the stress development process in the homogeneous and non-homogeneous rock mass. The rock-mass model consists of an elastic-viscous medium containing a layer (Fig. 1) that displays distinct geomechanical strain properties. When examining the process of stress equilizing in time, the Norton-Bailey power creep law was applied in the numerical analysis. The relationship between effective stresses and time, the modulus of elasticity, Poisson's coefficient, and creep compliance were obtained. It was demonstrated that the relationship between effective stress and time or creep compliance, for the assumed conditions in a homogeneous rock-mass, was approximated by hyperbolic functions (10 and 16). The process parameter included a certain value of creep compliance or of time at which there occurred a half-way equilizing of primary stresses. An analogous function binds effective stresses with creep compliance. Our model studies indicated a number of relationships between bulk and shear strain with time and creep compliance in the homogeneous and non-homogeneous rock mass, presented in Figs. 2-14, expressed by the functions of those specific parameters. The relationships obtained in this work resulted from our model assumptions. However, they demonstrated the influence of the geomechanical strain properties of rocks on the process of shaping the primary stress state in the rock mass and the tendency to reduce the principal stress differences in time. Our research results suggested the necessity to simulate the primary stress state as an initial condition of the geomechanical numerical analysis concerning the rock-mass behaviour showing rheological properties.

  14. The relationship between geology and rock weathering on the rock instability along Mugling-Narayanghat road corridor, Central Nepal Himalaya

    OpenAIRE

    Regmi, Amar Deep; YOSHIDA, Kohki; Nagata, Hidehisa; Pradhan, Ananta Man Singh; Pradhan, Biswajeet; Pourghasemi, Hamid Reza

    2013-01-01

    The present study was conducted along the Mugling-Narayanghat road section and its surrounding region that is most affected by landslide and related mass-movement phenomena. The main rock types in the study area are limestone, dolomite, slate, phyllite, quartzite and amphibolites of Lesser Himalaya, sandstone, mudstone and conglomerates of Siwaliks and Holocene Deposits. Due to the important role of geology and rock weathering in the instabilities, an attempt has been made to understand the r...

  15. GREY CLASSIFICATION FOR EVALUATING THE STABILITY OF DANGEROUS ROCK-BLOCK MASSES

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    This paper introduces a grey classification method for evaluating the stability of dangerous rockblock masses according to the Grey System Theory. This method is applied to the stability of the V# dangerous rockblock masses of Qingjiang water conservancy project, and better results are abtained. The method which is advanced in the article is very single and practical, and it can meet all kinds of project′s demands.

  16. Stability Assessment of Natural Caves Using Empirical Approaches and Rock Mass Classifications

    Science.gov (United States)

    Jordá-Bordehore, L.

    2017-08-01

    The stability of underground voids such as caves can be assessed, in an initial approximation, by geomechanical classifications such as the Barton Q index. From a geomechanical viewpoint, the stability of 137 large span natural caves was analyzed herein. The caves were graphically represented based on existing tunnel and underground graphs, according to width and rock quality index Q. Many natural caves analyzed by a tunnel-type engineering approach could result as apparently unstable when represented in empirical existing graphics and would require reinforcements incompatible with speleothems and large chamber heights. A new graph and equation are proposed herein for the maximum span, for the exclusive case of caves, resulting in a reliable representation of large stable natural caves. The main contribution is a new stability chart for natural caves, consisting of two zones: a zone where stable caves are represented and a zone where unstable caves and collapsed caves are located.

  17. Model Test Research on the End Bearing Behavior of the Large-Diameter Cast-in-Place Concrete Pile for Jointed Rock Mass

    Directory of Open Access Journals (Sweden)

    Jingwei Cai

    2016-01-01

    Full Text Available For large-diameter, cast-in-place concrete piles, the end bearing capacity of a single pile is affected by discontinuous surfaces that exist in natural rock masses when the bearing layer of the pile end is located in the rock layer. In order to study the influence of the jointed dip angle on the bearing characteristics of the pile end, the discrete element models are adopted to simulate the mechanical characteristics of the jointed rock masses, and the model tests of the failure mode of the jointed rock masses were also designed. The results of the numerical calculations and modeling tests show that the joints, which have a filtering effect on the internal stress of the bedrock located at the pile end, change the load transferring paths. And the failure mode of the jointed rock foundation also changes as jointed dip angle changes. The rock located at the pile end generally presents a wedge failure mode. In addition, the Q-S curves obtained by model tests show that the ultimate end bearing capacity of a single pile is influenced by the jointed dip angle. The above results provide an important theoretical basis for how to correctly calculate end resistance for a cast-in-place concrete pile.

  18. Evaluation of the Impact of Hydrostatic Pressure and Lode Angle on the Strength of the Rock Mass Based on the Hoek–Brown Criterion

    Directory of Open Access Journals (Sweden)

    Marczak Halina

    2015-06-01

    Full Text Available Determination of the global uniaxial compressive strength of rock mass on the basis of the Hoek-Brown failure criterion requires knowledge of the strength parameters: cohesion and the angle of internal friction. In the conventional method for the determination of these parameters given by Balmer, they are expressed by the minimum principal stress. Thus, this method does not allow for the assessment of an impact of hydrostatic pressure and stress path on the value of cohesion, friction angle and global uniaxial compression of rock mass. This problem can be eliminated by using the Hoek-Brown criterion expressed by the invariants of the stress state. The influence of hydrostatic pressure and the Lode angle on the strength parameters of the rock mass was analysed.

  19. Modified hydropower slope rock mass stability rating system%改进的水电边坡岩体稳定性分级法

    Institute of Scientific and Technical Information of China (English)

    张菊连; 沈明荣

    2011-01-01

    为克服现有基于边坡岩体分级SMR法的修正分级法存在的缺陷,采用较为合理的修正模型,结合36个水电工程边坡,提出了改进的水电边坡岩体分级M-CSMR法.该法使用边坡类型系数替代开挖修正得分,同时考虑了开挖、水流冲刷及掏蚀作用的影响;将坡高对边坡岩体稳定性的影响引入分级中,给出坡高分级及评分原则;对SMR法中各指标权值重新进行调整.与岩体分级RMR法、边坡岩体分级SMR法及水电边坡岩体分级CSMR法进行了比较,结果表明MCSMR分级法与经验评分最为接近,预测结果最好,最大绝对误差、平均绝对误差及剩余标准差均最小,因此M-CSMR是一种更优的水电边坡岩体分级方法.%In order to overcome the defects in the existing modified mass rating system originated from slope rock mass rating (SMR) system, a more rational correction model was adopted to establish a modified Chinese hydropower slope rock mass rating (M-CSMR) system based on thirty six hydropower slopes.The coefficients of slope types were used to take the place of excavation factor to comprehensively take into account the influences of excavation, water erosion and scour on rock mass stability; the influence of slope height on rock mass stability was introduced into this system, and its grading and rating principle were given; the weights of factors in the SMR system were re-adjusted.Compared with rock mass rating (RMR) system, slope rock mass rating (SMR) system and Chinese slope rock mass rating (CSMR) system, the M-CSMR system's evaluation results are closer to the empirical rating based on safety of factor, the prediction results are better, the maximum absolute error, the mean absolute error and the residual standard deviation are all smaller, thus MCSMR is a better hydropower slope rock mass rating system.

  20. Numerical Simulation of P-Wave Propagation in Rock Mass with Granular Material-Filled Fractures Using Hybrid Continuum-Discrete Element Method

    Science.gov (United States)

    Gui, Y. L.; Zhao, Z. Y.; Zhou, H. Y.; Wu, W.

    2016-10-01

    In this paper, a cohesive fracture model is applied to model P-wave propagation through fractured rock mass using hybrid continuum-discrete element method, i.e. Universal Distinct Element Code (UDEC). First, a cohesive fracture model together with the background of UDEC is presented. The cohesive fracture model considers progressive failure of rock fracture rather than an abrupt damage through simultaneously taking into account the elastic, plastic and damage mechanisms as well as a modified failure function. Then, a series of laboratory tests from the literature on P-wave propagation through rock mass containing single fracture and two parallel fractures are introduced and the numerical models used to simulate these laboratory tests are described. After that, all the laboratory tests are simulated and presented. The results show that the proposed model, particularly the cohesive fracture model, can capture very well the wave propagation characteristics in rock mass with non-welded and welded fractures with and without filling materials. In the meantime, in order to identify the significance of fracture on wave propagation, filling materials with different particle sizes and the fracture thickness are discussed. Both factors are found to be crucial for wave attenuation. The simulations also show that the frequency of transmission wave is lowered after propagating through fractures. In addition, the developed numerical scheme is applied to two-dimensional wave propagation in the rock mass.

  1. Measurement and study of the distributing law of in-situ stresses in rock mass at great depth

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    To solve the technical cruxes of the conventional system in deep rock mass, an automatic testing system for hydraulic fracturing that includes a single tube for hydraulic loop, a pressure-relief valve, central-tubeless packers, and a multichannel real-time data acquisition system was used for in-situ stresses measurement at great depths (over 1000 m) in a coalfield in Juye of Northern China.The values and orientations of horizontal principal stresses were determined by the new system. The virgin stress field and its distributing law were decided by the linear regression from the logged 37 points in seven boreholes. Besides, the typical boreholes arranged in both the adjacent zone and far away zone of the faults were analyzed, respectively. The results show that a stress concentration phenomenon and a deflection in the orientation of the maximal horizontal stress exist in the adjacent zone of the faults, which further provides theoretical basis for design and optimization of mining.

  2. Experimental Investigation of the Anisotropic Mechanical Properties of a Columnar Jointed Rock Mass: Observations from Laboratory-Based Physical Modelling

    Science.gov (United States)

    Ji, H.; Zhang, J. C.; Xu, W. Y.; Wang, R. B.; Wang, H. L.; Yan, L.; Lin, Z. N.

    2017-07-01

    Because of the complex geological structure, determination of the field mechanical parameters of the columnar jointed rock mass (CJRM) was a challenging task in the design and construction of the Baihetan hydropower plant. To model the mechanical behaviour of the CJRM, uniaxial compression tests were conducted on artificial CJRM specimens with geological structure similar to that found in the actual CJRM. Based on the test results, the anisotropic deformation and strength were mainly analysed. The empirical correlations of evaluating the field mechanical parameters were derived based on the joint factor approach and the modulus reduction factor method. The findings of the physical model tests were then used to estimate the field moduli and unconfined compressive strengths of the Baihetan CJRM. The results predicted by physical model tests were compared with those obtained from the field tests and the RMR classification system. It is concluded that physical model tests were capable of providing valuable estimations on the field mechanical parameters of the CJRM.

  3. FROMS3D: New Software for 3-D Visualization of Fracture Network System in Fractured Rock Masses

    Science.gov (United States)

    Noh, Y. H.; Um, J. G.; Choi, Y.

    2014-12-01

    A new software (FROMS3D) is presented to visualize fracture network system in 3-D. The software consists of several modules that play roles in management of borehole and field fracture data, fracture network modelling, visualization of fracture geometry in 3-D and calculation and visualization of intersections and equivalent pipes between fractures. Intel Parallel Studio XE 2013, Visual Studio.NET 2010 and the open source VTK library were utilized as development tools to efficiently implement the modules and the graphical user interface of the software. The results have suggested that the developed software is effective in visualizing 3-D fracture network system, and can provide useful information to tackle the engineering geological problems related to strength, deformability and hydraulic behaviors of the fractured rock masses.

  4. Stability of High Slope Interbedded Strata with Low Dip Angle Constituted by Soft and Hard Rock Mass

    Institute of Scientific and Technical Information of China (English)

    邓荣贵; 周德培; 张倬元

    2002-01-01

    Slopes consisting of interbedded strata of soft and hard rock mass, such as purplish red mudstone and grey-brown arkosic sandstone of Jurassic age, are very common in Sichuan basin of China. The mudstone is soft while the sandstone is hard and contains many opening or closing joints with a high dip angle. Some are nearly parallel and the others are nearly decussated with the trend of the slopes. Many natural slopes are in deformation or sliding because of those reasons. The stability of cutting slopes and supporting method to be taken for their stability in civil engineering are important. In this paper, the stability and deformation of the slopes are studied. The methods of analysis and support design principle are analyzed also. Finally, the method put forward is applied to study Fengdian high cutting slope in Sichuan section of the express way from Chengdu to Shanghai. The results indicate that the method is effective.

  5. 美国某地下核废料库岩体变形分析%Analysis on One underground Nuclear Waste Repository Rock Mass in USA

    Institute of Scientific and Technical Information of China (English)

    哈秋舲; 张田田

    2012-01-01

    在美国某地下核废料库的岩体力学分析中,现行研究均基于加载力学条件,未考虑岩体卸荷损伤.根据该地下核废料库实际加载区岩体和卸荷不同的力学条件,结合现行的加载岩体力学和卸荷岩体力学对地下核废料库的岩体变形进行综合分析.结果表明,综合分析结果与该地下核废料库的变形实测数据基本一致;研究结果可为该地下核废料库的支护提供支撑数据.%When analyzing the rock mass of a underground nuclear waste repository, the current studies are all based on the loading mechanical condition, and the unloading damage of rock mass is unconsidered. According to the different mechanical condition of actual engineering rock mass of loading and unloading, this paper implements a comprehensive analysis on the rock mass deformation of underground nuclear waste repository through the combination of present loading and unloading rock mass mechanics. It is found that the results of comprehensive analysis and actual measured data on the rock mass deformation of underground nuclear waste repository are basically the same, which provide supporting data for the underground nuclear waste repository.

  6. ESTIMATION OF ROCK MASS MECHANICAL PARAMETERS BASED ON ULTRASONIC VELOCITY OF ROCK MASS AND HOEK-BROWN CRITERION AND ITS APPLICATION TO ENGINEERING%基于岩体波速的 Hoek-Brown 准则预测岩体力学参数方法及工程应用

    Institute of Scientific and Technical Information of China (English)

    夏开宗; 陈从新; 刘秀敏; 郑允; 周意超

    2013-01-01

      According to the established calculation formulae of geological strength index(GSI) and disturbed factor D for rock masses estimated by ultrasonic velocity of rock mass,the rock mass mechanical parameters are predicted by Hoek-Brown criterion based on ultrasonic velocity(the method of rock mass ultrasonic velocity for short). Then,taking Lancang River cross domain engineering slope rock mass of China—Myanmar oil and gas pipelines(domestic section) for example,based on the rock physico-mechanical parameters which were obtained by laboratory test and the wave test data,the rock mass mechanical parameters can be assessed according to the method of rock mass ultrasonic velocity and the Hoek-Brown criterion. It is shown that the calculation results of the method of rock mass ultrasonic velocity accords well with that of the method proposed by E. Hoek. The rationality of the method of rock mass ultrasonic velocity is further explained by numerical results. In addition,the proposed method provides a new approach to determine the mechanical parameters of rock mass,when test data are scant.%  根据建立的由岩体波速估算地质强度指标 GSI 和岩体扰动参数 D 的计算公式,引入 Hoek-Brown 准则,给出岩体波速预测岩体力学参数方法(简称岩体波速法)。以中缅油气管道(国内段)澜沧江跨域工程边坡岩体力学参数研究为例,并以室内岩石物理力学参数和场区声波测试数据为基础,采用岩体波速法和 E. Hoek 建议法预测场区的岩体力学参数。结果表明:岩体波速法和 E. Hoek 建议法所得的结果平均相对误差均较小,两者基本等效,数值模拟结果更进一步验证了工程应用效果的合理性。该方法在试验资料不足的情况下,能为岩体力学参数的快速评价提供一条新途径。

  7. Animal urine as painting materials in African rock art revealed by cluster ToF-SIMS mass spectrometry imaging.

    Science.gov (United States)

    Mazel, Vincent; Richardin, Pascale; Touboul, David; Brunelle, Alain; Richard, Caroline; Laval, Eric; Walter, Philippe; Laprévote, Olivier

    2010-08-01

    The rock art site at the village of Songo in Mali is a very important Dogon ritual place where, since the end of the nineteenth century until today, takes place the ceremony of circumcision. During these ceremonies, paintings are performed on the walls of the shelter with mainly three colors: red, black and white. Ethnological literature mentions the use of animal urine of different species such as birds, lizards or snakes as a white pigment. Urine of these animals is mainly composed of uric acid or urate salts. In this article, time-of-flight secondary ion mass spectrometry (ToF-SIMS) is used to compare uric acid, snake urine and a sample of a white pigment of a Dogon painting coming from the rock art site of Songo. ToF-SIMS measurements in both positive and negative ion modes on reference compounds and snake urine proved useful for the study of uric acid and urate salts. This method enables to identify unambiguously these compounds owing to the detection in negative ion mode of the ion corresponding to the deprotonated molecule ([M-H](-) at m/z 167.01) and its fragment ions. Moreover, the mass spectra obtained in positive ion mode permit to differentiate uric acid and urate salts on the basis of specific ions. Applying this method to the Dogon white pigments sample, we show that the sample is entirely composed of uric acid. This proves for the first time, that animal urine was used as a pigment by the Dogon. The presence of uric acid instead of urate salts as normally expected in animal urine could be explained by the preparation of the pigment for its application on the stone. Copyright 2010 John Wiley & Sons, Ltd.

  8. A numerical model of hydro-thermo-mechanical coupling in a fractured rock mass

    Energy Technology Data Exchange (ETDEWEB)

    Bower, K.M.

    1996-06-01

    Coupled hydro-thermo-mechanical codes with the ability to model fractured materials are used for predicting groundwater flow behavior in fractured aquifers containing thermal sources. The potential applications of such a code include the analysis of groundwater behavior within a geothermal reservoir. The capability of modeling hydro-thermo systems with a dual porosity, fracture flow model has been previously developed in the finite element code, FEHM. FEHM has been modified to include stress coupling with the dual porosity feature. FEHM has been further developed to implicitly couple the dependence of fracture hydraulic conductivity on effective stress within two dimensional, saturated aquifers containing fracture systems. The cubic law for flow between parallel plates was used to model fracture permeability. The Bartin-Bandis relationship was used to determine the fracture aperture within the cubic law. The code used a Newton Raphson iteration to implicitly solve for six unknowns at each node. Results from a model of heat flow from a reservoir to the moving fluid in a single fracture compared well with analytic results. Results of a model showing the increase in fracture flow due to a single fracture opening under fluid pressure compared well with analytic results. A hot dry rock, geothermal reservoir was modeled with realistic time steps indicating that the modified FEHM code does successfully model coupled flow problems with no convergence problems.

  9. Delineating Groundwater Vulnerability and Protection Zone Mapping in Fractured Rock Masses: Focus on the DISCO Index

    Directory of Open Access Journals (Sweden)

    Helen Meerkhan

    2016-10-01

    Full Text Available Hard-rock catchments are considered to be source of valuable water resources for water supply to inhabitants and ecosystems. The present work aims to develop a groundwater vulnerability approach in the Caldas da Cavaca hydromineral system (Aguiar da Beira, Central Portugal in order to improve the hydrogeological conceptual site model. Different types of information were overlaid, generating several thematic maps to achieve an integrated framework of key sectors in the study site. Thus, a multi-technical approach was used, encompassing field and laboratory techniques, whereby different types of data were collected from fields such as geology, hydrogeology, applied geomorphology and geophysics and hydrogeomechanics, with the fundamental aim of applying the so-called DISCO index method. All of these techniques were successfully performed and an intrinsic groundwater vulnerability to contamination assessment, based on the multicriteria methodology of GOD-S, DRASTIC-Fm, SINTACS, SI and DISCO indexes, was delineated. Geographic Information Systems (GIS provided the basis on which to organize and integrate the databases and to produce all the thematic maps. This multi-technical approach highlights the importance of groundwater vulnerability to contamination mapping as a tool to support hydrogeological conceptualization, contributing to improving the decision-making process regarding water resources management and sustainability.

  10. Proceedings of the workshop on numerical modeling of thermohydrological flow in fractured rock masses

    Energy Technology Data Exchange (ETDEWEB)

    1980-09-01

    Nineteen papers were presented at the workshop on modeling thermohydrologic flow in fractured masses. This workshop was a result of the interest currently being given to the isolation of nuclear wastes in geologic formations. Included in these proceedings are eighteen of the presentations, one abstract and summaries of the panel discussions. The papers are listed under the following categories: introduction; overviews; fracture modelings; repository studies; geothermal models; and recent developments. Eighteen of the papers have been abstracted and indexed.

  11. Dynamic design method for deep hard rock tunnels and its application

    Institute of Scientific and Technical Information of China (English)

    Xia-Ting Feng; Chuanqing Zhang; Shili Qiu; Hui Zhou; Quan Jiang; Shaojun Li

    2016-01-01

    Numerous deep underground projects have been designed and constructed in China, which are beyond the current specifications in terms of scale and construction difficulty. The severe failure problems induced by high in situ stress, such as rockburst, spalling, damage of deep surrounding rocks, and time-dependent damage, were observed during construction of these projects. To address these problems, the dynamic design method for deep hard rock tunnels is proposed based on the disintegration process of surrounding rocks using associated dynamic control theories and technologies. Seven steps are basically employed: (i) determination of design objective, (ii) characteristics of site, rock mass and project, and identification of constraint conditions, (iii) selection or development of global design strategy, (iv) determination of modeling method and software, (v) preliminary design, (vi) comprehensive integrated method and dynamic feedback analysis, and (vii) final design. This dynamic method was applied to the construction of the headrace tunnels at Jinping II hydropower station. The key technical issues encountered during the construction of deep hard rock tunnels, such as in situ stress distribution along the tunnels, mechanical properties and constitutive model of deep hard rocks, determination of me-chanical parameters of surrounding rocks, stability evaluation of surrounding rocks, and optimization design of rock support and lining, have been adequately addressed. The proposed method and its application can provide guidance for deep underground projects characterized with similar geological conditions.

  12. Imaging the state of the rock mass in the Kiirunavaara iron ore mine, Sweden, using local event tomography

    Science.gov (United States)

    Lund, Björn; Berglund, Karin; Tryggvason, Ari; Dineva, Savka; Jonsson, Linda

    2017-04-01

    Induced seismic events in a mining environment are a potential hazard, but they can be used to gain information about the rock mass in the mine which otherwise would be very difficult to obtain. In this study we use approximately 1.2 million mining induced seismic events in the Kiirunavaara iron ore mine in northernmost Sweden to image the rock mass using local event travel-time tomography. In addition, relocation of the events significantly improves the possibility to infer structural information and rock damage. The Kiirunavaara mine is one of the largest underground iron ore mines in the world. The ore body is a magnetite sheet of 4 km length, with an average thickness of 80 m, which dips approximately 55° to the east. Mining production is now at a depth of 785 - 855 m. During 2015 the seismic system in the mine recorded on average approximately 1,000 local seismic events per day. The events are of various origins such as shear slip on fractures, non-shear events and blasts, with magnitudes of up to 2.5. We use manually picked P- and S-waves in the tomography and we require that both phases are present as we found that events from the routine processing need screening for anomalous P- versus S-travel times, indicating occasional erroneous phase associations. For the tomography we use the 3D local earthquake tomography code PStomo_eq (Tryggvason et al., 2002), which we adjusted to the mining scale. The study volume is 1.2 x 1.8 x 1.8 km and the velocity model grid size is 10x10x10 meter. The tomographic images show clearly defined regions of high and low velocities. Low velocity zones are associated with mapped clay zones and areas of mined out ore, and also with the near-ore tunnel infrastructure in the foot-wall. We also see how the low S-velocity anomaly continues to depth below the current mining levels, following the inferred direction of the ore. The tomography shows higher P- and S-velocities in the foot-wall away from the areas of mine infrastructure. We

  13. Correlation of non-mass-like abnormal MR signal intensity with pathological findings surrounding pediatric osteosarcoma and Ewing's sarcoma

    Energy Technology Data Exchange (ETDEWEB)

    Masrouha, Karim Z.; Haidar, Rachid; Saghieh, Said [American University of Beirut Medical Center, Department of Surgery, Beirut (Lebanon); Musallam, Khaled M. [American University of Beirut Medical Center, Internal Medicine Division of Hematology and Oncology, Beirut (Lebanon); Samra, Alexis Bou; Tawil, Ayman; Chakhachiro, Zaher [American University of Beirut Medical Center, Pathology, Beirut (Lebanon); Abdallah, Abeer; Khoury, Nabil J. [American University of Beirut Medical Center, Diagnostic Radiology, Beirut (Lebanon); Saab, Raya; Muwakkit, Samar; Abboud, Miguel R. [American University of Beirut Medical Center, Children' s Cancer Center of Lebanon, Beirut (Lebanon)

    2012-11-15

    The aim of this work was to determine the role of MRI in interpreting abnormal signals within bones and soft tissues adjacent to tumor bulk of osteosarcoma and Ewing's sarcoma in a pediatric population by correlating MR findings with histopathology. Thirty patients met the inclusion criteria, which included (1) osteosarcoma or Ewing's sarcoma, (2) MR studies no more than 2 months prior to surgery, (3) presence of abnormal MR signal surrounding the tumor bulk, (4) pathological material from resected tumor. The patients received standard neoadjuvant chemotherapy. Using grid maps on gross pathology specimens, the abnormal MR areas around the tumor were matched with the corresponding grid sections. Histopathology slides of these sections were then analyzed to determine the nature of the regions of interest. The MR/pathological correlation was evaluated using Mann-Whitney U test and Fisher's exact test. Twenty-seven patients had osteosarcoma and three patients had Ewing's sarcoma. Of the studied areas, 17.4% were positive for tumor (viable or necrotic). There was no statistically significant correlation between areas positive for tumor and age, gender, signal extent and intensity on MRI, or tissue type. There was, however, a statistically significant correlation between presence of tumor and the appearance of abnormal soft tissue signals. A feathery appearance correlated with tumor-negative areas whereas a bulky appearance correlated with tumor-positive regions. MR imaging is helpful in identifying the nature of abnormal signal areas surrounding bone sarcomas that are more likely to be tumor-free, particularly when the signal in the soft tissues surrounding the tumor is feathery and edema-like in appearance. (orig.)

  14. 岩体通信技术研究中应注意的几个问题%Discussion on some problems in communication in rock mass

    Institute of Scientific and Technical Information of China (English)

    张仲礼

    2011-01-01

    岩体通信是通信信号在地层中的传播与接收,属无线电通信的一个分支.阐述了电流场通信的概念;指出电流场通信在煤矿应用的安全性不仅与信号功率有关,而且与信号频率相关;提出了岩体通信设备研制中频率确定的基本原则和岩体通信领域需要进一步研究的问题.%Communication in rock mass is a branch of radio communication, specially dealing with the study of transmission and reception of communication signals in strata. The paper, based on description of advantages of the application of communication technology in rock mass in underground engineering and mines, further states the concept of communication in electrical current field. It is indicated that the safety of the application of communication in electrical current field in coal mines is not only related to the signal power, but also to signal frequency. And it proposed problems needed to further study in determination of basic principles of development of communication equipment in rock mass and in the field of communication in rock mass.

  15. Research on the Application of Energy Conservative Principal in Lining Design of Tunnel with V-class Surrounding Rock%能量守恒原理在吁级围岩隧道衬砌设计中的应用研究

    Institute of Scientific and Technical Information of China (English)

    胡磊; 王志杰; 许瑞宁; 马安震; 何晟亚

    2014-01-01

    There exists energy delivery and transformation in the closed surrounding rock - tunnel lining system during the process of tunnel construction. When thermal energy transformation is left out of consideration and the surrounding rock is treated as an elastic body, the release of static energy of surrounding rock equals the increase in the elastic strain energy of tunnel lining. According to this energy conservative principle, Liu Hongyan and other researchers[1 2] calculated the thickness of lining of single track tunnel subject to Ⅲ-class surrounding rock. Based on these research findings, this paper further studies the application of energy conservative principle in V-class tunnel lining design. V-class surrounding rock of the three-dimensional FLAC3D model is established, dynamically simulating the process of tunnel excavation. With MATLAB language to the program of elastic strain energy density function, elastic strain energy of each unit of solid model is obtained, thus, static energy curves of surrounding rock associated with excavation depth within the specific scope of monitoring surrounding rock are finally obtained. According to the above curves, we are able to obtain the release value of static energy of surrounding rock. Additionally, toughness tests of steel fiber reinforced concrete ( SFRC) members are conducted, which leads to the finding of the relationship between energy expenditure of SFRC trisection beam under critical conditions and that of SFRC tunnel lining. Thus, theoretical tunnel lining thickness can be defined by solving the energy equation deduced from the energy expenditure relationship, and proved to satisfy the safety requirements. The research results show that, the tunnel lining design method with energy conservative principles is no longer limited by the conditions of II,Ⅲ-class surrounding rock in small section tunnels, and it is also applicable to the lining design of large section tunnels with Ⅴ-class surrounding rock.%在

  16. Lichenometric age measured on rock-falls related to historic seismicity affecting Lorca and its surroundings (Murcia, SE Spain); Datacion mediante liquenometria de los desprendimientos rocosos asociados a la sismicidad historica en Lorca (Murcia, SE de Espana)

    Energy Technology Data Exchange (ETDEWEB)

    Perez-Lopez, R.; Martin-Gonzalez, F.; Martinez-Diaz, J. J.; Rodriguez-Pascua, M. A.

    2012-11-01

    During the earthquake at Lorca (Murcia, SE Spain) in 2011 (5.2 Mw, 4km depth) several rock-falls occurred, mobilizing an estimated volume of close to 2,000 m3. All these rock-falls took place within the Estancias and La Tercia mountain ranges, the topography of which is composed of Tortonian calcarenitic sandstones with steep scarps more than 30 m in height. We have conducted a lichenometric study to obtain the age of the ancient rock-falls within the Las Estancias Range. We have assumed an annual growth rate of 0.24 mm for lichen species classified as calcicolous and related to warm climatic conditions. Our aim was to corroborate the hypothesis that seismic events triggered these massive rock-falls. The city of Lorca had experienced two nearfield historic earthquakes (1674 EMS VIII and 1818 EMS VI) and one far-field tremor during the great Lisbon earthquake in 1755 (EMS VI). Results obtained here indicate that the earthquakes of 1674 and 2011 were quite similar, except that the 1674 one mobilised a greater quantity and twenty times the volume of blocks mobilised during the 2011 earthquake. Therefore, we conclude that the size of the earthquake of 1674 was possibly between 6.0 < M < 6.8, assuming similar focal and seismotectonic conditions to those of the instrumentally measured earthquake of 2011. (Author) 34 refs.

  17. Proposal of a New Parameter for the Weathering Characterization of Carbonate Flysch-Like Rock Masses: The Potential Degradation Index (PDI)

    Science.gov (United States)

    Cano, M.; Tomás, R.

    2016-07-01

    The susceptibility of clay bearing rocks to weathering (erosion and/or differential degradation) is known to influence the stability of heterogeneous slopes. However, not all of these rocks show the same behaviour, as there are considerable differences in the speed and type of weathering observed. As such, it is very important to establish relationships between behaviour quantified in a laboratory environment with that observed in the field. The slake durability test is the laboratory test most commonly used to evaluate the relationship between slaking behaviour and rock durability. However, it has a number of disadvantages; it does not account for changes in shape and size in fragments retained in the 2 mm sieve, nor does its most commonly used index (Id2) accurately reflect weathering behaviour observed in the field. The main aim of this paper is to propose a simple methodology for characterizing the weathering behaviour of carbonate lithologies that outcrop in heterogeneous rock masses (such as Flysch slopes), for use by practitioners. To this end, the Potential Degradation Index (PDI) is proposed. This is calculated using the fragment size distribution curves taken from material retained in the drum after each cycle of the slake durability test. The number of slaking cycles has also been increased to five. Through laboratory testing of 117 samples of carbonate rocks, extracted from strata in selected slopes, 6 different rock types were established based on their slaking behaviour, and corresponding to the different weathering behaviours observed in the field.

  18. Deviatoric stress transfer and stability of surrounding rock in large-section open-off cut roof%大断面切眼顶板偏应力运移及围岩稳定

    Institute of Scientific and Technical Information of China (English)

    何富连; 许磊; 吴焕凯; 李通达

    2014-01-01

    To study the control mechanism of large-section open-off cut roof, No. 5205 open-off cut in a coal mine is selected as an engineering case. The deviatoric stress of roof, fracture field and deformation law are investigated by UDEC4.0 in the change process of width from 6 to 10 m. The results show that:(1) The deviatoric stress of roof gradually increases in shallow part and decreases in deep part. The wider the open-off cut, the lower the deviatoric stress in shallow part and the higher in deep part and the same time the peak of deviatoric stress is moving to the deeper part;(2) The fracture fild in surrounding rock were divided into three areas:fracture transfixion area, fracture area and microfracture area, which distributed as semi-ellipse;(3) With the width of open-off cut increasing, The trend of microfracture area transformed to fracture area and fracture area transformed to fracture transfixion area are strengthed in the roof. Besides, the roof subsidence is aggravated. It believed that:(1) The stability of unstable triangle block is the more important to keep roof safe;(2) High-performance bolt can control fracture slip preferably;(3) Double-truss and anchor rope can be anchored in the shoulder non-fracture area and deep roof pre-stressed superimposed area, which can control the expansion and deformation of fracture transfixion area in the middle part of the roof. Based on this, the combined support technology of high-strength and high pre-tension bolt&net &bar and double-truss and anchor rope is proposed. The observed results of mining pressures show that the open-off cut is self-stabilized after it is dug out for 10 days; the relative convergence of roof-to-floor is 128 mm; the relative convergence of both sides is 96 mm; and the separation of roof is 4 mm.%为了探究大断面切眼顶板控制机理,以某煤矿5205切眼为工程背景,采用UDEC4.0模拟了切眼宽度6~10 m过程中,顶板偏应力、裂隙场、变形规律等响应特征

  19. SEEPAGE FIELD-STRAIN FIELD COUPLING ANALYSIS FOR ROCK MASSES OF COAL SEAM FLOOR DURING MINING ABOVE A CONFINED AQUIFER%煤层底板岩体采动渗流场-应变场耦合分析

    Institute of Scientific and Technical Information of China (English)

    姚多喜; 鲁海峰

    2012-01-01

    根据五沟煤矿1018 工作面地质及水文地质条件,应用三维快速拉格朗日(FLAC3D)流固耦合分析模块,采用变渗透系数方法,对该工作面底板岩体采动渗流应变机制进行数值模拟研究.分析结果表明:采动影响下,围岩渗透系数发生较大的变化,处在采空区正上方的泥岩段最大达到原始渗透系数的1293倍;根据渗流场分析,工作面采动并没有破坏底板隔水层的阻水性能,采动裂隙没有导通灰岩含水层,灰岩水涌入回采工作面形成水害可能性较小;工作面正下方岩体单元安全度小于1的区域最大深度为30 m.综合渗流场以及隔水底板单元安全度分析结果,10煤底板下灰岩水溃入工作面形成水害可能性较小.%Based on the geological and hydrogeological conditions of the face 1018 in Wugou coal mine, the fluid-solid coupling module in FLAC3D with changeable permeability coefficient is adopted to simulate the whole process of damage and failure of rock masses at floor of the coal seam No. 10. The results indicate that the permeability coefficient of surrounding rocks changes a lot due to mining. The maximum permeability coefficient reaches 1 293 times of the original one, which happens at the immediate roof of mined-out area. According to the analysis of seepage field, mining does not destroy water resistance of floor aquifer. Mining fissures do not connect limestone aquifers, and water in the limestone is less likely to flow into stopes to cause damage. The maximum depth of rock masses with element safety degree less than one is about 30 m. According to the change of permeability coefficient of and the analytical results of element safety degree of rock masses, safe mining of the face 1018 can be ensured.

  20. Three-dimensional problems of wall-rock stability in the vicinity of a cleaned working with control exercised over the stress-strain state of the mass

    Energy Technology Data Exchange (ETDEWEB)

    Bulat, A.F.; Chekhov, V.N. [S.P. Timoshenko Inst. of Mechanics, Kiev (Ukraine)

    1995-02-01

    As the depth of mining operations increases, control over the stress-stain state (SSS) of the rock mass to ensure safe and effective exploitation of coal deposits is becoming a basic underground procedural process. An arbitrary change in the SSS of the mass under conditions where it is acted upon by large compressive loads may lead, in turn, however, to local buckling and fracture of the free surface of the rock in the near-face zone of a cleaned working during the mining of mineral resources. Individual classes of rock-stability problems that arise in the three-diumensional statement are formulated in this paper on the basis of analysis of actual conditions and technology for the mining of mineral resources at great depths. The rock mass is treated as a inhomogeneous semi-restrained medium of laminar structure; these studies were therefore conducted within the framework of the model of a piecewise-homogeneous medium on the basis of approaches developed previously. 8 refs., 2 figs., 2 tabs.

  1. Mass Dependent Fractionation of Hg Isotopes in Source Rocks, Mineral Deposits and Spring Waters of the California Coast Ranges, USA

    Science.gov (United States)

    Smith, C. N.; Kesler, S. E.; Blum, J. D.; Rytuba, J. J.

    2007-12-01

    We present here the first study of the isotopic composition of Hg in rocks, ore deposits, and active hydrothermal systems from the California Coast Ranges, one of Earth's largest Hg-depositing systems. The Franciscan Complex and Great Valley Sequence, which form the bedrock in the California Coast Ranges, are intruded and overlain by Tertiary volcanic rocks including the Clear Lake Volcanic Sequence. These rocks contain two types of Hg deposits, hot-spring deposits that form at shallow depths (geothermal systems that release Hg to the present surface. The Franciscan Complex and Great Valley Sequence contain clastic sedimentary rocks with higher concentrations of Hg than volcanic rocks of the Clear Lake Volcanic Field. Mean Hg isotope compositions for all three rock units are similar, although the range of values in Franciscan Complex rocks is greater than in either Great Valley or Clear Lake rocks. Hot spring and silica-carbonate Hg deposits have similar average isotopic compositions that are indistinguishable from averages for the three rock units, although δ202Hg values for the Hg deposits have a greater variance than the country rocks. Precipitates from dilute spring and saline thermal waters in the area have similarly large variance and a mean δ202Hg value that is significantly lower than the ore deposits and rocks. These observations indicate there is little or no isotopic fractionation during release of Hg from its source rocks into hydrothermal solutions. Isotopic fractionation does appear to take place during transport and concentration of Hg in deposits, especially in their uppermost parts. Boiling of hydrothermal fluids is likely the most important process causing of the observed Hg isotope fractionation. This should result in the release of Hg with low δ202Hg values into the atmosphere from the top of these hydrothermal systems and a consequent enrichment in heavy Hg isotopes in the upper crust through time.

  2. Determination of lanthanides in rock samples by inductively coupled plasma mass spectrometry using thorium as oxide and hydroxide correction standard

    Science.gov (United States)

    Raut, Narendra M.; Huang, Li-Shing; Aggarwal, Suresh K.; Lin, King-Chuen

    2003-05-01

    Determination of lanthanides by Inductively Coupled Plasma Mass Spectrometry (ICP-MS) using modified mathematical correction method has been studied. Normally, the ICP-MS analysis of middle and heavier lanthanides becomes difficult by severe spectroscopic overlap of M +, MO + or MOH + ions from lighter lanthanides and Ba. A correction method based on a single element oxide yield measurement, is a simple approach to correct for the above spectroscopic overlaps. But the uncertainty in the oxide and hydroxide yields measurement of lanthanides and barium over a long period of time can lead to inaccurate results even under fixed plasma conditions. To correct this, thorium was adopted as an oxide and hydroxide correction standard. Using a ratio of lanthanide oxide yield to thorium oxide yield, the lanthanide correction factors (LCF) were established and incorporated in the mathematical correction scheme. The same factors were also established for hydroxide correction. The proposed modified correction scheme was applied to the determination of lanthanides by ICP-MS from the USGS Standard Rock samples AGV-1 and G-2. The results are in good agreement with the reported values. The method also proved to be useful in isotopic ratio measurement of lanthanides having severe isobaric overlaps.

  3. Maternal thyroid hormones enhance hatching success but decrease nestling body mass in the rock pigeon (Columba livia).

    Science.gov (United States)

    Hsu, Bin-Yan; Dijkstra, Cor; Darras, Veerle M; de Vries, Bonnie; Groothuis, Ton G G

    2017-01-01

    Thyroid hormones (THs) - triiodothyronine (T3) and thyroxine (T4) - are essential for embryonic development in vertebrates. All vertebrate embryos are exposed to THs from maternal origin. As maternal TH levels are known to be essential to embryonic development, the natural variation of maternal THs probably represents a pathway of maternal effects that can modify offspring phenotype. However, potential fitness consequences of variation of maternal TH exposure within the normal physiological range and without confounding effects of the mother have never been experimentally investigated. We experimentally manipulated the levels of yolk T3 and T4 within the physiological range in a species in which the embryo develops outside the mother's body, the Rock Pigeon (Columba livia) eggs. Making use of the natural difference of yolk testosterone between the two eggs of pigeon clutches, we were also able to investigate the potential interaction between THs and testosterone. Elevated yolk TH levels enhanced embryonic development and hatching success, and reduced body mass but not tarsus length between day 14 and fledging. The yolk hormones increased plasma T4 concentrations in females but reduced it in males, in line with the effect on metabolic rate at hatching. Plasma concentrations of T3 and testosterone were not significantly affected. The effects of treatment did not differ between eggs with high or low testosterone levels. Our data indicate that natural variation in maternal yolk TH levels affects offspring phenotype and embryonic survival, potentially influencing maternal and chick fitness.

  4. Estimation Of The Mining Damage Risk In The Hypothetical Impact Area Of The Concurrent Processes Of Rock Mass Disorders

    Science.gov (United States)

    Piwowarski, Wiesław; Isakow, Zbigniew; Juzwa, Jacek

    2015-12-01

    The aim of this work is the estimation of the risk of mining damage occurrence, based on uncertain information regarding the impact of the concurrent processes of deformation and vibration. This problem concerns the experimental and theoretical description of the so-called critical phenomena occurring during the reaction mining area ↔ building object. Post-mining deformations of the rock mass medium and paraseismic vibrations can appear at a considerable distance from the sub-area of the mining operation - hence, the determination of the measures of their impacts is usually somewhat subjective, while the estimation of the mining damage based on deterministic methods is often insufficient. It is difficult to show the correlation between the local maximum of the impact of the velocity vector amplitude and the damage to the building - especially if the measures of interaction are not additive. The parameters of these impacts, as registered by measurements, form finite sets with a highly random character. Formally, it is adequate to the mapping from the probability space to the power set. For the purposes of the present study, the Dempster - Shafer model was used, where space is characterised by subadditive and superadditive measures. Regarding the application layer, the conclusions from the expert evaluations are assumed to be the values of random variables. The model was defined, and the risk of damage occurrence was estimated.

  5. The Importance of Physical Models for Deriving Dust Masses in Supernova Ejecta I: Radiatively Heated Dust Surrounding the Crab's Pulsar Wind Nebula

    CERN Document Server

    Temim, Tea

    2013-01-01

    Recent far-infrared (IR) observations of supernova remnants (SNRs) have revealed significantly large amounts of newly-condensed dust in their ejecta, comparable to the total mass of available refractory elements. The dust masses derived from these observations assume that all the grains of a given species radiate at the same temperature, regardless of the dust heating mechanism or grain radius. In this paper, we derive the dust mass in the ejecta of the Crab Nebula, using a physical model for the heating and radiation from the dust. We adopt a power-law distribution of grain sizes and two different dust compositions, and calculate the heating rate of each dust grain by the radiation from the pulsar wind nebula (PWN). We find that the grains attain a continuous range of temperatures, depending on their size and composition. The best-fit model to the observed IR spectrum consist of amorphous carbon grains with a total mass of 0.027+/-0.003 Msun. We find that the power-law size distribution of dust grains is cha...

  6. Lessons Learned from Near Field Modeling and Data Collected at the SPE Chemical Explosions in Jointed Rock Masses

    Science.gov (United States)

    Vorobiev, O.; Ezzedine, S. M.; Hurley, R.; Antoun, T.; Glenn, L.

    2016-12-01

    This work describes the near-field modeling of wave propagation from underground chemicalexplosions conducted at the Nevada National Security Site (NNSS) in fractured granitic rock. Lab testsperformed on granite samples excavated from various locations at the SPE site have shown littlevariability in mechanical properties. Granite at this scale can be considered as an isotropic medium. Wehave shown, however, that on the scale of the pressure waves generated during chemical explosions(tens of meters), the effective mechanical properties may vary significantly and exhibit both elastic andplastic anisotropies due to local variations in joint properties such as spacing orientation, joint aperture,cohesion and saturation. Since including every joint in a discrete fashion in computational model is notfeasible, especially for large-scale calculations ( 1.5 km domain), we have developed a computationaltechnique to upscale mechanical properties for various scales (frequencies) using geophysicalcharacterization conducted during recent SPE tests at the NNSS. Stochastic representation of thesefeatures based on the field characterizations has been implemented into LLNL's Geodyn-L hydrocode.Scale dependency in mechanical properties is important in order to understand how the ground motionscales with yield. We hope that such an approach will not only provide a better prediction of theground motion observed in the SPE (where the yield varies from 100 kg to few tons of TNT equivalent)but also will allow us to extrapolate results of the SPE to sources with bigger yields. We have validatedour computational results by comparing the measured and computed ground motion at various rangesfor experiments of various yields (SPE1-SPE5). Using the new model we performed severalcomputational studies to identify the most important mechanical properties of the rock mass specific tothe SPE site and to understand their roles in the observed ground motion in the near-field. We willpresent a series

  7. Quantitative analysis of major and trace elements in NH4HF2-modified silicate rock powders by laser ablation - inductively coupled plasma mass spectrometry.

    Science.gov (United States)

    Zhang, Wen; Hu, Zhaochu; Liu, Yongsheng; Yang, Wenwu; Chen, Haihong; Hu, Shenghong; Xiao, Hongyan

    2017-08-29

    In this paper, we described a NH4HF2 digestion method as sample preparation for the rapid determination of major and trace elements in silicate rocks using laser ablation-inductively coupled plasma mass spectrometry (LA-ICP-MS). Sample powders digested by NH4HF2 at 230 °C for 3 h form ultrafine powders with a typical grain size d80 rocks have a consistent grain morphology and size, allowing us to produce pressed powder pellets that have excellent cohesion and homogeneity suitable for laser ablation micro-analysis without the addition of binder. The influences of the digestion parameters were investigated and optimized, including the evaporation stage of removing residual NH4HF2, sample homogenization, selection of the digestion vessel and calibration strategy of quantitative analysis. The optimized NH4HF2 digestion method was applied to dissolve six silicate rock reference materials (BCR-2, BHVO-2, AGV-2, RGM-2, GSP-2, GSR-1) covering a wide range of rock types. Ten major elements and thirty-five trace elements were simultaneously analyzed by LA-ICP-MS. The analytical results of the six reference materials generally agreed with the recommended values, with discrepancies of less than 10% for most elements. The analytical precision is within 5% for most major elements and within 10% for most trace elements. Compared with previous methods of LA-ICP-MS bulk analysis, our method enables the complete dissolution of refractory minerals, such as zircon, in intermediate-acidic intrusive rocks and limits contamination as well as the loss of volatile elements. Moreover, there are many advantages for the new technique, including reducing matrix effects between reference materials and samples, spiking the internal standard simply and feasibly and sample batch processing. The applicability filed of the new technique in this study was focused on the whole-rock analysis of igneous rock samples, which are from basic rocks to acid rocks (45% rock analysis. Copyright © 2017

  8. Methods and results of investigation of the stressed state of rock masses and the development of effective means of controlling mine pressure during underground excavation of ore

    Energy Technology Data Exchange (ETDEWEB)

    Aitmatov, I.T.; Akhmatov, V.I.; Borshch-Komponiets, V.I.; Vlokh, N.P.; Egorov, P.V.; Kuznetsov, S.V.; Kurlenya, M.V.; Leont' ev, A.V.; Markov, G.A.; Murashev, V.I.

    1988-05-01

    Experimental and theoretical work conducted in the Soviet Union in determining the stressed state of rock masses and developing underground strata control measures are reviewed. Methods of determining stresses in a rock mass were classified into two groups: mechanical and geophysical. A geodynamic model of the stressed state of the upper layers of the earth's crust was developed based on direct measurements in shafts using methods and apparatus developed in the USSR. Fundamental laws governing the initial stressed state of the earth's crust show that within the limits of a geologically homogeneous block, gravitational and tectonic components of the overall stress field are present with gradients of the stress field and its random components. A study was made of the stress-strain state of chamber roofs; the results made it possible to substantiate the limiting spans of fissured roofs in cleaned chambers.

  9. 基于长期强度的节理岩体洞室蠕变特性研究%Study of creep characteristics of tunnel opening in joint rock mass based on long-term strength

    Institute of Scientific and Technical Information of China (English)

    于超云; 唐春安

    2014-01-01

    In order to reveal the creep properties of tunnel opening in joint rock mass, the Rock Failure Process Analysis System is used by the introduction of long-term strength of rock and the elastic-brittle consid-ered constitutive for meso-unit, which is different from the traditional methods of elastic-plastic or viscoelastic plastic constitutive to analyze the rheological properties of jointed rock on the view of macroscopic. The numer-ical simulations of jointed rock cavern under different conditions are investigated, and the effects of joint inter-val and joint angle on the creep and failure characteristics are analyzed. The calculation results show that the uniaxial creep deformation for rock mass decreases with the increase of joint interval and it increases with the increase of dip angle of joint plane if the angle is smaller than 45 ° , while the result will be quite on the contra-ry if the angle is larger than 45 ° . If the angle is 45 ° , a large number of failures in surrounding rock emerge and the characteristic accelerating creep stages are exhibited.%为了进一步探究节理岩体蠕变特性,摆脱传统意义上从宏观弹塑或粘弹塑本构的角度分析岩体流变特性的方法,将细观单元视为弹脆性的本构关系,采用考虑岩石长期强度的岩石破裂过程分析系统,通过对不同工况下的节理岩体洞室数值模拟,得到了节理间距和节理夹角对围岩蠕变特性及其破坏特征的影响规律。结果表明:节理岩体洞室围岩的蠕变量随着节理面间距的增大而减小;当节理面的水平夹角小于45°时,节理岩体洞室围岩蠕变量随着节理面夹角的增大而增大,但当节理面倾角大于45°时,蠕变量反而随着节理面倾角的增大而减小,当节理面倾角等于45°时,围岩出现大量破坏,并表现出加速蠕变的特征。

  10. In-situ stress measurements of rock mass: dome effect of the Peribonka project; Mesure des contraintes en rocher : effet de dome, project Peribonka

    Energy Technology Data Exchange (ETDEWEB)

    Babin, D.; Bouchard, R. [Techmat Inc., Jonquiere, PQ (Canada); Whalen, A. [Hydro-Quebec, Montreal, PQ (Canada). Geology and Rock Mechanics

    2006-07-01

    In order to determine the state of stress that exists perpendicular to natural planes found within the anorthositic rock mass at the site of the future Peribonka project, 43 hydrojacking tests were conducted in 2003 and 2004. The future project is currently under construction 200 km north of the town of Saguenay, Quebec. The primary objective was to determine the minimum stress field near the proposed headrace tunnels in order to calculate the required length of steel lining. Rock mass in-situ stress measurements were determined from geotechnical studies of boreholes. They were used to validate the optimal location of the headrace tunnels and the underground powerhouse. Seven different methods were used measure the state of stress. The rock mass, being dome shaped, affected the results in as they were consistently below the expected value. However, the value was sufficient to sustain the water pressure generated inside the headrace tunnels for the future powerhouse. Due to the topographical effects of the land, values were affected by the presence of two major shear zones, along the Peribonka and Manouane rivers. Therefore, the minimum stress field decreased significantly towards these structures. The results of the preliminary testing identified the ideal location of the future hydroelectric powerhouse. The results will also help reduce costs of future construction and minimize risks. 11 refs., 1 tab., 6 figs.

  11. Control of Formation of Lithological Reservoirs by Surrounding Mudstone

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Taking the Jiyang depression as an example, this paper discusses the control of the formation of lithological reservoir by surrounding rocks by integrated application of geological analysis, physical simulation, and the analysis of oil & gas accumulation mechanism. Geological statistical shows that the major burial depth and interval of lithological reservoirs in the Jiyang depression are related to the hydrocarbon generation in and expulsion from the Lower Tertiary source rocks and the time of the formation of most lithological reservoirs coincides with the peak of hydrocarbon generation and expulsion. The lithological traps located in the center of effective source rocks are propitious to high oil saturation than those located on the margin of effective source rocks. The hydrocarbon charge degree of the lithological reservoir has a positive correlation with the intensity of hydrocarbon expulsion from surrounding source rocks.Geological analyses and NMR experiments also show that the oil saturation of surrounding source rocks control the hydrocarbon potential of lithological traps, and a critical value for oil saturation of surrounding mudstone is required, that is, when the oil saturation of surrounding mudstone is lower than this critical value, no oil and gas accumulate in the lithological trap. The control of surrounding mudstone on the oil-bearing properties of lithological reservoirs is also analyzed by the mechanisms of hydrocarbon generation and expulsion as well as accumulation.

  12. New Directions: Questions surrounding suspended particle mass used as a surrogate for air quality and for regulatory control of ambient urban air pollution

    Science.gov (United States)

    Hoare, John L.

    2014-07-01

    The original choice of particulate matter mass (PM) as a realistic surrogate for gross air pollution has gradually evolved into routine use nowadays of epidemiologically-based estimates of the monetary and other benefits expected from regulating urban air quality. Unfortunately, the statistical associations facilitating such calculations usually are based on single indices of air pollution whereas the health effects themselves are more broadly based causally. For this and other reasons the economic benefits of control tend to be exaggerated. Primarily because of their assumed inherently inferior respirability, particles ≥10 μm are generally excluded from such considerations. Where the particles themselves are chemically heterogeneous, as in an urban context, this may be inappropriate. Clearly all air-borne particles, whether coarse or fine, are susceptible to inhalation. Hence, the possibility exists for any adhering potentially harmful semi-volatile substances to be subsequently de-sorbed in vivo thereby facilitating their transport deeper into the lungs. Consequently, this alone may be a sufficient reason for including rather than rejecting during air quality monitoring the relatively coarse 10-100 μm particle fraction, ideally in conjunction with routine estimation of the gaseous co-pollutants thereby facilitating a multi-pollutant approach apropos regulation.

  13. A preliminary study of the Xingshugou gold mineralization spots in the eastern segment of Kunlun orogenic belt and the dating of its surrounding rocks%东昆仑东段杏树沟金矿(化)点的成矿特征及其围岩时代的确定

    Institute of Scientific and Technical Information of China (English)

    时超; 李荣社; 何世平; 于浦生; 王超; 潘术娟; 张海迪

    2012-01-01

    东昆仑成矿带是中国西部重大成(找)矿潜力的贵金属-有色金属成矿带.对东昆仑东段都兰县诺木洪南部产于下石炭统哈拉郭勒组(C1h)中的杏树沟金矿(化)点进行了初步研究,认为该金矿(化)点受近东西向韧脆性剪切构造的控制,矿化带内中酸性脉岩发育,与构造蚀变岩型金矿有相似的特征,可以与东昆仑其它金矿对比,具有一定的成矿潜力.含矿围岩为一套火山碎屑岩-碎屑岩建造,矿化蚀变主要为褐铁矿化、孔雀石化和黄铁矿化.在围岩的灰岩夹层中发现大量珊瑚、腕足和腹足类化石,其中Siphonodendron asiatica Yabe et Hayasaka和Siphonodendron asiatica minor Minato这2种珊瑚化石是首次在哈拉郭勒组发现,这不仅丰富了哈拉郭勒组的化石组合类型,而且将杏树沟金矿(化)点的围岩时代进一步限定为早石炭世维宪期.%The Eastern Kunlun metallogenic belt is a precious metil—nonferrous metal ore—forming belt with great prospecting potential in western China. Some gold mineralization spots in Early Carboniferous Halaguole Formation were preliminarily studied during the investigation of Nomhon Township in Dulan County, which lies in the eastern segment of Kunlun orogenic belt. And it is thus believed that gold mineralization was affected by the EW—trending ductile shearing, with the development of acid dykes in these mineralization spots. These mineralization spots are similar to altered rock type gold deposits. The gold mineralization spots have some ore-forming potential because they are comparable with other ore deposits(spots) in eastern Kunlun metallogenic belt. The mineralization consists mainly of limonitization, pyritization and malachitization, with the surrounding rocks being pyroclastic rocks and clastic rocks. Fossils of corals, brachiopods and gastropod were found in the limestone interbed of the surrounding rocks in Halaguole Formation, and'two coral fossils, i

  14. 高应力大断面破碎围岩巷道二次强力支护支架设计%Design of Secondary High-Capacity Support to Large-Section Tunnel with Fractured Surrounding Rock Excavated on High-Stress Condition

    Institute of Scientific and Technical Information of China (English)

    陈新明; 郜进海

    2012-01-01

    To design high capacity support to deep large-section tunnel excavated in high-stress condition with fractured surrounding rock, for different section patterns of supports, the stresses and displacements of tunnel surrounding rock were analyzed with the change of lateral pressure coefficients. Particularly, the effect of height of double-layered I-section beam on the bearing capacity was investigated. As a result, an arched support with bottom arch superimposed and fully-closed I-section beam was developed with horse-shoe shaped structure. The bearing capacity of developed structure is 2.5 times higher than that of support using I-section beam. Underground field test shows that the deformation of the surrounding rock could be effectively controlled when the proposed secondary arched support is adopted.%为解决深部高应力大断面破碎围岩巷道支护难的问题,分析了不同支架断面形式随侧压系数的变化巷道围岩应力和位移的变化特征,以及双层工字钢梁的高度对承载受力大小影响特征.开发了适用于高应力大断面破碎围岩巷道拱形叠加底拱全封闭工字钢支架,该支架采用矿用工钢上下重叠并连接成整体的全封闭马蹄形结构,支架的整体承载能力比工字钢对棚提高了2.5倍以上.井下试验结果表明,拱形叠加底拱全封闭工字钢支架二次强力支护可以有效控制巷道围岩变形.

  15. Study on Surrounding Rock Classification of Railway Tunnel with HiPParion Laterite Stratum in West Piedmont of Lvliang Mountain%吕梁山西麓三趾马红土铁路隧道围岩分级研究

    Institute of Scientific and Technical Information of China (English)

    郭乐; 蔡云廷; 王家鼎

    2014-01-01

    The Hipparion laterite stratum in west piedmont of Lvliang Mountain is characterized by thick deposition, good continuity and lots of type sections, and has always been the research hotspot of Hipparion laterite. But, the study on its engineering geology features and geo-mechanics properties still remains very weak. So, surrounding rock classification in Hipparion laterite stratum is a new geological question faced by tunnel construction of Lvliang section of Middle and Southern Shanxi Railway project. Based on on-site monitoring, laboratory test and practical experience, this study researched the physical and mechanical indexes and strength property of Hipparion laterite, and analyzed relevant effects on Hipparion-laterite surrounding rock stability, including the underground water effect, fissuring effect, sandy soil interlayer effect, and the coupling effect of various factors. Finally, this study quantitatively discussed how to class the Hipparion-laterite surrounding rocks respectively under the conditions of homogeneity and multiple factors.%吕梁山西麓地区三趾马红土地层沉积厚度大、连续性好、典型剖面多,历来为三趾马红土研究的热点地区,但有关其工程地质特征及岩土力学性质方面的研究非常薄弱。三趾马红土围岩分级是山西中南部铁路通道工程吕梁段隧道建设面临的一项工程地质新问题。通过现场监测、室内试验研究及工程实践经验,研究三趾马红土的物理力学指标及强度特性,对影响三趾马红土围岩稳定性的地下水作用、裂隙作用、砂土夹层作用及各因素耦合作用进行分析,最后对三趾马红土在均质和多因素条件下围岩分级进行定量化探讨。

  16. DECOVALEX III/BENCHPAR PROJECTS. Implications of Thermal-Hydro-Mechanical Coupling on the Near-Field Safety of a Nuclear Waste Repository in a Homogeneous Rock Mass. Report of BMT1B/WP2

    Energy Technology Data Exchange (ETDEWEB)

    Jing, L. [Royal Inst. of Technology, Stockholm (Sweden). Engineering Geology; Nguyen, T.S. [Canadian Nuclear Safety Commission, Ottawa, ON (Canada)] (eds.)

    2005-02-15

    This report presents the works performed for the second phase (BMT1B) of BMT1 of the DECOVALEX III project for the period of 1999-2002. The works of BMT1 is divided into three phases: BMT1A, BMT1B and BMT1C. The BMT1A concerns with calibration of the computer codes with a reference T-H-M experiment at Kamaishi Mine, Japan. The objective is to validate the numerical approaches, computer codes and material models, so that the teams simulating tools are at a comparable level of maturity and sophistication. The BMT1B uses the calibrated codes to perform scoping calculations, considering varying degrees of THM coupling and varying permeability values of the surrounding rock for a reference generic repository design without fractures. The aim is to identify the coupling mechanisms of importance for construction, performance and safety of the repository. The chosen measures for evaluating the long term safety and performance of the repository are the maximal temperature created by the thermal loading from the emplaced wastes, the time for re-saturation of the buffer, the maximal swelling stress developed in the buffer, the structural integrity of the rock mass and the permeability evolution in the rock mass. Six teams participated in BMT1B: IRSN/CEA (France), CNSC (Canada), ANDRA/INERIS (France), JNC (Japan), BGR/ISEB-ZAG (Germany) and SKI/KTH (Sweden). All teams used FEM approach except the ANDRA/INERIS team who used the FDM approach, with different codes. All research teams except ISEB/ZAG used models with full THM coupling capabilities. The governing equations in these models were derived within the framework of Biot's theory of consolidation and have for primary unknown variables: temperature, pore fluid pressure and displacements of the solid skeleton. Since the original Biot's theory of consolidation is applicable to saturated materials and isothermal conditions, the research teams have to extend Biot's theory in order to deal with thermal effects and

  17. Practices Surrounding Event Photos

    NARCIS (Netherlands)

    Vyas, Dhaval; Nijholt, Antinus; van der Veer, Gerrit C.; Kotzé, P.; Marsden, G.; Lindgaard, G.; Wesson, J.; Winckler, M.

    Sharing photos through mobile devices has a great potential for creating shared experiences of social events between co-located as well as remote participants. In order to design novel event sharing tools, we need to develop indepth understanding of current practices surrounding these so called

  18. Rock Goes to School on Screen: A Model for Teaching Non-"Learned" Musics Derived from the Films "School of Rock" (2003) and "Rock School" (2005)

    Science.gov (United States)

    Webb, Michael

    2007-01-01

    What can be learned from two films with "rock" and "school" in their titles, about rock in school and about music and schooling more broadly? "School of Rock" (2003), a "family comedy," and "Rock School" (2005), a documentary, provoke a range of questions, ideological and otherwise, surrounding the inclusion of rock in formal instructional…

  19. 伊旗昊达煤矿围岩活动规律数值模拟研究%Numerical Simulation Research on Surrounding Rock Activities Regularity of Yiqihaoda Mine

    Institute of Scientific and Technical Information of China (English)

    魏永强

    2013-01-01

    伊旗昊达煤矿位于内蒙古自治区伊金霍洛旗境内,属浅埋煤层。研究有助于掌握伊旗昊达煤矿综采工作面围岩活动规律、矿山压力显现规律,为煤矿巷道支护设计、工作面开采方案设计提供依据。根据昊达煤矿的地质条件,应用FLAC软件对工作面及回采巷道进行了数值模拟。分析工作面回采过程中,围岩应力与变形的分布特征。保证工作面安全高效生产,使伊旗昊达煤矿在安全生产基础上进步提高煤炭产量,创造更大的经济效益。%Yiqihaoda mine is located in the territory of Inner Mongolia Autonomous Region Yinjinhuoluo, a shallow seam. The study helps to grasp the Yiqihaoda fully mechanized coal faces activity patterns, seam rules for coal roadway design, face provide a basis for the design of mining plan. According to Haoda mine geological conditions, apply software FLAC to numerical simulate roadway face. Analysis of the mining face during rock stress and deformation distribution. Ensure safe and efficient production of face, so the Iraqi flag Hao of mine production safety on the basis of progress to improve coal production and create greater economic benefits.

  20. Study on Splitting Failure Criterion of Surrounding Rock under Point Yield%裂纹尖端屈服条件下的围岩劈裂破坏判据研究

    Institute of Scientific and Technical Information of China (English)

    刘宁; 张春生

    2011-01-01

    The new fracture criterion is set up because the elastic fracture mechanics is not applicable for the plastic zone. Considering the interaction among cracks, the sliding multi-cracks model is adopted to simulate the splitting failure of rock in axial pressure. The plastic radius is calculated by Mises yield criterion and the dissipation energy for plastic deformation in total volume is also computed. The splitting failure criterion is established with principle of energy balance. The criterion is applied to the excavation of Langyashan pumped storage power station. The distribution charts of splitting failure zone are obtained, which coincides with results obtained by Lajtai empirical formula. It shows that the method is effective and feasible, which provides prediction criterion for splitting failure of underground engineering excavation in high geostress.%针对裂纹尖端附近出现塑性区时线弹性断裂力学理论不适用的问题,采用滑移裂纹组模型模拟岩石在轴向压力下的劈裂破坏,根据Mises屈服准则求出塑性区半径和整个体积中塑性变形引起的耗散能,基于能量平衡原理得到小范围屈服条件下的劈裂判据,将该判据应用于琅琊山抽水蓄能水电站机组的开挖分析中,计算获得了劈裂破坏区范围分布图,并与Lajtai经验公式进行比较,结果较为一致,表明该方法可行、有效,为地下工程开挖引起的劈裂破坏提供了预测判据.

  1. Borehole radar response characteristics of point unfavorable geo-bodies:forward simulation of its surrounding rock and filling condition%点状不良地质体钻孔雷达响应特征——围岩及充填效应正演分析

    Institute of Scientific and Technical Information of China (English)

    钟声; 王川婴; 吴立新; 唐新建; 王清远

    2012-01-01

    Borehole radar is a well geophysical method for obtaining the high-resolution information of deep underground environment. According to the common point unfavorable geo-bodies in borehole radar exploration, such as cavities, karst caves and buried objects, etc., the forward simulation of response of the tool to point unfavorable geo-bodies of different surrounding rock and filling condition is investigated with finite difference time domain (FDTD) method. The influence of surrounding rock and filling condition on response characteristics of borehole radar is analyzed. The results indicate that the relative value of dielectric constant of surrounding rock and filling substance affects the contrast of radar reflection profile, and when the relative value of dielectric constant increasing, it is easier to ascertain the subsurface media distribution. While high-conductivity surrounding rock can attenuate most of radar signal, it is almost impossible to detect the cavities with single borehole reflection method. According to the different borehole radar cross-sectiorn and its response characteristics, the filling condition in the cavities can be qualitatively distinguished.%钻孔地质雷达探测是一种有效获取高分辨率深部岩体信息的井中地球物理方法.针对钻孔地质雷达探测工作中常见的空洞、岩溶和地下埋藏物等点状不良地质体,利用时域有限差分数值模拟方法,对岩土体内点状不良地质体围岩介质和充填状况进行了雷达响应正演研究,分析了这些点状不良地质体围岩介质和充填状况对钻孔地质雷达反射信号的影响.研究结果表明,围岩与空洞内充填物的相对介电常数相对值,决定着雷达反射剖面信号的强弱对比,介电常数相对值较大时,更易确定目标地质体的前、后部界面位置,而低阻围岩的雷达波信号大部分被围岩介质吸收,通过单孔反射方法几乎不可能探测到空洞的存在.通过反射信

  2. Coupled Chemical and Thermal Processes During Contact Metamorphism: Constraining Rates and Duration with Time-Dependent 3-D Heat and Mass Transport Modeling of Fluid-Rock Systems

    Science.gov (United States)

    Dutrow, B. L.; Henry, D.; Gable, C. W.; Heydari, E.; Travis, B. J.

    2016-12-01

    Hydrothermal, metamorphic and metasomatic rocks develop through a complex set of coupled thermal, chemical and mechanical processes that contain non-linear feedbacks. The integrated outcome results in a mineral assemblage with a specific texture that records the rates, magnitude and duration of the controlling processes. However, it is often difficult to extract this coupled information from the rock record due to the competing and time-integrated nature of the final product. A particularly problematic case arises when advective metasomatism accompanies thermal energy transport. Advective transport of reactive components by thermally driven flowing fluids can dramatically alter the original bulk rock chemistry. In some instances, these chemical transformations are slow but in others, these alterations can occur over short time scales (yrs). To facilitate investigations of coupled, complex systems and to constrain the rates, duration and relative importance of governing processes during a thermal event, high-resolution 3-D time dependent computational modeling is used. An example of the integrated effects of thermal and chemical transport is found in subsurface Louisiana. Here, an 11m alkali igneous dike intruded Late Jurassic sandy limestones transforming these into new mineral assemblages rich in alkali, alkaline earth elements and F; hydrogrossular, diopside, pectolite (pct), apophyllite, fluorite, and feldspars. Increased temperatures (Ts) and significant mass transport of components from the dike into the host rocks are required. A series of coupled heat and mass transport calculations constrain the rates and duration of the thermal pulse and provide insights into the time-scale of mass transport within this system. For example, calculations incorporating silica transport indicate that at the pct zone (1.5m), thermal conditions remained above 150oC for 2.8 yrs assuming anisotropic permeability (K) and 4.2 yrs (layered K) reaching Tmax at 0.36 (aniso) or 0.53 yr

  3. Effect of intermittent joints on the mechanical properties of rock mass%断续节理对岩体力学性能的影响

    Institute of Scientific and Technical Information of China (English)

    金爱兵; 李兵; 邓富根

    2012-01-01

    采用颗粒流数值模拟程序,建立不同节理状态的岩石试样模型,对其进行双轴试验模拟,从岩桥长度、节理长度和倾角三个方面对断续节理影响下的岩体破裂形式和力学性质进行了数值模拟分析.岩桥的破裂方式为翼裂纹扩展下的拉剪复合破坏,模型破裂大致经历了翼裂纹的扩展、次生裂纹的延伸以及岩桥的贯通三个过程,而且表现出明显的蠕变特性以及延性破坏.岩桥长度的变化对峰值强度和弹性模量影响较小;相比岩桥长度,节理岩样的力学特性对节理长度更加敏感.对于不同的节理倾角,岩石试件表现出不同的初始破裂形式,0°倾角岩样的破裂方式为翼裂纹的扩展和次生裂纹的延伸,中间岩桥没有被贯通,15°倾角岩样的初裂强度和峰值强度最大.%The models of rock mass with different joint states were established by using particle flow code (PFC) numerical simulation procedures, and then their biaxial test was simulated. The effects of intermittent joints on the rupture forms and mechanical properties of rock mass were numerically analyzed from three aspects of rock bridge length, joint length, and dip angle. The failure mode of rock bridges is mainly tensile-shear failure because of the extension of wing cracks, but the failure mode of the models can be concluded to be the extension of wing cracks and secondary cracks and the failure of rock bridges, exhibiting obvious creep properties and ductile failure. The peak strength and elastic modulus are less influenced by the change in length of rock bridges; however, compared to the length of rock bridges, the mechanical properties of the jointed rock samples are more sensitive to the length of intermittent joints. As far as models with the different dip angles of intermittent joints are concerned, the initial rupture forms of the models are different, the failure mode of the model with the dip angle

  4. 节理塑性对岩体性能的影响分析(英文)%Impact of Joint Plasticity to Properties of Rock Mass

    Institute of Scientific and Technical Information of China (English)

    赵德安

    2002-01-01

    节理岩体的受力性能既取决于材料本身,又取决于节理面的力学性能.特别是剪切引起的节理面塑性性能对节理乃至整个岩体的力学反应都会有一定的影响.采用有限元方法并利用考虑节理塑性的弹塑性节理单元仿真裂缝,探讨了节理面塑性对节理体弹性性能的宏观影响.%Properties of the jointed rock mass depend not only on the material itself but also on the behaviour of the joints. The shearing induced plastic behaviour of a joint has certain impact on the mechanical response of the joint and on the jointed rock mass. This paper investigates the influence on the damage elasticity of the jointed mass due to the plasticity in joints. The analysis is based on a numerical model using an elasto-plastic joint element to simulate the discontinuities.

  5. Yucca Mountain Project thermal and mechanical codes first benchmark exercise: Part 3, Jointed rock mass analysis; Yucca Mountain Site Characterization Project

    Energy Technology Data Exchange (ETDEWEB)

    Costin, L.S.; Bauer, S.J.

    1991-10-01

    Thermal and mechanical models for intact and jointed rock mass behavior are being developed, verified, and validated at Sandia National Laboratories for the Yucca Mountain Site Characterization Project. Benchmarking is an essential part of this effort and is one of the tools used to demonstrate verification of engineering software used to solve thermomechanical problems. This report presents the results of the third (and final) phase of the first thermomechanical benchmark exercise. In the first phase of this exercise, nonlinear heat conduction code were used to solve the thermal portion of the benchmark problem. The results from the thermal analysis were then used as input to the second and third phases of the exercise, which consisted of solving the structural portion of the benchmark problem. In the second phase of the exercise, a linear elastic rock mass model was used. In the third phase of the exercise, two different nonlinear jointed rock mass models were used to solve the thermostructural problem. Both models, the Sandia compliant joint model and the RE/SPEC joint empirical model, explicitly incorporate the effect of the joints on the response of the continuum. Three different structural codes, JAC, SANCHO, and SPECTROM-31, were used with the above models in the third phase of the study. Each model was implemented in two different codes so that direct comparisons of results from each model could be made. The results submitted by the participants showed that the finite element solutions using each model were in reasonable agreement. Some consistent differences between the solutions using the two different models were noted but are not considered important to verification of the codes. 9 refs., 18 figs., 8 tabs.

  6. An experimental study of the creep properties of deep surrounding rocks and creep model identification%深部围岩流变特性试验研究及其模型辨识

    Institute of Scientific and Technical Information of China (English)

    刘正; 高文华; 刘栋; 邓修甫

    2012-01-01

    By means of stepwise incremental cycling loading and unloading, the experiment is conducted on uniaxial creep properties of siltstone at the floor of coal seam II in the eastern roadway beneath 300 m of the Shuijingtou coalmine of the Niumasi Mining Company of Hunan Xiangmei Group. The axial creep deformation properties are discribed in details in this paper. The relationship among creep rate, time and stress level is discussed. The properties of the instantaneous elastic modulus and the deformation modulus are explored. The test results show that the attenuation creep occurs and the creep rate is inconspicuously influenced by stress level when the stress level is lower than the long-term strength of siltstone. Constant rate creep occurs when the stress level is higher than the long-term strength of siltstone. Through scientific analysis of the experimental data, the creep model is identified and parameters of the model are determined based on the principle of least square. According to creep characteristics of rock under stepwise loading and unloading at different stress levels, a modified Nishihara model is established for simulating the creep characteristics. Calculation results show that the modified Nishihara model not only better describes attenuation creep under lower stress level, but also accurately describes attenuation creep and constant rate creep under higher stress levels.%采用分级增量循环加卸载方式,对湖南湘煤集团牛马司矿业公司水井头煤矿-300m东大巷二煤层底板粉砂岩进行了单轴蠕变特性试验,详细探讨了轴向蠕变变形特征,蠕变速率与时间和应力水平的关系,瞬时弹性模量和变形模量变化特征.试验结果表明,当应力水平低于岩石的长期强度时,粉砂岩只发生衰减蠕变,应力水平对蠕变速率变化的影响不明显;当应力水平高于岩石的长期强度时,岩石等速蠕变阶段明显.对流变试验数据进行深入分析的基础上,进行

  7. Synthetical deformation analysis of anchor bolt in jointed rock mass%节理岩体锚杆的综合变形分析

    Institute of Scientific and Technical Information of China (English)

    张伟; 刘泉声

    2012-01-01

    在总结国内外对节理岩体中锚杆加固机制的试验研究和理论探讨基础上,综合考虑锚杆的切向和轴向变形能力,建立节理锚固锚杆在剪切荷载作用下的变形模型,将节理锚固锚杆的变形区划分为弹性变形段和挤压破坏段,引入表征挤压破坏段长度的变量,对锚杆与岩体的相互作用机制进行理论分析,推导了剪切荷载与剪切位移和轴向荷载与轴向位移的关系.通过分析锚杆的屈服破坏形式,得到了确定挤压破坏段长度的方法.最后,通过算例分析了挤压破坏段长度与锚杆直径、岩体强度、锚固角度等参数的关系,得到了以下结论:(1)节理锚固锚杆抗剪作用的实质是锚杆调动岩体的抗压强度抵抗节理切向荷载.在抗压强度较高的硬岩中,挤压破坏段局限于节理面附近,锚杆影响范围小;而在抗压强度较低的软岩中,挤压破坏段较大,而且会产生较大的剪切变形,锚杆影响范围较大.(2)锚杆屈服破坏形式与岩质和锚杆直径有关.硬质岩体发生剪切屈服,而较软岩体中容易发生弯曲屈服;小直径锚杆一般直接剪切屈服,而大直径锚杆可能发生弯曲屈服.锚杆屈服破坏后出现塑性铰,挤压破坏段范围在节理一侧约为直径的1~2倍,继续增加剪切荷载,挤压破坏段长度不再增大.(3)随岩质的不同,锚杆锚固节理的最优锚固角变化较大.岩质较硬时,最优锚固角度较小,反之则较大.%Based on the former experimental and theoretical researches on the reinforcement mechanisms of anchor bolt in jointed rock mass at home and abroad, and comprehensive considering of the tangential and axial deformability of anchor bolt, a deformation model of joint bolts under shear load is proposed. The deformation of joint bolts is divided into two parts: elastic deformation zone and crushing failure zone. A variable is introduced to express the length of crushing failure zone. Mechanism

  8. Asymmetric Rock Pressure on Shallow Tunnel in Strata with Inclined Ground Surface

    Institute of Scientific and Technical Information of China (English)

    ZHOU Xiao-jun; YANG Chang-yu

    2007-01-01

    By building a tunnel model with a semi-circular crown, the asymmetric rock pressure applied to the shallow tunnel in strata with inclined ground surface is analyzed. Formulae, which not only include the parameters related to both tunnel structure and surrounding rock mass, but the overburden depth, are developed. The computation for four tunnel models show that the method presented is feasible and convenient. Furthermore, the influence of the overburden depth on the rock pressure is elaborated, and the criterion to identify the deep or shallow tunnels is formulated as well.

  9. Theoretical and numerical studies of crack initiation and propagation in rock masses under freezing pressure and far-field stress

    Directory of Open Access Journals (Sweden)

    Yongshui Kang

    2014-10-01

    Full Text Available Water-bearing rocks exposed to freezing temperature can be subjected to freeze–thaw cycles leading to crack initiation and propagation, which are the main causes of frost damage to rocks. Based on the Griffith theory of brittle fracture mechanics, the crack initiation criterion, propagation direction, and crack length under freezing pressure and far-field stress are analyzed. Furthermore, a calculation method is proposed for the stress intensity factor (SIF of the crack tip under non-uniformly distributed freezing pressure. The formulae for the crack/fracture propagation direction and length of the wing crack under freezing pressure are obtained, and the mechanism for coalescence of adjacent cracks is investigated. In addition, the necessary conditions for different coalescence modes of cracks are studied. Using the topology theory, a new algorithm for frost crack propagation is proposed, which has the capability to define the crack growth path and identify and update the cracked elements. A model that incorporates multiple cracks is built by ANSYS and then imported into FLAC3D. The SIFs are then calculated using a FISH procedure, and the growth path of the freezing cracks after several calculation steps is demonstrated using the new algorithm. The proposed method can be applied to rocks containing fillings such as detritus and slurry.

  10. 地下工程围岩变形快速化原位数字近景摄影测量系统研究%Study on in-situ digital close-range photogrammtry system for rapid surrounding rock deformation measurement in underground engineering

    Institute of Scientific and Technical Information of China (English)

    胡祥超; 吴祖堂; 朱宝良; 赵建伟; 鲁辉

    2014-01-01

    围岩变形测量贯穿整个地下工程施工过程。为降低与施工活动的相互干扰影响,对测量系统的原位化、快速化、小型化及自动化提出了迫切需求。提出了一种能够大幅提高系统相对测量精度的分段间接围岩收敛变形参数测量方法;研制了可应用于数字近景摄影测量的便携式精密三维活动控制场,其网型结构可灵活配置且无需重新校验;在此基础上,采用非量测数码相机和直接线性变换算法建立了一套便携式围岩变形原位测量系统。验证性实验结果表明系统相对测量精度高,具有便携性及小型化、自动化的特点,易于实现现场快速化、原位化地下工程围岩变形参数监测。%Surrounding rock measurement is a very important job during the underground engineering construction. There are urgent requirements for the in-situ, rapidity and miniaturization performances of the measurement system in order not to affect the construction progress. According to practical working area situation, a indirect section deformation measurement method of surrounding rock was proposed. A novel portable precision 3D control filed was developed which could be configured to a specific state of controlling net and not need to be checked again. A digital close-range photogrammetry measurement system was setup based on non-metric digital camera and DLT algorithm. There are conclusions from the experiment results that the measurement accuracy of the system is high which has advantages of portability, miniaturization and automation, as easy to implement in-situ and rapid surrounding rock deformation measurements.

  11. Method for evaluating coral reef rock mass integrity%珊瑚礁岩体完整性评价方法

    Institute of Scientific and Technical Information of China (English)

    汪进超; 王川婴

    2014-01-01

    目前,针对珊瑚礁的钻探勘察工作十分有限,获取完整的珊瑚礁地质信息则更加困难,而开展珊瑚礁的研究对我国海洋资源的开发和利用具有重要意义。结合西沙琛航岛地质调查,应用数字钻孔摄像技术,获得大量第一手地质资料,由于传统的岩体完整性指数(RMDI)法并不完全适用于珊瑚礁岩体的评价,考虑到珊瑚礁岩体的孔洞尺寸效应,提出珊瑚礁孔密度的概念,并建立孔密度函数和块度函数,从而改变传统RMDI法中的值,重新构建珊瑚礁岩体完整性密度函数(DIDF),最终确定珊瑚礁 RMDI 值,对珊瑚礁岩体的完整性进行评价,并应用于南海西沙群岛琛航岛数字钻孔摄像工程地质勘测中CK1孔的完整性评价,与其他评价结果一致,结果表明:高精度的钻孔图像能为珊瑚礁岩体完整性评价提供可靠的结果;孔密度函数能反映钻孔壁孔洞对珊瑚礁岩体影响程度的轴向分布状况;DIDF能反映钻孔孔壁珊瑚礁岩体完整程度的轴向分布状况;RMDI法用于评价珊瑚礁岩体完整性是可行的,能实现全孔或局部孔段的珊瑚礁岩体完整性评价。%At present, relatively few drilling surveys have been conducted on coral reefs, and comprehensive geological info on coral reefs is difficult to obtain. However, research on coral reef is of great importance to our development and exploitation of maritime resources. The survey of Chenhang Island in Paracell(Xisha) Islands saw China’s first usage of digital borehole camera technology, which resulted in a large amount of first-hand geological data, but the traditional rock mass integrity index (RMDI) method is not suitable for coral reef rock mass. To evaluate the size effect of cavities on coral reef rock mass, we proposed the concept of coral reef cavity density, and established the coral reef cavity density and block functions. Afterwards, the value

  12. FEM Analyses for T-H-M-M Coupling Processes in Dual-Porosity Rock Mass under Stress Corrosion and Pressure Solution

    Directory of Open Access Journals (Sweden)

    Yu-Jun Zhang

    2012-01-01

    Full Text Available The models of stress corrosion and pressure solution established by Yasuhara et al. were introduced into the 2D FEM code of thermo-hydro-mechanical-migratory coupling analysis for dual-porosity medium developed by the authors. Aiming at a hypothetical model for geological disposal of nuclear waste in an unsaturated rock mass from which there is a nuclide leak, two computation conditions were designed. Then the corresponding two-dimensional numerical simulation for the coupled thermo-hydro-mechanical-migratory processes were carried out, and the states of temperatures, rates and magnitudes of aperture closure, pore and fracture pressures, flow velocities, nuclide concentrations and stresses in the rock mass were investigated. The results show: the aperture closure rates caused by stress corrosion are almost six orders higher than those caused by pressure solution, and the two kinds of closure rates climb up and then decline, furthermore tend towards stability; when the effects of stress corrosion and pressure solution are considered, the negative fracture pressures in near field rise very highly; the fracture aperture and porosity are decreases in the case 1, so the relative permeability coefficients reduce, therefore the nuclide concentrations in pore and fracture in this case are higher than those in case 2.

  13. Study of anisotropic equivalent elastic parameters of jointed rock mass%节理岩体各向异性等效弹性参数研究

    Institute of Scientific and Technical Information of China (English)

    狄圣杰; 徐卫亚; 单治钢

    2013-01-01

    Analytical formulas of anisotropic equivalent elastic parameters are established by using mechanical method of complex material. An example is made to show the feasibility and efficiency of the analytical formulas. Meanwhile, the coordinate transformation and jointed factor of regular jointed rock mass are considered. The rules of equivalent elastic parameters of regular jointed rock mass are studied. Variation rules of equivalent elastic parameters under different jointed factors are analyzed. Combining with the properties of columnar jointed rock mass in Baihetan dam site, the anisotropic characteristics and values of elastic parameters are analyzed. The results show that the jointed rock mass can degenerate into isotropic medium when the stiffness is equal; and the calculated values by using the method in the paper are well in accord with the test results in the dam site. The cylinder deflection has more effect on the equivalent elastic parameters. The results also show that after deflection, the horizontal elastic modulus and vertical modulus are reduced by 54% and 17% respectively. According to the curves, the higher the angle of cylinder, the greater reduction the elastic modulus would have. This change rule of equivalent elastic parameters revealed obvious anisotropic property of columnar jointed rock mass.%采用复合材料力学分析方法,针对规则节理岩体考虑坐标转换及刚度系数,建立各向异性等效弹性参数的解析公式.通过算例证明了解析公式的可行性,同时对规则节理岩体等效参数规律性进行了研究,分析在不同的节理刚度比值下等效弹性参数的变化规律.结合白鹤滩坝址区柱状节理岩体特征,探讨了其等效弹性参数取值和各向异性特征.研究表明:所采用方法在刚度取值相等时岩体可退化为各向同性介质,且该方法计算结果与实测结果较为吻合;同时发现柱体偏转对等效弹性参数的影响较大,偏转后水平向和

  14. 金川水电站地下厂房裂隙围岩渗控效应数值模拟与评价%Numerical simulation and assessment of seepage control effects on surrounding fractured rocks of underground powerhouse in Jinchuan Hydropower Station

    Institute of Scientific and Technical Information of China (English)

    孙超伟; 柴军瑞; 许增光; 覃源

    2016-01-01

    针对金川水电站工程区复杂的地质条件和渗控措施,分别建立基于排水孔等效模拟的坝基整体模型和基于密集排水孔“弃孔算法”精细模拟的左岸厂区子模型,采用Signorini 型变分不等式和自适应罚函数相结合的稳定渗流分析方法对厂区围岩的长期渗控效应进行论证和敏感性分析。在数值模拟中,为了克服传统分析所采用的均质各向同性渗透系数不能反映裂隙岩体渗透特性的不足,首先根据两岸和坝基岩体优势裂隙组的空间展布情况,基于统计学方法初步确定其渗透系数张量并获得主值及主方向,再根据钻孔压水试验资料确定的等效渗透系数对其进行修正,并通过坝址区的地下水位反分析对该方法进行了验证。结果表明,运行期工况下防渗排水系统对山体地下水位具有控制作用,主变洞和发电机层底板处于自由面之上,厂房和调压室底板稍有承压性。帷幕的渗透特性、辅助排水孔幕以及排水孔间距对渗流场分布影响很小但能显著减小厂房洞室及排水廊道的渗漏量,因此应保证防渗帷幕的施工质量并建议设置辅助排水孔幕,建议中层廊道以下的排水孔间距设为3 m,中层廊道以上的排水孔间距放宽到4.5 m。%A global model of equivalent modeling and a submodel of accurate modeling based on“abandoned hole algorithm”for densely deployed drainage holes are established respectively to simulate the complicated seepage control measures and geological conditions for the underground hydropower cavern area at the left bank of Jinchuan Hydropower Station. The long-term seepage control effects of the surrounding rocks of the underground powerhouse and the sensitivity analysis of seepage control measures for the project design are performed by using the stationary seepage analysis method and combining the variational inequality formulation of Signorini’s type

  15. Observational study of rock mass response to mining induced seismic events and controlled blasting experiments at deep level gold mines in South Africa

    Science.gov (United States)

    Milev, A.; Durrheim, R. J.; Nakatani, M.; Yabe, Y.; Naoi, M. M.; Ogasawara, H.

    2012-12-01

    The strong ground motion generated by mining induced seismic events was studied to characterize the rock mass response and to estimate the site effect on the surface of the underground excavations. A stand-alone instruments, especially designed for recording strong ground motions, were installed underground at a number of deep level gold mines in South Africa. The instruments were recording data at the surface of the stope hangingwalls. A maximum value of 3 m/s was measured. Therefore data were compared to the data recorded in the solid rock by the mine seismic networks to determine the site response. The site response was defined as the ratio of the peak ground velocity measured at the surface of the excavations to the peak ground velocity inferred from the mine seismic data measured in the solid rocks. The site response measured at all mines studied was found to be 9 ± 3 times larger on average. In addition a number of simulated rockbursts were conducted underground in order to estimate the rock mass response when subjected to strong ground motion. The rockbursts were simulated by means of large blasts detonated in solid rock close to the sidewall of a tunnel. The numerical models used in the design of the simulated rockbursts were calibrated by small blasts taking place at each experimental site. A dense array of shock type accelerometers was installed along the blasting wall to monitor the attenuation of the strong ground motion as a function of the distance from the source. The attenuation of peak particle velocity was found to be proportional to R-1.7. In order to improve the understanding of the rock mass behaviour around deep level mining the rate of tilt was monitor and then compare to the seismic ground motion. A good correspondence between the rate of tilt and seismic ground motion was found. The rate of coseismic and aseismic tilt, as well as seismicity recorded by the mine seismic network, are approximately constant until the daily blasting time

  16. Mass Independent Fractionation of Sulphur Isotopes in Precambrian Sedimentary Rocks: Indicator for Changes in Atmospheric Composition and the Operation of the Global Sulphur Cycle

    Science.gov (United States)

    Peters, M.; Farquhar, J.; Strauss, H.

    2005-12-01

    Large mass independent fractionation (MIF) of sulphur isotopes in sedimentary rocks older than 2.3 Ga and the absence of this isotopic anomaly in younger rocks seem to be the consequence of a change in Earth's atmospheric composition from essentially oxygen-free or to oxygen-rich conditions. MIF is produced by photochemical reactions of volcanogenic sulphur dioxide with UV radiation in the absence of an ozone shield. The products of such processes are elemental sulphur with positive and sulphate with negative Δ33S values. Here we present isotope data (32S, 33S, 34S) for sedimentary pyrites from Archaean and Palaeoproterozoic rocks of the Kaapvaal Craton (South Africa), the Pilbara Craton (Australia) and the Greenland Shield (Isua Supercrustal Belt). Their ages range from 3.85 to 2.47 Ga. Large positive Δ33S values up to +9.13 ‰ in several Archaean units from the Kapvaal and Pilbara Cratons are attributed to low atmospheric oxygen at that time. Interestingly, very low Δ33S values between -0.28 and +0.57 ‰ appear to characterize the Witwatersrand succession of South Africa (3.0 Ga). This rather small MIF signature was previously detected in rocks of the same age in Western Australia (OHMOTO et al., 2005). The signature is interpreted as a global signal, which could be the consequence of a shielding effect induced by one or more atmospheric components. The most probable chemical compounds for this process are methane and carbon dioxide. Rocks of the Kameeldoorns Fm. (2.71 Ga), Kaapvaal Craton, display also low values between -0.46 and +0.33 ‰, which are consistent with the small (absent) MIF signal in rocks of the Hardey Fm. (2.76 Ga) of Western Australia (OHMOTO et al., 2005). Very low carbon isotope values between -51 and -40 ‰ in late Archaean kerogens (2.6 - 2.8 Ga) indicate a high concentration of methane in the atmosphere (PAVLOV et al., 2001). This high methane level could produce an organic haze, which absorbed most of the UV radiation and prevented

  17. Principles of rock mechanics

    Energy Technology Data Exchange (ETDEWEB)

    Turchaninov, I.A.; Iofis, M.A.; Kasparyan, E.V.

    1979-01-01

    This book presents the principles of rock mechanics in a systematic way, reflecting both the historic development and the contemporary status of theoretical and experimental techniques used for the determination of the properties and stress state of rock masses, calculation of elements of systems for exploitation of useful mineral deposits and the design of mine openings. The subject of rock mechanics is discussed and methods and basic approaches are analyzed. The most widely used methods for determining the properties of rock in specimens and in situ are described. Problems of determining the stress strain state of the rock around mine openings by both experimental and analytic methods are discussed. The primary results of the study of the stress state of rock around main, development and production openings are presented. Problems of the movement of rock due to extraction of minerals are analyzed in detail, as are the conditions and causes of the development of rock bursts and sudden release of rock and gas in both surface and underground mines. Procedures for preventing or localizing rock bursts or sudden outbursts are described. (313 refs.)

  18. Comparative analyses of model tests and in-situ monitoring of zonal disintegration of rock mass in deep tunnels%深部巷道围岩分区破裂现象的试验与现场监测对比分析研究

    Institute of Scientific and Technical Information of China (English)

    陈旭光; 张强勇; 杨文东; 李术才; 刘德军; 王汉鹏

    2011-01-01

    With the development of national economy and the drying up of shallow resources, the embedded depth of rock mass engineering becomes more and more deep. The phenomenon of zonal disintegration appears and is monitored in surrounding rock mass of deep tunnels. The special geological engineering phenomenon has attracted scholars' great attention in the field rock mechanics. However, the knowledge on the fracture shape and forming mechanism of the zonal disintegration is not quite enough. There is doubt about whether or not the connection on the in-situ TV observation can represent the whole tunnel impersonally. There is argument that the fractured zones are the concentric circle of the cavity or the spirals and slip lines- The issue determines the essence of the zonal disintegration and whether or not it is an unexplained new phenomenon by using the theory in existence. In order to know about the phenomenon in substance, geo-mechanical model tests are carried out on the deep mine tunnel of Dingji Coal Mine