Grouted Pile and Its Bearing Capacity
Institute of Scientific and Technical Information of China (English)
无
2000-01-01
The grouting method applied in bored pile is an improvement to the conventional bored pile. Load tests have proved that grouting under the bored pile tip is an effective method to enhance the bearing capacity of the pile and to reduce the pile settlement. In this paper, the grouting technology is described and pile-load test results are discussed. In order to put the grouting method into design practice, the authors analyze the working mechanism of soil compaction. And, based on the theory of cavities expansion in soil mass, approximate formulae are proposed for estimating the bearing capacity of the grouted pile. The theoretical prediction agrees well with the load test results.
Bearing Behaviors of Stiffened Deep Cement Mixed Pile
Institute of Scientific and Technical Information of China (English)
WU Mai; ZHAO Xin
2006-01-01
A series of investigations were conducted to study the bearing capacity and load transfer mechanism of stiffened deep cement mixed (SDCM) pile.Laboratory tests including six specimens were conducted to investigate the frictional resistance between the concrete core and the cementsoil.Two model piles and twenty-four full-scale piles were tested to examine the bearing behavior of single pile.Laboratory and model tests results indicate that the cohesive strength is large enough to ensure the interaction between core pile and the outer cement-soil.The full-scale test results show that the SDCM piles exhibit similar bearing behavior to bored and cast-in-place concrete piles.In general, with the rational composite structure the SDCM piles can transmit the applied load effectively, and due to the addition of the stiffer core, the SDCM piles possess high bearing capacity.Based on the findings of these experimental investigations and theoretical analysis, a practical design method is developed to predict the vertical bearing capacity of SDCM pile.
Bearing capacity and mechanical behavior of CFG pile composite foundation
Institute of Scientific and Technical Information of China (English)
陈秋南; 赵明华; 周国华; 张主华
2008-01-01
CFG pile (i.e., pile constructed by granular materials of cement, fly-ash and gravel) composite foundation is applied in subsoil treatment widely and successfully. In order to have a further study of this kind of subsoil treatment technology, the influencing factors and calculation methods of the vertical bearing capacity of single CFG pile and the CFG pile composite foundation were discussed respectively. And based on the obtained solutions, effects by the cushion and measurements to reduce negative friction area were analyzed. Moreover, the developing law of settlement and bearing capacity eigenvalue controlled by the material strength with the increase of load were given for the CFG composite foundation. The in-situ static load test was tested for CFG pile. The results of test show that the maximum test load or half of the ultimate load is used from all the points of test, the average bearing capacity eigenvalue of single pile is 390 kN, and slightly greater than the design value of bearing capacity. The bearing capacity eigenvalues of composite foundation for 3 piles are greater than 300 kPa, and the mechanical properties of CFG pile composite foundation are almost identical in the case of the same load and cushion thickness. The pile-soil stress ratio and the load-sharing ratio can be adjusted through setting up cushion thickness.
Vertical bearing capacity of pile based on load transfer model
Institute of Scientific and Technical Information of China (English)
ZHAO Ming-hua; YANG Ming-hui; ZOU Xin-jun
2005-01-01
The load transfer analytical method is applied to study the bearing mechanism of piles with vertical load in this paper. According to the different hardening rules of soil or rock around the pile shaft, such as work-softening, ideal elasto-plastic and work-hardening, a universal tri-linear load transfer model is suggested for the development of side and tip resistance by various types of soil (rock) with the consideration of sediment at the bottom of the pile. Based on the model, a formula is derived for the relationship between the settlement and load on the pile top to determine the vertical bearing capacity, taking into account such factors as the characteristics of the stratum, the side resistance along the shaft, and tip resistance under the pile tip. A close agreement of the calculated results with the measured data from a field test pile lends confidence to the future application of the present approach in engineering practice.
Bearing Capacity of Mixed Pile with Stiffness Core
Institute of Scientific and Technical Information of China (English)
YUE Jianwei; JIANG Xinliang; LING Guangrong
2006-01-01
To study load transfer mechanism and bearing capacity of a mixed pile with stiffness core (MPSC), which is formed by inserting a precast reinforced concrete pile (PRCP), in-situ tests involving MPSCs with different lengths, diameters, water cement ratios and PRCPs, cement mixed piles, and drilling hole piles, were carried out.Limit bearing capacities, load-settlement curves and stress distribution of MPSCs and mixed piles were obtained.The load transfer between cement soil and PRCP was analyzed by finite element method (FEM).Test results and FEM analysis show that an MPSC has fully utilized the big friction from a cement mixed pile and the high compressive strength from a PRCP which transfers outer top load into the inner cement soil, and that inserting a PRCP into a mixed pile changes the stress distribution of a mixed pile and improves frictional resistance between a mixed pile and soil.The length and the section area on PRCP of an MPSC both have an optimum value.Adopting MPSC is effective in improving the bearing capacity of soft soil ground.
The Influence of Time on Bearing Capacity of Driven Piles
DEFF Research Database (Denmark)
Jensen, J. Lysebjerg; Augustesen, A.; Sørensen, Carsten S.
2004-01-01
In Danish engineering practice, one of the ways to determine the ultimate bearing capacity of an axially loaded pile is by means of geostatic formulas. In the equation describing the contribution from the shaft friction to the total bearing capacity for piles located entirely or partly in clay......, a regeneration factor appears. The regeneration factor accounts for effects of dissipation of pore pressure due to pile driving and true time effects such as ageing on the ultimate bearing capacity. Normally the factor is 0.4 but in this paper, the influence of the undrained shear strength and time...... on the regeneration factor is investigated. A relation between the quantities is proposed, which in the end may imply an economical benefit in the design of pile foundations....
Experimental Study on Post Grouting Bearing Capacity of Large Diameter Bored Piles
Directory of Open Access Journals (Sweden)
Wang Duanduan
2015-01-01
Full Text Available Post grouting can improve the inherent defects such as the formation of the mud cake at pile side and the sediment at pile end in the process of bored pile construction. Thus post grouting has been widely used in Engineering. The purpose of this paper is to research the influences of post grouting to pile bearing capacity more systematically and intuitively. Combined with the static load test of four test piles in Weihe River Bridge test area of new airport highway in Xi’an, the bearing capacity and settlement of routine piles and post grouting piles are comparatively analyzed. The test results show that under the same geological condition, post grouting can improve the properties of pile tip and pile shaft soil of bored piles significantly, enhance the ultimate resistance, improve the ultimate bearing capacity and reduce the pile tip settlement. Then post grouting can aim to optimize pile foundation.
Directory of Open Access Journals (Sweden)
Zhao Feng
2015-01-01
Full Text Available The slurry wall bored grouting has some defects. The pile-base post grouting technique can efficiently make up these defects and greatly improve the bearing capacity. Based on the pile-base post grouting technique and its process analysis, this paper carries out a detailed analysis about the improvement of mechanism of bearing capacity and mechanism of spherical expansion by the use of pile-base post grouting technique, as well as the estimation method of the bearing capacity of pile-base post grouting pile, which has a certain reference value for theoretical research and technical application of the technique.
The effect of loading rate on pile bearing capacity of saturated sand
Archeewa, E.
2005-01-01
Pile load tests are commonly used by engineers to determine its bearing capacity. At present, there are three methods of pile load tests: the static, the dynamic and the quasi-static test. The static pile load test is done by applying an axial load on the pile with a long duration. The dynamic and q
Contribution to Estimating Bearing Capacity of Pile in Clayey Soils
Directory of Open Access Journals (Sweden)
Drusa Marián
2016-12-01
Full Text Available The estimation of real geotechnical parameters is key factor for safe and economic design of geotechnical structures. One of these are pile foundations, which require proper design and evaluation due to accessing more deep foundation soil and because remediation work of not bearable piles or broken piles is a crucial operation. For this reason, geotechnical field testing like cone penetration test (CPT, standard penetration (SPT or dynamic penetration test (DP are realized in order to receive continuous information about soil strata. Comparing with rotary core drilling type of survey with sampling, these methods are more progressive. From engineering geologist point of view, it is more important to know geological characterization of locality but geotechnical engineers have more interest above the real geotechnical parameters of foundation soils. The role of engineering geologist cannot be underestimated because important geological processes in origin or during history can explain behaviour of a geological environment. In effort to streamline the survey, investigation by penetration tests is done as it is able to provide enough information for designers. This paper deals with actual trends in pile foundation design; because there are no new standards and usable standards are very old. Estimation of the bearing capacity of a single pile can be demonstrated on the example of determination of the cone factor Nk from CPT testing. Then results were compared with other common methods.
Contribution to Estimating Bearing Capacity of Pile in Clayey Soils
Drusa, Marián; Gago, Filip; Vlček, Jozef
2016-12-01
The estimation of real geotechnical parameters is key factor for safe and economic design of geotechnical structures. One of these are pile foundations, which require proper design and evaluation due to accessing more deep foundation soil and because remediation work of not bearable piles or broken piles is a crucial operation. For this reason, geotechnical field testing like cone penetration test (CPT), standard penetration (SPT) or dynamic penetration test (DP) are realized in order to receive continuous information about soil strata. Comparing with rotary core drilling type of survey with sampling, these methods are more progressive. From engineering geologist point of view, it is more important to know geological characterization of locality but geotechnical engineers have more interest above the real geotechnical parameters of foundation soils. The role of engineering geologist cannot be underestimated because important geological processes in origin or during history can explain behaviour of a geological environment. In effort to streamline the survey, investigation by penetration tests is done as it is able to provide enough information for designers. This paper deals with actual trends in pile foundation design; because there are no new standards and usable standards are very old. Estimation of the bearing capacity of a single pile can be demonstrated on the example of determination of the cone factor Nk from CPT testing. Then results were compared with other common methods.
Dynamic load testing on the bearing capacity of prestressed tubular concrete piles in soft ground
Yu, Chuang; Liu, Songyu
2008-11-01
Dynamic load testing (DLT) is a high strain test method for assessing pile performance. The shaft capacity of a driven PTC (prestressed tubular concrete) pile in marine soft ground will vary with time after installation. The DLT method has been successfully transferred to the testing of prestressed pipe piles in marine soft clay of Lianyungang area in China. DLT is investigated to determine the ultimate bearing capacity of single pile at different period after pile installation. The ultimate bearing capacity of single pile was founded to increase more than 70% during the inventing 3 months, which demonstrate the time effect of rigid pile bearing capacity in marine soft ground. Furthermore, the skin friction and axial force along the pile shaft are presented as well, which present the load transfer mechanism of pipe pile in soft clay. It shows the economy and efficiency of DLT method compared to static load testing method.
Bearing Capacity Estimation of Bridge Piles Using the Impulse Transient Response Method
Directory of Open Access Journals (Sweden)
Meng Ma
2016-01-01
Full Text Available A bearing capacity estimation method for bridge piles was developed. In this method, the pulse echo test was used to select the intact piles; the dynamic stiffness was obtained by the impulse transient response test. A total of 680 bridge piles were tested, and their capacities were estimated. Finally, core drilling analysis was used to check the reliability of this method. The results show that, for intact piles, an obvious positive correlation exits between the dynamic stiffness and bearing capacity of the piles. The core drilling analysis proved that the estimation method was reliable.
Reliability Analysis of Bearing Capacity of Large-Diameter Piles under Osterberg Test
Directory of Open Access Journals (Sweden)
Lei Nie
2013-05-01
Full Text Available This study gives the reliability analysis of bearing capacity of large-diameter piles under osterberg test. The limit state equation of dimensionless random variables is utilized in the reliability analysis of vertical bearing capacity of large-diameter piles based on Osterberg loading tests. And the reliability index and the resistance partial coefficient under the current specifications are calculated using calibration method. The results show: the reliable index of large-diameter piles is correlated with the load effect ratio and is smaller than the ordinary piles; resistance partial coefficient of 1.53 is proper in design of large-diameter piles.
Regressive approach for predicting bearing capacity of bored piles from cone penetration test data
Directory of Open Access Journals (Sweden)
Iyad S. Alkroosh
2015-10-01
Full Text Available In this study, the least square support vector machine (LSSVM algorithm was applied to predicting the bearing capacity of bored piles embedded in sand and mixed soils. Pile geometry and cone penetration test (CPT results were used as input variables for prediction of pile bearing capacity. The data used were collected from the existing literature and consisted of 50 case records. The application of LSSVM was carried out by dividing the data into three sets: a training set for learning the problem and obtaining a relationship between input variables and pile bearing capacity, and testing and validation sets for evaluation of the predictive and generalization ability of the obtained relationship. The predictions of pile bearing capacity by LSSVM were evaluated by comparing with experimental data and with those by traditional CPT-based methods and the gene expression programming (GEP model. It was found that the LSSVM performs well with coefficient of determination, mean, and standard deviation equivalent to 0.99, 1.03, and 0.08, respectively, for the testing set, and 1, 1.04, and 0.11, respectively, for the validation set. The low values of the calculated mean squared error and mean absolute error indicated that the LSSVM was accurate in predicting the pile bearing capacity. The results of comparison also showed that the proposed algorithm predicted the pile bearing capacity more accurately than the traditional methods including the GEP model.
Analytical Model for the End-Bearing Capacity of Tapered Piles Using Cavity Expansion Theory
Directory of Open Access Journals (Sweden)
Suman Manandhar
2012-01-01
Full Text Available On the basis of evidence from model tests on increasing the end-bearing behavior of tapered piles at the load-settlement curve, this paper proposes an analytical spherical cavity expansion theory to evaluate the end-bearing capacity. The angle of tapering is inserted in the proposed model to evaluate the end-bearing capacity. The test results of the proposed model in different types of sands and different relative densities show good effects compared to conventional straight piles. The end-bearing capacity increases with increases in the tapering angle. The paper then propounds a model for prototypes and real-type pile tests which predicts and validates to evaluate the end-bearing capacity.
Study on load-bearing characteristics of a new pile group foundation for an offshore wind turbine.
Lang, Ruiqing; Liu, Run; Lian, Jijian; Ding, Hongyan
2014-01-01
Because offshore wind turbines are high-rise structures, they transfer large horizontal loads and moments to their foundations. One of the keys to designing a foundation is determining the sensitivities and laws affecting its load-bearing capacity. In this study, this procedure was carried out for a new high-rise cap pile group foundation adapted to the loading characteristics of offshore wind turbines. The sensitivities of influential factors affecting the bearing properties were determined using an orthogonal test. Through a combination of numerical simulations and model tests, the effects of the inclination angle, length, diameter, and number of side piles on the vertical bearing capacity, horizontal bearing capacity, and bending bearing capacity were determined. The results indicate that an increase in the inclination angle of the side piles will increase the vertical bearing capacity, horizontal bearing capacity, and bending bearing capacity. An increase in the length of the side piles will increase the vertical bearing capacity and bending bearing capacity. When the length of the side piles is close to the central pile, the increase is more apparent. Finally, increasing the number of piles will increase the horizontal bearing capacity; however, the growth rate is small because of the pile group effect.
Study on Load-Bearing Characteristics of a New Pile Group Foundation for an Offshore Wind Turbine
Directory of Open Access Journals (Sweden)
Ruiqing Lang
2014-01-01
Full Text Available Because offshore wind turbines are high-rise structures, they transfer large horizontal loads and moments to their foundations. One of the keys to designing a foundation is determining the sensitivities and laws affecting its load-bearing capacity. In this study, this procedure was carried out for a new high-rise cap pile group foundation adapted to the loading characteristics of offshore wind turbines. The sensitivities of influential factors affecting the bearing properties were determined using an orthogonal test. Through a combination of numerical simulations and model tests, the effects of the inclination angle, length, diameter, and number of side piles on the vertical bearing capacity, horizontal bearing capacity, and bending bearing capacity were determined. The results indicate that an increase in the inclination angle of the side piles will increase the vertical bearing capacity, horizontal bearing capacity, and bending bearing capacity. An increase in the length of the side piles will increase the vertical bearing capacity and bending bearing capacity. When the length of the side piles is close to the central pile, the increase is more apparent. Finally, increasing the number of piles will increase the horizontal bearing capacity; however, the growth rate is small because of the pile group effect.
Numerical simulation of the influence of soil core on the bearing capacity of pipe pile
Directory of Open Access Journals (Sweden)
G.Ya. Bulatov
2010-03-01
Full Text Available The cost of the foundation can be up to 20-30% of the total building cost. Reducing consumption of materials and quality selection of the required characteristics of the pile can reduce both the estimated cost and time of work.In terms of compact construction and the high land prices the most relevant is high-rise building. But it is hard to build in soft ground conditions (for example, in St. Petersburg. The situation is complicated by insufficiently explored methods of selection and design of piles (especially steel-tube piles for specific cases of construction, as well as by the absence of regulatory documents related to the high-performance technology.The article considers the clarification methods for calculating the bearing capacity of tubular steel piles. An additional contribution of soil core to the overall bearing capacity due to accounting an effect of its "natural" selflocking in the cavity of the steel pipe is considered.The conclusions about the effectiveness of the piles, depending on different initial parameters are made.
BEARING CAPACITY OF A HORIZONTALLY LOADED SINGLE PILE SUPPORT WITH SLEEPERS
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Buslov Anatoliy Semenovich
2015-09-01
Full Text Available The supports of a overhead wiring used in transport take up substantial loads both because of wires and constructions holding them and wind, dynamic and other extraordinary impacts. In case of using single-member piles a question about their stability appears. For this reason different sleepers constructions are used. In order to improve the bearing capacity of horizontally loaded single pile supports of the contact systems used in urban, road and rail transport, power lines, etc.., it is recommended to use sleepers as horizontally laid under the ground in the depth of support beams. The calculation methods for different support sleepers of different lengths and cross sections are not well investigated. The proposed calculation method allows determining the carrying capacity of horizontally loaded bearings with soil pieces of different structural dimensions and their location in the soil, which allows choosing the best option for cost and material consumption. The calculations offered by the authors prove the efficiency of sleepers use in order to increase the bearing capacity of horizontally loaded piles and the possibility to chose their size.
CFG桩复合地基承载力分析%Analysis of bearing capability of CFG pile composite foundation
Institute of Scientific and Technical Information of China (English)
贾剑青; 王宏图; 李晶; 张宪; 范晓刚
2011-01-01
The CFG pile is used to consolidate the foundation in one passenger dedicated line.The field experiments including low strain dynamic testing,bearing capability of single pile and the composite foundation are done,and the bearing capability of composite foundation is calculated,too.The results show that the first and second class piles account for 93.9% and 6.1% respectively,and the bearing capability eigenvalues of single pile and composite foundation are larger than the designed values.The 3D FEM model is established to simulate the stresses of CFG pile top and inter-pile soil changing with load level,and the stress ratio between CFG pile and inter-pile soil is analyzed,too.The following results are got from the calculation results of FEM： 1） the stresses of CFG pile top and inter-pile soil increase with load level,but the increasing rate of the former is larger than the latter;2） the stress ratio between CFG pile and inter-pile soil increases quickly when the load level is low,and it tends to convergent gradually with load increasing.%某客运专线某标段采用CFG桩加固技术。对CFG桩进行了低应变动测、单桩承载力试验、复合地基承载力试验及理论计算。结果表明：一类桩占93.9%,二类桩占6.1%;单桩承载力及复合地基承载力特征值均大于设计值。建立了三维有限元模型,模拟分析了CFG桩顶及桩间土应力随加载水平的变化关系以及CFG桩及桩间土应力分担比。模拟结果表明：1）随着荷载的增加,CFG桩顶应力及桩间土应力也随之增大,但CFG桩顶应力的增长速率大于桩间土;2）加载初期,CFG桩与桩间土应力分担比逐渐增大,且增长速度较快;随着荷载的增加,桩土应力分担逐渐趋于稳定。
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.
Experimental study on load bearing behavior of large-scaled caps with pile groups
Institute of Scientific and Technical Information of China (English)
Guo Chao; Lu Bo; Gong Weiming; Qiu Hongxing
2009-01-01
The objective of this investigation was to study the behavior of deep pile caps and the ultimate load-carrying capacity. Four 1/10 scaled models of nine-pile caps were cast and tested on vertical loads to failure. The destruction shapes of pile caps, the correlation between load and displacement, and the internal stresses were analyzed systematical-ly. The results demonstrated that the failures of all the four models are resulted from punching shear; the internal flow of the forces in nine-pile caps can be approximated by "strut-and-fie" model. Furthermore, the failure loads of these spec-imens were predicted by some of the present design methods and the calculated results were compared with the experi-mental loads. The comparative results also indicated that the "strut-and-tie" model is a more reasonable design method for deep pile caps design.
爆炸荷载下桩基竖向动承载力研究%Study on vertical bearing capacity of pile foundation under blast loading
Institute of Scientific and Technical Information of China (English)
王后裕; 姚焕忠; 言志信; 张剑寒; 杨进勇
2013-01-01
针对地面抗爆工程建设中桩基设计问题,采用动三轴试验、动力有限元方法等手段,开展了爆炸作用下地基土的动力特性及桩基抗爆承载力研究,结果表明桩基竖向极限抗爆承载力为其竖向极限静承载力2倍以上,高于按照现行桩基规范得到的1.25 ～1.5倍范围值,表明将常规抗震设计的办法直接用于抗爆炸冲击荷载的桩基设计时偏保守.%For the problem of pile foundation design of ground protective projects subjected to blast loading,a series of resrearches of dynamic property of soil and bearing capacity of pile under shock waves are carried out by the methods of dynamic triaxial test and dynamic FEM and so on.The result shows that the dynamic bearing capacity of pile is two times greater than that of static bearing capacity and 1.25 ～ 1.5 times greater than that of current pile code method.Therefore it is conservative to estimate the dynamic bearing capacity of pile with current pile code method.
STUDY ON BEARING PROPERTIES OF PILE WITH ENLARGED BASE SUBJECT TO UPLIFT LOADING%扩底桩抗拔承载性状研究
Institute of Scientific and Technical Information of China (English)
柯江
2012-01-01
Based on Abaqus software, the bearing properties of pile with enlarged base subject to uplift loading were studied by creating the finite element model of pile and soil. The results show that the bearing capacity of pile with enlarged base to the limit, a separate were produced between pile bottom and soil, the axial force of pile had mutations at the upper and lower of the enlarged head, the enlarged head could bear the most load of pile, the plastic strain occurred mainly in the soil near the enlarged head.%基于Abaqus软件,建立桩土有限元模型研究了扩底桩在上拔荷载作用下的承载性状.结果表明:扩底桩达到抗拔极限承载力时,桩底与土体产生了分离,扩底桩抗拔承载时的桩身轴力在扩大头的上下出现突变,扩大头承受了桩的大部分荷载,塑性应变主要发生在扩大头附近的土体中.
Institute of Scientific and Technical Information of China (English)
尤苏南
2013-01-01
Use Excel's strong functions of data looking for, data calculation and data processing, carry out the estimation of vertical bearing capacity of single-pile comply with the common formula, large diameter pile formula, socket-pile formula, anti-pull up pile formula, later inject mortar formula etc. only need to set up its function, formula and simple macro order, enter the stratum data and the parameter of pile foundation calculation. Specially fit for the pile foundation scheme selection for the large and complicated project with different location, different device, different pile type, different pile diameter and different pile end bearing layer, largely enhance the work efficiency.% 利用Excel强大的数据查找、计算、处理功能，只需进行Excel的函数、公式、简单宏命令设置，输入地层数据和桩基计算参数，就能按桩基的通用公式、大直径桩公式、嵌岩桩公式、抗拔桩公式、后注浆公式等，进行单桩竖向承载力估算。尤其适用于大型或复杂工程中不同工点、不同装置、不同桩型、不同桩径、不同桩端持力层等多种条件下的桩基方案比选，可以大大提高工作效率。
桩基承载能力的有限元分析%Finite Element Analysis of Bearing Capacity of Pile Foundation
Institute of Scientific and Technical Information of China (English)
彭银辉; 吕世斌; 耿立伟
2012-01-01
针对工程实例,利用ABAQUS有限元软件建立单桩承载力的有限元计算模型,研究桩基承载特性,并与桩基静载试验所得实测数据比较。结果表明,模拟计算结果与工程实际基本吻合,说明采用的计算方法和模型是合理可行的。同时研究了在不同桩土界面摩擦系数条件下桩的沉降和轴向力变化情况,为不同工程地质条件的桩基设计提供参考。%On account of practical case,finite element calculation model of single pile bearing capacity is established with ABAQUS to study the bearing characteristics of pile foundation and compare with actual measurement data of static loading test of pile foundation.The result shows that simulated calculation result is basically consistent with actual engineering,which indicates that the adopted calculation method and model are reasonable and feasible.Meanwhile,the change of settlement and axial force of pile under different frictional coefficient of pile soil is studied,providing references for pile foundation design in different engineering geological conditions.
Relationship between pile foundation bearing capacity and its dynamic stiffness%桩基承载力与其动刚度的关系
Institute of Scientific and Technical Information of China (English)
刘建磊; 马蒙; 张勇; 缴玉森
2015-01-01
为分析桩基承载力与机械阻抗法中动刚度的关系，在同一场地设计了4根相同尺寸的带有不同程度缺陷的模型桩(缩颈桩或断桩)，对模型桩进行了机械阻抗法动测和静载试验。建立了桩—土有限元模型，利用模型桩测试数据对有限元模型进行校准，并分析了完整桩在冲击动荷载和静载试验中对主要物理参数的敏感性；同时分析了缩颈、扩颈缺陷对桩基动刚度的影响规律。研究结果表明：对于相同形式、相近地层环境中的桩基，动刚度能很好地反映静力特性；动刚度对影响桩基承载能力的缺陷较为敏感，合理动刚度下限值可以作为桩基承载力的预警值。%In order to investigate the relationship between the bearing capacity of pile foundation and its dynamic stiffness in the impulse transient response method ( T RM ) ,four model piles,with same size but different damage ( necking or breaking) ,were designed in a same test field. Dynamic response was measured with T RM and static load test was performed. A pile-soil finite element model was built,calibrated by model pile tests. Sensitivity of main parameters were analyzed for intact piles under impulse and static loads,and the effect of necking or expanding defects on dynamic stiffness were studied. It revealed that dynamic stiffness reflected the corresponding static characteristics for pile foundations with the same type and located in similar ground environment. Dynamic stiffness is sensitive to the defects which affect the pile bearing capacity,and a reasonable lower bound of dynamic stiffness can be used as a precaution for pile bearing capacity.
On Bearing Behavior of Rigid - flexible Multi-pile Composite Sub-grades%刚柔多元桩复合地基承载性能有限元分析
Institute of Scientific and Technical Information of China (English)
阎风翔
2014-01-01
The present research imitates the bearing behavior of rigid - flexible multi - pile composite foundation using finite element software ABAQUS and obtains the pile body stress characteristics and deformation law. The load of rigid pile is obviously bigger than that of the flexible pile. As for the same type pile,stress of angle pile is the largest,stress of side pile is smaller,and stress of center pile is the smallest. The biggest pile body stress is not at the top of piles,but in a certain position of them. Laws of deformation and bearing capacity of composite foundation are opposite:the deformation of pile top is largest,the deformation of pile group center is the largest,that of the side pile is smaller,and that of the angle pile is the smallest.%采用有限元软件ABAQUS模拟刚柔多元桩复合地基，得出其桩顶、桩身应力特点和变形规律。刚性桩承担的荷载明显大于柔性桩承担的荷载；对于同种桩型，角桩的应力最大，边桩次之，中桩最小；沿桩身应力最大部位不在桩顶，而是位于桩身的某一位置；复合地基的变形规律与承载力规律恰好相反，桩顶处变形最大，并且群桩中心处变形最大，边桩次之，角桩最小。
Pressured Grouting Method (PGM) in Pile Engineering
Institute of Scientific and Technical Information of China (English)
吴兴序; 于志强; 王旭
2002-01-01
Application of pressured grouting method (PGM) in pile engineering can tackle problems encountered during construction of bored piles. Bearing capacity of piles can be increased through compaction of subsoils around piles. This paper reports research efforts of this technique by the pile research team in Southwest Jiaotong University in last decade with respect to the construction process, test findings, and primary research conclusions. The social-economical benefits of this method and application market in pile engineering are also analyzed.
PHC管桩受弯承载力的分析%ANALYSIS ON THE FLEXURAL BEARING CAPACITY OF PHC PIPE PILE
Institute of Scientific and Technical Information of China (English)
高安; 张亮
2013-01-01
利用ABAQUS有限元软件,建立4个PHC管桩有限元模型,分析桩型(AB型和A型)、箍筋间距和箍筋直径对PHC管桩受弯承载力的影响.比较了公式和有限元计算得出的极限弯矩之间的差异.分析结果表明,AB型管桩的受弯承载力大于A型管桩的受弯承载力,减小箍筋间距和增大箍筋直径不能提高PHC管桩的极限弯矩,有限元分析得到的结果大于公式计算的结果.%Through the finite element software of ABAQUS,the impact of the pile type and stirrup on PHC pipe pile' s flexural bearing capacity is analyzed. The difference of the ultimate bending moment between the formula and finite element is compared. The results show that: the flexural bearing capacity of AB - type is greater than that of A - type. Decreasing stirrup spacing and increasing stirrup diameter can t improve the ultimate bending moment of PHC pipe pile. The result of finite element is bigger than the result of the formula.
Institute of Scientific and Technical Information of China (English)
张麒蛰; 卓卫东; 范立础
2013-01-01
In order to obtain the axial bearing capacity of a batter pile , the calculation formula for the axially bearing capacity of a batter pile was deduced based on the non-uniform distribution char-acteristics of the friction resistance around the batter pile shaft and the mechanism of pile -soil deformation compatibility .The results calculated by the proposed formula and the method given by the design code of pile were compared to explore the influence of the factors , such as pile inclina-tion, diameter, length and utmost friction resistance around pile shaft , on axial bearing capacity. The calculated results showed that the value of the pile axially bearing capacity calculated by the proposed formula decreased with the increase of pile inclination .For different pile diameters , the pile axially bearing capacity was 7%smaller than that calculated by the code's formula.The shorter of the pile length or the lesser of the utmost friction resistance of the pile was , the smaller bearing capacity calculated by the code's formula was than the values calculated by the proposed formula . Finally , with the increase of the pile length or utmost friction resistance , the value of bearing capaci-ty calculated by this proposed formula was greater than the value calculated by the code's formula. The proposed formula also takes into account of the influence of pile inclination and the mechanism of pile-soil deformation compatibility .It can be a reference to calculate axial bearing capacity of bat-ter piles.%为进一步研究斜桩轴向承载力计算方法，基于斜桩的桩周摩阻力不均匀分布的特性和桩-土受力变形协调的原则，推导了斜桩轴向承载力计算公式，通过对比本文公式与规范公式的计算结果，揭示了桩身倾角、桩径、桩长和桩侧极限摩阻力等因素对斜桩轴向容许承载力的影响规律。结果表明：鉴于规范公式未考虑斜桩桩身倾角对承载力的影响，本文公式计算得
Grouting for Pile Foundation Improvement
Van der Stoel, A.E.C.
2001-01-01
The aim of this research was to examine the use of grouting methods for pile foundation improvement, a generic term that is used here to define both foundation renovation (increasing the bearing capacity of a pile foundation that has insufficient bearing capacity) and foundation protection (safeguar
Institute of Scientific and Technical Information of China (English)
2013-01-01
斜群桩受水平荷载作用时，群桩中的基桩受到径向荷载、轴向荷载和弯矩的共同作用。为研究轴向荷载对斜桩水平承载特性的影响，完成了3根单桩以及1组1×2斜桩的大尺寸模型试验。试验结果表明：轴向拉力作用会降低斜桩的水平刚度和极限承载力；而轴向压力作用则会使其水平刚度和极限承载力提高。基于桩侧浅层土体楔形破坏假定，推导了考虑轴向荷载影响的斜桩水平极限土抗力计算公式，提出了桩侧土抗力的p-y曲线方法，并通过模型试验及现场试验验证其合理性。%When batter pile group are under lateral load, the foundation piles in pile group are subjected to radial load, axial load and bending moment. In order to study the influence of axial load on lateral bearing capacity of batter piles, large-scale model tests of three single piles and a 1×2 batter pile group have been conducted in a larger soil tank. It is found that the upward axial force on the pile top decreases the lateral stiffness and the lateral ultimate bearing capacity of batter pile; while the downward axial force enhances the horizontal stiffness and the lateral ultimate bearing capacity of batter pile. Based on the assumption of wedge failure of the shallow soil around piles, considering the influence of axial load on piles, a formula for calculating the lateral ultimate resistance force of soil is deduced. Then, a p-y curve method for resistance force of soil around piles is proposed. Finally, the formula and the proposed p-y curve method for batter pile are verified by model tests and field tests.
Institute of Scientific and Technical Information of China (English)
蒋刚; 孙君; 王旭东
2011-01-01
When the composite piled foundation reaches the general ultimate bearing capacity status, an increment of the ultimate bearing capacity for natural foundation is induced by "barrier effect" of piles.The analysis of the problem can be simplified for both the sum of the vertical ultimate bearing capacity of foundation and the increment of the ultimate bearing capacity of foundation soil horizontally sliding around piles.Based on the finite element plastic lower bound limit method, the numerical solutions for the vertical ultimate bearing capacity of foundation and the horizontal resistance sliding around piles varying with soil depth are obtained, and the sliding resistance formula is also established.The sliding resistance coefficient &s reduces with the increase of pile spacing.The increment of the ultimate bearing capacity △fu decreases with the increase of pile spacing.The results indicate that the resistance sliding around piles in the composite piled foundation is being and can not be ignored, and that the ultimate bearing capacity of the composite piled foundation has certain increment, which can be regarded as the security reserve of foundation.%复合桩基在达到整体极限承载状态时,因桩的"遮拦作用"使得地基极限承载力较天然地基有一定提高.其分析可简化为地基竖向极限承载力和地基土水平向绕桩作用产生的极限承载力提高值的叠加.利用下限有限元方法,求解得到地基的极限承载力和不同深度处土体绕桩阻力的数值解,并建立了绕桩阻力计算公式.绕桩阻力系数ks随桩间距的增加而逐渐减小.地基极限承载力提高值△fu随桩间距的增加而逐渐降低.计算表明:复合桩基下绕桩阻力存在并不可忽视,承台下地基极限承载力有明确的提高,可以作为地基的安全储备.
Institute of Scientific and Technical Information of China (English)
王新泉; 陈永辉; 陈龙; 齐昌广
2011-01-01
研究目的:利用ABAQUS有限元分析软件,建立Y形桩、圆形桩和方形桩三种桩型的有限元计算模型,桩采用弹性模型,土体采用Mohr -Coulomb弹塑性模型.在相同布桩方式和相同面积置换率工况下,研究在路堤荷载分级加载过程中,三种桩型的盖板顶沉降、桩间土沉降、盖板顶和桩间土差异沉降、盖板顶平均应力、桩底平均应力等的变化规律.研究结论:通过对比得知:在相同荷载作用下,圆形桩盖板顶产生的沉降最大,其次为方形桩、Y形桩；圆形桩桩间土产生的沉降最大,方形桩前期大于Y形桩,之后又小于Y形桩；盖板顶与桩间土差异沉降基本呈现圆形桩最大,其次为Y形桩、方形桩；盖板顶和桩底平均应力,呈现方形桩最大,其次为圆形桩、Y形桩.%Research purposes: Based on the ABAQUS finite element analysis software, three kinds of finite element calculation models for Y - Section Pile, square pile and circular pile were established. The elastic model was employed for the pile, while Mohr - Coulomb elastic - plastic model for the soil. Under the case with the same pile layout and area exchange rate, the variations of the total and different settlements of cover plate and soil among adjacent piles, pile - top and pile - end average stress were investigated in the process of stage embankment loading.Research conclusions: It is known by comparison that the maximum settlement of cover plate occurs in the circular pile, followed by the square and Y - section piles; the settlement of soil between piles for circular pile is largest, while that for square pile firstly greater and then less than Y - section pile; the different settlement between cover plate and inter - pile soil for circular pile is of maximum, followed by Y - section and square piles; the pile - top and pile - end average stress for square pile is greater than circular and Y - section piles in turn.
大直径钻孔灌注桩的竖向承载性能%Vertical bearing capacity of large-diameter bored pile
Institute of Scientific and Technical Information of China (English)
刘念武; 龚晓南; 俞峰
2015-01-01
T he self‐balancing test w as conducted on tw o 2 .2 m diameter drilled piles in order to analyze the bearing capacity of large diameter bored piles .The test results were compared with in‐situ test results . Results show that the change of load‐displacement of pile with post‐grouting is slower than pile without post‐grouting .The end resistance reached the limit state when pile tip displacements approached 20 mm (1% D ,D is the pile diameter) .The side resistance increased firstly and maintained a stable trend with the increase of pile‐soil relative displacement .The critical displacement was 1 .5‐3 .0 mm .Post‐grouting can improve the side resistance over a certain depth from the pile tip ,and the improvement in round gravel mixed pebble bed is 18 percent . Resistive loads up and dow n the side of the load cell is different and transformation coefficient is 0 .92 and 0 .91 , respectively . Side resistance and undrained vane‐shear strength has a linear relationship and has a better goodness of fit .The ultimate side resistance of round gravel mixed can be estimated by dynamic sounding (63 .5 kg) hits .%为了分析大直径钻孔灌注桩的承载性能，对2根直径分别为2．2m的钻孔灌注桩开展自平衡试验，将试验结果与原位测试结果进行对比分析．通过对测试结果的分析发现，注浆后荷载箱的向上及向下荷载‐位移曲线的变化更加缓慢，当桩端位移为20 mm（1％ D ，其中 D为桩径）左右时，端阻达到极限状态，未注浆桩和注浆桩的极限端阻分别为2834、3561 kPa ．桩身侧阻随着桩土相对位移的增大呈先增大后保持稳定的趋势，淤泥质粉土层、黏土夹粉砂层、圆砾混卵石层的侧阻在桩土相对位移为1．5～3．0mm时达到稳定．注浆能够提高桩端以上一定深度的桩身侧阻，圆砾混卵石层中侧阻的提高幅度约为18％．荷载箱上下的侧阻随位移的变化模式不同，未注浆桩
Analysis on Effect of Karst Cave on Bearing Characteristics of Rock-socketed Pile%溶洞对嵌岩桩承载特性的影响分析
Institute of Scientific and Technical Information of China (English)
周栋梁; 廖辉煌; 戴国亮
2013-01-01
岩溶发育地质中的嵌岩桩,由于溶洞的存在,其受力机理与承载特性非常复杂.利用ABAQUS有限元分析软件,分析研究岩溶发育地质中溶洞对嵌岩桩的承载特性的影响,设计了四种不同的数值模拟分析对比方案,得出了岩溶地质中嵌岩桩的不同承载特性及桩侧摩阻力和桩端阻力的规律性结果,能使桩基设计达到优化的目的.%Rock-socked pile in karst geology, due to existence of karst cave, has complex force mechanism and bearing characteristics. In this paper, with ABAQUS finite element analysis software, the effect of karst cave developed in karst geology on bearing characteristics of rock-socketed pile is analyzed to the extent that four numerical simulation schemes for comparison are designed. As a result, regularity of bearing characteristics, side friction and end resistance of such rock-socketed pile are obtained and the pile foundation design could be optimized.
Experimental Investigations on the Efficiency Coefficient of Pile Groups
Directory of Open Access Journals (Sweden)
Sara Darsi
2016-06-01
Full Text Available Several factors influence on behavior of piles group such as type of soil, number of piles in the group and the distance between piles. In this paper, using a small laboratory model, the influence of these factors on the behavior of piles group has been examined.For this purpose a group of piles in different distances and variable number of piles was allocated in sand under anpressure axial load. The piles are preferably metal; thus to reduce weight a hollow type has been selected.In order to calculate the coefficient of piles group efficiency, a single pile has been experimented. Experimental observations show that the number of piles in the group and the distances between piles in sand have considerable effect on bearing capacity and the coefficient of pile group efficiency and the coefficient of efficiency in this type of soil have constantly been more than 1 and limited to 1 by increasing the distance between piles.
A semi-analytical method for the analysis of pile-supported embankments
Institute of Scientific and Technical Information of China (English)
Wan-huan ZHOU; Ren-peng CHEN; Lin-shuang ZHAO; Zheng-zhong XU; Yun-min CHEN
2012-01-01
In this paper,a semi-analytical method for the analysis of pile-supported embankments is proposed.The mathematic model describes the cooperative behavior of pile,pile cap,foundation soil,and embankment fills.Based on Terzaghi's ID consolidation theory of saturated soil,the consolidation of foundation soil is calculated.The embankments with two different types of piles:floating piles and end-bearing piles are investigated and discussed.The results of axial force and skin friction distributions along the pile and the settlements of pile-supported embankments are presented.It is found that it takes a longer time for soil consolidation in the embankment with floating piles,compared with the case using end-bearing piles.The differential settlement between the pile and surrounding soil at the pile top is larger for the embankment with end-bearing piles,compared with the case of floating piles.
Branca, Mario; Quidacciolu, Rossana G.; Soletta, Isabella
2013-01-01
The construction of a voltaic pile (battery) is a simple laboratory activity that commemorates the invention of this important device and is of great help in teaching physics. The voltaic pile is often seen as a scientific toy, with the "pile" being constructed from fruit. These toys use some strips of copper and zinc inserted in a piece…
Research on method of pressure grouting piling of driven tube
Institute of Scientific and Technical Information of China (English)
Dianqi PAN; Zupei ZHANG; Diancai PAN; Yong CHEN; Maosen TAN
2006-01-01
The pressure grouting pile of driven tube can improve the load bearing capacity of the single pile from the mechanism of pressure grouting pile of driven tube. On the basis of analyzing the mechanism, the authors designed the machines and tools of pressure grouting, determined the operating manufacture and technology parameter on the pressure grouting secondly. The result shows that the pressure grouting pile of driven tube not only changes the pile type but also reduce the length of the pile and its engineering cost, it enhances the load bearing capacity of single pile an the same time.
Experimental study on pile-end post-grouting piles for super large bridge pile foundations
Institute of Scientific and Technical Information of China (English)
Weiming GONG; Guoliang DAI; Haowen ZHANG
2009-01-01
The application of pile-end post-grouting piles for super-large bridge pile foundations in some important projects was introduced in this paper. There are totally 21 test piles. The maximum pile diameter varies from 2.5 m to 3 m, and the maximum length is 125m; the bearing capacity of the post-grouting piles is over ten thousands tons. Based on the test results, the bearing capacity,displacement, and beating characteristics before and after grouting were analyzed. The results show that the beating capacity of the piles is increased in different degrees after grouting although the technical parameters, including the patterns of grouting pipes, pressure, dosages of cement, duration of grouting lasting time, are different. However,the obtained values are very discrete. In addition, the calculation formula for the post-grouting piles under specified grouting condition was deduced based on the statistics analysis results of 57 test piles. The research results have been applied in the design of bridge foundation.
Institute of Scientific and Technical Information of China (English)
郑俊杰; 赖汉江; 董友扣; 张军
2012-01-01
Based on a two-dimensional discrete element method program PFC2D, a numerical model was established to simulate the bearing characteristics of pile-supported embankment. The variations of contact forces, stresses, vertical displacements and pile-soil stress ratios were analyzed. Further- more, a parametric study was carried out to investigate the performance of pile-supported embankment and the selected influencing factors consist of the pile spacing, the width of pile cap, the friction angle of cushion and the particle shape of cushion. The numerical results show that the soil arching struc- ture in embankment fill mainly exists above the pile cap of one time clear pile spacing. The wider the pl e cap as well as the smaller the pile spacing are, the higher pile-soil stress ratio but the weaker sta bility of soil arching structure will be. If the surface of soil particle is rougher as well as the friction angle is greater, pile-soil stress ratio will be higher and the stability of soil arching structure will be stronger. With an increase of surcharge loads, the soil arching structure presents a changing process of forming-failure-reforming.%采用离散元法软件PFC2D,建立了桩承式路堤承载特性颗粒流试验模型.分析了路堤荷载下填土颗粒间接触力、应力和竖向位移等的分布规律以及桩土应力比的变化规律,并研究了桩间距、桩帽宽度、颗粒间内摩擦角和颗粒形状等因素对桩承式路堤承载特性的影响.结果表明：填土颗粒中土拱结构主要存在于桩顶1倍桩净间距高度范围内;桩帽宽度越大,桩间距越小,桩土应力比越大但土拱结构稳定性越弱;填土颗粒表面越粗糙,内摩擦角越大,桩土应力比越大且土拱结构稳定性越强;随着路堤荷载的增加,填土颗粒中土拱结构呈现出形成-破坏-再形成的变化规律.
Institute of Scientific and Technical Information of China (English)
高笑娟; 李跃辉; 吕冰; 钟国华
2015-01-01
为了研究桩在水平动荷载作用下的受力和变形规律，自制了一套能施加动荷载的加载装置，并对两根承力盘位置不同的模型桩进行了水平动荷载试验，研究了桩顶所加荷载幅值、加载频率、承力盘的位置等因素对支盘桩桩身弯矩和桩侧土压力的影响规律。结果表明：随着桩顶荷载幅值的增加，桩身上部正弯矩和弯矩的最大值均呈现增大趋势，桩侧土中压力亦逐渐增大；随着加载频率的增大，桩身上部弯矩先变大，后又减小，土中压力一直呈增大趋势；承力盘位置靠上的桩在同样条件下桩身正弯矩和最大弯矩值较小，桩侧土中的压力也较小。%A dynamic loading equipment was made to study the load bearing capacity and deformation law of model pile under periodic load. In this paper the horizontal periodic load tests of two model piles with different plate position were carried out in the self-made soil box. The influence of the load amplitude, loading frequency, position of plate on the pile section moment and soil pressure were researched. The results show that the moment in pile body and the maximum moment increase with the increasing of load amplitude, and the soil pressure also in-crease at the same time. With the increase of the loading frequency, the moment in pile body increases firstly but decreases later, and the soil pressure keeps increasing. For the two model piles with different plate position, the moment in pile body and the soil pressure of the pile with plate nearer pile top are less than that of the other pile. Those results may be used in the practical engineering.
Discussion on Calculation of Vertical Bearing Capacity of Rock-socketed Pile%嵌岩桩竖向承载力计算问题探讨
Institute of Scientific and Technical Information of China (English)
吕世明; 范开敏
2014-01-01
The formulas for bearing capacity of the rock-socketed pile in current industry standards are different from each other.The cause of the difference is pointed out based on analyzing the existing data comprehensively, and also some of the other problems.The results of comparative analysis show that the standard empirical formu-lae have the advantages as easy calculating and convenient spreading,which are calculated by the use of uniaxial compressive strength,but there is limitation of weak control for the influencing factors,and the calculated results tend to be conservative.Although theoretical analytic solutions are usually more closer to the in-site measured values than empirical values,it is not suitable for engineering works because of the multitudinous variables and complex calculation;so it is recommended that the design and application of the rock-socketed pile should focus on the accumulation of experiences and the establishment of regional standards.Furthermore,a method is pro-posed to determine the optimal embedding depth,and it is corresponding to the depth when the lateral resistance or end resistance accounting for the total load of the embedded section about 40% to 60%,by the way,the cal-culation of the bearing capacity of the pile at this depth is achieved by the introduction of partial coefficients.%在综合分析现有文献的基础上，指出现行各行业规范中嵌岩桩承载力计算公式产生差异的缘由及存在的问题。通过对比分析指出，规范经验公式采用岩石单轴抗压强度计算嵌岩桩承载力具有计算简单、便于推广应用的优点，但也存在对影响因素控制性差的局限，计算结果往往偏保守；理论计算通常较规范经验值更接近于现场实测值，但其参数繁多、计算复杂而不便于应用。建议嵌岩桩设计应在现行国家标准规范的基础上，注重地区经验的积累并建立健全地方标准。通过对嵌岩深度问题的深入分析
1987-01-01
Machine-oriented structural engineering firm TERA, Inc. is engaged in a project to evaluate the reliability of offshore pile driving prediction methods to eventually predict the best pile driving technique for each new offshore oil platform. Phase I Pile driving records of 48 offshore platforms including such information as blow counts, soil composition and pertinent construction details were digitized. In Phase II, pile driving records were statistically compared with current methods of prediction. Result was development of modular software, the CRIPS80 Software Design Analyzer System, that companies can use to evaluate other prediction procedures or other data bases.
Experiments of Multi-element Composite Foundation with Steel Pipe Pile and Gravel Pile
Institute of Scientific and Technical Information of China (English)
WANG Xian-zhi; ZHENG Jun-jie
2008-01-01
A set of self-developed apparatus for foundation physical model were utilized to conduct model tests of the multi-element composite foundation with a steel pipe pile and several gravel piles. Some load-bearing characteristics of the multi-element composite foundation, including the curves of foundation settlement, stresses of piles, pile-soil stress ratio, and load-sharing ratio of piles and soil, were obtained to study its working performances in silty sand soil. The experimental results revealed that the multi-element composite foundation with steel pipe pile and gravel pile contributed more than the gravel pile composite foundation in improving the bearing capacity of the silty fine sand.
Schilder, Constanze; Kohlhoff, Harald; Hofmann, Detlef; Basedau, Frank; Habel, Wolfgang R.; Baeßler, Matthias; Niederleithinger, Ernst; Georgi, Steven; Herten, Markus
2013-05-01
Static and dynamic pile tests are carried out to determine the load bearing capacity and the quality of reinforced concrete piles. As part of a round robin test to evaluate dynamic load tests, structure integrated fibre optic strain sensors were used to receive more detailed information about the strains along the pile length compared to conventional measurements at the pile head. This paper shows the instrumentation of the pile with extrinsic Fabry-Perot interferometers sensors and fibre Bragg gratings sensors together with the results of the conducted static load test as well as the dynamic load tests and pile integrity tests.
Optimization Mathematical Model of Pile Forces for Offshore Piled Breasting Dolphins
Institute of Scientific and Technical Information of China (English)
周锡礽; 王东芹; 王晖; 朱福明
2004-01-01
An optimization mathematical model of the pile forces for piled breasting dolphins in the open sea under various loading conditions is presented. The optimum layout with the well distributed pile forces and the least number of piles is achieved by the multiplier penalty function method. Several engineering cases have been calculated and compared with the result of the conventional design method. It is shown that the number of piles can be reduced at least by 10% ～ 20%and the piles' bearing state is improved greatly.
Institute of Scientific and Technical Information of China (English)
曹权; 施建勇; 雷国辉; 艾英钵; 陈鸿
2011-01-01
以有效应力原理为基础,结合考虑应变软化、桩径和弹性区孔压分布等因素的桩周土固结解,推导出软土中单桩桩侧承载力时效性的理论解.与传统桩的承载力时效性简化分析方法不同,该理论解不仅考虑了多土层地基中各土层刚度指数的差异对固结过程的影响,还考虑了各土层因固结系数不同对孔压消散速率的影响.通过现场不同间歇期的单桩载荷试验测试结果验证了其合理性.%Based on the theory of effective stress, consolidation solution around the pile which is taken into account the influence of strain softening, magnitude of pile radius and range of excess pore water pressure, a theoretical relationship about time-effect of bearing capacity of single pile is developed, which can be used to predict the variation of shaft bearing capacity of a jacked-in pile with time in saturated soft clay. Different from the traditional way, the effect of different stiffness indices and different consolidation coefficients on the consolidation process in varied clays and highly stratified deposits are considered in the new consolidation solution. Besides, the rationality of the solution is verified by the pile load tests in different time periods after installation.
Institute of Scientific and Technical Information of China (English)
无
2005-01-01
The famous physicist made for his scholars this riddle. A fellow encountered a bear in a wasteland. There was nobody else there. Both were frightened and ran away. Fellow to the north, bear to the west. Suddenly the fellow stopped, aimed his gun to the south and shot the bear. What colour was the bear?
预制桩竖向承载性能设计理论研究%A STUDY ON VERTICAL LOAD BEARING PERFORMANCES OF PREFAB PILES
Institute of Scientific and Technical Information of China (English)
李素华; 杨位洸
2001-01-01
A new method is presented to analyze the vertical load bearing performances of prefab piles with optimization and back analysis techniques. In combination with optimization theory, back analysis method and a new improved elastic theory method， a program is developed not only to stimulate the load-settlement curve(Q-S curve) of static load testing， but also to analyze the soil mechanical parameters around the pile by using back analysis method with optimization techniques on the basis of measured load-settlement information of static testing.This technique has been verified in large numbers of practical engineering with satisfactory results.%对预制桩的竖向承载性能进行计算研究， 提出了一种分析预制桩竖向承载性能的新方法。 将优化反分析理论与改进的弹性理论法相结合， 所编制的预制桩轴向承载性能优化反分析计算程序， 不仅可模拟计算预制桩静载试验的荷载沉降曲线， 而且可根据静载试验实测的桩顶荷载沉降曲线反演分析计算出桩周土力学参数。 对大量的静载试验资料进行优化反分析计算， 并对所得到的土力学参数进行统计分析， 得出一整套较能反映实际、 实用可靠的土力学参数值， 用于指导设计并模拟计算预制桩的竖向承载性能。
Institute of Scientific and Technical Information of China (English)
轩勇; 刘军勇
2013-01-01
结合实体公路工程,通过现场试验段土压力监测,计算复合地基承载力发挥值；结合破坏模式,对其复合地基承载力发挥值进行分析.研究结果表明:粒料桩复合地基按照土体先破坏计算的复合地基承载力发挥值,接近现场载荷试验结果,复合地基承载力可通过桩墩间土压力进行计算确定；不论是强夯置换砾石墩还是振动砾石桩,其破坏形式是桩(墩)间土先破坏引起的整个复合地基的破坏.%Combining with substantial highway engineering,efficiency factor of bearing capacity of composite foundation was calculated through soil pressure monitoring at the section for site test and,with failure mode,it was analyzed as well.The study result shows that for granular pile composite foundation,the efficiency factor of bearing capacity calculated in terms of earth mass failure taken place first is close to the result of on-site load test and the bearing capacity may be calculated through soil pressure between piles/piers.In addition,the failure mode is such that the whole composite foundation is destroyed in the event that the soil between piles (piers) is destructed at first,regardless of dynamic replacement gravel pier or vibration gravel pile.
Institute of Scientific and Technical Information of China (English)
凌道盛; 任涛; 王云岗
2013-01-01
Based on the p-y curve method for plumb pile in sand proposed by Reese, a new p-y curve method and its corresponding finite element method for analyzing horizontal bearing characteristics of single batter pile are presented. Firstly, according to the mechanical behavior of the shallow soil near a batter pile, a three-dimensional wedge model is put forward to describe the passive region which is in the limit state. By using limit equilibrium analysis method, the expression of ultimate soil resistance of batter pile is derived. Then, the influences of pile angle and the friction between pile and soil are numerically studied; and the method for determining the initial modulus of p-y curve of batter pile is given. By modifying the p-y curve for plumb pile in sands proposed by Reese, the p-y curve for batter pile in sand is obtained. Using the virtual work principle, the finite element formulations for horizontal bearing analysis of single batter pile are deduced; and the iteration algorithm is put forwards. The corresponding program is coded by authors; and numerical examples are taken to illustrate the effectiveness of the method. Finally, a printed centrifuge model test of batter pile is analyzed by the presented method. The numerical results show fine agreement with those of model test.%基于Reese建议的砂土p-y曲线,提出了适用于斜桩水平承载特性分析的修正p-y曲线及相应的有限元分析方法.根据桩前土体受力特点,假设桩前浅层土体达到极限破坏状态时桩侧被动破坏区为一个三维楔形体,采用极限平衡分析方法导出了斜桩桩侧极限土抗力表达式,对比研究了斜桩倾角、桩-土界面摩擦系数等因素对极限土抗力的影响规律,并给出了斜桩初始地基反力模量确定方法.在此基础上,修正Reese提出的直桩p-y曲线,提出了砂土地基中斜桩p-y曲线确定方法.利用虚功原理,导出了斜桩水平承载特性分析的有限单元列式,编制相应
Institute of Scientific and Technical Information of China (English)
王秉宇; 崔建波; 王士杰; 孙东岭
2012-01-01
采用高应变实测曲线拟合法确定基桩承载力及桩侧摩阻力的分布,通过基桩承载力动、静试验结果的对比,分析了高应变实测曲线拟合法的测试精度和可靠性,探究了高应变动测法确定基桩承载力的误差来源及因由,为合理确定桩基工程设计参数提供可靠保证.%This essay will determine, the bearing capacity of the pile and shaft resistance by the curve match method of high strain dynamic testing. By the pile of bearing capacity of the contrast between the testing results of static loading and dynamic high strain, analyses the reliability and surveying precision of the curve match method and exdores the error sources and reason, which reasonably determine the pile foundation engineering of design parameters.
Institute of Scientific and Technical Information of China (English)
王少东; 方光秀
2014-01-01
针对利用现行规范公式计算 PHC管桩的竖向极限承载力值存在结果偏低的问题，根据竖向静载荷文献资料，基于灰色理论 GM（1，1）模型和 Usher曲线模型预测单桩的极限承载力，并采用 MATLAB软件实现预测模型算法。工程实例分析表明：灰色预测模型的预测精度与竖向静载试验数据级数选取、预测距离有密切关系；Usher曲线模型对桩极限承载力的预测精度大大高于灰色模型，此结果可为类似工程地质条件下 PHC管桩单桩竖向极限承载力的预测提供借鉴。%In view of the current specification formula for calculating the ultimate bearing capacity of PHC pipe piles vertical value is generally low,according to the literature data of vertical static load,using the theory of grey GM(1,1)model and Usher curve model for predicting ultimate bearing capacity of single pile,to realize the predictive model algorithm by using MATLAB software.The analysis of proj ect instance shows that:the prediction accuracy of grey forecasting model is closely related to the selection of vertical static load test data series and prediction distance;Usher curve model has higher precision than the grey model for the forecast of ultimate bearing capacity of pile,which can provide appreciation for the similar engineering geology PHC pipe piles under the condition of the single pile vertical ultimate bearing capacity prediction.
Institute of Scientific and Technical Information of China (English)
姚文娟; 钟倩倩; 郭志兴; 胡宝琳; 仇元忠
2011-01-01
Based on the catastrophe theory, a cusp catastrophe model of super-long pile under vertical sta-tic load was established, and the predictor formula was derived. Based on the above analysis, dynamic load was tested, the double cusps catastrophe model of super-long pile under combined load was proposed and used in the analysis of the dynamic stability. Dynamic analysis showed that; The relationship among the amplitude H, the Frequency q and the nonlinear coefficient a was conformed to the double cusps ca-tastrophe model when combined load was applied on super-long pile; there was a certain relationship a-mong the change value of dynamic loading frequency, the previous deformation value of pile and the non-linear coefficient of systems in the process of destabilization of super-long pile; important influence on the response characteristics of super-long pile was obtained under the different dynamic loading path. Project example results show that: the cusp catastrophe model is applicable in predicting vertical ultimate bearing capacity of super-long pile.%应用突变理论建立了超长桩在竖向静荷载作用下的尖点突变模型,推导得到了超长桩的竖向极限承载力预测公式.在静荷载分析的基础上,引入动荷载,建立了超长桩在动静组合荷载作用下的双尖点突变模型,并对其动力稳定性进行了分析.动力分析表明:动静组合荷载作用下超长桩的振幅H、频率关系q与结构非线性系数a三者之间符合双尖点突变模型；超长桩失稳时动载频率的变化值与桩顶预变形值及系统非线性系数有一定的关系；动载作用“路径”对超长桩的响应特征有很大的影响.工程算例表明:应用尖点突变理论对超长桩的竖向极限承载力进行预测具有较好的适用性.
Institute of Scientific and Technical Information of China (English)
雷华阳; 刘利霞; 霍海峰; 陆培毅; 付瑞清; 付海峰
2012-01-01
exposing height is less than 1.7m. ultimate horizontal bearing capacity of high cap pipe piles stays constantly, when the exposing height is more than 1. 7 m, it decreases rapidly. Increasing the soil strength, the modulus and diameter of piles could be favorable to the horizontal bearing capacity, while changing the length has little influence.
Tension Tests On Bored Piles In Sand
DEFF Research Database (Denmark)
Krabbenhøft, Sven; Clausen, Johan; Damkilde, Lars
2006-01-01
The lengths of the bored piles varied from 2 m to 6 m and all were of a diameter of 140 mm. The piles were tested to failure in tension and the load-displacement relations were recorded. The investigation has shown pronounced differences between the load bearing capacities obtained by different...
Institute of Scientific and Technical Information of China (English)
邵晶晶
2011-01-01
结合某工程，在同一场地，对不同桩长条件下的预应力混凝土管桩进行了静载荷和动力测试对比试验，取得了一些对比资料和实测成果，并对其原因进行简要分析，从而得出了一些有益的结论，具有一定指导意义。%Combining with a project, this paper made static load and dynamic test contrast test to prestressed concrete pipe pile at the same site and for different pile long, gained some contrast materials and the measured results, and briefly analysed the reasons, so as to abtain some useful conclusions, had some guiding significant.
Institute of Scientific and Technical Information of China (English)
袁伟; 闫澍旺; 赵亮
2011-01-01
The soil around pile foundation in the wharf will suffer from strength reduction under the cycle wave loading conditions, which would further influence the vertical bearing capacity of the pile foundation. Through the indoor dynamic biaxial GDS to simulate' the cycle wave loading and apply these loads to the soil sample of Tianjin port, the strength reduction laws of soil under the dynamic cycle loads in different depths are obtained. Next, with the help of ABAQUS, combining the working loads with cycle wave loading on the pile foundation, the distribution laws of soil dynamic stress around the pile are analyzed. After synthesizing the dynamic biaxial test, the final results are obtained, which show the soil suffered from strength reduction spreads to the depth up to 5 m, the maximum strength reduction rate nearby soil can reach 85.3 % and the vertical bearing capacity of wharf pile foundation reduction rate is 5.73 % .%码头桩基在波浪循环荷载的长期作用下,桩周一定范围的土体会出现强度弱化,进而会一定程度的影响基桩竖向承载力.该文首先通过室内GDS动态三轴仪对天津港码头地基土样作用模拟的波浪循环荷载,研究不同深度土体受到不同幅值的循环动应力荷载作用后其强度的折减规律.然后通过ABAQUS有限元软件计算模拟码头桩基在上部既有结构相互作用的同时,桩身上部受波浪循环荷载,桩周土动应力的分布规律.结合室内动三轴试验结果,计算得到该码头桩基在波浪循环荷载作用下桩周土体弱化的影响深度约为5m,桩周土体的强度折减率最大达到85.3％,码头桩基竖向承载力的折减率为5.73％.
Energy Technology Data Exchange (ETDEWEB)
Schallert, Matthias [Gesellschaft fuer Schwingungsuntersuchungen und Dynamische Pruefmethoden (GSP) mbH, Mannheim (Germany); Hofmann, Detlef; Habel, Wolfgang R. [Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin (Germany)
2008-07-01
Reinforced concrete piles are often used for structures on non-sufficiently bearing soil areas. Assessment of bearing capacity and bearing behaviour of large concrete piles remains a difficult task under specific soil conditions and pile geometries. Usually static and dynamic pile tests are carried out for quality assurance. From dynamic measurements taken only from the pile head, the bearing behaviour and structural integrity can be derived using the one-dimensional theory of wave propagation. More precise information about the pile features can be achieved by highly resolving fibre-optic sensors based on Fabry-Perot technology, distributed over several locations along the pile length. Small scale piles and real driven piles have been tested. This paper describes the sensor, the sensor installation, and experimental results of tests in laboratory as well as test results for recording the wave propagation in the small scale piles. (orig.)
Application of PCC pile in soil improvement of highway
Institute of Scientific and Technical Information of China (English)
刘芝平; 刘汉龙; 谭慧明
2008-01-01
The construction process and load-bearing behaviors of Cast-in-place concrete thin-wall pipe piles are analyzed based on its application on Yantong Expressway Project. The low strain test, static load test and field excavation were also carried out, and the bearing capacity of the new pile can meet the requirements of design. With the increase of pile diameter, the bearing capacity is increased. The settlement of composite foundation is decreased, when the replacement ratio of pile is increased. The test results also show that the load carried by inner soils is neglectable. According to the tests and application, it can be concluded that the new type of pile is convenient to construction with high bearing capacity and reliable quality, which has great potential in practical engineering.
Johnson, Alfred A.; Carleton, John T.
1978-05-02
A graphite-moderated, water-cooled nuclear reactor including graphite blocks disposed in transverse alternate layers, one set of alternate layers consisting of alternate full size blocks and smaller blocks through which cooling tubes containing fuel extend, said smaller blocks consisting alternately of tube bearing blocks and support block, the support blocks being smaller than the tube bearing blocks, the aperture of each support block being tapered so as to provide the tube extending therethrough with a narrow region of support while being elsewhere spaced therefrom.
Institute of Scientific and Technical Information of China (English)
王维玉; 赵拓; 孟艳杰
2012-01-01
Through CFG pile composite foundation dynamic test, a test model was built by using finite element analysis software. The analyses were made for the horizontal acceleration, vertical acceleration, horizontal displacement, vertical displacement and stress, which were dynamic response about the same position different depth and the same depth different locations. The analysis results of the dynamic response were in good agreement with the test results. The factors of dynamic response were studied by numerical simulation. Compared with the dynamic response results of natural foundation, we obtained the conclusions in guiding the significance. A basis is supplied for load bearing capacity, deformation and dynamic characteristics of a CFG pile composite foundation.%该文以CFG桩复合地基在爆破地震作用下的现场动力试验为背景,应用有限元软件建立有限元动力分析的数值模拟模型,从水平加速度、竖向加速度、水平位移、竖向位移及应力几个方面对复合地基同一位置不同深度和同一深度不同位置的动力响应进行了分析,其分析结果与试验结果吻合较好.通过数值模拟对动力响应的影响因素进行了比较研究.并与天然地基的动力响应结果进行对比,得出了有指导意义的结论.为今后探讨CFG桩复合地基的承载力、变形和动力特性提供了研究基础.
Assessment of Time Functions for Piles Driven in Clay
DEFF Research Database (Denmark)
Augustesen, Anders; Andersen, Lars; Sørensen, Carsten Steen
The vertical bearing capacity of piles situated in clay is studied with regard to the long-term set-up. A statistical analysis is carried out on the basis of data from numerous static loading tests. The database covers a wide range of both soil and pile properties, which ensures a general....... Hence, it is suggested that a constant set-up factor should be applied for the prediction of pile capacities at a given time after initial driving....
Institute of Scientific and Technical Information of China (English)
张明远; 黎生南; 彭文韬; 宋华珠
2011-01-01
More and more large-diameter and super-long steel pipe piles are applied to engineering in recent years. But so far , few people have focused on studing their bearing characteristics. Computational theory of ordinary piles is referenced in the foundation design. Vertical bearing and settlement features are simulated for large-diameter and super-long steel pipe piles based on the fast Lagrangian analysis of continua in three dimensions (FLAC3D). Then comparison between simulation results and the results of vertical static load bearing capacity test is conducted and they are complemented and verified each other. The consistent results demonstrate that the method of using the finite difference procedure in this paper to preliminarily simulate the vertical load-bearing characteristics and settlement characteristics of large-diameter and super-long steel pipe pile is feasible. The study shows that the large-diameter and super-long steel pipe pile is a typical end-bearing friction pile. The pile lateral friction resistance changes intricately with depth, which is closely related to the soil characteristics. And the transferring speed of pile axial force depends on the action of pile lateral friction resistance in the different soil. These conclusions are of significance for the reasonable large-diameter and super-long steel pipe pile foundation designed in engineering applications.%近年来,超长大直径钢管桩在工程中的应用已越来越多,但对其承载特性的研究却很少,设计中仍然参考普通桩的计算理论.本文采用三维连续介质快速拉格朗日法(FLAC3D)对实际工程中一超长大直径开口钢管桩试桩的竖向承载特性及沉降特性进行了数值模拟分析,并将模拟结果与静载荷竖向承载特性试验实测结果进行了对比,两者相互补充和相互验证,取得了比较一致的结果,表明了本文所编制的有限差分程序用以初步模拟分析超长大直径钢管桩承载特性的可行
Energy Technology Data Exchange (ETDEWEB)
Robert, J.; Raievski, V. [Commissariat a l' Energie Atomique, Paris (France). Centre d' Etudes Nucleaires; Hainzelin, J. [Chantiers de l' Atlantique (Penhoet-Loire), 75 - Paris (France)
1959-07-01
The programme of the high flux laboratory pile EL3 was laid down in october 1954. It is a heavy-water moderated and cooled pile. The fuel rods are of uranium metal with 1.6 per cent - 2 per cent of molybdenum, with aluminium canning. The maximum thermal flux in the moderator is 10{sup 14} n/cm{sup 2}/s. Studies began in january 1955, construction in may 1955, and the first divergence took place in July 1957. This report gives a general description of the pile and its adjacent buildings, the physical study of the pile, and certain technological studies carried out for the construction of EL3. (author) [French] Le programme de la pile laboratoire a haut flux EL3, a ete fixe en octobre 1954. C'est une pile moderee et refroidie a l'eau lourde. Les barres de combustible sont en uranium metal a 1,6 pour cent - 2 pour cent de molybdene, gainees a l'aluminium. Le flux thermique maximum dans le moderateur est de 10{sup 14} n/cm{sup 2}/s. Les etudes ont commence en janvier 1955, la construction en mai 1955, la premiere divergence a eu lieu en juillet 1957. On trouvera dans ce rapport, une description generale de la pile et de ses batiments annexes, l'etude physique de la pile et un certain nombre d'etudes technologiques executees pour la construction d'EL3. (auteur)
Institute of Scientific and Technical Information of China (English)
万鹏洲
2016-01-01
Combined with practical construction of screw pile from Hohhot to Zhunger Railway Engineering,key construc-tion techniques and bearing behaviors of railway foundation treatment with screw pile in saline soil area are mainly re-searched by combining field test and theoretical analysis of numerical simulation.The construction technology and technical parameters are summarized and bearing mechanism of screw pile and settlement rate of subgrade are analyzed,which is beneficial to the formation of the complete set of construction technology of railway foundation treatment with screw pile in saline soil area.Based on the research,it is found that the screw pile has many characteristics such as high bearing capaci-ty,low sedimentation rate,high efficiency of forming pile and remarkable economic benefits,which fully reflects the appli-cation advantages of this new style pile in railway foundation treatment.%结合呼和浩特至准格尔铁路工程螺杆桩实际施工，采用现场试验和模型数据理论分析相结合的研究方法，重点研究了盐渍土地区螺杆桩的施工关键技术和承载受力特性，总结了施工工艺和技术参数，分析了螺杆桩的承载机理和路基沉降速率，形成了螺杆桩在盐渍土地区铁路地基处理的成套施工技术。通过研究发现螺杆桩具有承载力高、沉降率低、成桩效率高、经济效益显著等诸多特点，充分体现了这种新型桩在铁路地基处理中推广应用的优势。
Institute of Scientific and Technical Information of China (English)
闫明
2014-01-01
为了准确得到桩基的承载力，在实测曲线拟合方面提出了采取遗传算法来代替传统人工试凑的方法，以通过编程实现自动求解，并结合工程实例试验，将采用遗传算法的拟合结果与静载荷试验结果作了对比，证实了该方法的可行性与可靠性。%In order to get the accurate bearing capacity of pile foundation,this paper used the genetic algorithm to replace the traditional manual test in measured curve fitting method,through the program realization of automatic solution,and combining with practical engineering test,con-trasted the fitting results and static load test results of genetic algorithm,verified the feasibility and reliability of the method.
Nonlinear calculating method of pile settlement
Institute of Scientific and Technical Information of China (English)
贺炜; 王桂尧; 王泓华
2008-01-01
To study calculating method of settlement on top of extra-long large-diameter pile, the relevant research results were summarized. The hyperbola model, a nonlinear load transfer function, was introduced to establish the basic differential equation with load transfer method. Assumed that the displacement of pile shaft was the high order power series of buried depth, through merging the same orthometric items and arranging the relevant coefficients, the solution which could take the nonlinear pile-soil interaction and stratum properties of soil into account was solved by power series. On the basis of the solution, by determining the load transfer depth with criterion of settlement on pile tip, the method by making boundary conditions compatible was advised to solve the load-settlement curve of pile. The relevant flow chart and mathematic expressions of boundary conditions were also listed. Lastly, the load transfer methods based on both two-broken-line model and hyperbola model were applied to analyzing a real project. The related coefficients of fitting curves by hyperbola were not less than 0.96, which shows that the hyperbola model is truthfulness, and is propitious to avoid personal error. The calculating value of load-settlement curve agrees well with the measured one, which indicates that it can be applied in engineering practice and making the theory that limits the design bearing capacity by settlement on pile top comes true.
Hsu, Shu-Wei
2010-01-01
We present a method for directly modeling piles of objects in multi-body simulations. Piles of objects represent some of the more interesting, but also most time-consuming portion of simulation. We propose a method for reducing computation in many of these situations by explicitly modeling the piles that the objects may form into. By modeling pile behavior rather than the behavior of all individual objects, we can achieve realistic results in less time, and without directly modeling the frictional component that leads to desired pile shapes. Our method is simple to implement and can be easily integrated with existing rigid body simulations. We observe notable speedups in several rigid body examples, and generate a wider variety of piled structures than possible with strict impulse-based simulation. © 2010 ACM.
Institute of Scientific and Technical Information of China (English)
HE Ben; WANG LiZhong; HONG Yi
2016-01-01
This study presents the results of field and numerical investigations of lateral stiffness,capacity,and failure mechanisms for plain piles and reinforced concrete piles in soft clay.A plastic-damage model is used to simulate concrete piles and jet-grouting in the numerical analyses.The field study and numerical investigations show that by applying jet-grouting surrounding the upper 7.5D (D =pile diameter) of a pile,lateral stiffness and bearing capacity of the pile are increased by about 110％ and 100％,respectively.This is partially because the jet-grouting increases the apparent diameter of the pile,so as to enlarge the extent of failure wedge and hence passive resistance in front of the reinforced pile.Moreover,the jet-grouting provides a circumferential confinement to the concrete pile,which suppresses development of tensile stress in the pile.Correspondingly,tension-induced plastic damage in the concrete pile is reduced,causing less degradation of stiffness and strength of the pile than that of a plain pile.Effectiveness of the circumferential confinement provided by the jet-grouting,however,diminishes once the grouting cracks because of the significant vertical and circumferential tensile stress near its mid-depth.The lateral capacity of the jet-grouting reinforced pile is,therefore,governed by mobilized passive resistance of soil and plastic damage of jet-grouting.
Experimental study on DX pile performance in frozen soils under lateral loading
Institute of Scientific and Technical Information of China (English)
XiaoBing Liu; LiHong Chen; ZhongYang Yu; JianXiao Hu; Wen Peng
2013-01-01
Experiments about working mechanism and mechanical characteristics of the DX model pile foundation under lateral dynamic and static loading were conducted by using a model system of the dynamic frozen soil-pile interaction. The horizontal displacement-force relationship of the pile head and bending moment distribution along the body in frozen soils of different temperatures were discussed. According to test results, both the horizontal displacement-force relationship of the DX pile head and bending moment distribution of the DX pile body are smaller than that of equal-diameter piles under same lateral loads. The piles with different plate positions show different displacements and bending moments. This phenomenon is mainly related to the soil temperature and bearing plates locations. Thus, dynamic response analysis of the pile foundation should be taken into account.
Reliability Evaluation of Vertical Bearing Capacity of Post-grouting Bored Piles%后注浆灌注桩桩端竖向承载力可靠性分析
Institute of Scientific and Technical Information of China (English)
张杰; 朱晓丽
2015-01-01
后注浆钻孔灌注桩目前广泛应用于软土地区中，其承载力较大，沉降较小，因此对其承载力的估算一直受到重视。研究桩端位于砂土层中的桩端后注浆灌注桩竖向抗压承载力可靠度，并编写了相应Matlab程序。考虑到在实际进行可靠度计算时，极限状态方程的确立、随机变量的选择对最后得到的可靠度指标有很大影响，比较了2个随机变量、4个随机变量以及6个随机变量这样3种情况计算同一算例的可靠度指标。对于极限状态方程的确定，本文建立了3种不同的极限状态方程，研究结果发现极限状态方程的选取对可靠度指标的影响较小，可按照实际工程掌握数据选取随机变量。由于进行可靠度研究时，随机变量的均值和标准差都是基于大量数据确定的，会有误差存在，因此研究各个随机变量的敏感性能对实际工程计算可靠度指标的精度提高有所帮助。%Post-grouting bored piles are widely used in soft soil area, whose carrying capacity is large and settlement is small, so estimation of carrying capacity is much accounted of.In this paper, the study was mainly about the reliability evaluation of vertical bearing capacity of the base-grouting bored piles which is lo-cated in the sandy soil and wrote the Matlab program about it.Considering the limit state equation, the choice of the random variables has a great influence on the reliability index.Three conditions, which are of 2 random vari-ables, 4 random variables and 6 random variables, were used to calculate the reliability evaluation of the same example.About selecting limit state equation, three different limit state equations were chosen.And the limit state equation has little effect on reliability evaluation showed in the result.So random variable can be chosen ac-cording to the practical engineering.Considering the mean value and standard deviation of random variables base on mass
Basal Reinforced Piled Embankments
Van Eekelen, S.J.M.
2015-01-01
A basal reinforced piled embankment consists of a reinforced embankment on a pile foundation. The reinforcement consists of one or more horizontal layers of geosynthetic reinforcement (GR) installed at the base of the embankment. The design of the GR is the subject of this thesis. A basal reinforce
Institute of Scientific and Technical Information of China (English)
邓俊杰; 陈龙珠; 邢爱国; 宋春雨
2011-01-01
为解决常规锤击、电动中低频振动法进行桩基施工时引起较为严重的噪声、振动和增大电网负荷等问题,发达国家已在应用液压高频振动施工技术,但沉桩的土动力学机理以及单桩静力荷载-沉降特性等尚缺乏深入的室内外试验研究.利用大吨位液压高频振动锤,在某深厚饱和软土场地对直径500 mm、长度26～29 m的预应力管桩进行了沉桩施工试验,观测了邻近地基土超静孔压随沉桩深度而上升及其后续消散的过程;在休止期满后进行了单桩怪向静载荷试验,并将实测极限承载力与其它常规施工方法的进行了比较分析.试验结果对推广应用液压高频振动沉桩新技术,具有重要的学术和应用参考价值.%To solve the serious noise and vibration problems as well as the high pressure on the capacity of city power supply caused by the existing piling methods with falling hammers and low-frequency electric vibrators, a new piling technique using high-frequency hydraulic vibrators has been used in some developed european countries and the USA.The piling mechanism related to soil dynamics at high frequency and the bearing capacity of piles after installation with the hydraulic vibrators should be investigated in laboratory and construction sites.Using a high-frequency hydraulic vibrator manufactured by a Shanghai machinery company, pre-casted/pre-stressed concrete pipe piles with diameter of 500 mm and length of 26-29 m are driven into the saturated soft ground in the Minhang campus of Shanghai Jiaotong University in China, and the induced excess pore water pressures of adjacent soil at different depths are investigated for about one month.After the specified interruption period of 28 days after piling, the ultimate bearing capacity of each pile is studied by means of the conventional static loading tests and compared with that of piles installed with falling hammers and statically jetting.The experimental
Analysis of Negative Skin Friction on Single Pile above a Tunnel
Institute of Scientific and Technical Information of China (English)
王志亮; 刘学庆
2003-01-01
A finite element program with two different soil models is adopted to study the negative skin friction of an unloaded single pile embedded in the settlement trough of a tunnel. The results show that it is necessary to consider the nonlinear property of soil and to set interface elements between piles and soil in analysis of the negative skin friction of piles. Among a pile group, the pile located above the tunnel centerline bears larger downdrag than the ones far away from tunnel centerline.
Institute of Scientific and Technical Information of China (English)
李万庆; 闫冠勇; 孟文清; 石华旺
2011-01-01
针对BP神经网络学习时间长、收敛速度慢等缺陷,借助小波分析理论,将母小波平移和伸缩构成的小波基作为神经网络的激励函数,通过指导网络的初始化和参数选取,使网络以较简单的拓扑结构实现函数逼近,利用网络训练建立起承载力与其影响因素之间的非线性关系.在相同结构和参数下,与BP神经网络进行分析对比.结果表明:利用小波变换对数据时频局域化分析的能力并结合人工神经网络的自学习功能,使得小波神经网络预测模型具有较强的逼近和容错能力,预测结果比传统的BP神经网络具有更快的收敛速度和更高的精度.%Aiming at the long training time and slow convergence rate of BP neural network, wavelet basis consisted by the translation and stretch of mother wavelet constitutes the activation function of neural network basing on the theory of wavelet analysis. The neural network can use simple topology to approximate function by the guidance of network initialization and parameters selection. The nonlinear relationship between the bearing capacity of CFG piles composite foundation and its main factors is established by using the trained network. Under the same structure and parameters, the prediction results are analyzed and compared with the BP neural network. The result shows that this forecast model makes full use of the wavelet transformation to analysis the data of time - frequency localization and is combined with the self- learning function of artificial neural network,which makes it have a strong a-bility to approach and fault tolerance. The precision and speed by using the trained wavelet neural network is higher and its predicting result is more accurate than that of BP network.
Institute of Scientific and Technical Information of China (English)
宇德忠; 程培峰; 季成; 崔志刚
2015-01-01
为了准确掌握岛状多年冻土地区桥梁钻孔灌注桩的回冻时间及桩基回冻后的承载力，在岛状多年冻土地区选择2个试验地点，每个试验地点浇筑了2根15 m长的试验桩，并在其中一根试验桩处布设温度监测系统，采集桩基回冻过程中的温度数据，根据温度监测结果判断桩基回冻状态，在桩基完成回冻后进行静载与动测试验，测出桩基极限承载力。监测及试验结果表明：试验桩所在区域岛状多年冻土地温约为－1.9℃，桩基完成回冻后桩身内部温度与桩侧1 m处的土体温度变化趋势相同，相同深度处的温差小于0.1℃；用静载法实测出的各土层回冻后的桩侧摩阻力值修正高应变动测法桩–土力学模型中的土层参数，计算曲线与实测曲线拟合较好；动测与静载试验所得到的桩基极限承载力误差为3.91%，试验结果相符合。研究成果可为类似冻土条件下的桩基设计及承载力检测提供理论依据。%To accurately know the refreezing time and capacity of the bridge bored pile constructed in polygonal permafrost regions,two test sites were chosen. Within each site,two 15 m test piles were built. The temperature monitoring system was established in one of the two sites to record and monitor the pile refreezing process. Based on the refreezing condition,static load and dynamic load tests were performed to determine the bearing capacity of the pile. Test results indicate that the mean permafrost temperature is-1.9℃. The trend of temperature change within the pile in refreezing process is similar to that of the permafrost temperature change 1 m beside the pile, which indicates that the difference of temperature change is smaller than 0.1℃. The calculated pile capacity fits well with the testing data by introducing the refreezing pile lateral frictional parameter to modify the soil mechanical model. The capacity error obtains from static load test
DePino, Andrew, Jr.
1994-01-01
Describes the relationships a high school built with neighborhood industry, a national laboratory, a national museum, and a large university while trying to build a scale model of the original atomic pile. Provides suggestions for teachers. (MVL)
Comprehensive Detection and Analysis of Defects in Foundation Pile of Bridge
Institute of Scientific and Technical Information of China (English)
WANG Qi-ren; HE Ji-shan; YANG Tian-chun
2003-01-01
In the process of piling ,there are many various defects in foundation pile of bridge such as mud-bearing,sediment-bearing, isolation, honeycomb, broken piles, and so on, showing physical and mechanical features of low-density and low-intensity. In fact, by using the comprehensive detection of acoustic transmission method, the reflected wave method as well as drill coring sample method, and the rational utilization of engineering geological condition in field, the characteristics, size and location of common defects of foundation pile of bridge can be accurately detected and judged and the integrity of piles and the quality of concrete can be impersonally estimated.comprehensive detecting and analyzing methods on this kind of piles are introduced briefly. The physical characters of defects and basic features of detecting curves and their corresponding relation are emphasized, and causes are analyzed in in detail in this paper.
Seismic Dynamic Damage Characteristics of Vertical and Batter Pile-supported Wharf Structure Systems
Directory of Open Access Journals (Sweden)
Li Jiren
2015-10-01
Full Text Available Considering a typical steel pipe pile-supported wharf as the research object, finite element analytical models of batter and vertical pile structures were established under the same construction site, service, and geological conditions to investigate the seismic dynamic damage characteristics of vertical and batter pile-supported wharf structures. By the numerical simulation and the nonlinear time history response analysis of structure system and the moment–axial force relation curve, we analyzed the dynamic damage characteristics of the two different structures of batter and vertical piles under different seismic ground motions to provide reasonable basis and reference for designing and selecting a pile-supported wharf structure. Results showed that the axial force of batter piles was dominant in the batter pile structure and that batter piles could effectively bear and share seismic load. Under the seismic ground motion with peak ground acceleration (PGA of 350 Gal and in consideration of the factors of the design requirement of horizontal displacement, the seismic performance of the batter pile structure was better than that of the vertical pile structure. Under the seismic ground motion with a PGA of 1000 Gal, plastic failure occurred in two different structures. The contrastive analysis of the development of plastic damage and the absorption and dissipation for seismic energy indicated that the seismic performance of the vertical pile structure was better than that of the batter pile structure.
Numerical analysis of pile lateral behavior of pile supported embankment
Institute of Scientific and Technical Information of China (English)
荆志东; 刘力; 郑刚; 姜岩
2008-01-01
A finite difference numerical method was adopted to evaluate the pile lateral behavior of pile supported embankment. A published case history was used to verify the proposed methodology. By simulating the case history, the determination of parameters needed were verified. Then three embankments constructed on different ground conditions with different soil-pile relative stiffnesses were analyzed to study pile lateral behaviors including pile deflection and bending moment. The results show that pile deflections and bending moments induced by soil lateral deformation and embankment vertical load are different for piles at different positions under the same embankment. The relative stiffness between pile and soil affected by the properties of different reinforcing piles such as concrete pile and deep mixing method pile exert important effects on the pile lateral behavior and the pile’s failure modes. Consequently, it is necessary to consider the different piles lateral behaviors and possible failure modes at different positions and the different piles proprieties with different reinforcing methods in the embankment stability analysis.
Soil-Pile Interaction in the Pile Vertical Vibration Based on Fictitious Soil-Pile Model
Guodong Deng; Jiasheng Zhang; Wenbing Wu; Xiong Shi; Fei Meng
2014-01-01
By introducing the fictitious soil-pile model, the soil-pile interaction in the pile vertical vibration is investigated. Firstly, assuming the surrounding soil of pile to be viscoelastic material and considering its vertical wave effect, the governing equations of soil-pile system subjected to arbitrary harmonic dynamic force are founded based on the Euler-Bernoulli rod theory. Secondly, the analytical solution of velocity response in frequency domain and its corresponding semianalytical solu...
Institute of Scientific and Technical Information of China (English)
姚天虹
2014-01-01
Steel sheet pile is widely applied in excavation and support of foundation pit with weak foundation for its rapid construction speed and low cost. Based on the application of ESP-Ⅳsteel sheet pile cofferdam with water-proof measures in a large bridge in Zhongshan, Guangdong province, many aspects are introduced briefly, such as the tips of steel sheet pile cofferdam, the key points of steel sheet pile insertion, the leaking stoppage of the cofferdam, the fabrication of guide frame and the demolition of the cofferdam.%钢板桩在地基软弱基坑开挖支护时广泛使用，其具有施工速度快、成本低的特点。该文通过采用自身具备止水措施的FSP-Ⅳ型钢板桩围堰在广东中山市小榄水道特大桥中的运用实例，简要介绍了钢板桩围堰施工的注意事项、插打钢板桩的要点、钢板桩围堰的堵漏、导向架制作、钢板桩围堰的拆除等内容。
Field test study of DX piles%DX桩群桩现场试验研究
Institute of Scientific and Technical Information of China (English)
陈立宏; 唐松涛; 贺德新
2011-01-01
DX桩(三岔双向挤扩灌注桩)作为一种新型的变截面桩型在承载力和沉降方面比普通直孔灌注桩具有明显的优势.但对于DX桩的承载机制和沉降特性的研究,特别是DX桩群桩的研究还不充分.主要通过现场的模型桩试验,对DX桩单桩和群桩的承载力和沉降特性进行了研究.分析了相同条件下单桩和群桩的特性,同时比较了相同桩长、桩径以及相同承载力条件下DX桩和直孔桩的差异,为DX桩的设计提供了参考.%Cast-in-place pile with expanded branches and bells by 3-way extruding arms (DX pile), a new variable cross-section pile,has obvious advantages in bearing capacity and settlement control compared to conventional pile.However, studies of bearing mechanism and settlement characteristic.especially group DX piles.are not sufficient.The bearing capacity and settlement characteristics of single DX pilc and group DX piles are analyzed via in-situ model test.Special attention is paid on single and group DX piles comparison under same conditions; at the meantime, the single DX pile and conventional pile with the same pile length,diameter, and the same bearing capacity are compared so as to provide the theoretical references for the bearing capacity design of the DX piles in the engineering practice.
Research on Bored Bearing Characteristics in Xi’an
Directory of Open Access Journals (Sweden)
Zhang Lipeng
2015-01-01
Full Text Available To analyze the influence of different soil properties on pile foundation load-bearing characteristics, taking a section of railway in Xi’an and a bridge of Xi’an as test area, and by field static load test to study load transfer characteristics after the test piles under axial pressure, including the distribution of axial force, pile lateral friction, tip resistance traits, ultimate bearing capacity determine, and compare with the theory bearing capacity. Experimental results show that, adjacent soil properties change large, axial force and lateral friction mutation at the junction of corresponding soil layer. Silty clay in different parts is below ground, and its lateral friction plays much difference. Pile lateral friction plays an important role in bearing capacity, but the role of round gravel soil end bearing capacity to pile bearing capacity can’t be ignored. Tests calculate pile bearing capacity significantly larger than standardized formula calculation bearing capacity, which are respectively 55.35% and 119.1%. And give the similar project condition the suggested values of pile bearing capacity and soil friction, to provide reference for similar pile foundation design.
Directory of Open Access Journals (Sweden)
V. A. Sernov
2015-01-01
Full Text Available In recent time piled foundations are extensively applied due to an increase of storeys in buildings constructed in Minsk and load increment on the soil. Preference is given to this approach even in the case when relatively firm soil occurs in the top part of the foundation bed. In this case maximum usage of the foundation bed bearing capacity and reduction of foundation cost are considered as top-priority tasks for designers. One of the ways to increase the bearing capacity of piled foundations is the necessity to take into account resistance of foundation bed soil located under raft bottom. The raft as well as a shallow foundation is capable to transfer a significant part of building load into the soil. Such approach makes it possible to reduce a number of piles in the foundation or shorten their length. Then it results in shortening of the construction period and significant reduction in zero cycle. However up to the present moment reliable calculation methods that permit to take into account soil resistance in the raft base. An analysis of previous investigations on the matter executed by various researchers and a number of field investigations have been carried out with the purpose to develop the proposed methods.The paper presents results of field investigations on foundations consisting of short stamped tapered piles which are joined together with the help of the raft fragment. Strength and deformation characteristics of the bases are increasing while making such foundations in the fill-up soil. In this case the filled-up ground layer becomes a bearing layer both for piles and rafts as well. Improvement of high-plastic clay-bearing soil properties is ensured by ramming dry concrete mix under pile foot. The paper describes an experience on application of the piled-raft foundation in complicated engineering and geological conditions while constructing the Orthodox Church in Minsk.
A simplified analysis method for piled raft and pile group foundations with batter piles
Kitiyodom, Pastsakorn; Matsumoto, Tatsunori
2002-11-01
A simplified method of numerical analysis has been developed to estimate the deformation and load distribution of piled raft foundations subjected to vertical, lateral, and moment loads, using a hybrid model in which the flexible raft is modelled as thin plates and the piles as elastic beams and the soil is treated as springs. Both the vertical and lateral resistances of the piles as well as the raft base are incorporated into the model. Pile-soil-pile, pile-soil-raft and raft-soil-raft interactions are taken into account based on Mindlin's solutions for both vertical and lateral forces. The validity of the proposed method is verified through comparisons with several existing methods for single piles, pile groups and piled rafts. Workable design charts are given for the estimation of the lateral displacement and the load distribution of piled rafts from the stiffnesses of the raft alone and the pile group alone. Additionally, parametric studies were carried out concerning batter pile foundations. It was found that the use of batter piles can efficiently improve the deformation characteristics of pile foundations subjected to lateral loads.
Flexible pile thermal barrier insulator
Anderson, G. E.; Fell, D. M.; Tesinsky, J. S. (Inventor)
1978-01-01
A flexible pile thermal barrier insulator included a plurality of upstanding pile yarns. A generally planar backing section supported the upstanding pile yarns. The backing section included a plurality of filler yarns forming a mesh in a first direction. A plurality of warp yarns were looped around said filler yarns and pile yarns in the backing section and formed a mesh in a second direction. A binder prevented separation of the yarns in the backing section.
Laterally Loaded Piles in Clay
DEFF Research Database (Denmark)
Christensen, Helle; Niewald, Gitte
1992-01-01
The ultimate lateral resistance of a pile element moved horizontally can be analyzed by the theory of plasticity. At a certain depth the movements around the pile are purely horizontal and upper bound solutions can be estimated theoretically under undrained circumstances. Model tests...... in the laboratory show ultimate resistances close to the estimated limits and p - y curves close to curves based on test results from full-scale piles. Rough and smooth piles with circular and square cross sections are investigated....
Institute of Scientific and Technical Information of China (English)
王湛; 刘宇峰; 娄学谦; 戴宇文; 桑登峰
2014-01-01
Piles with super-large diameters and deep penetration are widely used in ocean and bridge engineering;however,traditional capacity test methods used for such piles have limitations.Focusing on the imperfections of nor-mal static load and Osterberg cell (O-cell)methods,the statnamic testing method is investigated on the basis of the Second Penang Bridge project in Malaysia.The capacities of piles with super-large diameters and deep penetration in sandy strata are studied.Compared with the results of the O-cell method used on the same pile,the applicability of statnamic testing for super-large diameter,deep-penetration piles is analyzed.Results indicate that the equivalent stat-ic capacities resulting from the Unloading Point Method (UPM)and the Segmental Unloading Point Method (SUPM)are 30% larger than the results when using the O-cell method.Because of the influences of dynamic soil re-sistance and pore pressure,the side friction of statnamic testing is also larger than that when using the O-cell meth-od.Therefore,the statnamic method still requires modification.%大直径超长桩在海洋工程和桥梁工程中应用广泛，但目前常用的测试方法均有各自的局限性。针对普通静载费时费力，自平衡测试方法研究不够完善等不足，基于马来西亚槟城二桥工程，采用现场实测方法对砂土地层中大直径超长嵌岩桩的静动法测试进行研究。通过对同一根桩上的自平衡法测试结果进行对比，分析静动法测试大直径超长桩承载力的适用性。通过对比发现，静动法测试结果用传统卸荷点法和分段卸荷点法处理得到的等效静承载力比自平衡法大30%左右；且由于土动摩阻和孔隙水压力影响，静动法测得的桩身摩阻力也大于自平衡测试结果，需要进行修正。
Institute of Scientific and Technical Information of China (English)
孙晓晨; 朱杰江
2016-01-01
The bearing capacity of residue pile should be reassessed and then the internal relations and differences between the new pile and the residue one should be analyzed in soft soil area. Load⁃settlement relationship is expected to be obtained from above research. A three dimensional elastic⁃plastic finite element model is established by ABAQUS, old and new pile effect and the corresponding differential settlement are studied, and the load influencing factors of old and new piles are discussed. Research results show that with the increase of length to diameter ratio, the old and new pile settlement difference is slightly decreasing. With the increase of new pile diameter, pile of old and new different settlement are substantially reduced. With the increase of pile spacing and diameter ratio, the old pile settlement decreases sharply.%软土地区旧桩重新利用时须重新评估其承载能力，计算明确旧桩承载力与新桩承载力之间的内在联系与差异。采用ABAQUS软件构建新旧桩共同作用的三维弹塑性有限元分析模型，研究了新旧桩共同作用效应及相应的差异沉降，并对影响新旧桩荷载⁃沉桩关系的影响因素进行讨论。研究成果表明：随着长径比的增加，新旧桩的沉降差小幅减小；随着新桩桩径的增加，新旧桩的沉降差大幅减小；随着桩距与直径比值的增加，旧桩沉降大幅减小。
Theoretical study on setup of expanded-base pile considering cavity contraction
Institute of Scientific and Technical Information of China (English)
齐昌广; 刘干斌; 王艳; 邓岳保
2015-01-01
When an expanded-base pile is installed into ground, the cavity expansion associated with penetration of the enlarged pile base is followed by cavity contraction along the smaller-diameter pile shaft. In order to account for the influence of cavity contraction on the change of bearing capacity of expanded-base pile, a theoretical calculation methodology, predicting the setup of expanded-base pile, was established by employing the cavity contraction theory to estimate the shaft resistance of expanded-base pile, and horizontal consolidation theory to predict the dissipation of excess pore pressure. Finally, the numerical solutions for the setup of expanded-base pile were obtained. The parametric study about the influence of cavity contraction on setup of expanded-base pile was carried out, while a field test was introduced. The parametric study shows that the decrements in radial pressure and the maximum pore water pressure after considering cavity contraction are increased as the expanded ratio (base diameter/shaft diameter) and rigidity index of soil are raised. The comparison between calculated and measured values shows that the calculated results of ultimate bearing capacity for expanded-base pile considering cavity contraction agree well with the measured values; however, the computations ignoring cavity contraction are 2.5−3.0 times the measured values.
Theoretical study on setup of expanded-base pile considering cavity contraction
Institute of Scientific and Technical Information of China (English)
齐昌广; 刘干斌; 王艳; 邓岳保
2015-01-01
When an expanded-base pile is installed into ground, the cavity expansion associated with penetration of the enlarged pile base is followed by cavity contraction along the smaller-diameter pile shaft. In order to account for the influence of cavity contraction on the change of bearing capacity of expanded-base pile, a theoretical calculation methodology, predicting the setup of expanded-base pile, was established by employing the cavity contraction theory to estimate the shaft resistance of expanded-base pile, and horizontal consolidation theory to predict the dissipation of excess pore pressure. Finally, the numerical solutions for the setup of expanded-base pile were obtained. The parametric study about the influence of cavity contraction on setup of expanded-base pile was carried out, while a field test was introduced. The parametric study shows that the decrements in radial pressure and the maximum pore water pressure after considering cavity contraction are increased as the expanded ratio(base diameter/shaft diameter) and rigidity index of soil are raised. The comparison between calculated and measured values shows that the calculated results of ultimate bearing capacity for expanded-base pile considering cavity contraction agree well with the measured values; however, the computations ignoring cavity contraction are 2.5-3.0 times the measured values.
Soil-Pile Interaction in the Pile Vertical Vibration Based on Fictitious Soil-Pile Model
Directory of Open Access Journals (Sweden)
Guodong Deng
2014-01-01
Full Text Available By introducing the fictitious soil-pile model, the soil-pile interaction in the pile vertical vibration is investigated. Firstly, assuming the surrounding soil of pile to be viscoelastic material and considering its vertical wave effect, the governing equations of soil-pile system subjected to arbitrary harmonic dynamic force are founded based on the Euler-Bernoulli rod theory. Secondly, the analytical solution of velocity response in frequency domain and its corresponding semianalytical solution of velocity response in time domain are derived by means of Laplace transform technique and separation of variables technique. Based on the obtained solutions, the influence of parameters of pile end soil on the dynamic response is studied in detail for different designing parameters of pile. Lastly, the fictitious soil-pile model and other pile end soil supporting models are compared. It is shown that the dynamic response obtained by the fictitious soil-pile model is among the dynamic responses obtained by other existing models if there are appropriate material parameters and thickness of pile end soil for the fictitious soil-pile model.
Fermi, Enrico
The Patent contains an extremely detailed description of an atomic pile employing natural uranium as fissile material and graphite as moderator. It starts with the discussion of the theory of the intervening phenomena, in particular the evaluation of the reproduction or multiplication factor, K, that is the ratio of the number of fast neutrons produced in one generation by the fissions to the original number of fast neutrons, in a system of infinite size. The possibility of having a self-maintaining chain reaction in a system of finite size depends both on the facts that K is greater than unity and the overall size of the system is sufficiently large to minimize the percentage of neutrons escaping from the system. After the description of a possible realization of such a pile (with many detailed drawings), the various kinds of neutron losses in a pile are depicted. Particularly relevant is the reported "invention" of the exponential experiment: since theoretical calculations can determine whether or not a chain reaction will occur in a give system, but can be invalidated by uncertainties in the parameters of the problem, an experimental test of the pile is proposed, aimed at ascertaining if the pile under construction would be divergent (i.e. with a neutron multiplication factor K greater than 1) by making measurements on a smaller pile. The idea is to measure, by a detector containing an indium foil, the exponential decrease of the neutron density along the length of a column of uranium-graphite lattice, where a neutron source is placed near its base. Such an exponential decrease is greater or less than that expected due to leakage, according to whether the K factor is less or greater than 1, so that this experiment is able to test the criticality of the pile, its accuracy increasing with the size of the column. In order to perform this measure a mathematical description of the effect of neutron production, diffusion, and absorption on the neutron density in the
Comparison of Design Methods for Axially Loaded Driven Piles in Cohesionless Soil
DEFF Research Database (Denmark)
Thomassen, Kristina; Andersen, Lars Vabbersgaard; Ibsen, Lars Bo
2012-01-01
For offshore wind turbines on deeper waters, a jacket sub-structure supported by axially loaded piles is thought to be the most suitable solution. The design method recommended by API and two CPT-based design methods are compared for two uniform sand profiles. The analysis show great difference...... in the predictions of bearing capacities calculated by means of the three methods for piles loaded in both tension and compression. This implies that further analysis of the bearing capacity of axially loaded piles in sand should be conducted....
Field study of plastic tube cast-in-place concrete pile
Institute of Scientific and Technical Information of China (English)
陈永辉; 曹德洪; 王新泉; 杜海伟; 张霆
2008-01-01
The compositions, technical principles and construction equipments of a new piling method used for ground improvement plastic tube cast-in-place concrete pile were introduced. The results from static load tests on single piles with different forms of pile shoes and on their composite foundations were analyzed. The distribution patterns of axial force, shaft friction and toe resistance were studied based on the measurements taken from buried strain gauges. From the point of engineering application, the pile has merits in convenient quality control, high bearing capacity and reliable quality, showing higher reasonability, advancement and suitability than other ground improvement methods. The pile can be adopted properly to take place of ordinary ground improvement method, achieving greater economical and social benefits.
Non-probabilistic fuzzy reliability analysis of pile foundation stability by interval theory
Institute of Scientific and Technical Information of China (English)
无
2007-01-01
Randomness and fuzziness are among the attributes of the influential factors for stability assessment of pile foundation.According to these two characteristics, the triangular fuzzy number analysis approach was introduced to determine the probability-distributed function of mechanical parameters. Then the functional function of reliability analysis was constructed based on the study of bearing mechanism of pile foundation, and the way to calculate interval values of the functional function was developed by using improved interval-truncation approach and operation rules of interval numbers. Afterwards, the non-probabilistic fuzzy reliability analysis method was applied to assessing the pile foundation, from which a method was presented for nonprobabilistic fuzzy reliability analysis of pile foundation stability by interval theory. Finally, the probability distribution curve of nonprobabilistic fuzzy reliability indexes of practical pile foundation was concluded. Its failure possibility is 0.91%, which shows that the pile foundation is stable and reliable.
Slime thickness evaluation of bored piles by electrical resistivity probe
Chun, Ok-Hyun; Yoon, Hyung-Koo; Park, Min-Chul; Lee, Jong-Sub
2014-09-01
The bottoms of bored piles are generally stacked with soil particles, both while boreholes are being drilled, and afterward. The stacked soils are called slime, and when loads are applied on the pile, increase the pile settlement. Thus to guarantee the end bearing capacity of bored piles, the slime thickness should be precisely detected. The objective of this study is to suggest a new method for evaluating the slime thickness, using temperature compensated electrical resistivity. Laboratory studies are performed in advance, to estimate and compare the resolution of the electrical resistivity probe (ERP) and time domain reflectometry (TDR). The electrical properties of the ERP and TDR are measured using coaxial type electrodes and parallel type two-wire electrodes, respectively. Penetration tests, conducted in the fully saturated sand-clay mixtures, demonstrate that the ERP produces a better resolution of layer detection than TDR. Thus, field application tests using the ERP with a diameter of 35.7 mm are conducted for the investigation of slime thickness in large diameter bored piles. Field tests show that the slime layers are clearly identified by the ERP: the electrical resistivity dramatically increases at the interface between the slurry and slime layer. The electrical resistivity in the slurry layer inversely correlates with the amount of circulated water. This study suggests that the new electrical resistivity method may be a useful method for the investigation of the slime thickness in bored piles.
Mono pile foundation. Final report
Energy Technology Data Exchange (ETDEWEB)
Lyngesen, S.; Brendstrup, C.
1997-02-01
The use of mono piles as foundations for maritime structures has been developed during the last decades. The installation requirements within the offshore sector have resulted in equipment enabling driving of piles up to 3-4 m to large penetration depths. The availability of this equipment has made the use of large mono piles feasible as foundations for structures like wind turbines. The mono pile foundations consists of three parts; the bare pile, a conical transition and a boat landing. All parts are prefitted at the yard in order to minimise the installation work that has to be carried out offshore. The study of a mono pile foundations for a 1.5 MW wind turbine has been conducted for two locations, Horns Rev and Roedsand. Three different water depths: 5, 8 and 11 m have been investigated in the study. The on-site welding between pile and conical transition is performed by an automatic welding machine. Final testing and eventually repair of the weld are conducted at least 16 hours after welding. This is followed by final installation of J-tube, tie-in to subsea cables and installation of the impressed current system for corrosive protection of the mono pile. The total cost for procurement and installation of the mono pile using the welded connection is estimated. The price does not include procurement and installation of access platform and boat landing. These costs are estimated to 250.000 DKK. Depending on water depth the cost of the pile ranges from 2,2 to 2,7 million DKK. Procurement and fabrication of the pile are approx. 75% of the total costs. The remaining 25% are due to installation. The total costs are very sensitive to the unit price of pile steel. During the project it became obvious that ice load has a very large influence on the dimensions of the mono pile. (EG)
THE NEW STRUCTURE OF A PLATE-PILE FOUNDATION
Directory of Open Access Journals (Sweden)
SAMORODOV О. V.
2016-01-01
Full Text Available Raising of problem. In the construction of high-rise buildings with significant loads on foundations and bedding at the base of not rocky soils tend to use the most common pile foundation to reduce the deformation and correspond to regulations [1] on the maximum permissible deformation. Monitoring of the stress-strain state (SSS pile foundations constructed buildings shows the existing reserves of bearing capacity on the one hand - soil bases of the second group of limit states, on the other - the foundation of the first group of limit states by regulating the SSS foundation during construction and exploitation. Therefore, are increasingly using more progressive structure of foundations consisting of piles and of plate, as well as methods for their construction [2 - 10], however, in their design there are a number of disadvantages associated with the ambiguity of the application of methods for the calculation of such structures, which allows to do only partial conclusions and recommendations. Purpose. Is proposing the new structure of a plate-pile foundation, which overcomes the drawbacks of the existing design solutions and methods of consruction their, as well as is proposing an engineering method of a determination of basic parameters. Conclusion. Is proposes the new structure of a plate-pile foundation and the method of a determination of basic parameters his in the design of a soil base to the maximum permissible deformation Su buildings. Efficiency of application this type plate-pile foundation obtained by rational distribution resistance between a plate and piles, when under load from the building to the first work fully incorporated plate that allows maximum deformed for plate, and then the piles - due to of the hinge connection with the plate. Thus, depending on the maximum permissible deformation for buildings resistance of plate part of a full load of more than 50%, that significantly reduces the consumption of concrete.
Pachla, Henryk
2016-12-01
The formation of a pile in the existing foundation and soil creates a new foundation construction which has a structure of foundation-pile-soil. This construction must be able to transfer loads from the foundation to the pile and from the pile to the soil. The pile structure has to transfer an imposed load. From the point of view of continuum mechanics determination of the capacity of such a system is preceded by the analysis of contact problem of three contact surfaces. Each of these surfaces is determined by different pairs of materials. The pair which creates a pile anchorage is a material from which the foundation is built (structure of stone and grout, brick and grout, concrete or reinforced concrete and grout. The pile structure is formed by grout and steel rebar. The pile formed in soil is created by a pair of grout and soil. What is important is that on contact surfaces the materials adhering to one another are subjected to different deformation types that are controlled by mechanical properties and geometry of these surfaces. In the paper, additional conditions that should be fulfilled for the foundation-pile-soil system to make load transfer from foundation to soil possible and safe are presented. The results of research done by the author on foundation-pile contact surface are discussed. The tests were targeted at verifying the bearing capacity of anchorage and deformation of piles made of grout and other materials from which foundations are built. The specimens were tested in tension and compression. The experiments were conducted on the amount specimens which is regarded as small sample to enable the statistical analysis of the results.
Force analysis of pile foundation in rock slope based on upper-bound theorem of limit
Institute of Scientific and Technical Information of China (English)
ZHAO Ming-hua; LIU Jian-hua; LIU Dai-quan; WANG You
2008-01-01
Based on the characteristic that the potential sliding surfaces of rock slope are commonly in the shape of either line or fold line, analysis thought of conventional pile foundation in the flat ground under complex load condition was applied and the upper-bound theorem of limit analysis was used to compute thrust of rock layers with all possible distribution shapes. The interaction of slope and pile was considered design load in terms of slope thrust, and the finite difference method was derived to calculate inner-force and displacement of bridge pile foundation in rock slope under complex load condition. The result of example shows that the distribution model of slope thrust has certain impact on displacement and inner-force of bridge pile foundation. The maximum displacement growth rate reaches 54% and the maximum moment and shear growth rates reach only 15% and 20%, respectively, but the trends of inner-force and displacement of bridge pile foundation are basically the same as those of the conventional pile foundation in the flat ground. When the piles bear the same level lateral thrust, the distribution shapes of slope thrust have different influence on inner-force of pile foundation, especially the rectangle distribution, and the triangle thrust has the smallest displacement and inner-force of pile foundation.
Use of geothermal piles combined with pile foundations
Directory of Open Access Journals (Sweden)
Ivan Kuzytskyi
2016-07-01
Full Text Available The possibility of use of geothermal piles in conditions of cold climate is considered. Full-scale experiment is conducted for using this technology in Kiev. Obtained results testify about a possibility for using the system in conditions of Ukraine, but this technology requires more detailed study and simulation of multiannual cycle of use of geothermal piles
Directory of Open Access Journals (Sweden)
Miriam Gonçalves Miguel
2005-07-01
Full Text Available A cidade de Londrina, Estado do Paraná, possui um perfil geotécnicoconstituído de uma camada superficial de solo argilo-siltoso, poroso, laterítico e muitas vezes colapsível, que se estende até a profundidade máxima de 12 metros. As estacas utilizadas em obras de pequeno a médio porte se encontram totalmente embutidas nesta camada, sofrendo a influência de seu comportamento laterítico e colapsível. Os métodos clássicos brasileiros de estimativa de capacidade de carga de estacas tornam-se conservadores, frente aos resultados reais, quando aplicados em solos lateríticos e, contra a segurança, quando aplicados em solos colapsíveis, isto é, na condição crítica ao colapso. Este trabalho avalia os coeficientes de ajuste das resistências de ponta e ao atrito lateral para esses métodos, no caso de estacas apiloadas, sendo estes coeficientes obtidos pela retro-análise de resultados de provas de carga estática à compressão, realizadas no Campo Experimental de Engenharia Geotécnica da Universidade Estadual de Londrina.The city of Londrina, Paraná, has a typical geotechnical profile defined by a superficial layer of porous silty clay with maximum depth of about 12 meters, that shows lateritic characteristics, andmany times, collapsibility. Casts in place piles are often used for small buildings in the region and are fully embedded in this soil layer. Therefore, this type of foundation is subjected to the lateritic and occasionally collapsible influence of soil. Brazilian pile bearing capacity methods may yield conservative results when applied to tropical soils, as far as the lateritic origin in concerned. On the other hand, it can be unsafe if collapsibility prevails. This paper evaluates coefficients to adjust both point and lateral resistance of cast in place small diameter piles in the situation described. The work was carried out at the Londrina State University Geotechnical Experimental Site, and back analysis from static
Polar bear use of a persistent food subsidy: insights from non-invasive genetic sampling in Alaska
Peacock, Elizabeth; Herreman, Jason
2013-01-01
Remains of bowhead whales (Balaena mysticetus) harvested by Iñupiat whalers are deposited in bone piles along the coast of Alaska and have become persistent and reliable food sources for polar bears (Ursus maritimus). The importance of bone piles to individuals and the population, the patterns of use, and the number, sex, and age of bears using these resources are poorly understood. We implemented barbed-wire hair snaring to obtain genetic identities from bears using the Point Barrow bone pile in winter 2010–11. Eighty-three percent of genotyped samples produced individual and sex identification. We identified 97 bears from 200 samples. Using genetic mark–recapture techniques, we estimated that 228 bears used the bone pile during November to February, which would represent approximately 15% of the Southern Beaufort Sea polar bear subpopulation, if all bears were from this subpopulation. We found that polar bears of all age and sex classes simultaneously used the bone pile. More males than females used the bone pile, and males predominated in February, likely because 1/3 of adult females would be denning during this period. On average, bears spent 10 days at the bone pile (median = 5 days); the probability that an individual bear remained at the bone pile from week to week was 63% for females and 45% for males. Most bears in the sample were detected visiting the bone pile once or twice. We found some evidence of matrilineal fidelity to the bone pile, but the group of animals visiting the bone pile did not differ genetically from the Southern Beaufort Sea subpopulation, nor did patterns of relatedness. We demonstrate that bowhead whale bone piles may be an influential food subsidy for polar bears in the Barrow region in autumn and winter for all sex and age classes.
Numeric simulation analysis of load-settlement relation of pile in layer foundation
Institute of Scientific and Technical Information of China (English)
WANG You-qing
2006-01-01
Considering the level distribution of soil layers, the soils surrounding pile are simulated with level finite layer elements. Supposing that the vertical deformation of the soil elements surrounding pile varies in the form of exponent function with radial distance, and considering the nonlinear constitutive relation of stress and strain, the stiffness matrix is established. The mechanics behavior of the pile-soil interface is simulated with a nonlinear interface element. This method can truly express the behavior of the pile-soil system. The load-settlement relation Q-S curves of two big diameter prototype piles on bearing test are analyzed, and satisfying results are obtained. This method is reasonable in theory and feasible in engineering.
Introduction to Single Piles under Lateral Loading
DEFF Research Database (Denmark)
Augustesen, Anders; Ibsen, Lars Bo
The purpose of this chapter is to give a short introduction to single piles subjected to lateral loading. First, the observed behaviour of laterally loaded piles is described, i.e. the effects of loading conditions, installation procedure, pile type etc. on pile behaviour are presented (section 1...
Microbiologically Influenced Corrosion of Pilings
2014-03-04
reported in all climatic conditions on unprotectej suJ pilings m contact with saline water (ie scawater and hrackisli ’.vater’’ tliat is siibj^ct... Pilings 6. AUTHOR(S) Brenda J. Little and Richard I. Ray 7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) Naval Research Laboratory...ACRONYM(S) ONR 11. SPONSOR/MONITOR’S REPORT NUMBER(S| 13. SUPPLEMENTARY NOTES Ao/£/o/3lz<l 14. ABSTRACT Sheet piles , used as retaining walls
DETERMINING DRIVING RESISTANCE WITH REBOUND OF PILE-TOP DURING PILE DRIVING
Institute of Scientific and Technical Information of China (English)
陈仁朋; 胡亚元; 陈云敏
2001-01-01
This paper presents a method to determine driving resistance with rebound of pile-top during pile driving. The soil around the pile shaft is assumed to be rigid-plastic, while that under the pile-tip is assumed to be ideally elastoplastic. The driving force acting on the pile-top is simplified to a triangular impact force. The kinematic equation of the pile-tip is established. From the one-dimensional wave equation, the movements of the pile-tip and pile-top are determined. The rebound at the pile-top can be written in a very concise form. It is shown that the shaft resistance makes the rebound at the pile-top decrease. In particular, when the pile is very long or the soil around the pile is very stiff, the decrease is very obvious.
Viscoelastic behavior of concrete pile
Institute of Scientific and Technical Information of China (English)
丁科; 唐小弟
2008-01-01
Based on constitutive theory of viscoelasticity,the viscoelastic behaviour of concrete pile was investigated.The influence of viscosity coefficient on the stress,displacement and velocity response was discussed.With the increase of viscosity coefficient,the amplitude of stress wave decreases,and the maximum value of the stress wave shifts to deeper position of the pile.In other words,the viscosity coefficient behaves as lag effect to stress wave.
Target reliability index for serviceability limit state of single piles
Institute of Scientific and Technical Information of China (English)
边晓亚; 郑俊杰; 徐志军; 章荣军
2015-01-01
The objective is to develop an approach for the determination of the target reliability index for serviceability limit state (SLS) of single piles. This contributes to conducting the SLS reliability-based design (RBD) of piles. Based on a two-parameter, hyperbolic curve-fitting equation describing the load−settlement relation of piles, the SLS model factor is defined. Then, taking into account the uncertainties of load−settlement model, load and bearing capacity of piles, the formula for computing the SLS reliability index (βsls) is obtained using the mean value first order second moment (MVFOSM) method. Meanwhile, the limit state function for conducting the SLS reliability analysis by the Monte Carlo simulation (MCS) method is established. These two methods are finally applied to determine the SLS target reliability index. Herein, the limiting tolerable settlement (slt) is treated as a random variable. For illustration, four load test databases from South Africa are compiled again to conduct reliability analysis and present the recommended target reliability indices. The results indicate that the MVFOSM method overestimatesβsls compared to that computed by the MCS method. Besides, both factor of safety (FS) and slt are key factors influencingβsls, so the combination of FS andβsls is welcome to be used for the SLS reliability analysis of piles when slt is determined. For smaller slt, pile types and soils conditions have significant influence on the SLS target reliability indices; for larger slt, slt is the major factor having influence on the SLS target reliability indices. This proves that slt is the most key parameter for the determination of the SLS target reliability index.
Simulation analysis for O-cell test of pile and the interaction of upper pile and lower pile
Institute of Scientific and Technical Information of China (English)
ZHENG Ying-jie; ZHANG Ke-xu; ZHANG Er-qi
2009-01-01
In this paper, the soil-pile system of O-cell test of pile is simplified as an axi-symmetrie problem.By using aggregation of quadrilateral isoparametrie elements to simulate pile and soil, setting Goodman' s elements between pile and soils, a method of numerical simulation analysis on O-cell test of pile is presented with the consideration of nonlinear mechanical behavior of soils and pile-soil interface.The method is applied to the a-nalysis of a case of O-cell test of pile.The load-displacement curves and axial force curves of upper pile and lower pile obtained from the O-cell test of pile are fitted, and parameters of the mechanical model of soils and interface are determined.Analysis results validate that the numerical simulation analysis method put forward in this paper is applicable.Furthermore, the interaction and influence of upper pile and lower pile in the O-cell test are also studied with the method.The result shows that if load box is located in a soil layer with fine me-chanical behavior, the interaction of upper pile and lower pile in O-cell test can be ignored generally.
Foglia, Aligi; Kohlmeier, Martin; Wefer, Maik
2016-01-01
Vibro-driven piles can potentially become cost-reducing alternatives to standard impact-driven piles for offshore wind turbine support structures. If these foundations are to be used to support jacket sub-structures, their bearing behaviour in tension has to be explored. In a novel geotechnical testing facility two large-scale vibro-driven piles for jacket sub-structures have been axially tested in tension. In this contribution the experimental tests are thoroughly described and the test resu...
Effect of Passive Pile on 3D Ground Deformation and on Active Pile Response
Bingxiang Yuan; Rui Chen; Jun Teng; Tao Peng; Zhongwen Feng
2014-01-01
Using a series of model tests, this study investigated the effect of a passive pile on 3D ground deformation around a laterally loaded pile and on that laterally loaded pile’s response in sand. The active pile head was subjected to lateral loads, and the passive pile was arranged in front of the active pile. In the model tests, the distance between the two pile centers was set to zero (i.e., a single pile test), 2.5, 4, and 6 times the pile width (B). The 3D ground surface deformations around...
Analysis of Interaction Factors Between Two Piles
Institute of Scientific and Technical Information of China (English)
CAO Ming; CHEN Long-zhu
2008-01-01
A rigorous analytical method is presented for calculating the interaction factor between two identical piles subjected to vertical loads. Following the technique proposed by Muki and Sternberg, the problem is decomposed into an extended soil mass and two fictitious piles characterized respectively by Young's modulus of the soil and that of the difference between the pile and soil. The unknown axial forces along fictitious piles are determined by solving a Fredholm integral equation of the second kind, which imposes the compatibility condition that the axial strains of the fictitious piles are equal to those corresponding to the centroidal axes of the extended soil. The real pile forces and displacements can subequally be calculated based on the determined fictitious pile forces, and finally, the desired pile interaction factors may be obtained. Results confirm the validity of the proposed approach and portray the influence of the governing parameters on the pile interaction.
A new method for testing pile by single-impact energy and P-S curve
Xu, Zhao-Yong; Duan, Yong-Kang; Wang, Bin; Hu, Yi-Li; Yang, Run-Hai; Xu, Jun; Zhao, Jin-Ming
2004-11-01
By studying the pile-formula and stress-wave methods ( e.g., CASE method), the authors propose a new method for testing piles using the single-impact energy and P-S curves. The vibration and wave figures are recorded, and the dynamic and static displacements are measured by different transducers near the top of piles when the pile is impacted by a heavy hammer or micro-rocket. By observing the transformation coefficient of driving energy (total energy), the consumed energy of wave motion and vibration and so on, the vertical bearing capacity for single pile is measured and calculated. Then, using the vibration wave diagram, the dynamic relation curves between the force ( P) and the displacement ( S) is calculated and the yield points are determined. Using the static-loading test, the dynamic results are checked and the relative constants of dynamic-static P-S curves are determined. Then the subsidence quantity corresponding to the bearing capacity is determined. Moreover, the shaped quality of the pile body can be judged from the formation of P-S curves.
Kikutani, Yoshikuni; Hibara, Akihide; Uchiyama, Kenji; Hisamoto, Hideaki; Tokeshi, Manabu; Kitamori, Takehiko
2002-11-01
We made a 'pile-up' microreactor in which ten levels of microchannel circuits were integrated to form a single glass entity. Solutions were distributed to each layer via cylindrical holes with a diameter much larger than that of the microchannel. Fabrication of the pile-up reactor was completed using only conventional photolithography, wet etching and thermal bonding techniques, and no special facilities or instruments were required. An amide formation reaction between amine in aqueous solution and acid chloride in organic solution was carried out using the pile-up reactor. The yield of the amide formation reaction is dependent on the size of the specific surface area between the two solutions, and the small space inside the microchannels is good for acquiring a large specific surface area without any stirring processes. The maximum throughput for the ten-layered pile-up reactor was ten times larger than that of a single-layered one, yet the reaction yield was still high. Productivity of the pile-up reactor for the reaction was as high as on a gram per hour scale. This value suggests that many conventional plants producing fine chemicals can be replaced by microreactors through the numbering-up technology.
Field testing of stiffened deep cement mixing piles under lateral cyclic loading
Raongjant, Werasak; Jing, Meng
2013-06-01
Construction of seaside and underground wall bracing often uses stiffened deep cement mixed columns (SDCM). This research investigates methods used to improve the level of bearing capacity of these SDCM when subjected to cyclic lateral loading via various types of stiffer cores. Eight piles, two deep cement mixed piles and six stiffened deep cement mixing piles with three different types of cores, H shape cross section prestressed concrete, steel pipe, and H-beam steel, were embedded though soft clay into medium-hard clay on site in Thailand. Cyclic horizontal loading was gradually applied until pile failure and the hysteresis loops of lateral load vs. lateral deformation were recorded. The lateral carrying capacities of the SDCM piles with an H-beam steel core increased by 3-4 times that of the DCM piles. This field research clearly shows that using H-beam steel as a stiffer core for SDCM piles is the best method to improve its lateral carrying capacity, ductility and energy dissipation capacity.
Displacement and deformation analysis for uplift piles
Institute of Scientific and Technical Information of China (English)
无
2008-01-01
On the assumptions that the shear resistance increases linearly with increasing shear displacement between the uplift pile and surrounding soil,that the axis force is distributed as parabola along the pile length,that elastic distortion occurs when the pile is loaded,that the displacement of pile is in accord with that of the soil,and that the uplift pile failure is regarded as the soil failure,arational calculation method was proposed for calculating the deformation,ultimate displacement and shear resistance of piles.The distributions of frictional resistance and the shear displacement along the pile length were obtained with the method.The comparisons were made between the measurement results and the present results.The present theoretical results agree well with the measurement results,with the average difference being less than 12% before failure.The comparisons show that the proposed method is reasonable for uplift design and engineering construction of piles.
Saitou, Yutaka; Kikuchi, Yoshiaki; Kusakabe, Osamu; Kiyomiya, Osamu; Yoneyama, Haruo; Kawakami, Taiji
Steel sheet pipe pile foundations with large diameter steel pipe sheet pile were used for the foundation of the main pier of the Tokyo Gateway bridge. However, as for the large diameter steel pipe pile, the bearing mechanism including a pile tip plugging effect is still unclear due to lack of the practical examinations even though loading tests are performed on Trans-Tokyo Bay Highway. In the light of the foregoing problems, static pile loading tests both vertical and horizontal directions, a dynamic loading test, and cone penetration tests we re conducted for determining proper design parameters of the ground for the foundations. Design parameters were determined rationally based on the tests results. Rational design verification was obtained from this research.
Directory of Open Access Journals (Sweden)
M. A. Lisnevskyi
2015-08-01
Full Text Available Purpose. Taking into consideration that the bearing capacity of the foundation may be insufficient, in the study it is assumed that pile foundation can be used to reduce the impact of the construction of new retaining structures on roads and railways near the existing buildings or in areas of dense urban development and ensure the stability of the foundation. To reduce the volume of excavation it is necessary to choose the economic structure of the retaining wall. To do this, one should explore stress-strain state (SSS of the retaining walls, to develop methods to improve their strength and stability, as well as to choose the most appropriate method of their analysis. Methodology. In the design of retaining walls foundation mat and piles are considered as independent elements. Since the combined effect of the retaining wall, piles and foundation mat as well as the effect of soil or rock foundation on the structure are considered not fully, so there are some limitations in the existing design techniques. To achieve the purpose the box tests of retaining walls models without piles and with piles for studying their interaction with the surrounding soil massif were conducted. Findings. Laboratory simulation of complex systems «surrounding soil – retaining wall – pile» was carried out and on the basis of the box test results were analyzed strains and its main parameters of the stress-strain state. Analysis of the results showed that the structure of a retaining wall with piles is steady and stable. Originality. So far, in Ukraine has not been carried out similar experimental box tests with models of retaining walls in such combinations. In the article has been presented unique photos and test results, as well as their analysis. Practical value. Using the methodology of experimental tests of the retaining wall models with piles and without them gives a wider opportunity to study stress-strain state of such structures.
DRIVEN POLYSTRONG REINFORCED CONCRETE PILES AND NEW DESIGN OF PILE CAPS
Directory of Open Access Journals (Sweden)
I. I. Bekbasarov
2015-01-01
Full Text Available The paper presents constructional and technological features for manufacturing driven piles with variable strength of pile shaft. Economical efficiency of their production has been shown in the paper. The paper provides a pile cap design that ensures perception of hammer impacts with the help of lateral edges of the pile cap. Driven reinforced concrete piles which are manufactured from three shaft sections having various strength have been proposed in the paper. Material strength (concrete grade and diameter of bars and length of shaft sections are given on a case by case basis in accordance with nature and rate of stresses in piles during their driving process. Manufacturing of polystrong piles provides an opportunity to select them for a particular construction site with due account of their preservation during driving process.A pile cap has been developed that as opposed to existing analogous designs makes it possible to transmit impact efforts from a hammer to the pile through lateral surface of its head part. The pile cap provides the possibility to increase an area for perception of hammer impact efforts by the pile and in doing so it is possible significantly to reduce a damage risk and destruction of pile concrete during its driving. Application of polystrong piles and their driving with the help of new pile cap are considered as a basis for defect-free and resource-saving technology for pile foundations in the construction.
Pullout capacity of batter pile in sand.
Nazir, Ashraf; Nasr, Ahmed
2013-03-01
Many offshore structures are subjected to overturning moments due to wind load, wave pressure, and ship impacts. Also most of retaining walls are subjected to horizontal forces and bending moments, these forces are due to earth pressure. For foundations in such structures, usually a combination of vertical and batter piles is used. Little information is available in the literature about estimating the capacity of piles under uplift. In cases where these supporting piles are not vertical, the behavior under axial pullout is not well established. In order to delineate the significant variables affecting the ultimate uplift shaft resistance of batter pile in dry sand, a testing program comprising 62 pullout tests was conducted. The tests are conducted on model steel pile installed in loose, medium, and dense sand to an embedded depth ratio, L/d, vary from 7.5 to 30 and with various batter angles of 0°, 10°, 20°, and 30°. Results indicate that the pullout capacity of a batter pile constructed in dense and/or medium density sand increases with the increase of batter angle attains maximum value and then decreases, the maximum value of Pα occurs at batter angle approximately equal to 20°, and it is about 21-31% more than the vertical pile capacity, while the pullout capacity for batter pile that constructed in loose sand decreases with the increase of pile inclination. The results also indicated that the circular pile is more resistant to pullout forces than the square and rectangular pile shape. The rough model piles tested is experienced 18-75% increase in capacity compared with the smooth model piles. The suggested relations for the pullout capacity of batter pile regarding the vertical pile capacity are well predicted.
Pullout capacity of batter pile in sand
Directory of Open Access Journals (Sweden)
Ashraf Nazir
2013-03-01
Full Text Available Many offshore structures are subjected to overturning moments due to wind load, wave pressure, and ship impacts. Also most of retaining walls are subjected to horizontal forces and bending moments, these forces are due to earth pressure. For foundations in such structures, usually a combination of vertical and batter piles is used. Little information is available in the literature about estimating the capacity of piles under uplift. In cases where these supporting piles are not vertical, the behavior under axial pullout is not well established. In order to delineate the significant variables affecting the ultimate uplift shaft resistance of batter pile in dry sand, a testing program comprising 62 pullout tests was conducted. The tests are conducted on model steel pile installed in loose, medium, and dense sand to an embedded depth ratio, L/d, vary from 7.5 to 30 and with various batter angles of 0°, 10°, 20°, and 30°. Results indicate that the pullout capacity of a batter pile constructed in dense and/or medium density sand increases with the increase of batter angle attains maximum value and then decreases, the maximum value of Pα occurs at batter angle approximately equal to 20°, and it is about 21–31% more than the vertical pile capacity, while the pullout capacity for batter pile that constructed in loose sand decreases with the increase of pile inclination. The results also indicated that the circular pile is more resistant to pullout forces than the square and rectangular pile shape. The rough model piles tested is experienced 18–75% increase in capacity compared with the smooth model piles. The suggested relations for the pullout capacity of batter pile regarding the vertical pile capacity are well predicted.
Pile Load Capacity – Calculation Methods
Directory of Open Access Journals (Sweden)
Wrana Bogumił
2015-12-01
Full Text Available The article is a review of the current problems of the foundation pile capacity calculations. The article considers the main principles of pile capacity calculations presented in Eurocode 7 and other methods with adequate explanations. Two main methods are presented: α – method used to calculate the short-term load capacity of piles in cohesive soils and β – method used to calculate the long-term load capacity of piles in both cohesive and cohesionless soils. Moreover, methods based on cone CPTu result are presented as well as the pile capacity problem based on static tests.
Institute of Scientific and Technical Information of China (English)
戴庆斌
2012-01-01
带肋填砂管桩是对普通预应力混凝土管桩改进后形成的一种新的管桩应用类型。基于弹塑性理论的带肋填砂管桩沉降计算方法，既考虑桩身在荷载传递作用下的弹性压缩沉降，也考虑桩端以下土层的弹性和弹塑性变形沉降，并给出端阻力和桩侧阻力的分配系数确定方法。根据该模型计算结果，可进一步分析有关数据的特点及其产生的原理。结果表明，该模型的计算结果与实测结果较吻合，具有一定的应用价值。%Ribbed and sand-filled tube pile is a new applied tube pile after the improvement of the general prestressed concrete pile. The settlement calculation of ribbed and sand-filled tube pile based on elastic-plastic theory not only takes into account of the compression settlement under the load transfer of the pile, but also the soil elastic and plastic settlement below the pile tip, and the method of coefficients between resistances of the pile tip and the pile side is presented. According to the result, the relevant statistics and their principle can be studied. Results indicates that the calculation agrees well with the measurement, and is of practical value.
Erective Sea Embankment with PCC Piles
Institute of Scientific and Technical Information of China (English)
LIU Han-long; FEI Kang; DENG An; ZHANG Ting
2005-01-01
The sea embankment is a critical civil works in marine and coastal engineering. In this study, an innovative technique is proposed for constructing erective sea embankments. In the construction of sea embankments, this technique integrates PCC pile installation, PVDs drainage systems, and geotextile reinforcements, resulting in sea embankments with PCC piles. In the application of a sea embankment with PCC piles, PCC piles are employed as the retaining structures;the soft sea ground inside PCC piles is drained and improved by PVDs and vacuum-surcharge combined preloading; geotextile-reinforced backfills lying over the improved soft ground form the embankment body. Brief descrptions of the fundamentals, design and construction of the sea embankment with PCC piles are presented. A case study on the stability of sea embankment with PCC piles is presented as well.
Behaviour of jacked and driven piles in sandy soil
Yang, J; Tham, LG; Lee, PKK; Chan, ST; Yu, F.
2006-01-01
As an alternative to conventional dynamic pile installation methods, pile jacking is an environmentally friendly technique that could become more widely accepted. Great concern has arisen over the performance of jacked piles as compared with that of driven piles. This paper describes a comprehensive field study that was aimed at investigating the differences and similarities between the behaviour of jacked H-piles and that of driven H-piles. The instrumented piles, varying in length from 32 t...
Mathematical Model and Analysis of Negative Skin Friction of Pile Group in Consolidating Soil
Directory of Open Access Journals (Sweden)
Gangqiang Kong
2013-01-01
Full Text Available In order to calculate negative skin friction (NSF of pile group embedded in a consolidating soil, the dragload calculating formulas of single pile were established by considering Davis one-dimensional nonlinear consolidation soils settlement and hyperbolic load-transfer of pile-soil interface. Based on effective influence area theory, a simple semiempirical mathematical model of analysis for predicting the group effect of pile group under dragload was described. The accuracy and reliability of mathematical models built in this paper were verified by practical engineering comparative analysis. Case studies were studied, and the prediction values were found to be in good agreement with those of measured values. Then, the influences factors, such as, soil consolidation degree, the initial volume compressibility coefficient, and the stiffness of bearing soil, were analyzed and discussed. The results show that the mathematical models considering nonlinear soil consolidation and group effect can reflect the practical NSF of pile group effectively and accurately. The results of this paper can provide reference for practical pile group embedded in consolidating soil under NSF design and calculation.
Institute of Scientific and Technical Information of China (English)
曹兆虎; 刘汉龙; 孔纲强; 周航
2015-01-01
A small-scale physical modelling method was developed to investigate the pile bearing capacity and the soil displacement around the pile using transparent soil and particle image velocimetry(PIV) technique. Transparent sand was made of baked quartz and a pore fluid with a matching refractive index. The physical modelling system consists of a loading system, a laser light, a CCD camera, an optical platform and a computer for image analyzing. A distinctive laser speckle was generated by the interaction between the laser light and transparent soil. Two laser speckle images before and after deformation were used to calculate the soil displacement field using PIV. Two pipe piles with different diameters under oblique pullout loads at angles of 0°, 30°, 45°, 60° and 90° were used in tests. The load-displacement response, oblique pullout ultimate resistances and soil displacement fields were then studied. The test results show that the developed physical modelling method and transparent soil are suitable for pile-soil interaction problems. The soil displacements around the pipe piles will improve the understanding on the capacity of pipe piles under oblique pullout loads.
Huy, N.Q.
2010-01-01
Pile testing, which plays an importance role in the field of deep foundation design, is performed by static and non-static methods to provide information about the following issues: (Poulos, 1998) - The ultimate capacity of a single pile. - The load-displacement behavior of a pile. - The performance of a pile during the test conditions. - The integrity of a pile (pile integrity test). For the purposes of verification the design axial capacity and the static load – settlement behavior of piles...
扩底桩受压有限元分析%Finite element analysis of pile with enlarged base subject to compressed loading
Institute of Scientific and Technical Information of China (English)
柯江
2015-01-01
Through applying ABAQUS finite element software,it establishes nonlinear pile-soil finite element model. The bearing properties of pile with enlarged base subject to compressed loading were analyzed. The results show that the bearing capacity of pile with enlarged base to the limit,the enlarged head could bear the most load of pile,and the slope of the enlarged head and soil produced a separate.%采用 ABAQUS 有限元软件，建立了桩土非线性有限元模型，分析了扩底桩受压承载特性，得出：扩底桩达到受压极限承载力时，扩大头承受了桩的大部分荷载，扩大头斜面与土体产生了分离。
桩伴侣与基桩抗震的概念设计%Pile Partner and the Conceptual Earthquake-resistant Design of Foundation Pile
Institute of Scientific and Technical Information of China (English)
薛江炜; 葛忻声; 蔡景珞; 杨勇
2013-01-01
It is uncertain that the lateral components such as basement wall and cap side wall bearing horizontal load,so the conventional pile foundation with low cap might endure lateral force that is larger,and even cause its damage.The applying of pile partner to improve traditional foundation pile structure form is put for ward,especially when there is few frictional force between pile cap and soil,or the soil modulus is small.The partner can be component for anti-earthquake concept design under rare earthquake action,pile partner may be sacrificed firstly to keep pile perform well.The improper design of composite foundation will destroy or weaken the isolation effect of pillow,and can be solved by reserving buffer space between pile and partner.%地下室外墙、承台侧壁等侧向构件承担水平荷载具有很大的不确定性,常规采用的低承台桩基有可能承受较大的甚至导致破坏的水平力,建议用桩伴侣改善传统基桩的构造形式,特别是对于承台与桩间土摩擦力小或者桩身范围地基土模量低的两类状况.在罕遇地震时,作为抗震概念设计的耗能构件,首先牺牲伴侣,避免或延迟桩头的破坏；复合地基如果设计不当会破坏或削弱褥垫层隔震的效果,可在伴侣与桩之间预留缓冲空间.
Institute of Scientific and Technical Information of China (English)
陈培震; 栾茂田; 罗强
2012-01-01
采用大型有限元软件ABAQUS,针对大直径超长群桩的有效桩长进行三维有限元数值分析.采用极限承载力控制法,对竖向荷载下不同布桩形式的大直径超长群桩基础的有效桩长进行研究.结果表明:有效桩长随桩数的增多而增大,随桩距的增大而减小；桩数增多,有效桩长对应的群桩的极限承载力降低,桩距的变化对有效桩长对应的群桩的极限承载力影响不大.%Based on the framework of FEM software ABAUQS, the three-dimensional numerical analysis for effective length of super-long and large-diameter pile groups is provided. For the pile groups of different arrangements under vertical loading, the effective pile-length was analyzed with the method of bearing capacity control. The results show that the effective pile-length increases with pile number while decreases with the space between piles. The corresponding bearing capacity decreases with pile number while the space between piles has little effect on the corresponding bearing capacity.
Thermal Conductivity Of Rubble Piles
Luan, Jing
2015-01-01
Rubble piles are a common feature of solar system bodies. They are composed of monolithic elements of ice or rock bound by gravity. Voids occupy a significant fraction of the volume of a rubble pile. They can exist up to pressure $P\\approx \\epsy\\mu$, where $\\epsy$ is the monolithic material's yield strain and $\\mu$ its rigidity. At low $P$, contacts between neighboring elements are confined to a small fraction of their surface areas. As a result, the effective thermal conductivity of a rubble pile, $\\kcon\\approx k(P/(\\epsy\\mu))^{1/2}$, can be orders of magnitude smaller than, $k$, the thermal conductivity of its monolithic elements. In a fluid-free environment, only radiation can transfer energy across voids. It contributes an additional component, $\\krad=16\\ell\\sigma T^3/3$, to the total effective conductivity, $\\keff=\\kcon +\\krad$. Here $\\ell$, the inverse of the opacity per unit volume, is of order the size of the elements and voids. An important distinction between $\\kcon$ and $\\krad$ is that the former i...
Test Setup for Axially Loaded Piles in Sand
DEFF Research Database (Denmark)
Thomassen, Kristina
The test setup for testing axially static and cyclic loaded piles in sand is described in the following. The purpose for the tests is to examine the tensile capacity of axially loaded piles in dense fully saturated sand. The pile dimensions are chosen to resemble full scale dimension of piles used...... in offshore pile foundations today....
Static Tension Tests on Axially Loaded Pile Segments in Sand
DEFF Research Database (Denmark)
Thomassen, Kristina; Andersen, Lars Vabbersgaard; Ibsen, Lars Bo
This paper provides laboratory test results of static axially loaded piles in sand. With a newly developed test setup, the pile-soil interface friction was investigated by using an open-ended steel pile segment with a diameter of 0.5 m. Use of a pile length of 1 m enabled the pile-soil interface...
Institute of Scientific and Technical Information of China (English)
杨阳; 王国才; 金菲力
2012-01-01
The setting mode of pile group has much effect on pile group's bearing capacity and settlement under inclined loadings. In order to reveal this effect, the nonlinear finite element software is used and a 3-D model is developed to simulate the battered pile group under inclined loadings. The effect of inclined angle, pile-soil elastic modulus, battered pile length and number, etc. , on the settlement of battered pile group, is analyzed. The results indicate that: the geometry of soil, the inclined angle of battered pile, pile rigidity, length and number, etc. , has much effect on the settlement of battered pile group. Some useful conclusions are obtained for the design and construction of pile group that subjected to inclined loadings.%斜向荷载作用下桩群的设置方式对其承载力和沉降有较大影响.为揭示这一影响规律,采用非线性有限元软件对斜向荷载作用下桩群中设置的斜桩进行三维建模,分析了斜桩的倾角、桩-土弹性模量、斜桩桩长以及桩数等因素对群桩沉降的影响.结果表明:地基土质情况、斜桩的倾角、刚度和桩长与桩数等对倾斜群桩的沉降影响较大,所得结论对斜向荷载作用下群桩基础的设计与施工具有一定的指导意义.
Global and local scour at pile groups
DEFF Research Database (Denmark)
Sumer, B. Mutlu; Bundgaard, Klavs; Fredsøe, Jørgen
2005-01-01
This paper presents the results of an experimental investigation on scour around pile groups with different configurations exposed to steady current. Two kinds of tests were carried out: rigid-bed tests and actual scour tests. In these, the mean and turbulence properties of the flow were measured...... across the pile groups. The pile-group configurations were such that the global scour was distinguished from the local scour. The results show that the global scour can be quite substantial....
Global and local scour at pile groups
DEFF Research Database (Denmark)
Sumer, B. Mutlu; Bundgaard, Klavs; Fredsøe, Jørgen
2005-01-01
This paper presents the results of an experimental investigation on scour around pile groups with different configurations exposed to steady current. Two kinds of tests were carried out: (1) Rigid-bed tests, and (2) Actual scour tests. In the former tests, the mean and turbulence properties...... of the flow were measured across the pile groups. The pile group configurations were such that the global scour was distinguished from the local scour. The results show that the global scour can be quite substantial....
Suro, S. M.; Bakar, I.; Sulaeman, A.
2016-07-01
Short Piled Raft is a modified piled raft foundation system, which represents combination between raft foundation and pile foundation, but the length of pile is relatively shorter. The basic concept of the Short Piled Raft foundation system considers the passive soil pressure creating a stiff condition of slab-pile system. This means that the thin concrete slab floats on the supporting soil, while the piles serve as stiffeners concrete slab and also to reduce settlement of the foundation. Slab to pile ratio of such system has been mentioned by several researchers, however the optimum pile spacing of stability performance for obtaining minimum settlement on peat haven't been clearly discussed. In this study, finite element method to simulate the stability performance related to settlement of Short Piled Raft foundation system was used. Short Piled Raft foundation system with concrete slab of 7.0 m x 7.0 m square was assumed to be built on peat with the thickness of 3.5 m. The material properties of pile and raft were constant. The outer diameter of galvanized steel pipe as pile was 0.30 m; raft thickness was considered to be constant of 0.15 m and the length of pile was 3.0 m, while the pile spacing varied from 0.50 to 3.00 m. Point load varied from 0 to 100 kN with increment of 20 kN was also considered as a static load, acted on the centre of the concrete slab. Optimization was done by comparing each numerical result of simulations, thus conclusion can easily be drawn. The optimum pile spacing was 1.00 m which produced minimum settlement of 30.11 mm under the load of 100 kN.
Influence of reaction piles on test pile response in a static load test
Institute of Scientific and Technical Information of China (English)
Qian-qing ZHANG; Shu-cai LI; Zhong-miao ZHANG
2013-01-01
This work presents a new analytical method to analyze the influence of reaction piles on the test pile response in a static load test.In our method,the interactive effect between soil and pile is simulated using independent springs and the shear displacement method is adopted to analyze the influence of reaction piles on test pile response.Moreover,the influence of the sheltering effect between reaction piles and test pile on the test pile response is taken into account.Two cases are analyzed to verify the rationality and efficiency of the present method.This method can be easily extended to a nonlinear response of an influenced test pile embedded in a multilayered soil,and the validity is also demonstrated using centrifuge model tests and a computer program presented in the literature.The present analyses indicate that the proposed method will lead to an underestimation of the test pile settlement in a static load test if the influence of the presence of reaction piles on the test pile response is neglected.
Effect of pile-cap connection on behavior of torsionally loaded pile groups
Institute of Scientific and Technical Information of China (English)
Ling-gang KONG; Li-min ZHANG
2008-01-01
To evaluate the respouses of fixed and pinned pile groups under torsiun, a method is presented to analyze the nonlinear behavior of free-standing pile groups with rigid pile caps. The method is capable of simulating the nonlinear soil response in the near field usingp-y and τ-θ curves, the far-field interactions through Mindlin's and Randolph's elastic solutions, and the coupling effect of lateral resistance on torsional resistance of the individual piles using an empirical factor. Based on comparisons of the solutions for fixedand pinned-head, 1×2, 2×2, and 3×3 pile groups subjected to torsion, it was found that pile-cap connection significantly influences the torsional capacity of pile groups and the assignment of applied torques in the pile groups. In this study, the applied torques for the pinned-head pile groups are only 44%～64% of those for the corresponding fixed-head pile groups at a twist angle of 2°. Such a difference is mainly due to the change of the lateral resistances of individual piles in the groups.
Analysis of pile load-transfer under pile-side softening
Institute of Scientific and Technical Information of China (English)
刘杰; 张可能
2003-01-01
A set of analytical equations for the variation of the axial force along depth and the pile-top load-settle-ment curve were established, using tri-linear softening model to pile-side soil and bilinear hardening model to pile-end soil . Influences of the pile-side and pile-end soil behavior on the load-settlement curve were discussed, indica-ting that the lowering reason for the variation step degree of the axial force along depth is the softening of the pile-side soil to result in the side friction lowering when the pile-top load is increased. To verify the reliability of thismethod, the parameters used in calculation are obtained from the test in Zhuzhou area. The obtained results are thencompared with the tested results. Contrast shows that the calculated results and the tested values are very close,which illustrates that the proposed method is reliable.
Model Tests of Pile Defect Detection
Institute of Scientific and Technical Information of China (English)
无
2001-01-01
The pile, as an important foundation style, is being used in engineering practice. Defects of different types and damages of different degrees easily occur during the process of pile construction. So,dietecting defects of the pile is very important. As so far, there are some difficult problems in pile defect detection. Based on stress wave theory, some of these typical difficult problems were studied through model tests. The analyses of the test results are carried out and some significant results of the low-strain method are obtained, when a pile has a gradually-decreasing crosssection part, the amplitude of the reflective signal originating from the defect is dependent on the decreasing value of the rate of crosssection β. No apparent signal reflected from the necking appeares on the velocity response curve when the value of β is less than about 3.5 %.
Institute of Scientific and Technical Information of China (English)
绳怀海; 孙海涛; 祝凤春
2011-01-01
Combining with engineering case,in order to accurately detects pile-side and pile-end resistance distribution condition,it carries on dynamic and statistic load test and high strain dynamic detection for the pile foundation,and analyzes and evaluates the detection results.In the end,it obtains that is feasible to use high strain dynamic detection of pile foundation to determine the foundation pile bearing capacity.%结合某工程实例,为了准确测定桩侧、桩端阻力分布情况,对基桩进行了动静载测试及高应变动力检测,并对检测结果进行了分析评价,得出用基桩高应变动力检测确定基桩承载力是可行的。
Institute of Scientific and Technical Information of China (English)
曹兆虎; 刘汉龙; 孔纲强; 周航
2015-01-01
A small-scale physical modelling method was developed to investigate the pile bearing capacity and the soil displacement around the pile using transparent soil and particle image velocimetry (PIV) technique. Transparent sand was made of baked quartz and a pore fluid with a matching refractive index. The physical modelling system consists of a loading system, a laser light, a CCD camera, an optical platform and a computer for image analyzing. A distinctive laser speckle was generated by the interaction between the laser light and transparent soil. Two laser speckle images before and after deformation were used to calculate the soil displacement field using PIV. Two pipe piles with different diameters under oblique pullout loads at angles of 0°, 30°, 45°, 60° and 90° were used in tests. The load−displacement response, oblique pullout ultimate resistances and soil displacement fields were then studied. The test results show that the developed physical modelling method and transparent soil are suitable for pile−soil interaction problems. The soil displacements around the pipe piles will improve the understanding on the capacity of pipe piles under oblique pullout loads.
Directory of Open Access Journals (Sweden)
M. R. Honarvar
2008-01-01
Full Text Available Offshore platforms in seismically active areas should be designed to survive in the event of severe ground excitations with no global structural failure. The annulus between the pile and leg in jacket-type offshore platforms can be filled with cement grout as a means of reducing horizontal deflections, inhibiting corrosion and preventing local damages. This paper discusses an experimental approach which can be used to demonstrate the effect of grouting on enhanced structural performance of jackets. In this regard, the lateral load bearing behavior of grouted and un-grouted jackets are investigated experimentally with special attention to effect of grout on pile-leg interaction. Results are presented on the cyclic inelastic behavior of two scaled frame models of a representative platform which was recently installed in the Persian gulf. The objective of this effort was to improve the understanding of the behavior of jackets subjected to lateral motions and specially the effects of exact real pile-leg interaction. it should be noted that this paper addresses the exact and realistic pile-leg interaction. It is concluded that grouting can not be considered as a definite method of improving strength and structural nonlinear dynamic behavior. Although it generally increases the lateral stiffness, but some side effects and points are to be considered. In this paper, the two separate lateral load bearing mechanisms -namely portal (braced mechanism and frame bending mechanism- are distinguished and the effect of grout on each one is shown.
A new method for testing pile by single-impact energy and P-S curve
Institute of Scientific and Technical Information of China (English)
许昭永; 段永康; 王彬; 胡毅力; 杨润海; 许峻; 赵晋明
2004-01-01
By studying the pile-formula and stress-wave methods (e.g., CASE method), the authors propose a new method fortesting piles using the single-impact energy and P-S curves. The vibration and wave figures are recorded, and thedynamic and static displacements are measured by different transducers near the top of piles when the pile is impacted by a heavy hammer or micro-rocket. By observing the transformation coefficient of driving energy (totalenergy), the consumed energy of wave motion and vibration and so on, the vertical bearing capacity for single pileis measured and calculated. Then, using the vibration wave diagram, the dynamic relation curves between the force(P) and the displacement (S) is calculated and the yield points are determined. Using the static-loading test, thedynamic results are checked and the relative constants of dynamic-static P-S curves are determined. Then the subsidence quantity corresponding to the bearing capacity is determined. Moreover, the shaped quality of the pilebody can be judged from the formation of P-S curves.
Institute of Scientific and Technical Information of China (English)
Feng ZHANG; Katsunori OKAWA; Makoto KIMURA
2008-01-01
In this paper, dynamic behavior of a grouppile foundation with inclined piles in loose sand has been investigated with centrifuge model tests. The test results are also simulated with elastoplastic dynamic finite ele-ment method, in which, not only sectional force of piles, stress of ground, but also deformation of piles are calcu-lated using a three-dimensional elastoplastic dynamic finite element analysis (Code name: DGPILE-3D). The numerical analyses are conducted with a full system in which a superstructure, a pile foundation and surround-ing ground are considered together so that interaction between pile foundation and soils can be properly simu-lated because the nonlinearities of both the pile and the ground are described with suitable constitutive models. Different types of piles, vertical pile or inclined pile, are considered in order to verify the different characteristics of a group pile foundation with inclined piles. The validity of the calculation is verified by the model tests.
Institute of Scientific and Technical Information of China (English)
ZHOU Hongbo; CHEN Zhuchang
2007-01-01
Based on the comparative analysis of end effect on skin friction of displacement-pile (driven pile),the end effect on skin friction of bored pile is studied.The end effect on skin friction between driven pile and bored pile is different and the end effect on skin friction of bored pile is reduce of skin friction in the soil layer adjacent to the pile end.The degradation degree of skin friction is deduced with the increase of the distance from pile end.The concept of additional mud cake formed by the effect of cushion at the bottom of borehole during pouring concrete is introduced to explain the mechanism of end effect on skin friction of the bored pile.The test results of post-grouting piles indicate that the post-grouting technique is an effective way to improve the end effect on skin friction of bored pile.
3D finite element analysis on pile-soil interaction of passive pile group
Institute of Scientific and Technical Information of China (English)
ZHAO Ming-hua; LIU Dun-ping; ZHANG Ling; JIANG Chong
2008-01-01
The interaction between pile and soft soil of the passive pile group subjected to soil movement was analyzed with three-dimensional finite element model by using ANSYS software. The soil was assumed to be elastic-plastic complying with the Drucker-Prager yield criterion in the analysis. The large displacement of soil was considered and contact elements were used to evaluate the interaction between pile and soil. The influences of soil depth of layer and number of piles on the lateral pressure of the pile were investigated, and the lateral pressure distributions on the (2×1) pile group and on the (2×2) pile group were compared. The results show that the adjacent surcharge may result in significant lateral movement of the soft soil and cousiderable pressure on the pile. The pressure acting on the row near the surcharge is higher than that on the other row, due to the "barrier" and arching effects in pile groups. The passive load and its distribution should be taken into account in the design of the passive piles.
Vertical vibration of a large diameter pipe pile considering transverse inertia effect of pile
Institute of Scientific and Technical Information of China (English)
郑长杰; 刘汉龙; 丁选明; 周航
2016-01-01
Considering the transverse inertia effect of pile, the vertical dynamic response of a large diameter pipe pile in viscoelastic soil layer is studied. The wave propagations in the outer and inner soil are simulated by three-dimensional elastodynamic theory and those in the pile are simulated by Rayleigh-Love rod theory. The vertical and radial displacements of the outer and inner soil are obtained by utilizing Laplace transform technique and differentiation on the governing equations of soils. Then, based on the continuous conditions between the pile and soils, the displacements of the pile are derived. The frequency domain velocity admittance and time domain velocity response of the pile top are also presented. The solution is compared to a classical rod model solution to verify the validity. The influences of the radii and Poisson ratio of pile on the transverse inertia effect of pile are analyzed. The parametric study shows that Poisson ratio and outer radius of pile have significant influence on the transverse inertia effect of large diameter pipe piles, while the inner radius has little effect.
Directory of Open Access Journals (Sweden)
Kacprzak Grzegorz
2015-06-01
Full Text Available A common engineering solution for excessive settlement with raft foundation (s is the use of piles in order to reduce the vertical displacements, in this method, the whole structural load is transferred to the piles. This is an overly cautious approach, and there remains a need to find an optimal design method for a building’s foundations. Such a solution may be the piled raft foundation, which allows a reduction of the number of piles due to the integration of the raft in the bearing capacity of the foundation. The aim of the article is to estimate the contribution of foundation elements such as the raft and the piles in the bearing capacity of a residential building located in Warsaw, where the geological conditions are characterized by organic soil layers, principally of gyttja.
Institute of Scientific and Technical Information of China (English)
张艳美; 潘振华; 张鸿儒; 王震; 黄春霞
2015-01-01
To meet the requirements of bearing capacity and anti-liquefaction of liquefiable founda-tions,the reinforcement of liquefiable soil using CFG piles combined with gravel piles is used in engineering.In this study,a composite foundation with multi-type piles composed of gravel piles and CFG piles was analyzed.In composite foundations with multi-type piles,gravel piles are sup-plemented piles that are mainly used to accelerate the foundation drainage consolidation.CFG piles are the main piles that undertake greater seismic load and reduce the dynamic pore pressure and post-earthquake settlement of the foundation.A composite foundation with multi-type piles com-posed of gravel and CFG piles can improve the bearing capacity and liquefaction resistance of a liquefiable foundation.A three dimensional numerical model was established and the dynamic characteristics of a composite foundation with multi-type piles was studied through numerical simulation;the influence of design parameters such as the ratio of pile type,pile diameter,pile length,CFG pile body stiffness,and gravel pile body permeability on dynamic characteristics of a composite foundation with multi-type piles was analyzed.The results show that the dynamic de-formation of a composite foundation,including gravel pile composite foundation,CFG pile com-posite foundation,and composite foundation with multi-type piles is obviously smaller than that of a natural foundation during earthquakes,and the dynamic deformation decreases with increase in the number of CFG piles.When the ratio of gravel piles and CFG piles is 4:5,the dynamic de-formation curve of a composite foundation with multi-type piles is close to that of the CFG pile composite foundation and the influence of the increase in the amount of CFG piles on the reduc-tion in the dynamic deformation of the composite foundation is no longer obvious.When the ratio of gravel piles and CFG piles is 4:5,the dynamic pore water pressure of the composite foundation
30 CFR 77.214 - Refuse piles; general.
2010-07-01
... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Refuse piles; general. 77.214 Section 77.214... Installations § 77.214 Refuse piles; general. (a) Refuse piles constructed on or after July 1, 1971, shall be..., tipples, or other surface installations and such piles shall not be located over abandoned openings...
30 CFR 77.215-4 - Refuse piles; abandonment.
2010-07-01
... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Refuse piles; abandonment. 77.215-4 Section 77... MINES Surface Installations § 77.215-4 Refuse piles; abandonment. When a refuse pile is to be abandoned... refuse pile shall be abandoned in accordance with a plan submitted by the operator and approved by...
Numerical Analysis of Piles in Layered Soils: A Parametric Study
Directory of Open Access Journals (Sweden)
Ravi Kumar Reddy C
2015-04-01
Full Text Available In this paper, numerical analysis of a pile-soil interaction problem is presented considering the parameters influencing the axial load-deformation behavior of the pile embedded in a layered soil medium. The analysis is demonstrated with parametric solutions of a pile with underlain model soil strata under the axial force. An attempt is made to ascertain the extent of influence of elastic properties of the pile, geometry of the pile, end conditions of the pile and the elastic properties of the underlain soil strata on the response of the piles under axial loads lying in a model soil layers in terms of the settlement of the pile and the internal deformation of the pile. The study revealed that the increase in modulus of elasticity of pile improves the settlement resistance of the pile, increase in the ratio of cross sectional dimensions causes decrease in the top deformations of the pile, the settlement of the pile reduced to a great extent when the cross section of the pile adopted is non circular instead of circular and increase in the elastic modulii of top and bottom layers of soil has decreased the settlement of the pile to a great extent, but elastic modulus of soil layers other than top and bottom has got negligible influence on the settlement of the pile.
Energy Technology Data Exchange (ETDEWEB)
Furet, J. [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires
1962-07-01
We have been led to study the problem of safety in atomic pile control as a result of our participation on the one hand in the planning of C.E.A. atomic piles, and on the other hand in the pile safety sub omission considering atomic pile safety of operational or planned C.E.A. piles. We have thus had to consider the wishes occurring in piles during their operation and also their behaviour in the dynamic state The present work deals mainly with the importance of intrinsic safety devices, with the influence of reactivity variations on the power fluctuations during accidental operation, and with the development of robust and reliable safety appliances. The starting p accident has been especially studied both for low-flux piles where a compromise is necessary between the response time of the safety appliances and the statistical fluctuations and for high lux piles where xenon poisoning has an effect on the lower limit of the velocity of reactivity liberation. The desirability has been stressed of automation as a safety factor in atomic pile control. The details required for an understanding of the diagrams of the apparatus are given. (author) [French] Nous avons aborde le probleme de la securite dans le controle des piles atomiques a la suite de notre participation d'une part aux avant rojets de piles atomiques du CE.A. et d'autre part a l'examen au sein de la sous ommission de surete des piles, de la securite des piles du CE.A. en fonctionnement ou en projet. Nous avons ete amenes a nous interesser alors aux risques encourus par les piles pendant leur fonctionnement et par la meme a leur comportement en regime dynamique. Ce travail traite principalement de l'importance des securites intrinseques, de l'influence des variations de reactivite sur les evolutions de puissance en regime d'accident et du developpement d'appareillages de securite robustes et de fonctionnement tres sur. L'accident de demarrage a ete particulierement
Efficient stock piling of 40mm shells
Directory of Open Access Journals (Sweden)
J. N. Nanda
1958-10-01
Full Text Available A problem was posed as to discuss efficient stock-piling of 40mm shells. There is, in fact no data from which emergency requirements can be deduced. A figure has been quoted by Army authorities that E rounds per month are required during an emergency. The size of the emergency stock pile will depend upon the difference of the normal peace time production, and also on the time taken for the crash programme of emergency production to come into fulfillment. In addition the delivery time from factories to the stock piles is also kept in view.
Menke, John R.; Boeker, Gilbert F.
1976-05-11
1. An improved journal bearing comprising in combination a non-rotatable cylindrical bearing member having a first bearing surface, a rotatable cylindrical bearing member having a confronting second bearing surface having a plurality of bearing elements, a source of lubricant adjacent said bearing elements for supplying lubricant thereto, each bearing element consisting of a pair of elongated relatively shallowly depressed surfaces lying in a cylindrical surface co-axial with the non-depressed surface and diverging from one another in the direction of rotation and obliquely arranged with respect to the axis of rotation of said rotatable member to cause a flow of lubricant longitudinally along said depressed surfaces from their distal ends toward their proximal ends as said bearing members are rotated relative to one another, each depressed surface subtending a radial angle of less than 360.degree., and means for rotating said rotatable bearing member to cause the lubricant to flow across and along said depressed surfaces, the flow of lubricant being impeded by the non-depressed portions of said second bearing surface to cause an increase in the lubricant pressure.
Applicability of recycled aggregates in concrete piles for soft soil improvement.
Medeiros-Junior, Ronaldo A; Balestra, Carlos Et; Lima, Maryangela G
2017-01-01
The expressive generation of construction and demolition waste is stimulating several studies for reusing this material. The improvement of soft soils by concrete compaction piles has been widely applied for 40 years in some Brazilian cities. This technique is used to improve the bearing capacity of soft soils, allowing executing shallow foundations instead of deep foundations. The compaction piles use a high volume of material. This article explored the possibility of using recycled aggregates from construction waste to replace the natural aggregates in order to improve the bearing capacity of the soft soil, regarding its compressive strength. Construction wastes from different stages of a construction were used in order to make samples of concrete with recycled aggregates. The strength of concretes with natural aggregates was compared with the strength of concretes with recycled (fine and coarse) aggregates. Results show that all samples met the minimum compressive strength specified for compaction piles used to improve the bearing capacity of soft soils. The concrete with recycled aggregate from the structural stage had even higher resistances than the concrete with natural aggregates. This behaviour was attributed to the large amount of cementitious materials in the composition of this type of concrete. It was also observed that concrete with recycled fine aggregate has a superior resistance to concrete with recycled coarse aggregate.
The Effect of Soil-Pile Interface Behaviour on Laterally Loaded Piles
DEFF Research Database (Denmark)
Zania, Varvara; Hededal, Ole
2011-01-01
In current practice it is either the p – y curve concept, or analytical solutions assuming different formulations for ultimate soil resistance that are being used to evaluate the lateral pile response. The adequacy of the p – y curves or of the assumed pressure distribution and ultimate soil...... resistance have been questioned. In this study the lateral capacity of three-dimensional numerical models of rigid piles embedded in cohesionless soil was estimated. The potential variability of the friction properties along the perimeter of the pile was considered. The interface properties affect...... the ultimate soil resistance and the stiffness of the soil–pile response....
Study on rock-socketed PHC pile foundation by test%嵌岩PHC桩基试验研究
Institute of Scientific and Technical Information of China (English)
吴建; 陈超; 高倚山; 金红星
2012-01-01
工程领域采用的PHC桩基多以粘性土、砂性土层为持力层,文中给出了在复杂中软土地基条件下,以风化岩为持力层,进行PHC桩嵌岩试验的工程实例。通过沉桩试验、高应变动测、静载荷试验等,综合讨论了PHC桩实施嵌岩的可行性,总结分析了岩土工程勘察的侧重点,提出了加强桩身强度、优化桩靴设计和控制沉桩锤击力等措施确保嵌岩桩身质量的一些认识。%Bearing stratum of PHC piles generally adopts clay and sandy soil in construction project.In the condition of complicated soft soil foundation,this paper makes experiments on rock-socketed PHC pile,which adopts weathered bedrock as bearing stratum.By pile driving test,high-strain dynamic test and static loading test,this paper analyzes the feasibility of PHC pile driven into bedrock.And this paper summarizes the key point of geotechnical engineering investigation and suggests some measures in order to ensure the quality of rock-socketed PHC pile,such as strengthening pile body,optimizing pile shoe and controlling hammer energy.
Local Scour Around Piles Under Wave Action
Institute of Scientific and Technical Information of China (English)
陈国平; 左其华; 黄海龙
2004-01-01
The model tests are performed with regular waves, and the effect of wave height, wave period, water depth, scdiment size and pile diameter is evaluated. The shape and size of local scour around piles are studied. There are three typical scour patterns due to wave action. It is found that a relationship exists between the erosion depth and the wave number. An empirical formula of the maximum local scour is thus derived.
Schwartz, C.C.; Miller, S.D.; Haroldson, M.A.; Feldhamer, G.; Thompson, B.; Chapman, J.
2003-01-01
The grizzly bear inspires fear, awe, and respect in humans to a degree unmatched by any other North American wild mammal. Like other bear species, it can inflict serious injury and death on humans and sometimes does. Unlike the polar bear (Ursus maritimus) of the sparsely inhabited northern arctic, however, grizzly bears still live in areas visited by crowds of people, where presence of the grizzly remains physically real and emotionally dominant. A hike in the wilderness that includes grizzly bears is different from a stroll in a forest from which grizzly bears have been purged; nighttime conversations around the campfire and dreams in the tent reflect the presence of the great bear. Contributing to the aura of the grizzly bear is the mixture of myth and reality about its ferocity. unpredictable disposition, large size, strength, huge canines, long claws, keen senses, swiftness, and playfulness. They share characteristics with humans such as generalist life history strategies. extended periods of maternal care, and omnivorous diets. These factors capture the human imagination in ways distinct from other North American mammals. Precontact Native American legends reflected the same fascination with the grizzly bear as modern stories and legends (Rockwell 1991).
Institute of Scientific and Technical Information of China (English)
洪辉煌
2015-01-01
在介绍静载荷试验和高应变法的基础上,结合工程实例对它们的检测结果进行对比,由此检验高应变法检测大直径人工挖孔桩的精度.%Based on the introduction of high strain dynamic testing and static loading test,and combined with the engineering example,the testing results were compared in this paper. Thereout,it could check up the testing precision of high strain dynamic testing on large diameter manual hole digging pile.
Study on pile drivability with one dimensional wave propagation theory
Institute of Scientific and Technical Information of China (English)
陈仁朋; 王仕方; 陈云敏
2003-01-01
Pile drivability is a key problem during the stage of design and construction installation of pile foundations. The solution to the one dimensional wave equation was used to determine the impact force at the top of a concrete pile for a given ram mass, cushion stiffness, and pile impedance. The kinematic equation of pile toe was established and solved based on wave equation theory. The movements of the pile top and pile toe were presented, which clearly showed the dynamic displacement, including rebound and penetration of pile top and toe. A parametric study was made with a full range of practical values of ram weight, cushion stiffness, dropheight, and pile impedance. Suggestions for optimizing the parameters were also presented. Comparisons between the results obtained by the present solution and in-situ measurements indicated the reliability and validity of the method.
The Effect of the Propeller Jet on Pile Groups
Institute of Scientific and Technical Information of China (English)
Kubilay Cihan
2014-01-01
The objective of this study is to determine the effect of jet propeller on the damage of berthing structures combined of armoured slope with pile groups. For this purpose, scour measurements were performed for four types berthing structures, which were armoured slope with tandem arrangements of piles for two and three piles and with side by side arrangements of piles for two and three piles. The effect of gap between piles on damage was investigated. The damage level induced by propeller jet between piles was determined. The gaps were 1, 2, 3, and 4 times the pile diameter. Three different values of Rpm (690, 820, and 950) were chosen for the tests. The diameter of circular piles is 40 mm. The slope ratio was 1/3 and the diameter of propeller was 10 cm.
Directory of Open Access Journals (Sweden)
Jin Yu
2013-01-01
Full Text Available Low-grade concrete-cored sand-gravel (CCSG pile composite foundation is a new kind of composite foundation for thick and soft clay ground treatment. An analytical solution was derived for calculating the consolidation process of this composite foundation by considering coefficients of horizontal permeability in smear zone, the radial flow within the sand-gravel shell, and the impervious property of concrete-cored pile. The results show that Terzaghi’s one-dimensional consolidation solution and the consolidation analytical solution of ordinary composite foundation were special cases of this solution. Curves of the average consolidation degree of the composite foundation under various nondimensional parameters were observed using the program based on the theoretical formula. Meanwhile, a series of in situ measurements including the settlement of pile and soil, the pore water pressure, and the total stress under embankment load were obtained on the CCSG pile composite foundation on a section of Zhenjiang-Liyang highway. The analyzed results show that the new style composite foundation patent technology has many advantages such as small differential postconstruction settlement (differential is not good, small is, reliable quality, high bearing capacity, and stability. And the consolidation of composite foundation is largely affected by the nondimensional parameters. The analytical solution is finally verified with the actual measurement data.
Wavelet analyses for stress wave detection of piles
Institute of Scientific and Technical Information of China (English)
WANG; Jingtao; (王靖涛)
2003-01-01
The theoretical foundation for application of wavelet analysis to pile integrity detection has been presented. The mechanism of spectral variations of reflected pulse from various defects in piles is explained by using the wave scattering theory. The theoretical analyses have been verified through the tests of model piles and a lot of engineering piles. A quantitative evaluation method for estimating damage degree of piles is proposed. The characteristic indexes describing spectrum variations of reflected signals and their critical values are given. They can be used not only to evaluate the damage degree but also to identify the kinds of pile defects.
Test Procedure for Axially Loaded Piles in Sand
DEFF Research Database (Denmark)
Thomassen, Kristina
The test procedure described in the following is used when examining the effects of static or cyclic loading on the skin friction of an axially loaded pile in dense sand. The pile specimen is only loaded in tension to avoid any contribution from the base resistance. The pile dimensions are chosen...... to resemble full scale dimension of piles used in offshore pile foundations today. In this report is given a detailed description of the soil preparation and pile installation procedures as well data acquisition methods....
Institute of Scientific and Technical Information of China (English)
吁燃; 王曙光
2016-01-01
为了充分发挥碎石桩与素混凝土桩的优点，将碎石桩与素混凝土桩组合成多型桩复合地基。通过理论计算，分析碎石桩与素混凝土桩组成的多型桩复合地基受力原理。以某高速公路深层软土路基的处理为例，采用多型桩复合地基对该软土路基进行处理，取得了良好的经济效益。%The multi-type-pile composite foundation of gravel pile and plain concrete pile is composed to exert the advantages of crushed stone pile and concrete pile.The load-bearing principle of multi-type-pile composite foundation composed of gravel pile and plain concrete pile is analyzed.Taking an engineering of deep soft soil treatment in the highway for example,the multi-type-pile composite foundation is used,and it achieves good economic performances.
Institute of Scientific and Technical Information of China (English)
尚正祥; 胡伟; 席娜丽
2012-01-01
结合构建的饱和土结构性动力本构模型以及通用有限元程序,以城市高架桥梁建设中常采用的单柱墩基础为原型,建立了摩擦桩-土-结构体系、端承桩-土-结构体系的有限元-无限元计算模型.分完全粘结、滑移无开裂、开裂无滑移、开裂滑移四种情况考察了桩土界面力学行为对两种系统动力反应特性的影响,得出如下结论:无论是端承桩还是摩擦桩,界面力学行为对桩截面的剪应力和桩身水平位移分布形态影响均不大.四种情况中,完全粘结时,摩擦桩在近地表处桩截面剪应力值最大,开裂滑移时最小,而端承桩则刚好相反.水平位移分布均可分为线性增大和加速非线性增大两个阶段,以近地表处为分界点,且均以开裂滑移时最大,完全粘结时最小.界面力学行为极大地改变了端承桩桩身加速度时程的分布形态,但对摩擦桩则几乎没有改变；对于不同界面力学行为,两种桩型在近地表处均出现加速度峰值,完全粘结时值最大,开裂滑移时最小.相比摩擦桩而言,界面力学行为对端承桩的影响要大的多,研究分析时应引起足够的重视.%Conbining dynamic constitutive model of saturated soil with general finite element program, the finite -infinite element models of end bearing and friction pile foundations were established. Four situations of interface between pile and soil including absolutely jointed, slippage, crack, both slippage and crack were considered to study the interface' s effect on pile foundation's dynamic characteristics. The results are as follows; no matter end bearing pile or friction ones, the interface' s mechanical behavior has a little influence on the distributions of pile section ' s shear stress and pile' s horizontal displacement. In these four situations, frictional pile section' s shear stress arrives at the maximum when interface is absolutely jointed, and arrives at the minimum ones when
素混凝土桩复合地基荷载传递机理的试验研究%STUDY ON LOADS TRANSFERRING MECHANISM OF COMPOSITE GROUNDS WITH CONCRETE PILES
Institute of Scientific and Technical Information of China (English)
池跃君; 宋二祥; 金淮; 高文新
2001-01-01
The distribution and change of axial force of piles and pile friction in composite grounds are very important characters of composite grounds. The axial force of piles was measured by means of in-situ test and on the basis of this the pile friction was worked out. Contrasted with compressible piles and compound piles, the mechanism of concrete piles is different. Contrasted with compressible piles, the loads on concrete piles can be transferred though the whole piles. Contrasted with compound piles, the concrete piles provide negative pile friction around upper piles that leads to the force of piles top is not the maximum. The maximum is at neutrality point. With loads increasing, the negative pile friction decreases and the neutrality point moves upward and part of the negative pile friction transforms into a positive pile friction. It is the pile friction that makes piles bear more loads at the beginning of loading and makes pile friction of lower piles be fully utilized. Thus the interaction between piles and surrounding soil is present in the process of loading. At the same time, the bearing capacity of soil around piles is reinforced.%为研究带有垫层的素混凝土桩复合地基中桩身轴力、桩侧摩阻力的分布及发展过程，设计了一组足比例尺单桩复合地基试验，在桩身内埋设钢弦式应力计测出了桩身轴力，并由此得出桩侧摩阻力。从实测结果与散体桩、无垫层带台单桩的桩身轴力、侧摩阻力分布对比分析可以看出，三者传力机理是不同的。与散体桩相比，素混凝土桩复合地基中荷载沿桩身全长传递。与无垫层带台单桩相比，桩侧摩阻力从加荷开始在桩周上部土层即出现负摩阻，使得桩身轴力最大点不在桩顶而在中性点处。带有垫层的素混凝土桩复合地基中桩侧负摩阻力的大小随荷载加大而变小，同时中性点位置逐渐上移，相当一部分上部土层的摩阻力随着荷载的
Transient response of piles-bridge under horizontal excitation
Institute of Scientific and Technical Information of China (English)
朱斌; 陈仁朋; 陈云敏
2003-01-01
Moving ships and other objects drifting on water often impact a bridge's pile foundations. The mechanical model of the piles-bridge structure under horizontal forcing was established, and a time-domain approach based on Finite-difference Method was developed for analyzing the dynamic response of the piles-bridge structure. For a single pile, good agreement between two computed results validated the present approach. The slenderness ratio of the pile, the pile-soil stiffness ratio and the type of the structure influence the dynamic response of the piles-bridge structure. The computed results showed that the stiffness of the structure determines the dynamic response of the piles-bridge structure under horizontal forcing.
Transient response of piles-bridge under horizontal excitation
Institute of Scientific and Technical Information of China (English)
朱斌; 陈仁朋; 陈云敏
2003-01-01
Moving ships and other objects drifting on water often impact a bridge' s pile foundations. The mechanical model of the piles-bridge structure under horizontal forcing was established, and a time-domain approach based on Finite-difference Method was developed for analyzing the dynamic response of the piles-bridge structure. For a single pile, good agreement between two computed results validated the present approach.The slenderness ratio of the pile, the pile-soil stiffness ratio and the type of the structure influence the dynamic response of the piles-bridge structure. The computed results showed that the stiffness of the structure determines the dynamic response of the piles-bridge structure under horizontal forcing.
Picking up Clues from the Discard Pile
2008-01-01
As NASA's Phoenix Mars Lander excavates trenches, it also builds piles with most of the material scooped from the holes. The piles, like this one called 'Caterpillar,' provide researchers some information about the soil. On Aug. 24, 2008, during the late afternoon of the 88th Martian day after landing, Phoenix's Surface Stereo Imager took separate exposures through red, green and blue filters that have been combined into this approximately true-color image. This conical pile of soil is about 10 centimeters (4 inches) tall. The sources of material that the robotic arm has dropped onto the Caterpillar pile have included the 'Dodo' and ''Upper Cupboard' trenches and, more recently, the deeper 'Stone Soup' trench. Observations of the pile provide information, such as the slope of the cone and the textures of the soil, that helps scientists understand properties of material excavated from the trenches. For the Stone Soup trench in particular, which is about 18 centimeters (7 inches) deep, the bottom of the trench is in shadow and more difficult to observe than other trenches that Phoenix has dug. The Phoenix team obtained spectral clues about the composition of material from the bottom of Stone Soup by photographing Caterpillar through 15 different filters of the Surface Stereo Imager when the pile was covered in freshly excavated material from the trench. The spectral observation did not produce any sign of water-ice, just typical soil for the site. However, the bigger clumps do show a platy texture that could be consistent with elevated concentration of salts in the soil from deep in Stone Soup. The team chose that location as the source for a soil sample to be analyzed in the lander's wet chemistry laboratory, which can identify soluble salts in the soil. The Phoenix Mission is led by the University of Arizona, Tucson, on behalf of NASA. Project management of the mission is by NASA's Jet Propulsion Laboratory, Pasadena, Calif. Spacecraft development is by Lockheed
Elrod, David A.
1993-11-01
The rolling element bearings (REB's) which support many turbomachinery rotors offer high load capacity, low power requirements, and durability. Two disadvantages of REB's are: (1) rolling or sliding contact within the bearing has life-limiting consequences; and (2) REB's provide essentially no damping. The REB's in the Space Shuttle Main Engine (SSME) turbopumps must sustain high static and dynamic loads, at high speeds, with a cryogenic fluid as lubricant and coolant. The pump end ball bearings limit the life of the SSME high pressure oxygen turbopump (HPOTP). Compliant foil bearing (CFB) manufacturers have proposed replacing turbopump REB's with CFB's CFB's work well in aircraft air cycle machines, auxiliary power units, and refrigeration compressors. In a CFB, the rotor only contracts the foil support structure during start up and shut down. CFB damping is higher than REB damping. However, the load capacity of the CFB is low, compared to a REB. Furthermore, little stiffness and damping data exists for the CFB. A rotordynamic analysis for turbomachinery critical speeds and stability requires the input of bearing stiffness and damping coefficients. The two basic types of CFB are the tension-dominated bearing and the bending-dominated bearing. Many investigators have analyzed and measured characteristics of tension-dominated foil bearings, which are applied principally in magnetic tape recording. The bending-dominated CFB is used more in rotating machinery. This report describes the first phase of a structural analysis of a bending-dominated, multileaf CFB. A brief discussion of CFB literature is followed by a description and results of the present analysis.
Elrod, David A.
1993-01-01
The rolling element bearings (REB's) which support many turbomachinery rotors offer high load capacity, low power requirements, and durability. Two disadvantages of REB's are: (1) rolling or sliding contact within the bearing has life-limiting consequences; and (2) REB's provide essentially no damping. The REB's in the Space Shuttle Main Engine (SSME) turbopumps must sustain high static and dynamic loads, at high speeds, with a cryogenic fluid as lubricant and coolant. The pump end ball bearings limit the life of the SSME high pressure oxygen turbopump (HPOTP). Compliant foil bearing (CFB) manufacturers have proposed replacing turbopump REB's with CFB's CFB's work well in aircraft air cycle machines, auxiliary power units, and refrigeration compressors. In a CFB, the rotor only contracts the foil support structure during start up and shut down. CFB damping is higher than REB damping. However, the load capacity of the CFB is low, compared to a REB. Furthermore, little stiffness and damping data exists for the CFB. A rotordynamic analysis for turbomachinery critical speeds and stability requires the input of bearing stiffness and damping coefficients. The two basic types of CFB are the tension-dominated bearing and the bending-dominated bearing. Many investigators have analyzed and measured characteristics of tension-dominated foil bearings, which are applied principally in magnetic tape recording. The bending-dominated CFB is used more in rotating machinery. This report describes the first phase of a structural analysis of a bending-dominated, multileaf CFB. A brief discussion of CFB literature is followed by a description and results of the present analysis.
The Tensile Capacity Of Bored Piles In Frictional Soils
DEFF Research Database (Denmark)
Krabbenhøft, Sven; Andersen, Allan; Damkilde, Lars
2008-01-01
Three series of 10 piles each were installed in two different locations. The length of the piles varied from 2 to 6 m and the diameters were 14 and 25 cm. The piles were constructed above the groundwater table using continuous flight augers and the concrete was placed by gravity free fall....... The piles were tested to failure in axial uplift and the load-displacement relations were recorded....
Application Study of Self-balanced Testing Method on Big Diameter Rock-socketed Piles
Directory of Open Access Journals (Sweden)
Qing-biao WANG
2013-07-01
Full Text Available Through the technological test of self-balanced testing method on big diameter rock-socketed piles of broadcasting centre building of Tai’an, this paper studies and analyzes the links of the balance position selection, the load cell production and installation, displacement sensor selection and installation, loading steps, stability conditions and determination of the bearing capacity in the process of self-balanced testing. And this paper summarizes key technology and engineering experience of self-balanced testing method of big diameter rock-socketed piles and, meanwhile, it also analyzes the difficult technical problems needed to be resolved urgently at present. Conclusion of the study has important significance to the popularization and application of self-balanced testing method and the similar projects.
Institute of Scientific and Technical Information of China (English)
马永峰; 周丁恒; 邴启超; 周训军
2015-01-01
The soft foundation treatment of large-scale refinery is very complex. In view of this condition, a series of in-situ tests of PHC pipe pile, including low/high strain dynamic test, horizontal and compressive static load test of single pile, were carried out. Based on results of low/high strain test, the quality and completeness of the pile was analyzed. The bearing capacity of single pile was verified by re-sults of high strain test and static load test. And some economical comparison was carried out among various piles of different diameter. The results of static load test showed that the bearing capacity of single pile has reached the standards; when the diameter of PHC pipe pile is 400mm, the ultimate bearing capacity of single pile is affected by pile length greatly;however for PHC pipe pile of 500 mm or 600 mm, the influence from pile length is smaller;the ultimate bearing capacity of single piles that have the same length increases with pile diameter, and the increasing forms are different among piles of various length;the horizontal bearing capacity of PHC pipe pile with concrete core is 50%larger than that of pile without concrete core;In economic terms, the best choice for compressive PHC pipe pile is Ø500 type, the bearing strata of PHC pipe piles should be intensively-weathered to medium-weathered mudstone or completely-weathered to medium-weathered sandstone.%针对大型炼厂工程软弱地基处理的复杂性,开展了PHC管桩的现场试验,完成了PHC管桩施工后的低应变、高应变动力测试及单桩水平、抗压静载荷试验。基于低、高应变测试结果分析了桩身质量及完整性；以高应变测试和静载荷试验结果验证了单桩承载能力；对不同桩径的PHC管桩经济性做了比较分析。静载荷试验结果表明,PHC管桩单桩承载力能达到设计要求；PHC管桩桩径为400 mm时,桩长对单桩极限承载力影响较大,桩径为500 mm或600 mm时,桩长影响较小；同一桩长
Design Optimization of Piles for Offshore Wind Turbine Jacket Foundations
DEFF Research Database (Denmark)
Sandal, Kasper; Zania, Varvara
Numerical methods can optimize the pile design. The aim of this study is to automatically design optimal piles for offshore wind turbine jacket foundations (Figure 1). Pile mass is minimized with constraints on axial and lateral capacity. Results indicate that accurate knowledge about soil...
Design Optimization of Piles for Offshore Wind Turbine Jacket Foundations
Sandal, Kasper; Zania, Varvara
2016-01-01
Numerical methods can optimize the pile design. The aim of this study is to automatically design optimal piles for offshore wind turbine jacket foundations (Figure 1). Pile mass is minimized with constraints on axial and lateral capacity. Results indicate that accurate knowledge about soil characteristics can translate into significant cost reductions.
Stress wave propagation in reinforced concrete piles during driving
Zorn, N.F.
1983-01-01
The aim of this report is to give an insight into what happens in a reinforced concrete pile during driving, and to contribute to design requirements for the loading case pile driving. Since the behaviour of stress waves in piles is influenced by a various number of parameters, the fewest of which r
30 CFR 77.215-3 - Refuse piles: certification.
2010-07-01
... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Refuse piles: certification. 77.215-3 Section... COAL MINES Surface Installations § 77.215-3 Refuse piles: certification. (a) Within 180 days following written notification by the District Manager that a refuse pile can present a hazard, the person...
30 CFR 77.215-1 - Refuse piles; identification.
2010-07-01
... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Refuse piles; identification. 77.215-1 Section... COAL MINES Surface Installations § 77.215-1 Refuse piles; identification. A permanent identification marker, at least six feet high and showing the refuse pile identification number as assigned by...
30 CFR 77.215-2 - Refuse piles; reporting requirements.
2010-07-01
... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Refuse piles; reporting requirements. 77.215-2... COAL MINES Surface Installations § 77.215-2 Refuse piles; reporting requirements. (a) The proposed location of a new refuse pile shall be reported to and acknowledged in writing by the District...
30 CFR 77.215 - Refuse piles; construction requirements.
2010-07-01
... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Refuse piles; construction requirements. 77.215... COAL MINES Surface Installations § 77.215 Refuse piles; construction requirements. (a) Refuse deposited on a pile shall be spread in layers and compacted in such a manner so as to minimize the flow of...
29 CFR 1926.603 - Pile driving equipment.
2010-07-01
... 29 Labor 8 2010-07-01 2010-07-01 false Pile driving equipment. 1926.603 Section 1926.603 Labor... Operations § 1926.603 Pile driving equipment. (a) General requirements. (1) Boilers and piping systems which are a part of, or used with, pile driving equipment shall meet the applicable requirements of...
30 CFR 77.209 - Surge and storage piles.
2010-07-01
... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Surge and storage piles. 77.209 Section 77.209... Installations § 77.209 Surge and storage piles. No person shall be permitted to walk or stand immediately above a reclaiming area or in any other area at or near a surge or storage pile where the...
A new method of testing pile using dynamic P-S-curve made by amplitude of wave train
Institute of Scientific and Technical Information of China (English)
胡毅力; 许峻; 段永康; 许昭永; 杨润海; 赵晋明
2004-01-01
A new method of detecting the vertical bearing capacity for single-pile with high strain is discussed in this paper. A heavy hammer or a small type of rocket is used to strike the pile top and the detectors are used to record vibration graphs. An expression of higher degree of strain (deformation force) is introduced. It is testified theoretically that the displacement, velocity and acceleration cannot be obtained by simple integral acceleration and differential velocity when long displacement and high strain exist, namely when the pile phase generates a whole slip relative to the soil body. That is to say that there are non-linear relations between them. It is educed accordingly that the force P and displacement S are calculated from the amplitude of wave train and (dynamic) P-S curve is drew so as to determine the yield points. Further, a method of determining the vertical bearing capacity for single-pile is discussed. A static load test is utilized to check the result of dynamic test and determine the correlative constants of dynamic-static P(Q)-S curve.
A new method of testing pile using dynamic P-S-curve made by amplitude of wave train
Hu, Yi-Li; Xu, Jun; Duan, Yong-Kong; Xu, Zhao-Yong; Yang, Run-Hai; Zhao, Jin-Ming
2004-11-01
A new method of detecting the vertical bearing capacity for single-pile with high strain is discussed in this paper. A heavy hammer or a small type of rocket is used to strike the pile top and the detectors are used to record vibration graphs. An expression of higher degree of strain (deformation force) is introduced. It is testified theoretically that the displacement, velocity and acceleration cannot be obtained by simple integral acceleration and differential velocity when long displacement and high strain exist, namely when the pile phase generates a whole slip relative to the soil body. That is to say that there are non-linear relations between them. It is educed accordingly that the force P and displacement S are calculated from the amplitude of wave train and (dynamic) P-S curve is drew so as to determine the yield points. Further, a method of determining the vertical bearing capacity for single-pile is discussed. A static load test is utilized to check the result of dynamic test and determine the correlative constants of dynamic-static P( Q)- S curve.
Huy, N.Q.
2010-01-01
Pile testing, which plays an importance role in the field of deep foundation design, is performed by static and non-static methods to provide information about the following issues: (Poulos, 1998) - The ultimate capacity of a single pile. - The load-displacement behavior of a pile. - The performance
Displacement pile installation effects in sand
Beijer-Lundberg, A.
2015-01-01
Installation effects govern the post-installation behaviour of displacement piles in sand. These effects are currently not completely understood. Suitable experimental techniques to model these installation effects include field, laboratory and experimental models. In the current thesis a small-scal
On the Modelling of Pile Installation
Dijkstra, J.
2009-01-01
This thesis introduces two different types of physical model tests to investigate the stress and density change in the soil during installation of a jacked pile as well as two numerical modelling approaches to model the same process in a finite element code capable of large deformations.
Full size testing of sheet pile walls
Kuilen, J.W.G. van de; Linden, M.L.R. van der; Katsma, H.; Stolle, P.
1996-01-01
Azobé (Lophira alata) is widely used in timber sheet pile walls in the Netherlands. The boards in these walls are coupled and therefore load-sharing can be expected. A simulation model based on the finite element method DIANA (DIANA, 1992) was developed and load-sharing could be calculated. To check
Underwater noise generated by offshore pile driving
Tsouvalas, A.
2015-01-01
Anthropogenic noise emission in the marine environment has always been an environmental issue of serious concern. In particular, the noise generated during the installation of foundation piles is considered to be one of the most significant sources of underwater noise pollution. This is mainly attri
竖向荷载下群桩-土-承台相互作用数值分析%Numerical analysis of interaction of pile group-soil-raft under vertical load
Institute of Scientific and Technical Information of China (English)
杜家庆; 杜守继; 赵丹蕾; 唐文勇
2013-01-01
Besides the interaction of the multiple stress superposition from piles shaft friction, pile bottom resistance and contact stress between low caps and soil, the clamping action makes the cap-pile-soil interaction more complicated in pile foundation with large pile diameter and small spacing. 3D finite difference program is employed to evaluate the pile-soil-cap interaction with the change of vertical load, while the pile spacing and pile diameter remain constant in the analysis procedure. Analysis is carried out to explain the interaction of cap-pile-soil from the following aspects such as the lateral friction of soil in each layer, load on the top of characteristic piles, load-settlement relationship, vertical displacement of soil between piles, etc. The results show that: the clamping action on the upper soil among piles will decrease, and the pile shaft friction in the upper part will increase when the load exceeds 117.8 MN which is slightly larger than Pu/2 (Pu means ultimate bearing capacity of piles group); the lower part of pile shaft friction shows a trend of decrease due to the influence of the multiple stress superposition, and the decrease trend in characteristic piles has different influence scope; the load, which makes settlement of piles group achieve 5% of pile diameter, can be regarded as the vertical ultimate bearing capacity of piles group, and it is reasonable; when the ratio of piles group’s settlement to pile diameter exceeds 1%, the proportion of the load carried by piles decreases because of the cap contribution.% 在大桩径、小桩距的群桩条件下，不仅有来自桩侧、桩端和承台传递的多重应力叠加，还有群桩对桩间土的夹持作用影响，桩-土-承台之间作用更加复杂。用有限差分软件模拟固定桩距、桩径，变化竖向荷载下桩-土-承台的相互作用。从各层土的侧摩阻力、不同位置桩的桩顶荷载、荷载-沉降关系、桩间土体位移等方面的计算
Seismic Response Analysis of Portal Water Injection Sheet Pile
Institute of Scientific and Technical Information of China (English)
WANG Yuanbin; GUO Haiyan; ZHANG Chunhui
2007-01-01
To further the study on the newly developed portal water injection sheet pile under static loads, in this paper, by adopting the nonlinear calculation module of FEM software ANSYS, a model for the interaction between the soil and the sheet piles is set up,and the seismic response analysis for this type of space-retaining structure is performed. The effects of the embedded depth and the distance between the front pile and the back pile on the dynamic characteristics of the portal water injection sheet pile are studied.
The Settlement Behavior of Piled Raft Interaction in Undrained Soil
DEFF Research Database (Denmark)
Ghalesari, Abbasali Taghavi; Barari, Amin; Amini, Pedram Fardad;
2013-01-01
Offshore piled raft foundations are one of the most commonly used foundations in offshore structures. When a raft foundation alone does not satisfy the design requirements, the addition of piles may improve both the ultimate load capacity and the settlement performance of the raft. In this paper......, the behavior of a piled raft on undrained soil is studied based on a series of parametric studies on the average and differential settlement of piled raft using three-dimensional finite element analysis. The settlement behavior is found to be dependent on the number of piles and raft thickness....
NONLINEAR DYNAMICAL CHARACTERISTICS OF PILES UNDER HORIZONTAL VIBRATION
Institute of Scientific and Technical Information of China (English)
HU Yu-jia; CHENG Chang-jun; YANG Xiao
2005-01-01
The pile-soil system is regarded as a visco-elastic half-space embedded pile. Based on the method of continuum mechanics, a nonlinear mathematical model of pilesoil interaction was established-a coupling nonlinear boundary value problem. Under the case of horizontal vibration, the nonlinearly dynamical characteristics of pile applying the axis force were studied in horizontal direction in frequency domain. The effects of parameters, especially the axis force on the stiffness were studied in detail. The numerical results suggest that it is possible that the pile applying an axis force will lose its stability. So, the effect of the axis force on the pile is considered.
Institute of Scientific and Technical Information of China (English)
张京京; 孙立强; 闫澍旺
2014-01-01
Sixu expressway is located in the Huaibei Plain,which is covered by silt or silty sand. However,because this type of soil is prone to liquefaction under seismic loading,liquefaction re-sistance measures should be considered when engineering projects are planned for this region.The liquefaction resistance of a geotextile discrete material pile and the bearing capacity of a composite foundation are examined in this study.In addition,the reinforcement mechanism of the geotextile discrete material pile with a silt subgrade is determined.The pore water pressure dissipation,bear-ing capacity of the composite foundation,pile-soil stress ratio,and pile body stress were re-searched by using the finite difference method and field testing,which is beneficial for obtaining the reinforcement mechanism of the composite foundation.Moreover,this paper presents design proposals of a geotextile discrete material pile.The results indicate that under seismic loading,a geotextile discrete material pile can effectively drain and successfully achieve anti-liquefaction.The excess pore pressure ratio increases with distance from the pile axis,and the silt becomes more in-clined to liquefaction.An engineering example is used with numerical calculation to determine that effective pile spacing is 2 m,or approximately 3.3 times the pile diameter.Further,in the silt foun-dation,the bearing capacity of the single geotextile discrete material pile is 50% larger than that of gravel pile under the same conditions,and the composite foundation bearing capacity of the geo-textile discrete material pile is 25% more than that of gravel pile.In static load testing of the com-posite foundation,soil pressure boxes are respectively buried at the top of the pile,at the bearing plate,and at the contact surface of the pile and soil to determine the bearing capacity of the pile and soil under the action of static load.In the two types of composite foundations,the pile-soil stress ratio increases with an
Diehl, S.F.; Hageman, Phil L.; Smith, Kathleen S.; Herron, J.T.; Desborough, G.A.
2005-01-01
Two trenches were dug into the south Dinero mine-waste pile near Leadville, Colorado, to study the weathering of rock fragments and the mineralogic sources of metal contaminants in the surrounding wetland and Lake Fork Watershed. Water seeping from the base of the south Dinero waste-rock pile was pH 2.9, whereas leachate from a composite sample of the rock waste was pH 3.3. The waste pile was mostly devoid of vegetation, open to infiltration of precipitation, and saturated at the base because of placement in the wetland. The south mine-waste pile is composed of poorly sorted material, ranging from boulder-size to fine-grained rock fragments. The trenches showed both matrix-supported and clast-supported zones, with faint horizontal color banding, suggesting zonation of Fe oxides. Secondary minerals such as jarosite and gypsum occurred throughout the depth of the trenches. Infiltration of water and transport of dissolved material through the pile is evidenced by optically continuous secondary mineral deposits that fill or line voids. Iron-sulfate material exhibits microlaminations with shrinkage cracking and preferential dissolution of microlayers that evidence drying and wetting events. In addition to fluids, submicron-sized to very fine-grained particles such as jarosite are transported through channel ways in the pile. Rock fragments are coated with a mixture of clay, jarosite, and manganese oxides. Dissolution of minerals is a primary source of metals. Skeletal remnants of grains, outlined by Fe-oxide minerals, are common. Potassium jarosite is the most abundant jarosite phase, but Pb-and Ag-bearing jarosite are common. Grain-sized clusters of jarosite suggest that entire sulfide grains were replaced by very fine-grained jarosite crystals. The waste piles were removed from the wetland and reclaimed upslope in 2003. This was an opportunity to test methods to identify sources of acid and metals and metal transport processes within a waste pile. A series of
Friction effects on lateral loading behavior of rigid piles
DEFF Research Database (Denmark)
Zania, Varvara; Hededal, Ole
2012-01-01
The adequacy of the p -y curves used in the current practice for the design of rigid pile foundations with large diameter, like in the case of monopile foundations of offshore wind turbines, has been widely questioned. The current study aims at analyzing the lateral behavior of rigid piles, while...... taking into account the shear frictional resistance along the pile. For this purpose efficient three dimensional finite element models of different diameter have been developed. The increase of the side friction and of the diameter of the pile is shown to alter the failure pattern and increase...... the lateral capacity of the pile. The obtained p - y curves demonstrate the importance of the aforementioned parameters in the design of rigid piles, as the reduction of friction along the interface reduces not only the ultimate load but also the stiffness of the soil-pile response. Read More: http...
DEFF Research Database (Denmark)
Lada, Aleksandra; Ibsen, Lars Bo; Nicolai, Giulio
In the paper the experimental results of small-scale tests on a stiff monopile are presented to outline the change in stiffness during the cyclic loading and the change in the ultimate pile capacity. The results confirm the increase of stiffness and the increase in bearing capacity resulting from...... cyclic loading. Performed analysis provides a better understanding of the problem and reveals some correlations that can be useful in the future design of stiff monopiles....
Bonneau, Dominique; Souchet, Dominique
2014-01-01
This Series provides the necessary elements to the development and validation of numerical prediction models for hydrodynamic bearings. This book describes the rheological models and the equations of lubrication. It also presents the numerical approaches used to solve the above equations by finite differences, finite volumes and finite elements methods.
Institute of Scientific and Technical Information of China (English)
朱峰; 徐卫亚; 王环玲
2014-01-01
The pile-soil interaction under wave loads is an extremely complex and difficult issue in engineering. In this study, a physical model test is designed based on the principle of the gravity similarity to obtain time histories of wave forces of unsteady regular waves, and to measure the magnitude and the distribution of wave forces acting on the piles. A numerical model and relevant numerical methods for the pile-soil contact surface are adopted based on the principles of elastic dynamics. For a practical project, the time histories of wave forces on the piles are obtained through physical model tests. The deformations of the piles in the pile-soil interactions and the distribution of the bending moment on the piles are studied. It is shown that, with the increase of the period of wave pressures, the absolute value of the horizontal displacement of the piles increases, the embedment depth of the piles increases, and the scope of influence of soils increases. The change of the bending moment on the piles is consistent with that of its theoretical results, and the proposed numerical method can very well simulate the properties of the piles.
Institute of Scientific and Technical Information of China (English)
张永亮; 陈兴冲; 孙建飞
2013-01-01
Horizontal bearing characteristics of bridge pile foundations can be analyzed by using linear elastic subgrade reaction method(m-method) when displacement of pile foundation is generally smaller. However, displacement of pile foundations is often larger under the effect of strong earthquakes. In order to understand the horizontal bearing capacity and deformation characteristics of pile foundations considering nonlinear behaviors of pile shaft and subsoil,a model of pile foundations is constructed. Failure mechanism,bearing capacity, deformation characteristics and hysteresis characteristics of pile foundations are studied by using pseudo-static test. A nonlinear static calculation model of pile group foundations is put forward under horizontal load. The elastoplasticity of pile shafts in variable axial loads is simulated by distributed PMM plastic hinge;and nonlinearity of subsoil is simulated by the curves of p-y,t-z and q-z,respectively,which have been given in the code of American API;where p is horizontal soil resistance at lateral of pile shaft;y is horizontal displacement;t is vertical frictional resistance around piles shaft;q is vertical bearing resistance at pile tip;z is vertical relative displacement of interface between pile and soil. The results show that:(1) The numerical results are in good agreement with those obtained from experiments. (2) Hysteretic characteristics of pile foundations can be simulated using Clough degradation bilinear model. (3) Weak positions of pile shaft are 0-4 times around the radius of pile below pile top. The results can provide references for evaluating seismic performance of bridge pile foundation using capacity spectrum method.%线弹性地基反力法(m 法)仅适用于正常使用时桥梁桩基础变位较小的情况，但在强震作用下基础的变位较大。为了研究桩基础在地基土及桩身进入非线性状态下的水平承载能力及变形特性，通过群桩基础缩尺比例模型，采用拟
FORECASTING PILE SETTLEMENT ON CLAYSTONE USING NUMERICAL AND ANALYTICAL METHODS
Directory of Open Access Journals (Sweden)
Ponomarev Andrey Budimirovich
2016-06-01
Full Text Available In the article the problem of designing pile foundations on claystones is reviewed. The purpose of this paper is comparative analysis of the analytical and numerical methods for forecasting the settlement of piles on claystones. The following tasks were solved during the study: 1 The existing researches of pile settlement are analyzed; 2 The characteristics of experimental studies and the parameters for numerical modeling are presented, methods of field research of single piles’ operation are described; 3 Calculation of single pile settlement is performed using numerical methods in the software package Plaxis 2D and analytical method according to the requirements SP 24.13330.2011; 4 Experimental data is compared with the results of analytical and numerical calculations; 5 Basing on these results recommendations for forecasting pile settlement on claystone are presented. Much attention is paid to the calculation of pile settlement considering the impacted areas in ground space beside pile and the comparison with the results of field experiments. Basing on the obtained results, for the prediction of settlement of single pile on claystone the authors recommend using the analytical method considered in SP 24.13330.2011 with account for the impacted areas in ground space beside driven pile. In the case of forecasting the settlement of single pile on claystone by numerical methods in Plaxis 2D the authors recommend using the Hardening Soil model considering the impacted areas in ground space beside the driven pile. The analyses of the results and calculations are presented for examination and verification; therefore it is necessary to continue the research work of deep foundation at another experimental sites to improve the reliability of the calculation of pile foundation settlement. The work is of great interest for geotechnical engineers engaged in research, design and construction of pile foundations.
Research on loading performance test of super-long PHC pipe pile%超长PHC管桩承压性能试验研究
Institute of Scientific and Technical Information of China (English)
刘运庚
2012-01-01
According to the compressive static loading experiment on six PHC super-long pipe pile,the paper analyzes the compressive static performance of the PHC pipe pile,adopts the high strain dynamic testing method,concludes the side friction resistance and end-bearing friction at different soil layers,proves by the research result that the single-pile compressive loading capacity varies along with the different bearing stratums,the single ultimate loading capacity,the end-bearing friction,and its total friction increase with the addition of the pile length,and concludes the average of the recovery coefficient of the loading capacity(recovering coefficient of friction of soil around piles) is 1.13 according to the comparison between the test result from the pipe pile redriving and the driving tests.%根据6个PHC超长管桩的抗压静载试验,分析了PHC管桩的抗承载性能,采用高应变检测方法,得到了不同土层的侧摩阻力及桩端阻力值,研究结果表明：单桩抗压承载力因持力层的不同而不同;随着桩长的增加,单桩极限承载力、桩端阻力及其所占总阻力的比例相应增加;根据管桩复打和初打检测结果的比较,得到承载力恢复系数（桩周土阻力恢复系数）平均值为1.13。
Are cometary nuclei primordial rubble piles?
Weissman, P. R.
1986-01-01
Whipple's icy conglomerate model for the cometary nucleus has had considerable sucess in explaining a variety of cometary phenomena such as gas production rates and nongravitational forces. However, as discussed here, both observational evidence and theoretical considerations suggest that the cometary nucleus may not be a well-consolidated single body, but may instead be a loosely bound agglomeration of smaller fragments, weakly bonded and subject to occasional or even frequent disruptive events. The proposed model is analogous to the 'rubble pile' model suggested for the larger main-belt asteroids, although the larger cometary fragments are expected to be primordial condensations rather than collisionally derived debris as in the asteroid case. The concept of cometary nuclei as primordial rubble piles is proposed as a modification of the basic Whipple model, not as a replacement for it.
Directory of Open Access Journals (Sweden)
Chichkin A. F. / Чичкин Александр Федорович
2013-11-01
Full Text Available The article is devoted to the analysis of the results of dynamic sounding on construction platforms with various soil conditions in comparison to the tests of piles by static loading. The authors provide the comparison of the results of tests and calculations, on the basis of which the conclusion about competitiveness of dynamic sounding is made, and used in Penza city to set trial pile length with dynamic testing and statistics sounding / Анализируются результаты динамического зондирования на площадках строительства с различными грунтовыми условиями в сопоставлении с испытаниями свай статической нагрузкой. Приводятся сравнительные результаты испытаний и расчетов, на основании чего делается вывод о конкурентоспособности способа динамического зондирования, применяемого в г. Пензе для назначения длины пробных свай, с динамическими испытаниями свай и статическим зондированием
基于荷载传递法的单桩沉降解析解%Calculation of Single Pile Settlement Based on Load Transfer Method
Institute of Scientific and Technical Information of China (English)
刘忠; 唐漾; 杜欢欢; 朱思静; 彭刚
2013-01-01
In accordance with the performance characteristics of single pile under axial load and based on load transfer method,the bilinear load transfer function,which describes the characteristics of pile-soil interaction,is applied to obtain the analytical solution for load-settlement relation of single pile during the whole pile-soil deformation.This analytical solution is adopted in specific calculation and discussion about the value range of model parameters,the result of which agrees well with the experimental curve.It shows that the method described in this paper well describes the load transfer process of single pile.On the basis of specific parameters obtained from static load experiment,the load-settlement relation of single pile under axial load is calculated and the pile bearing capacity is estimated,which can offer references for the design of pile foundation.%针对轴向荷载作用下的单桩工作特性,基于荷载传递法,采用了描述桩-土相互作用特性的双折线荷载传递函数,得到了针对桩-土变形全过程的单桩荷载-沉降关系解析解.利用该解析解,计算了具体案例,讨论了模型参数的取值范围,计算结果与实验曲线吻合较好.结果表明,本文方法能较好地描述单桩荷载传递过程,根据静载实验获得的具体参数,计算轴向荷载作用下单桩荷载-沉降关系,并估算单桩的承载力,为桩基础设计提供参考依据.
Morphological clues to wet granular pile stability
Scheel, M.; Seemann, R.; Brinkmann, M.; di Michiel, M.; Sheppard, A.; Breidenbach, B.; Herminghaus, S.
2008-03-01
When a granular material such as sand is mixed with a certain amount of liquid, the surface tension of the latter bestows considerable stiffness to the material, which enables, for example, sand castles to be sculpted. The geometry of the liquid interface within the granular pile is of extraordinary complexity and strongly varies with the liquid content. Surprisingly, the mechanical properties of the pile are largely independent of the amount of liquid over a wide range. We resolve this puzzle with the help of X-ray microtomography, showing that the remarkable insensitivity of the mechanical properties to the liquid content is due to the particular organization of the liquid in the pile into open structures. For spherical grains, a simple geometric rule is established, which relates the macroscopic properties to the internal liquid morphologies. We present evidence that this concept is also valid for systems with non-spherical grains. Hence, our results provide new insight towards understanding the complex physics of a large variety of wet granular systems including land slides, as well as mixing and agglomeration problems.
Hydrodynamic Behavior of Curtainwall-Pile Breakwaters
Institute of Scientific and Technical Information of China (English)
O.Nejadkazem; A.R.M.Gharabaghi
2012-01-01
A numerical model is developed that can predict the interaction of regular waves normally incident upon a curtainwall-pile breakwater; the upper part of which is a vertical wall and the lower part consists of an array of vertical piles.The numerical model is based on an eigenfunetion expansion method,and utilizes a boundary condition nearby the vertical piles that accounts for wave energy dissipation.Numerical solution comprises a finite number of terms,which is a superposition of propagating waves and a series of evanescent waves.The modeling is validated by comparison with previous experimental studies and overall agreement between measurement and calculation is fairly good.The numerical results are related to reflection,transmission,and dissipation coefficient; wave run-up,wave force,and wave overturning moment are also presented.Effect of porosity,relative draft,and relative water depth are discussed; the choice of suitable range of them is described.The relative draft is more effective for shallow water waves.Model shows decrease in relative draft and leads to reduction of relative wave force,overturning moment,and nunup.It is shown that curtainwallpile breakwaters can operate both effectively and efficiently in the range of relative draft between 0.15 and 0.75.The range 0.5 to 0.2 is also recommended for porosity.
Institute of Scientific and Technical Information of China (English)
LIU Run; YAN Shu-wang; LI Zhi-hua
2009-01-01
Long steel piles with large diameters have been more widely used in the field of ocean engineering.Owing to the pile with a large diameter,soil plug development during pile driving has great influences on pile driveability and beating capacity.The response of soil plug developed inside the open-ended pipe pile during the dynamic condition of pile-driving is different from the response under the static condition of loading during service.This paper addresses the former aspect.A numerical procedure for soil plng effect prediction and pile driveability analysis is proposed and described.By taking into consideration of the pile dimension effect on side and tip resistance,this approach introduces a dimensional coefficient to the conventional static equilibrium equations for the plug differential unit and proposes an improved static equity method for the plug effect prediction.At the same time,this approach introduces a simplified model by use of one-dimensional stress wave equation to simulate the interaction between soft ping and pile inner wall.The proposed approach has been applied in practical engineering analyses.Results show that the calculated plug effect and pile driveability based on the proposed approach agree well with the observed data.
支盘应用于超长桩的有限元分析%Finite Element Analysis of Branch Applied to the Super Long Pile
Institute of Scientific and Technical Information of China (English)
白伟亮; 张立明
2015-01-01
采用有限元软件ABAQUS研究了在均质土的情况下，支盘位置对单桩承载性状的影响，通过研究得出了超长桩最佳的支盘位置。%Studied the influence of the branch location on the behavior of single pile bearing in the case of homogeneous soil With finite element software ABAQUS,obtained the best branch location of super-long pile through the studying.
Settlement calculation for long-short composite piled raft foundation
Institute of Scientific and Technical Information of China (English)
ZHAO Ming-hua; ZHANG Ling; YANG Ming-hui
2006-01-01
The mechanism of long-short composite piled raft foundation was discussed. Assuming the relationship between shear stress and shear strain of the surrounding soil was elasto-plastic, shear displacement method was employed to establish the different explicit relational equations between the load and the displacement at the top of pile in either elastic or elasto-plastic period. Then Mylonakis & Gazetas model was introduced to simulate the interaction between two piles or between piles and soil. Considering the effect of cushion, the flexible coefficients of interaction were provided. With the addition of a relevant program, the settlement calculation for long-short composite piled raft foundation was developed which could be used to account for the interaction of piles,soil and cushion. Finally, the calculation method was used to analyze an engineering example. The calculated value of settlement is 10.2 mm, which is close to the observed value 8.8 mm.
The Effects of Time on Soil Behaviour and Pile Capacity
DEFF Research Database (Denmark)
Augustesen, Anders
this into account. This implies that the design methods used today do not in general make use of the full capacity of piles. This thesis is based on a number of scientific papers and reports that deal with elements of pile design and time effects in soils in general. With regard to pile design, focus is placed...... foundations. Further, design methods that take no account of time will be subject to considerable error unless they consider a tightly specified age range. Time functions (relation between time after installation and capacity), which have been offered for quantifying set-up for piles in clay, are investigated....... Therefore, the design of piles has remained a constant source of attention, especially with regard to the methodology for predicting the capacity. Three very different design methods for piles in both clay and sand are assessed by comparing predicted capacities with measured capacities from established...
SCOUR MITIGATION AT BRIDGE PIERS USING SACRIFICIAL PILES
Institute of Scientific and Technical Information of China (English)
M. Anisul HAQUE; Md. Munsur RAHMAN; G.M. Tarekul ISLAM; M. Asad HUSSAIN
2007-01-01
To mitigate scour around bridge piers, sacrificial piles are economic method where natural processes are involved. The arrangement should be such that scoured materials from the sacrificial piles should have enough volume to fill the scour hole created upstream of the pier in such a way that sediments are trapped inside the scour hole. This concept differs from earlier study made with sacrificial piles that mainly deals to reduce the strength of horseshoe vortex. To determine the effect of sacrificial piles for scour mitigation, alternative arrangements of piles were tested in front of a rectangular pier under clear-water condition and found that when the group of piles is placed at a distance of twice the projected width of the pier, for which percentage of blockage of the pier width is 60%, the scour volume can be reduced upto 61% while the maximum scour depth can be reduced upto 50%.
Institute of Scientific and Technical Information of China (English)
李艳艳; 李泽高; 李和庆; 赵雄
2015-01-01
对5个预制桩身与承台组合体试件进行低周反复试验,分析构件的破坏形态、承载力及延性、锚固钢筋的受力,研究预制桩身与承台锚固钢筋的不同锚固形式对试件受力性能的影响.结果表明:通过连接板焊接锚固钢筋的试件,倾角锚固钢筋能延缓试件裂缝的发展,提高试件的承载能力;在桩身内安放钢筋笼并深入承台的锚固钢筋可明显改善管桩-承台组合体试件的整体性,提高组合体试件的承载能力、延性,改善组合体试件的变形能力,且斜角锚固钢筋试件的承载能力优于直角试件.%5 specimens of prefabricated pile combined with pile caps are tested under low cycle reciprocating loading.The failure patterns,the bearing capacity and the ductility,the forces in anchoring reinforcing bars,as well as the influence of different forms of the precast pile and pile cap anchoring reinforcing bars on the mechanical properties of the specimen are studied.It is shown that by anchoring reinforced connecting plate welded specimens,the inclined anchoring reinforcing bars can play a role in delaying the growth of cracks,increasing the beating capacity of the specimen.The specimens with the pile body and the anchoring reinforcing bars can significantly improve the integrity of the pile cap assembly of the specimen and increase the bearing capacity,the ductility,and the deformation ability,and the bearing capacity of the anchoring reinforcing bars of oblique angle is better than that of the rectangular specimens.
Analysis of Anti-Pulling Behaviors of Pile with Branch Plates%支盘桩抗拔承载特性分析
Institute of Scientific and Technical Information of China (English)
柯江
2013-01-01
支盘桩是一种新桩型,近年来在工程中得到比较广泛的应用,但对于支盘桩的研究多集中在受压承载特性,其抗拔承载特性的研究成果较少,在理论研究上还不够成熟,因此采用Abaqus软件,考虑了初始应力场,桩土之间的非线性接触以及土体材料的非线性,研究了支盘桩在上拔荷载作用下的承载特性,分析表明:在天然状态下土体对桩体的压力在支盘处最大,支盘桩达到抗拔极限承载力时,桩身轴力在支盘的上下出现突变,支盘下斜面以及桩底与土体产生了分离,塑性应变主要发生在支盘上的土体中；研究成果可为支盘桩的设计提供一定的理论依据.%The pile with branch plate is a new type of pile, widely used in engineering practice recently, but the study on the pile with branch plate focuses only on its compressive behaviors, there have been fewer studies on its an-ti-pulling behaviors, and the theory about this type of piles has not fully developed. Using software ABAQUS, the paper has studied the anti-pulling behaviors of pile with branch plates by considering the nonlinear contact between pile and soil, the initial stress field and the nonlinearity of soil material. The analysis shows that the soil pressure imposed on the pile was the largest at the branch plate under the natural condition, when the bearing capacity of pile with branch plates reached to the limit, the axial force of pile had mutations at the upper and lower of the branch plate, the lower slope of branch plate and soil produced a separation also between pile bottom and soil, the plastic strain occurred mainly in the upside of branch plate. The research results can provide some theoretical basis for the design of the pile with branch plate.
The reactor Cabri; La pile cabri
Energy Technology Data Exchange (ETDEWEB)
Ailloud, J.; Millot, J.P. [Commissariat a l' Energie Atomique, Cadarache (France). Centre d' Etudes Nucleaires
1964-07-01
exceptional circumstances... - experimental investigations on power excursions linked with precise initial conditions: the aim of this work is to define the basis for theoretical research, and the limits beyond which the risks of explosion cease to be negligible. The research work will be done so as to enable checking with outside reactor experiments and to continue them in the explosion field. - studies of the behaviour of the reactor control-instrumentation. - experimental investigations related with transient operation with initial short life (study of boiling, temperature measurements, vacuum pressure and fraction...) with the aim of defining the hypotheses of a theory on swimming-pool reactor kinetics related to heat transfer phenomena, - investigations of the behaviour of fuels in reactors (these experiments are planned to be carried out in loops) Preliminary experimental results. CABRI went critical on the 21 December 1963. The first transient experiments are expected for March 1964. (authors) [French] II devenait necessaire de construire en France une pile qui permette d'etudier les conditions de fonctionnement des installations futures, de choisir, tester et mettre au point les dispositifs de securite a adopter. On a choisi une pile a eau, type de pile qui correspond aux constructions les plus nouvelles du CEA en matiere de piles laboratoire ou d'universite; il importe en effet de pouvoir evaluer les risques presentes et d'etudier les possibilites d'augmentation de puissance constamment demandees par les utilisateurs: il est particulierement interessant d'eclaircir les phenomenes d'oscillation de puissance et les risques de calefaction (burn out). Les programmes de travaux sur CABRI seront harmonises avec les travaux effectues sur les Spert americains de meme type; lors de sa construction des contacts fructueux ont ete etablis avec les specialistes americains qui ont defini les premiers de ces reacteurs. La communication donne une
Sadeghi, H.
2015-12-01
Bridges are major elements of infrastructure in all societies. Their safety and continued serviceability guaranties the transportation and emergency access in urban and rural areas. However, these important structures are subject to earthquake induced damages in structure and foundations. The basic approach to the proper support of foundations are a) distribution of imposed loads to foundation in a way they can resist those loads without excessive settlement and failure; b) modification of foundation ground with various available methods; and c) combination of "a" and "b". The engineers has to face the task of designing the foundations meeting all safely and serviceability criteria but sometimes when there are numerous environmental and financial constrains, the use of some traditional methods become inevitable. This paper explains the application of timber piles to improve ground resistance to liquefaction and to secure the abutments of short to medium length bridges in an earthquake/liquefaction prone area in Bohol Island, Philippines. The limitations of using the common ground improvement methods (i.e., injection, dynamic compaction) because of either environmental or financial concerns along with the abundance of timber in the area made the engineers to use a network of timber piles behind the backwalls of the bridge abutments. The suggested timber pile network is simulated by numerical methods and its safety is examined. The results show that the compaction caused by driving of the piles and bearing capacity provided by timbers reduce the settlement and lateral movements due to service and earthquake induced loads.
Vertical Dynamic Impedance of Tapered Pile considering Compacting Effect
Directory of Open Access Journals (Sweden)
Wenbing Wu
2013-01-01
Full Text Available Based on complex stiffness transfer model, the vertical vibration of tapered pile embedded in layered soil is theoretically investigated by considering the compacting effect of the soil layer surrounding the tapered pile in the piling process. Allowing for the stratification of the surrounding soil and variable crosssection of the tapered pile, the pile-soil system is discretized into finite segments. By virtue of the complex stiffness transfer model to simulate the compacting effect, the complex stiffness of different soil segments surrounding the tapered pile is obtained. Then, substituting the complex stiffness into the vertical dynamic governing equation of tapered pile, the analytical solution of vertical dynamic impedance of tapered pile under vertical exciting force is derived by means of the Laplace technique and impedance function transfer method. Based on the presented solutions, the influence of compacting effect of surrounding soil on vertical dynamic impedance at the pile head is investigated within the low frequency range concerned in the design of dynamic foundation.
Institute of Scientific and Technical Information of China (English)
吴明; 彭建兵; 王淑贤; 孟舒然; 臧明东
2014-01-01
通过低应变动测、钻探取芯、静载试验等检测手段分析了某高层建筑钻孔灌注桩存在的问题及桩基事故产生的原因。在对桩基事故详细分析的基础上，给出了桩基承载力不足和沉降过大桩基事故处理的补打钻孔灌注桩加基础厚底板方案。实践表明，该加固方案是可行的，不仅可满足桩基承载力的要求，且可减小群桩基础的差异沉降。%This paper analyzes an accident of bored piles instrumented in a tall building and proposes the cause of the accident using low strain dynamic testing, drilling core and static load test. Based on the detailed analysis of the accident of bored piles, reinforcement scheme composed of bored pile and thick beam-slab raft foundation can be used to treat the accident of large settlement and shortage of bearing capacity of bored piles. Engineering practice indicates that this reinforcement scheme is feasible, and can meet the requirement of pile bearing capacity, as well as decrease the differential settlement of pile groups.
Institute of Scientific and Technical Information of China (English)
Lü Shu-hui; WANG Kui-hua; WU Wen-bing; C. J. LEO
2015-01-01
The dynamic response of pile in layered soil is theoretically investigated when considering the transverse inertia effect. Firstly, the fictitious soil-pile model is employed to simulate the dynamic interaction between the pile and the soil layers beneath pile toe. The dynamic interactions of adjacent soil layers along the vertical direction are simplified as distributed Voigt models. Meanwhile, the pile and fictitious soil-pile are assumed to be viscoelastic Rayleigh-Love rods, and both the radial and vertical displacement continuity conditions at the soil-pile interface are taken into consideration. On this basis, the analytical solution for dynamic response at the pile head is derived in the frequency domain and the corresponding quasi-analytical solution in the time domain is then obtained by means of the convolution theorem. Following this, the accuracy and parameter value of the hypothetical boundaries for soil-layer interfaces are discussed. Comparisons with published solution and measured data are carried out to verify the rationality of the present solution. Parametric analyses are further conducted by using the present solution to investigate the relationships between the transverse inertia effects and soil-pile parameters.
Institute of Scientific and Technical Information of China (English)
丰土根; 宋海洋; 王路博; 陈阳; 胡松
2015-01-01
Using Abaqus numerical analysis method,double equal piles,one equal pile and one squeezed branch pile,double squeezed branch piles models were built. Through lots of numerical simulation,analysis of the pile interaction coefficient under different situations,including pile load,pile spacing,soil Poisson's ratio and analysis of the influence to different double piles in surrounding load were carried out. Result shows that the pile-pile influence coefficient is approximately constant value in liner elastic deformation of loading piles ,and irrelevant to the load level and piles characters,but it decreased gradually until close to 0 in plase state,with the Poisson's ratio becomes large. The interaction coefficient gradually decreases,under the same conditions,the surrounding load have a greater impact on double equal piles than double squeezed branch piles and gradually decreases with the increase of poisson's ratio. The study provides a reference in practical engineering between different piles.%采用Abaqus数值分析方法,建立双等径桩、一等径桩一支盘桩、双挤扩支盘桩模型,通过大量的数值模拟计算,分析在不同桩顶荷载、不同桩间距、不同土体泊松比条件下桩的相互影响系数以及在桩周荷载条件下对不同双桩的影响,分析表明,在线弹性变形阶段,桩与桩的影响系数近似为恒定值,与荷载水平及桩的性状无关,进入塑性阶段后,则逐渐减小最后趋于0,随着泊松比的变大,桩之间的相互作用系数逐渐减小,在相同条件下,桩周荷载对双支盘桩的影响大于双等径桩且随泊松比的增大而减小. 研究结果为实际工程中桩之间的影响情况提供参考.
Institute of Scientific and Technical Information of China (English)
赵惠华; 李建军
2011-01-01
According to the design for the rock-socketed part＇s bearing piles with manual digging hole reinforced concrete in the comprehensive treatment of the residential buildings in some mining subsidence areas,the paper adopts the rock foundation loading experiment to identify the standard value of the saturated single pile strength in bearing course at pile ends and uses the dynamic detection method to test the quality of the engineering piles,and proves the effect of using rock-socketed part＇s bearing piles with manual digging hole reinforced concrete in treating the mining subsidence areas is better.%通过某采煤沉陷区综合治理工程住宅楼人工挖孔钢筋混凝土嵌岩端承桩设计,采用岩基载荷试验方法确定了桩端持力层岩石饱和单桩抗压强度标准值和采用动力检测法检测了工程桩的桩身质量,结果表明人工挖孔钢筋混凝土嵌岩端承桩在处理某采煤沉陷区效果较好。
载体桩在宁夏地区工程中的应用%Carrier pile in Ningxia area application in engineering
Institute of Scientific and Technical Information of China (English)
杨绍端; 王波; 刘晓涛; 杜方江
2011-01-01
The carrier pile has been used in Yinchuan technology professional college 21 #-23# students apartment building application as an example, using the carrier pile in vertical static load test and low strain of pile body completeness inspection method, the bearing capacity of pile body completeness is tested. By the test results and economic and technological comparison, we analyze the carrier in the application of engineering piles of the actual effect. The test results show that the carrier pile can bear capacity higher, lower cost, shorter construction period, which can use a lot of construction waste with economic and environmental protection, and a remarkable economic and social benefits, It will be a very broad application prospect in Ningxia.%以载体桩在银川科技职业学院21#～23#学生公寓楼的应用为实例，采用载体桩竖向静载荷试验及低应变桩身完整性检测的方法，对其承载力和桩身完整性进行了检测．通过检测结果及经济技术对比，分析了载体桩在本工程中应用的实际效果．试验结果表明，载体桩承载力高、造价低、工期短，可消耗大量建筑垃圾，既经济、环保，又有显著的经济效益和社会效益，在宁夏地区有着十分广泛应用的前景．
Analysis on pile-soil interaction of pile-supported composite foundation%桩承式加网复合地基桩土共同作用分析
Institute of Scientific and Technical Information of China (English)
王瑞芳; 王克宇
2015-01-01
By the method of shearing displacement analysis, the interactions between single pile with cap and soil are ana-lyzed, the formula of displacement and axial force for pile with cap under uniform loading are obtained. The finite element soft-ware, ABAQUS, is used to analyze the bearing performance of single pile in three dimensions, and the results are compared with those of the analytical calculation method. The comparison shows that the settlements of roadbed surface and pile top as well as the pile axial forces calculated by the above two methods are similar. The analytical calculation result is in consonance with the measured data, which verifies the accuracy of analytical calculation method.%采用剪切位移法分析了桩承式带桩帽单桩与桩间土的相互作用,得出均布荷载下带桩帽单桩的桩身位移、轴力公式. 用ABAQUS有限元软件对带帽单桩进行三维数值分析,将数值计算结果与解析公式结果进行比较,计算表明解析公式计算出的桩身轴力、桩顶沉降、路基表面沉降和有限元计算值接近. 将现场实测数据与解析计算结果进行比较,解析计算的沉降结果和实测沉降数据较吻合,说明所提出的解析法计算公式准确性较好,对工程应用有一定的参考价值.
Visualization of soil arching in flexible piled embankments
Indian Academy of Sciences (India)
Tuğba Eskışar
2015-10-01
Piled embankments rely on soil arching, but, when geogrid reinforcements are used, membrane action within the reinforcement contributes to load distribution. The arching of soil in unreinforced and reinforced piled embankments is evaluated in this study. A small-scale test apparatus is used to model the settlement up to 5 mm in an embankment with four pile elements. Visual inspection of the soil settlement and soil-reinforcement interaction is important to explain the mechanism of arching. In this study, X-ray Computed Tomography (CT) method was used as a non-destructive technique. The arching of soil between the piles was observed in the case of rigid piles and in the case of flexible piles with grid type of reinforcement. The load carrying capacity increased up to 33% in the case of geogrid reinforcement, and the differential settlement decreased around 35%, proving the efficiency of piled embankments with geogrid reinforcements. It is also shown that, using X-ray CT method and visualization techniques provides a better understanding of soil behavior in a reinforced embankment with the flexible pile foundation system.
Perturbation analysis on post-buckling behavior of pile
Institute of Scientific and Technical Information of China (English)
无
2007-01-01
The nonlinear large deflection differential equation, based on the assumption that the subsoil coefficient is the 2nd root of the depth, was established by energy method. The perturbation parameter was introduced to transform the equation to a series of linear differential equations to be solved, and the deflection function according with the boundary condition was considered. Then,the nonlinear higher-order asymptotic solution of post-buckling behavior of a pile was obtained by parameter-substituting. The influencing factors such as bury-depth ratio and stiffness ratio of soil to pile, slenderness ratio on the post-buckling behavior of a pile were analyzed. The results show that the pile is more unstable when the bury-depth ratio and stiffness ratio of soil to pile increase,and although the buckling load increases with the stiffness of soil, the pile may ruin for its brittleness. Thus, in the region where buckling behavior of pile must be taken into account, the high grade concrete is supposed to be applied, and the dynamic buckling behavior of pile needs to be further studied.
Optimization of pile design for offshore wind turbine jacket foundations
DEFF Research Database (Denmark)
Sandal, Kasper; Zania, Varvara
The aim of this study is to use numerical methods of structural design optimization to design piles for offshore wind turbine jacket foundations. Pile mass is minimized with constraints on axial and lateral capacity. Results indicate that accurate knowledge about soil characteristics can translate...
Optimization of pile design for offshore wind turbine jacket foundations
Sandal, Kasper; Zania, Varvara
2016-01-01
The aim of this study is to use numerical methods of structural design optimization to design piles for offshore wind turbine jacket foundations. Pile mass is minimized with constraints on axial and lateral capacity. Results indicate that accurate knowledge about soil characteristics can translate into significant cost reductions.
Assessment of timber piles in Clallam County, Washington
Pandey, Arun K.; Tyler, Ross; Arnette, Clyde G.; Anthony, Ronald W.
1998-03-01
Timber bridges are very common in state and rural highway systems. According to the National Bridge Inventory (NBI), there are 41,743 timber bridges in the United States and another 42,102 bridges with timber decks as a part of the superstructure. As these bridges age, there is a critical need for reliable inspection and assessment methods for evaluating timber members. Under an FHWA mandate, these bridges also need to be evaluated for scour susceptibility. Knowledge of the length of timber piles supporting the bridge is a vital component in calculating scour resistance of a bridge. However, records of timber pile lengths are often nonexistent or incomplete due to the construction practices for timber piles. This paper presents nondestructive evaluation (NDE) techniques used for assessing timber piles on 10 bridges in Clallam County, Washington. Stress wave velocity and resistance drilling techniques were used to determine the presence of and quantify the extent of decay in the piles. A longitudinal stress wave technique was used for determining the length of timber piles. Determination of piles with decay aided in establishing maintenance and repair needs on the bridge substructures. Pile length estimates enabled Clallam County Road Department to determine the scour-susceptibility of these bridges.
Physical Modelling of Cyclic Laterally Loaded Pile in Cohesionless Soil
DEFF Research Database (Denmark)
Hansen, Mette; Wolf, Torben K.; Rasmussen, Kristian L.
Offshore wind turbines are normally founded with large diameter monopiles and placed in rough environments subjected to variable lateral loads from wind and waves. A long-term lateral loading may create rotation (tilt) of the pile by change in the pile-soil system which is critical in the service...
The homogenisation of bulk material in blending piles.
Gerstel, A.W.
1979-01-01
In this thesis the homogenisation of bulk material in three types of piles is dealt with. The homogenisation implies that the fluctuations of a material proprety in the input flow of the pile are transformed into output fluctuations, whereby the latter ones are evened out. Analyses are presented con
Effect of piles on the seismic response of mosques minarets
Directory of Open Access Journals (Sweden)
Mohamed Ahmed Abdel-Motaal
2014-03-01
Minaret (60.0-m height was studied to investigate the effects of soil stiffness, pile length, diameter, and arrangement, on the minaret and pile dynamic behavior. Comparison between study results and conventional analysis method is illustrated. Study results, discussion, and conclusion are given.
Cause Analysis of Wuhan Tianheng Building Pile Accident
Institute of Scientific and Technical Information of China (English)
无
2001-01-01
The geological condition and the original structure feature and foundation design of Wuhan Tianheng building are described. The accident appearance of pile foundation in the construction execution of work is illustrated. The generating source of this pile foundation accident is analyzed in great details.``
Energy Technology Data Exchange (ETDEWEB)
Kapp, C. [NEK Umwelttechnik AG, Zuerich (Switzerland); Hude, N. von der [Bilfinger und Berger Bauaktiengesellschaft, Mannheim (Germany). Service Center Technik
1997-12-01
In the inner-city banking quarter of Frankfurt on the Main, one of the highest and most modern office buildings of Europe has been being erected since the summer of 1996. The intersecting rows of drill-foundation piles required to secure the deep excavation and the load-bearing piles were designed as heat piles. Thereby the harnessing of shallow geothermal energy was integrated into the overall HVAC concept, realizing a highly innovative project. Although the erection of heat piles had only been decided on when planning for a conventional energy system was completed, the decision permitted to dispense with some of the usual components in the control station. As executed simulations show, integration of the piles into the overall concept of the building is not easy because the piles are exclusively used to provide cooling energy. But the project demonstrates that heat piles can nowadays be used also on a large scale. (orig.) [Deutsch] Im Bankenviertel in der Innenstadt von Frankfurt am Main entsteht seit dem Sommer 1996 eines der hoechsten und modernsten Buerogebaeude Europas. Die zur Sicherung der tiefen Baugrube erforderlichen Pfaehle der ueberschnittenen Bohrpfahlwand sowie diejenigen zum Lastabtrag wurden als Energiepfaehle ausgebildet. Damit wurde die Nutzung der untiefen Geothermie in das Gesamtkonzept der Haustechnik integriert und so ein innovatives Energiekonzept umgesetzt. Obwohl der Einsatz der Energiepfaehle erst dann beschlossen worden ist, als bereits eine konventionelle Energieversorgung vorgesehen und planerisch umgesetzt worden war, konnte dank der Energiepfaehle auf einige herkoemmliche Komponenten in der Energiezentrale verzichtet werden. Aufgrund der durchgefuehrten Simulationsberechnungen gestaltet sich die Einbindung ins Gesamtgebaeudekonzept nicht einfach, da die Energiepfaehle lediglich zu Kuehlzwecken verwendet werden. Trotzdem zeigt dieses Beispiel, dass heute Energiepfahlsysteme auch in grossem Massstab eingesetzt werden koennen. (orig.)
H型长钢桩尖在密实土层中的应用%Application of long H?type steel pile tip in compact soil layer
Institute of Scientific and Technical Information of China (English)
孟晓宁; 于云山
2016-01-01
在钢筋混凝土桩基施工时,如果遇到工程区域地质持力层较密实且埋藏较浅或者持力层上面有较密实的覆盖层的情况,往往会造成沉桩困难、桩的入土深度不能满足使用要求等问题.结合具体工程的实践经验对此类工程问题进行分析,提出钢筋混凝土桩组合H型长钢桩尖的解决方案,并与普通钢筋混凝土桩基方案进行对比、通过计算及试桩试验对方案进行验证、对方案优点及适用性进行总结.%During the reinforced concrete pile foundation construction process, when the bearing stratum of engineering region is more compact and shallow buried or be covered by dense layer, the problems are tend to hap?pen, such as pile?sinking difficultly or embedded depth of pile cannot meet operating requirement. Combined with specific engineering practice experience and the analysis of such problems, the solution of reinforced concrete pile with long H?type steel pile tip was mentioned in this paper. The advantage and applicability of this solution was summarized by contrast with common reinforced concrete pile foundation, and it was verified by calculation and test piles.
Application of CFG Pile in Foundation Treatment%CFG桩在地基处理中的应用
Institute of Scientific and Technical Information of China (English)
高小强
2014-01-01
CFG (Cement Fly-ash Gravel) is composed of gr-avel, stone dust, sand, fly ash mixing cement with water. The application of CFG pile can effectively increase foundation bearing capacity and reduce the set lement, so as to ensure the economic construction. This article carried on the analysis to the application of CFG pile in foundation treatment.%CFG（Cement Fly-ash Gravel）由碎石、石屑、砂、粉煤灰掺水泥加水拌和而成。采用CFG桩能够有效地增加地基的承载力、降低沉降量，从而保证施工的经济性。文章对CFG桩在地基处理中的应用进行了分析。
Pre-Stressed Rope Reinforced Anti-Sliding Pile
Institute of Scientific and Technical Information of China (English)
XU Jun; WANG Chenghua
2006-01-01
Pre-stressed rope reinforced anti-sliding pile is a composite anti-sliding structure. It is made up of pre-stressed rope and general anti-sliding pile. It can bring traditional anti-sliding pile's retaining performance into full play, and to treat with landslide fast and economically. The difference between them is that the pre-stressed rope will transfix the whole anti-sliding pile through a prearranged pipe in this structure. The working mechanics, the design method and economic benefit are studied. The results show that the pre-stressed rope reinforced anti-sliding pile can treat with the small and middle landslides or high slopes well and possess the notable advantage of technology and economic.
Centrifuge modelling of drained lateral pile - soil response
DEFF Research Database (Denmark)
Klinkvort, Rasmus Tofte
of rigid piles. The tests have been performed in homogeneously dense dry or saturated Fontainebleau sand in order to mimic simplified drained offshore soil conditions. Approximately half of the tests have been carried out to investigate the centrifuge procedure in order to create a methodology of testing...... for monopiles today. Therefore it appears that the methodology for monopiles lacks scientific justification and a better understanding of rigid piles is needed. More than 70 centrifuge tests on laterally loaded rigid model piles have been carried out in connection with this thesis to get a better understanding...... that enables the transformation of result from tests in model scale to prototype scale. The grain size to pile diameter ratio, the non-linear stress distribution and the pile installation was identified from this investigation as important parameters in reliable scaling of centrifuge results. The remaining...
Optimum design methodologies for pile foundations in London
Directory of Open Access Journals (Sweden)
Christos Letsios
2014-12-01
Full Text Available Given the importance of pile foundations in geotechnical engineering for supporting high-significance structures such as bridges, high-rise buildings, power plant stations, offshore platforms and museums, it becomes a necessity to find the best pile foundation design in terms of performance and economy. The number of piles required might exceed several hundreds or even thousands while the pile foundation cost might exceed 20% of the construction cost of the superstructure. In this work the problem of finding optimized designs of pile foundations is examined and is performed in accordance to two design code recommendations, namely Eurocode 7 and DIN 4014. The proposed structural optimization procedure is implemented in two real-world cases both located in London, UK in order to assess the efficiency of the proposed design formulation.
The Analysis of Soil Resistance During Screw Displacement Pile Installation
Directory of Open Access Journals (Sweden)
Krasinski Adam
2015-02-01
Full Text Available The application of screw displacement piles (SDP is still increasing due to their high efficiency and many advantages. However, one technological problem is a serious disadvantage of those piles. It relates to the generation of very high soil resistance during screw auger penetration, especially when piles are installed in non-cohesive soils. In many situations this problem causes difficulties in creating piles of designed length and diameter. It is necessary to find a proper method for prediction of soil resistance during screw pile installation. The analysis of screw resistances based on model and field tests is presented in the paper. The investigations were carried out as part of research project, financed by the Polish Ministry of Science and Higher Education. As a result of tests and analyses the empirical method for prediction of rotation resistance (torque during screw auger penetration in non-cohesive subsoil based on CPT is proposed.
The Analysis of Soil Resistance During Screw Displacement Pile Installation
Krasinski, Adam
2015-02-01
The application of screw displacement piles (SDP) is still increasing due to their high efficiency and many advantages. However, one technological problem is a serious disadvantage of those piles. It relates to the generation of very high soil resistance during screw auger penetration, especially when piles are installed in non-cohesive soils. In many situations this problem causes difficulties in creating piles of designed length and diameter. It is necessary to find a proper method for prediction of soil resistance during screw pile installation. The analysis of screw resistances based on model and field tests is presented in the paper. The investigations were carried out as part of research project, financed by the Polish Ministry of Science and Higher Education. As a result of tests and analyses the empirical method for prediction of rotation resistance (torque) during screw auger penetration in non-cohesive subsoil based on CPT is proposed.
Centrifuge Modeling of Piles Subjected to Lateral Loads
Brant, Logan; Ling, Hoe I.
There are many applications where piles are employed to absorb and deflect lateral impact loads. Structural elements of this type are used to protect infrastructure and are commonly found at marine sites. A series of model tests have been conducted using Columbia University's centrifuge facility to better understand the performance of piles subjected to these loading conditions. A device was designed to install and laterally load single model piles during centrifuge flight. This device uniquely contains two lateral loading systems, one which allows static testing and another appropriate for dynamic tests. This research examines the behavior of tubular steel piles embedded within dry or saturated soil and subjected to varied rates of lateral loading. This investigation provides insight on the contribution of lateral loading rates to the behavior of piles.
Method of extracting coal from a coal refuse pile
Yavorsky, Paul M.
1991-01-01
A method of extracting coal from a coal refuse pile comprises soaking the coal refuse pile with an aqueous alkali solution and distributing an oxygen-containing gas throughout the coal refuse pile for a time period sufficient to effect oxidation of coal contained in the coal refuse pile. The method further comprises leaching the coal refuse pile with an aqueous alkali solution to solubilize and extract the oxidized coal as alkali salts of humic acids and collecting the resulting solution containing the alkali salts of humic acids. Calcium hydroxide may be added to the solution of alkali salts of humic acid to form precipitated humates useable as a low-ash, low-sulfur solid fuel.
Distributed fibre optic strain measurements on a driven pile
Woschitz, Helmut; Monsberger, Christoph; Hayden, Martin
2016-05-01
In civil engineering pile systems are used in unstable areas as a foundation of buildings or other structures. Among other parameters, the load capacity of the piles depends on their length. A better understanding of the mechanism of load-transfer to the soil would allow selective optimisation of the system. Thereby, the strain variations along the loaded pile are of major interest. In this paper, we report about a field trial using an optical backscatter reflectometer for distributed fibre-optic strain measurements along a driven pile. The most significant results gathered in a field trial with artificial pile loadings are presented. Calibration results show the performance of the fibre-optic system with variations in the strain-optic coefficient.
Influence of space of double row piles on soil arching effect
Directory of Open Access Journals (Sweden)
Zhao bo
2015-02-01
Full Text Available FLAC3d software, based on continuous theory, is used to analysis influence of space of double row piles on soil arching effect. The result shows that different from single row pile, double row piles will produce soil arching effect at front pile and rear pile severally, this phenomenon is called multiple soil arching effect; the residual load of front of front row pile will increase,the soil arch zone and the soil arching effect will decrease with the continuous increase of double row pile spacing.At the same time the soil arching effect of rear pile decreases, while the soil arching effect of front pile increases and finally the soil arching effect between front pile and rear pile will be equal.
Analysis of Wave Fields induced by Offshore Pile Driving
Ruhnau, M.; Heitmann, K.; Lippert, T.; Lippert, S.; von Estorff, O.
2015-12-01
Impact pile driving is the common technique to install foundations for offshore wind turbines. With each hammer strike the steel pile - often exceeding 6 m in diameter and 80 m in length - radiates energy into the surrounding water and soil, until reaching its targeted penetration depth. Several European authorities introduced limitations regarding hydroacoustic emissions during the construction process to protect marine wildlife. Satisfying these regulations made the development and application of sound mitigation systems (e.g. bubble curtains or insulation screens) inevitable, which are commonly installed within the water column surrounding the pile or even the complete construction site. Last years' advances have led to a point, where the seismic energy tunneling the sound mitigation systems through the soil and radiating back towards the water column gains importance, as it confines the maximum achievable sound mitigation. From an engineering point of view, the challenge of deciding on an effective noise mitigation layout arises, which especially requires a good understanding of the soil-dependent wave field. From a geophysical point of view, the pile acts like a very unique line source, generating a characteristic wave field dominated by inclined wave fronts, diving as well as head waves. Monitoring the seismic arrivals while the pile penetration steadily increases enables to perform quasi-vertical seismic profiling. This work is based on datasets that have been collected within the frame of three comprehensive offshore measurement campaigns during pile driving and demonstrates the potential of seismic arrivals induced by pile driving for further soil characterization.
Three-dimensional analysis of slopes reinforced with piles
Institute of Scientific and Technical Information of China (English)
高玉峰; 叶茂; 张飞
2015-01-01
Based on the upper bound of limit analysis, the plane-strain analysis of the slopes reinforced with a row of piles to the 3D case was extended. A 3D rotational failure mechanism was adopted to yield the upper bound of the factor of safety. Parametric studies were carried out to explore the end effects of the slope failures and the effects of the pile location and diameter on the safety of the reinforced slopes. The results demonstrate that the end effects nearly have no effects on the most suitable location of the installed piles but have significant influence on the safety of the slopes. For a slope constrained to a narrow width, the slope becomes more stable owing to the contribution of the end effects. When the slope is reinforced with a row of piles in small space between piles, the effects of group piles are significant for evaluating the safety of slopes. The presented method is more appropriate for assessing the stability of slopes reinforced with piles and can be also utilized in the design of plies stabilizing the unstable slopes.
Directory of Open Access Journals (Sweden)
Nauroy J. F.
2006-11-01
Full Text Available Les formations carbonatées rencontrées en de nombreuses zones d'activités pétrolières en mer posent de difficiles problèmes de dimensionnement et de mise en place des pieux. Sur plusieurs sites de sable carbonaté, la capacité portante des pieux battus se révèle beaucoup plus faible que prévu et des techniques de réparation doivent être étudiées. Dans ce contexte, l'ARGEMA (Association de Recherche en Géotechnique Marine, groupement français d'organismes de recherche, de compagnies pétrolières et de contracteurs offshore, a expérimenté une réparation d'un pieu expérimental de 30 cm de diamètre et 23 m de long battu dans un sable carbonaté. Le frottement latéral de ce pieu mobilisé juste après battage était très faible. La réparation a consisté à injecter du coulis de ciment à partir d'un forage situé à 40 cm du pieu. Cet article décrit les procédures et les caractéristiques des injections réalisées et leurs conséquences sur la capacité portante du pieu. Le frottement entre le pieu et le terrain s'accroît avec le volume de ciment injecté; les valeurs maximales obtenues sont du même ordre de grandeur que celles observées avec un pieu foré-cimenté. The calcareous formations encountered in many zones of offshore petroleum activity raise difficult problems for designing and installing foundation piles. On several sites with calcareous sands, the bearing capacity of driven piles proves to be much less than had been planned, and repair techniques have to be examined. Within this context, ARGEMA (Association de Recherche en Géotechnique Marine, a french group of research organizations, oil companies and offshore contractors, has tested a repair of an experimental pile 30 cm in diameter and 23 m long driven into a calcareous sand. The skin friction of this pile, mobilized just after driving, was found to be very low. The repair-job consisted in injecting grout from a drilled borehole located at some tens
Analysis of static and dynamic pile-soil-jacket behaviour
Energy Technology Data Exchange (ETDEWEB)
Azadi, Mohammad Reza Emami
1998-12-31
In the offshore industry, recent extreme storms, severe earthquakes and subsidence of the foundation of jacket platforms have shown that new models and methods must take into account the jacket- pile-soil foundation interaction as well as the non-linear dynamic performance/loading effects. This thesis begins with a review of the state of art pile-soil interaction model, recognizing that most existing pile-soil models have been established based on large diameter pile tests on specific sites. The need for site independent and mechanistic pile-soil interaction models led to the development of new (t-z) and (p-y) disk models. These are validated using the available database from recent large diameter pile tests in the North Sea and Gulf of Mexico. The established static disk models are applied for non-linear static analysis of the jacket-pile-soil system under extreme wave loading. Dynamic pile-soil interaction is studied and a new disk-cone model is developed for the non-linear and non-homogeneous soils. This model is applied to both surface and embedded disks in a soil layer with non-linear properties. Simplified non-linear as well as more complex analysis methods are used to study the dynamic response of the jacket platform under extreme sea and seismic loading. Ductility spectra analysis is introduced and used to study the dynamic performance of the jacket systems near collapse. Case studies are used to illustrate the effects of structural, foundation failure characteristics as well as dynamic loading effects on the overall performance of the jacket-pile-soil systems near ultimate collapse. 175 refs., 429 figs., 70 tabs.
Pile mixing increases greenhouse gas emissions during composting of dairy manure
The effect of pile mixing on greenhouse gas (GHG) emissions from stored dairy manure was determined using large flux chambers designed to completely cover pilot-scale manure piles. GHG emissions from piles that were mixed four times during the 80 day trial were about 20% higher than unmixed piles. ...
40 CFR 761.347 - First level sampling-waste from existing piles.
2010-07-01
... existing piles. 761.347 Section 761.347 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... from existing piles. (a) General. Sample piles that are either specifically configured for sampling... alternate sampling plan in accordance with § 761.62(c). (b) Specifically configured piles. A...
Laboratory Testing of Cyclic Laterally Loaded Pile in Cohesionless Soil
DEFF Research Database (Denmark)
Roesen, Hanne Ravn; Ibsen, Lars Bo; Hansen, Mette;
2013-01-01
Offshore wind turbines are normally founded with large diameter monopiles and placed in rough environments subjected to variable lateral loads from wind and waves. A long-term lateral loading may create rotation (tilt) of the pile by change in the pile-soil system which is critical...... in the serviceability limit state. In this paper small-scale testing of a pile subjected to cyclic, lateral loading is treated in order to investigate the effect of cyclic loading. The test setup, which is an improvement of a previous setup, is described and the first results of testing are compared with previous...
Numerical Simulation for the Soil-Pile-Structure Interaction under Seismic Loading
Directory of Open Access Journals (Sweden)
Lifeng Luan
2015-01-01
Full Text Available Piles are widely used as reinforcement structures in geotechnical engineering designs. If the settlement of the soil is greater than the pile, the pile is pulled down by the soil, and negative friction force is produced. Previous studies have mainly focused on the interaction of pile-soil under static condition. However, many pile projects are located in earthquake-prone areas, which indicate the importance of determining the response of the pile-soil structure under seismic load. In this paper, the nonlinear, explicit, and finite difference program FLAC3D, which considers the mechanical behavior of soil-pile interaction, is used to establish an underconsolidated soil-pile mode. The response processes of the pile side friction force, the pile axial force, and the soil response under seismic load are also analyzed.
Institute of Scientific and Technical Information of China (English)
吕亚茹; 丁选明; 刘汉龙; 崔允亮
2012-01-01
As one of the most important factors, pile-soil stress ratio can reflect the load transfer and deformation mechanism of composite foundation. Up to now, as a new pile, no uniform method has been found to calculate the pile-soil stress ratio for X-section pile. Sedimentation basin and filter chamber are typical buildings with concrete floor plate that is considered to be a rigid base. The bearing capacity of pile composite foundation under the rigid base is different from which under the soft base. The in-situ static load tests are carried out based on the foundation treatment project in Qiaobei sewage treatment plant. Besides, a finite element model is built to simulate the cast-in-place X-section concrete pile composite foundation under the rigid base by software ABAQUS. The pile-soil stress ratios are discussed considering some factors including elastic modulus of pile, compression modulus of surrounding soil, pile lengths, cushion thicknesses and compression modulus. The results reveal that the pile-soil stress ratio increases with the increasing of pile modulus, cushion modulus and pile length, while reduces with the increasing of modulus of surrounding soil and cushion thickness. The reasonable pile-soil stress ratio of X-section pile ranges from 20 to 25, corresponding to the pile modulus from 10 to 20 GPa, the cushion thickness from 20 to 40 cm, and the cushion modulus from 30 to 45 MPa.%桩土应力比是反映复合地基承载特性的重要参数之一,可反映复合地基的荷载传递和变形机制.做为一种新型桩,目前尚未得出统一的计算X形桩复合地基桩土应力比的公式.沉淀池、滤池等构筑物是典型的具有混凝土底板(刚性基础)的结构,刚性基础下桩复合地基的承载性能有别于柔性基础.故结合南京桥北污水处理厂地基处理工程做现场静载荷试验,应用有限元软件ABAQUS建立刚性荷载板下现浇X形混凝土桩复合地基的模型,模拟不同桩身弹性模量
As Traffic Piles Up, So Does Air Pollution
... 160914.html As Traffic Piles Up, So Does Air Pollution To minimize exposure, researchers recommend shutting windows and ... Doing so can reduce your exposure to toxic air pollution from a traffic jam by up to 76 ...
Improved Design Basis for Laterally Loaded Large Diameter Pile
DEFF Research Database (Denmark)
Leth, Caspar Thrane
in dry sand by use of centrifuge modelling and to compare the findings with the standard p-y curves. It has been chosen to apply piles with an embedment length of 6 to 10 times the diameter of the applied piles. The general static behaviour of monopiles in dry sand has based on centrifuge tests been...... in sand by use of physical modelling and comparison of the findings with standard p-y curves. The present research is based on use of the centrifuge facilities at Danish Technical University (DTU), the sole geotechnical centrifuge in Scandinavia. It became evident in the initial phase of the research...... that the available centrifuge facilities at DTU was outdated and the focus was changed to establish up-to-date centrifuge facilities for medium to large diameter piles, and to initiate the research on the behaviour of large diameter piles in sand under static and cyclic loading. Key elements in the establishment...
Lateral response of pile foundations in liquefiable soils
Directory of Open Access Journals (Sweden)
Asskar Janalizadeh
2015-10-01
Full Text Available Liquefaction has been a main cause of damage to civil engineering structures in seismically active areas. The effects of damage of liquefaction on deep foundations are very destructive. Seismic behavior of pile foundations is widely discussed by many researchers for safer and more economic design purposes. This paper presents a pseudo-static method for analysis of piles in liquefiable soil under seismic loads. A free-field site response analysis using three-dimensional (3D numerical modeling was performed to determine kinematic loads from lateral ground displacements and inertial loads from vibration of the superstructure. The effects of various parameters, such as soil layering, kinematic and inertial forces, boundary condition of pile head and ground slope, on pile response were studied. By comparing the numerical results with the centrifuge test results, it can be concluded that the use of the p-y curves with various degradation factors in liquefiable sand gives reasonable results.
Computerised analysis of sulphate action on model concrete piles
Digital Repository Service at National Institute of Oceanography (India)
Deshmukh, A.M.; Balasubramanian, S.; Venugopal, C.
Sulphate action severely affects the durability of marine structures. It is imperative to study precisely the effects of magnesium sulphate on pile foundations in the marine environment. In the present paper an attempt is made to assess and analyse...
Airborne thermography of temperature patterns in sugar beet piles
Moore, D. G.; Bichsel, S.
1975-01-01
An investigation was conducted to evaluate the use of thermography for locating spoilage areas (chimneys) within storage piles and to subsequently use the information for the scheduling of their processing. Thermal-infrared quantitative scanner data were acquired initially on January 16, 1975, over the storage piles at Moorhead, Minnesota, both during the day and predawn. Photographic data were acquired during the day mission to evaluate the effect of uneven snow cover on the thermal emittance, and the predawn thermography was used to locate potential chimneys. The piles were examined the day prior for indications of spoilage areas, and the ground crew indicated that no spoilage areas were located using their existing methods. Nine spoilage areas were interpreted from the thermography. The piles were rechecked by ground methods three days following the flights. Six of the nine areas delineated by thermography were actual spoilage areas.
Residual settlement calculation of geocell cushion over gravel piles
Institute of Scientific and Technical Information of China (English)
陈昌富; 杨宇; 肖淑君; 周志军
2008-01-01
The calculation of residual settlement of bidirectional reinforced composite foundation, which is composed of geocell cushion over gravel piles, was studied. The geocell cushion was modeled as a thin flexible plate with large deflection. Based on the Kirchhoff hypothesis, the governing differential equations and boundary conditions of the deformation of geocell cushion under working load were founded using von Karman method and solved by Galerkin method. On theses bases, the gravel piles and inter-pile soils were assumed as Winkler ground with variable spring stiffness so as to execute the approximate calculation of the residual settlement of the bidirectional reinforced composite foundation. The calculation method was verified by two laboratory experiments concerning settlement of embankments. One experiment was with just geocell cushion installed to treat the soft clay under embankments; another one was with both geocell cushion and gravel piles installed. The results show that the calculated settlement curve and the maximum settlement are closed to the observed ones.
Processing Satellite Imagery To Detect Waste Tire Piles
Skiles, Joseph; Schmidt, Cynthia; Wuinlan, Becky; Huybrechts, Catherine
2007-01-01
A methodology for processing commercially available satellite spectral imagery has been developed to enable identification and mapping of waste tire piles in California. The California Integrated Waste Management Board initiated the project and provided funding for the method s development. The methodology includes the use of a combination of previously commercially available image-processing and georeferencing software used to develop a model that specifically distinguishes between tire piles and other objects. The methodology reduces the time that must be spent to initially survey a region for tire sites, thereby increasing inspectors and managers time available for remediation of the sites. Remediation is needed because millions of used tires are discarded every year, waste tire piles pose fire hazards, and mosquitoes often breed in water trapped in tires. It should be possible to adapt the methodology to regions outside California by modifying some of the algorithms implemented in the software to account for geographic differences in spectral characteristics associated with terrain and climate. The task of identifying tire piles in satellite imagery is uniquely challenging because of their low reflectance levels: Tires tend to be spectrally confused with shadows and deep water, both of which reflect little light to satellite-borne imaging systems. In this methodology, the challenge is met, in part, by use of software that implements the Tire Identification from Reflectance (TIRe) model. The development of the TIRe model included incorporation of lessons learned in previous research on the detection and mapping of tire piles by use of manual/ visual and/or computational analysis of aerial and satellite imagery. The TIRe model is a computational model for identifying tire piles and discriminating between tire piles and other objects. The input to the TIRe model is the georeferenced but otherwise raw satellite spectral images of a geographic region to be surveyed
Review of the literature on leachates from coal storage piles
Energy Technology Data Exchange (ETDEWEB)
Davis, E.C.; Boegly, W.J. Jr.
1978-01-01
Runoff from coal storage piles associated with coal conversion or combustion facilities may represent a potential source of environmental pollution. This report is an assessment of existing information on coal pile leachate. The assessment indicates that few detailed studies have been conducted to date, and these are limited and the results are highly variable. More detailed long-range studies using various types of coal are recommended. These studies should be carried out both in the laboratory and in field-scale experiments.
Comparing dynamic and static test results of bored piles
Long, Michael
2007-01-01
Due to increasing time, cost and transportation difficulties, Irish contractors are seeking an alternative to conventional static pile load tests. As a result several firms have adopted dynamic testing techniques to supplement and in some cases to replace conventional static tests. In order to assess the reliability of the systems and to address the concerns of owners and consulting engineers, a database comprising 43 pairs of static and dynamic tests on piles from 24 sites aro...
Pile Structure Program, Projected Start Date : January 1, 2010 (Implementation).
Energy Technology Data Exchange (ETDEWEB)
Collins, Chris; Corbett, Catherine [Lower Columbia River Estuary Partnership; Ebberts, Blaine [U.S. Army Corps of Engineers
2009-07-27
The 2008 Federal Columbia River Power System Biological Opinion includes Reasonable and Prudent Alternative 38-Piling and Piling Dike Removal Program. This RPA directs the Action Agencies to work with the Estuary Partnership to develop and implement a piling and pile dike removal program. The program has since evolved to include modifying pile structures to enhance their habitat value and complexity by adding large woody debris. The geographic extent of the Pile Structure Program (PSP) includes all tidally-influenced portions of the lower Columbia River below Bonneville Dam; however, it will focus on the mainstem. The overarching goal of the PSP is to enhance and restore ecosystem structure and function for the recovery of federally listed salmonids through the active management of pile structures. To attain this goal, the program team developed the following objectives: (1) Develop a plan to remove or modify pile structures that have lower value to navigation channel maintenance, and in which removal or modification will present low-risk to adjacent land use, is cost-effective, and would result in increased ecosystem function. (2) Determine program benefits for juvenile salmonids and the ecosystem through a series of intensively monitored pilot projects. (3) Incorporate best available science and pilot project results into an adaptive management framework that will guide future management by prioritizing projects with the highest benefits. The PSP's hypotheses, which form the basis of the pilot project experiments, are organized into five categories: Sediment and Habitat-forming Processes, Habitat Conditions and Food Web, Piscivorous Fish, Piscivorous Birds, and Toxic Contaminant Reduction. These hypotheses are based on the effects listed in the Estuary Module (NOAA Fisheries in press) and others that emerged during literature reviews, discussions with scientists, and field visits. Using pilot project findings, future implementation will be adaptively managed
20051655 - Petronas, Capacity of Driven Piles Offshore Malaysia
DEFF Research Database (Denmark)
Augustesen, Anders
This document is the second of four notes concerning the effects of time (in this case ageing) on the vertical capacity of piles. It includes a critical review of the relevant publications described in note a.......This document is the second of four notes concerning the effects of time (in this case ageing) on the vertical capacity of piles. It includes a critical review of the relevant publications described in note a....
20051655 - Petronas, Capacity of Driven Piles Offshore Malaysia
DEFF Research Database (Denmark)
Augustesen, Anders; Andersen, Lars
This document is the third of four notes concerning the vertical capacity of piles. It includes an assessment of the effect of previous static load testing upon the measured capacity, i.e. preshearing effects.......This document is the third of four notes concerning the vertical capacity of piles. It includes an assessment of the effect of previous static load testing upon the measured capacity, i.e. preshearing effects....
Axial Non-linear Dynamic Soil-Pile Interaction - Keynote
Directory of Open Access Journals (Sweden)
Holeyman A.
2014-01-01
Full Text Available This keynote lecture describes recent analytical and numerical advances in the modeling of the axial nonlinear dynamic interaction between a single pile and its embedding soil. On one hand, analytical solutions are developed for assessing the nonlinear axial dynamic response of the shaft of a pile subjected to dynamic loads, and in particular to vibratory loads. Radial inhomogeneity arising from shear modulus degradation is evaluated over a range of parameters and compared with those obtained by other authors and by a numerical radial discrete model simulating the pile and soil movements from integration of the laws of motion. New approximate non linear solutions for axial pile shaft behaviour developed from general elastodynamic equations are presented and compared to existing linear solutions. The soil non linear behaviour and its ability to dissipate mechanical energy upon cyclic loading are shown to have a significant influence on the mechanical impedance provided by the surrounding soil against pile shaft movement. The limitations of over-simplified modelling of pile response are highlighted.
Emissions from prescribed burning of timber slash piles in Oregon
Aurell, Johanna; Gullett, Brian K.; Tabor, Dennis; Yonker, Nick
2017-02-01
Emissions from burning piles of post-harvest timber slash (Douglas-fir) in Grande Ronde, Oregon were sampled using an instrument platform lofted into the plume using a tether-controlled aerostat or balloon. Emissions of carbon monoxide, carbon dioxide, methane, particulate matter (PM2.5), black carbon, ultraviolet absorbing PM, elemental/organic carbon, filter-based metals, polycyclic aromatic hydrocarbons (PAHs), polychlorinated dibenzodioxins/dibenzofurans (PCDD/PCDF), and volatile organic compounds (VOCs) were sampled to determine emission factors, the amount of pollutant formed per amount of biomass burned. The effect on emissions from covering the piles with polyethylene (PE) sheets to prevent fuel wetting versus uncovered piles was also determined. Results showed that the uncovered ("wet") piles burned with lower combustion efficiency and higher emission factors for VOCs, PM2.5, PCDD/PCDF, and PAHs. Removal of the PE prior to ignition, variation of PE size, and changing PE thickness resulted in no statistical distinction between emissions. Results suggest that dry piles, whether covered with PE or not, exhibited statistically significant lower emissions than wet piles due to better combustion efficiency.
Numerical modeling of centrifuge cyclic lateral pile load experiments
Institute of Scientific and Technical Information of China (English)
Nikos Gerolymos; Sandra Escoffer; George Gazetas; Jacques Gamier
2009-01-01
To gain insight into the inelastic behavior of piles, the response of a vertical pile embedded in dry sand and subjected to cyclic lateral loading was studied experimentally in centrifuge tests conducted in Laboratoire Central des Ponts et Chaussees. Three types of cyclic loading were applied, two asymmetric and one symmetric with respect to the unloaded pile. An approximately square-root variation of soil stiffness with depth was obtained from indirect in-flight density measurements, laboratory tests on reconstituted samples, and well-established empirical correlations. The tests were simulated using a cyclic nonlinear Winkler spring model, which describes the full range of inelastic phenomena, including separation and re-attachment of the pile from and to the soil. The model consists of three mathematical expressions capable of reproducing a wide variety of monotonic and cyclic experimental p-y curves. The physical meaning of key model parameters is graphically explained and related to soil behavior. Comparisons with the centrifuge test results demonstrate the general validity of the model and its ability to capture several features of pile-soil interaction, including: soil plastification at an early stage of loading, "pinching" behavior due to the formation of a relaxation zone around the upper part of the pile, and stiffness and strength changes due to cyclic loading. A comparison of the p-y curves derived from the test results and the proposed model, as well as those from the classical curves of Reese et al. (1974) for sand, is also presented.
Institute of Scientific and Technical Information of China (English)
刘军; 洪峰
2011-01-01
Combined with the actual construction the principle and application of post-pressure grouting technology in pile tip and pile lateral of reinforced concrete bored cast-in pilate piles are introduced.There are many factors affecting pile foundation selection for construction works.Through the cost analysis and evaluation on the pile foundation of the construction works, some economic indicators for the selection of pile foundation under the present productive force and price level are gained.Which will be beneficial to improve the cost effectiveness and rationality of selection of it.The base-grouting treatment technique of bored concrete pile can improve the bearing capacity, so the application of this kind of pile become broad useage day by day.%结合工程实例，介绍了钢筋混凝土钻孔灌注桩桩端桩侧后压浆技术的原理及应用。影响建筑工程桩基选型的因素很多，通过典型工程桩基的造价分析与评价，得出当前生产力和物价水平条件下桩基选型的若干经济指标．有助于提高建筑工程桩基选型的经济性及合理性水平。由于灌注桩后注浆处理技术可使承载力显著提高．因而这种桩基日益得到广泛应用。
Institute of Scientific and Technical Information of China (English)
朱良虎; 刘先鹏; 居炎飞; 易振友
2012-01-01
According to site high-strain dynamic detection test and vertical compression static test for the steel pipe piles supporting some port bridge, CAPWAPC method is applied and relevant geologic data are analyzed in order to draw load-settlement curve diagram of steel pipe pile axial compression test, determine ultimate vertical bearing capacity of steel pipe pile, draw the distribution curves diagram of pile axial force and pile side frictional resistance, analyze the clogging effect of steel pipe pile end, suggest clogging effect coefficient, and make a comprehensive evaluation on the integrity of the steel pipe pile by comparing and analyzing dynamic and static test results of foundation pile.%根据某港区大桥基础钢管桩的现场高应变动力检测试验和垂直抗压静载荷试验,在详细分析工程地质资料和采用CAPWAPC法试验结果的基础上,绘制钢管桩轴向抗压试验的荷载-沉降关系曲线,判定钢管桩基础的垂直极限承载力;绘制桩身轴力和桩侧摩阻力的分布曲线,分析钢管桩桩底的闭塞效应,给出闭塞效应系数的推荐值;通过桩基动态和静态试验结果的对比分析,综合评估钢管桩的完整性.
Institute of Scientific and Technical Information of China (English)
李强; 郑辉; 王奎华
2011-01-01
采用与频率相关的桩土接触面模型建立了三维轴对称条件下摩擦桩在饱和土中的竖向耦合振动模型,通过势函数分解法和分离变量法求解了饱和土动力固结方程,利用桩土耦合条件得到摩擦桩竖向振动解,对桩周剪应力分布、桩顶的频率和时域响应进行了参数研究.结果表明,桩底支承系数和桩土接触面动刚度对桩土荷载传递有明显影响,频率相关的阻尼系数可以有效地抑制桩顶速度幅频的高频发散现象.最后通过与基桩实测结果对比,表明该模型可以较好地与基桩完整性测试结果吻合.%A dynamic model of a friction pile embedded in saturated soil is established on the basis of interface model with a frequent-dependent damping between the pile and the soil. With the use of potential functions and a variable separation method, the pile dynamic response to an arbitrary vertical load is analytically derived in a closed form under the assumption of the imperfect contact between the pile and soil and an elastic bearing at the pile toe. Furthermore, a parametric study is conducted to find out the main features of the soil-pile interaction, as aresult, the bearing stiffness at pile toe and soil stiffness of the pile shaft have major effects on dynamic load transfer at the contact surface of the pile and soil. And frequent dependent damping of the contact surface can restrain high frequency divergence effectively. Finally, it is shown that the theoretical curves of the present solution are in good agreement with those obtained from pile integrity test.
PHC管桩接桩问题的检测%Detection of the PHC pipe pile joint of pile problems
Institute of Scientific and Technical Information of China (English)
陈军
2009-01-01
概括了低应变动测、高应变动测、静载荷试验及孔内摄像等方法检测PHC管桩时的优缺点,分析了管桩接桩问题产生的原因,进而提出了针对此问题的检测方案,从而避免因桩的接头问题引起的建筑物不均匀沉降.%The merits and drawbacks of low strain dynamic testing, dynamic high strain testing, dead load testing and down hole imaging todetect PHC pipe pile were generalized. The pipe pile joint of pile problems occurring reasons were analyzed, then the detected plan against to the problem was proposed, therefore avoided buildings uneven settlement provoked by pile joints problems.
Directory of Open Access Journals (Sweden)
Ning Zhuang
2017-01-01
Full Text Available We report test results from an experimental study to investigate the effectiveness of carbon fiber-reinforced polymer (CFRP against reinforcing steel bar corrosion. Twelve reinforced-concrete pile specimens of 180 mm square by 1,600 mm long were cast. Three pile specimens were corroded to 5% steel mass loss and then strengthened with CFRP sheets; four specimens were strengthened by using CFRP sheets, whereas the remaining five specimens were not strengthened. The specimens were placed in a simulated marine environment, and corrosion was induced by an impressed current technique. At different theoretical corrosion degrees, nondestructive tests were performed to investigate the corrosion activity of the pile specimens, and destructive tests were performed to determine reinforcing steel bar mass loss. Based on the findings, the effectiveness of the CFRP-strengthened RC piles under aggressive marine environmental conditions was established.
Energy Technology Data Exchange (ETDEWEB)
Palmer, E. [Westinghouse Savannah River Company, AIKEN, SC (United States)
1997-04-28
Coal storage piles, their associated coal pile runoff basins and ash basins could potentially have adverse environmental impacts, especially on groundwater. This report presents and summarizes SRS groundwater and soil data that have been compiled. Also, a result of research conducted on the subject topics, discussions from noted experts in the field are cited. Recommendations are made for additional monitor wells to be installed and site assessments to be conducted.
Institute of Scientific and Technical Information of China (English)
薛江炜; 葛忻声; 杨勇; 蔡景珞
2013-01-01
Reference on lateral load test and numerical simulation of large diameter pipe pile by using cast-in-place concrete(PCC),finite element model of a single pile with or without pile partner under lateral load is established. Comparison calculations show that pile partner can ensure lateral loads delivering from pile cap to foundation soil, and double reduce stress and displacement of pile. Pile partner can also make some improvement on lateral bearing characters for the pile foundation with low cap even though the modulus of foundation soil is small. When pile partner is equipped,and the connection mode between pile cap and pile changing from rigid connection to hinge joint,pile body internal force can also be drastically reduced;and pile and pile caps by distance can only be considered to meet the requirement of vertical bearing capacity or optimization design of pile foundation stiffness to reduce differential settlement. Pillow is not necessary and can be cancelled in composite foundation when pile partner is applied. The height of pile partner has little influence on internal force and displacement of pile. Under rare earthquake action,pile partner may sacrifice firstly to keep pile perform well.%借鉴现浇混凝土大直径管桩(PCC 桩)水平承载足尺试验和数值模拟的成果，建立水平荷载作用下多个构造形式有无伴侣的单桩有限元数值模型。对比计算与分析表明，对于低承台桩基设置桩伴侣可确保承台向地基土传递水平荷载，成倍减小基桩的应力和位移；对于桩身范围地基土模量低的低承台桩基的水平承载性状也有一定的改善；配备桩伴侣后，将桩与承台的连接方式由刚接改为铰接也能大幅度减小桩身内力，桩顶与承台的距离可单纯考虑竖向承载力和变刚度调平基础底板沉降的需要；设置桩伴侣后可取消褥垫层；桩伴侣的高度变化对水平荷载作用下桩内力和位移影响很小；在罕遇
Aminfar, Ali; Ahmadi, Hamid; Aminfar, Mohammad Hossein
2016-06-01
Offshore jacket-type platforms are attached to the seabed by long batter piles. In this paper, results from a finite element analysis, verified against experimental data, are used to study the effect of the pile's inclination angle, and its interaction with the geometrical properties of the pile and the geotechnical characteristics of the surrounding soil on the behavior of the inclined piles supporting the jacket platforms. Results show that the inclination angle is one of the main parameters affecting the behavior of an offshore pile. We investigated the effect of the inclination angle on the maximum von Mises stress, maximum von Mises elastic strain, maximum displacement vector sum, maximum displacement in the horizontal direction, and maximum displacement in the vertical direction. The pile seems to have an operationally optimal degree of inclination of approximately 5°. By exceeding this value, the instability in the surrounding soil under applied loads grows extensively in all the geotechnical properties considered. Cohesive soils tend to display poorer results compared to grained soils.
The Supercritical Pile Model for GRBs
Kazanas, Demos
2006-01-01
We present the spectral and temporal radiative signatures expected within the Supercritical Pile model of Gamma Ray Bursts (GRB). This model is motivated by the need for a process that provides the dissipation necessary in GRB and presents a well defined scheme for converting the energy stored in the relativistic protons of the Relativistic Blast Waves (RBW) associated with GRB into radiation; at the same time it leads to spectra which exhibit a peak in the burst nuF(sub nu) distribution at an energy E(sub p) approximately equal to 1 MeV in the observer s frame, in agreement with observation and largely independent of the Lorentz factor GAMMA of the associated relativistic outflow. Furthermore, this scheme does not require (but does not preclude) acceleration of particles at the shock other than that provided by the isotropization of the flow bulk kinetic energy on the RBW frame. In the present paper we model in detail the evolution of protons, electrons and photons from a RBW to produce detailed spectra of the prompt GRB phase as a function of time from across a very broad range spanning roughly 4 log10 GAMMA decades in frequency. The model spectra are in general agreement with observations and provide a means for the delineating of the model parameters through direct comparison with trends observed in GRB properties.
水平偏心荷载下斜桩群桩受力性状的离心机模型试验%Centrifugal model tests on batter pile groups under eccentric lateral loads
Institute of Scientific and Technical Information of China (English)
顾明; 陈仁朋; 孔令刚; 陈云敏; 张浙杭
2014-01-01
A series of centrifugal model tests are conducted to investigate the behavior of pile groups in sand subjected to eccentric lateral loads, especially the role of batter pile groups in resisting lateral or eccentric loads. The preparation and the procedure of the tests are described. The test results reveal that the eccentric distance of the lateral loads will affect the lateral response of the pile groups to some extent within the experimental range, but have little effect on the torsional behavior of the pile groups. The bearing capacity of the plumb pile group under lateral loads with eccentric distance of 4.3D is higher than that of zero and 7.1D. The capacity of the batter pile groups subjected to lateral, eccentric or torsional loads is much higher than that of the plumb pile groups. Under the eccentric loads, the differences between the lateral displacements of individual piles within the batter pile groups are larger than those in the plumb pile groups, and they also increase with the eccentric distance of the lateral loads. The shear forces and lateral displacements at head of individual piles are different in direction. The axial forces of individual piles within the batter pile groups are dramatically larger than those in the plumb pile groups under the same load condition, which illustrates that batter pile groups can more effectively resist the lateral loads than the plumb pile groups by taking full advantages of the axial capacity of individual piles.%为研究斜桩群桩在水平偏心荷载下的受力性状，在砂土中开展了一系列离心机模型试验，着重对比了直桩群桩和斜桩群桩抵抗水平及偏心荷载的不同特性。详细介绍了模型试验的装置、方法以及内容。试验结果表明：水平荷载偏心距大小对群桩水平承载力有一定的影响，但是对群桩扭转承载力的影响较小。对于直桩群桩，在试验范围内小偏心距（4.3倍桩径）加载对应的水平承载力大
Seismic response of tall building considering soil-pile-structure interaction
Institute of Scientific and Technical Information of China (English)
无
2002-01-01
The seismic behavior of tall buildings can be greatly affected by non-linear soil-pile interaction during strongearthquakes. In this study a 20-storey building is examined as a typical structure supported on a pile foundation for differentconditions: (1) rigid base, i.e. no deformation in the foundation: (2) linear soil-pile system; and (3) nonlinear soil-pile system.The effects of pile foundation displacements on the behavior of tall building are investigated, and compared with the behavior ofbuildings supported on shallow foundation. With a model of non-reflective boundary between the near field and far field,Novak's method of soil-pile interaction is improved. The computation method for vibration of pile foundations and DYNANcomputer program are introduced comprehensively. A series of dynamic experiments have been done on full-scale piles,including single pile and group, linear vibration and nonlinear vibration, to verify the validity of boundary zone model.
Numerical Analysis of the Stability of Embankment Slope Reinforced with Piles
Institute of Scientific and Technical Information of China (English)
CUI Wei; ZHANG Zhigeng; YAN Shuwang
2007-01-01
The effects of stabilizing piles on the stability of an embankment slope are analyzed by numerical simulation. The shear strength reduction method is used for the analysis, and the soil - pile interaction is simulated with zero-thickness elasto-plastic interface elements. Effects of pile spacing and pile position on the safety factor of slope and the behavior of piles under these conditions are given. The numerical analysis indicates that the positions of the pile have significant influence on the stability of the slope, and the pile needs to be installed in the middle of the slope for maximum safety factors. In the end, the soil arching effect closely associated with the space between stabilizing piles is analyzed. The results are helpful for design and construction of stabilizing piles.
Experimental Investigations of Tension Piles in Sand Subjected to Static and Cyclic Loading
DEFF Research Database (Denmark)
Thomassen, Kristina
The present thesis regards the behavior of the piles in jacket pile foundations used for offshore wind turbines. The piles are often loaded in tension because of the combination of wind and wave conditions and the low self-weight of the wind turbine. The repeated cyclic loading can lead...... to accumulated upwards displacement of the piles and, thus, undesired deflection of the wind turbine structure. This study concerns the effect of cyclic loading on a pile installed in dense sand and loaded in tension. A new laboratory test setup was constructed to make these pile load tests. The thesis discusses...... the advantages and disadvantages of the test setup. The results of cyclic loading tests showed that the loading conditions are very important for the behavior of piles. Some wind and wave conditions can be beneficial and increase the pile capacity while other conditions can be damaging and reduce the pile...
单桩承载力预测的PSO-Gompertz模型%PSO-Gompertz Model for Single Pile Capacity Prediction
Institute of Scientific and Technical Information of China (English)
杜勇立
2012-01-01
According to the biological growth law, the Gompertz function model is used to the forecast of single-pile ultimate load after the load transmission mechanism of piles is analyzed, the Particle Swarm Optimization for parameter estimation of the model is provided, the prediction effects of PSO-Gompertz model and double common forecast models are compared with each other based on casestudy. The results show that the growth process of pile bearing capacity usually experience the stages of begin, development, maturity and saturation; the load-settlement (Q-s) curve of piles under static load can be described by the Gompertz function; PSO-Gompertz model works better than the hyperbola and index ones in the forecast of singlepile ultimate load.%在对桩的荷载传递规律进行分析的基础上,运用生物生长观点将Gompertz函数模型用于单桩极限荷载的预测中,给出模型参数估计的粒子群(PSO)方法,并在实例分析的基础上将PSO-Gompertz模型与常用预测模型进行了对比.结果表明:在桩顶静荷载作用下,单桩承载力的发展经历了发生、发展、成熟并趋于饱和的生长过程;桩的荷载Q～沉降s曲线可用logistic函数描述;PSO-Gompertz模型比双曲线模型、指数模型有更高的预测精度.
Institute of Scientific and Technical Information of China (English)
刘汉龙; 陈育民; 赵楠
2008-01-01
Pile foundation is widely used in the offshore engineering. The pile can be seriously destroyed by the soil liquefaction during strong earthquakes. The potentials of liquefaction and damages of pile foundation due to the liquefaction can be reduced by the implementation of the drainage in the liquefiable foundation. A patented pile technology, named rigidity-drain pile, was introduced. The partial section of the pile body was filled by materials with higher penetrability which forms some effective drainage channels in the pile. The principles and construction methods were presented. 3D models for both rigidity-drain pile and ordinary pile were built in FLAC3D code. The dynamic loadings were applied on the bottom of the model. According to the numerical results, in the case of the rigidity-drain pile, the water in the relevant distance range around the pile flows toward the pile drainage, the contour of the pore pressure shows a funnel form. Contrast to the ordinary pile, the rigidity-drain pile can dissipate the accumulated excess pore water, maintain effective stress and obviously reduce the possibility of surrounding soil liquefaction.
Institute of Scientific and Technical Information of China (English)
Ning WANG; Kui-hua WANG; Wen-bing WU
2013-01-01
In this paper,a model named fictitious soil pile was introduced to solve the boundary coupled problem at the pile tip.In the model,the soil column between pile tip and bedrock was treated as a fictitious pile,which has the same properties as the local soil.The tip of the fictitious soil pile was assumed to rest on a rigid rock and no tip movement was allowed.In combination with the plane strain theory,the analytical solutions of vertical vibration response of piles in a frequency domain and the corresponding semi-analytical solutions in a time domain were obtained using the Laplace transforms and inverse Fourier transforms.A parametric study of pile response at the pile tip and head showed that the thickness and layering of the stratum between pile tip and bedrock have a significant influence on the complex impedances.Finally,two applications of the analytical model were presented.One is to identify the defects of the pile shaft,in which the proposed model was proved to be accurate to identify the location as well as the length of pile defects.Another application of the model is to identify the sediment thickness under the pile tip.The results showed that the sediment can lead to the decrease of the pile stiffness and increase of the damping,especially when the pile is under a low frequency load.
Seismic Demands for Pile-Supported Wharf Structures with Batter Piles
Directory of Open Access Journals (Sweden)
Rouhollah Amirabadi
2012-09-01
Full Text Available This study develops an optimal Probabilistic Seismic Demand Model (PSDM for pile-supported wharves whit batter plies. Four bins with twenty non-near-field ground motions and three typical pile-supported wharf structures from western United States ports are used to determine an optimal PSDM by using Probabilistic Seismic Demand Analysis (PSDA. PSDA is used to compute the relationship between Engineering Demand Parameters (EDPs and earthquake Intensity Measures (IMs. An optimal PSDM should be practical, sufficient, effective and efficient-all tested through several IM-EDP pairs. It has been found that for these types of structures, the optimal model comprises a spectral IM, such as spectral acceleration and one of several EDPs. These EDPs are considered for local (moment curvature ductility factor, intermediate (displacement ductility factor and horizontal displacement of embankment and global (differential settlement between deck and behind land response quantities. The considered PSDMs are a critical component in performance-based seismic design and seismic risk assessment. Results can be used in probabilistic framework for performance-based design developed by Pacific Earthquake Engineering Research (PEER center.
Directory of Open Access Journals (Sweden)
Ter-Martirosyan Zaven Grigor'evich
2012-07-01
The authors provide their solution to the problem of interaction of a long compressible pile that has a double-layer linear deformable base. The paper demonstrates that taking account of compressible properties of the pile material leads to qualitatively new distribution of shearing stresses over the surface of a cylindrical pile. It is noteworthy that increase of the pile length and stiffness of the upper section of the base raise the share of the load perceived by the surface of the pile. Besides, in particular conditions of the soil environment, the load perceived by the lower section of the base may reach approximately 20-30 % of the total load.
WAVE CURRENT FORCES ON THE PILE GROUP OF BASE FOUNDATION FOR THE EAST SEA BRIDGE, CHINA
Institute of Scientific and Technical Information of China (English)
无
2007-01-01
On the basis of the two structures of the bridge foundation designed for the East Sea Bridge, the wave current forces on four types of oblique piles, the pile group and the single piles at different positions in the pile group considering the effect of the super structures were experimentally investigated. The relationship between the wave current forces and the associated wave parameters, and the comparison of the wave current forces on the pile groups and the single piles were systematically analyzed. The group effectiveness and the reduction coefficient for the wave current forces on the group were examined for engineering design.
Ground Vibration Isolation of Multiple Scattering by Using Rows of Tubular Piles as Barriers
Directory of Open Access Journals (Sweden)
Miao-miao Sun
2014-01-01
Full Text Available A new formal solution for the multiple scattering of plane harmonic waves by a group of arbitrary configuration tubular piles in an elastic total space is derived. Each order of scattering satisfies prescribed boundary conditions at the interface of tubular piles, which is delivered as the sum of incident and scattering waves. The first order performs the scattering wave by each scattered pile and the subsequent orders resulted from the excitation of each pile of first order of scattering from the remaining tubular piles. Advanced scattering orders can be regarded as the same manners. Several series of scattering coefficients are figured out with the aids of addition theorem so that the exact steady-state solution for the scattered displacement and stress is obtained. Particularly, when internal diameter of tubular piles tends to be infinitely small, it degenerates to a solid pile problem. By imposing the normalized displacement amplitudes and transmissibility indices, the influences of specific parameters such as scattering orders, internal and external diameter ratio of piles, pile material rigidity, position and distances between tubular pile and pile rows, and pile numbers are discussed. Certain recommended conclusions have been drawn as the guidelines of practical engineering design for discontinuous barrier of tubular piles.
Institute of Scientific and Technical Information of China (English)
韩竹青; 张宏; 胡宏彪; 程松; 卞正涛; 王生
2015-01-01
针对北京地铁15号线新建奥林匹克公园站顺行密贴下穿大屯路隧道的施工技术难点，对传统泵吸反循环钻孔灌注桩施工设备进行改进，使其满足导洞内复杂环境下桩基施工的要求，并对施工工艺进行优化，保证施工安全和成桩质量。桩基施工完成后，通过自平衡法静载试验得到单桩竖向抗压承载力特征值，采用超声波透射法和低应变反射波法对大直径桩桩身完整性进行检测。试验和检测结果均表明，大直径桩均为Ⅰ类桩，桩身完整性良好，实测的单桩竖向抗压承载力特征值均满足设计要求。说明暗挖导洞内大直径桩成套施工技术能够满足成桩质量和效率的要求，保证工程的施工安全。%According to the construction technology difficulty of Olympic Park Station in Beijing Subway Line 15 underneath passing the Datun Road tunnel,the traditional construction equipment system of bored piles with the pump suction reverse circulation method was improved to meet the pile foundation construction requirements under the complex conditions in a drift and the construction technology was optimized to ensure the construction safety and the high quality of the completed piles. After completing the pile foundation construction,the characteristic values of the single pile vertical bearing capacity are obtained by self-balanced static load tests and the integrity of large-diameter pile are tested by using ultrasonic transmission method and low strain reflected wave method. T he test and inspection results showed that large-diameter piles are Ⅰ class and have good integrity,the measured characteristic values of the single pile vertical bearing capacity can meet design requirements,which means the improved construction technology of large-diameter pile in underground excavation drift could meet the needs of the construction quality,efficiency and safety.
Improved Design Basis for Laterally Loaded Large Diameter Pile
DEFF Research Database (Denmark)
Leth, Caspar Thrane
. The expected development of offshore wind farms is towards larger farms, larger turbines and larger water depths. Monopiles have been applied widely and it is of interest to investigate the possibilities to further optimize the design and in particular the modelling of the soil-structure interaction...... on the structure and the productivity of the turbine. Current design practice for monopiles are based on p-y curves developed for slender piles with a diameter of 0.6 m. The focus on the structure stiffness has entailed a significant research on the soil-structure interaction for large diameter monopiles...... in dry sand by use of centrifuge modelling and to compare the findings with the standard p-y curves. It has been chosen to apply piles with an embedment length of 6 to 10 times the diameter of the applied piles. The general static behaviour of monopiles in dry sand has based on centrifuge tests been...
The Pressure Limitations on Flux Pile-Up Magnetic Reconnection
Litvinenko, Y. E.
1999-05-01
Flux pile-up magnetic reconnection was thought to be able to provide fast energy dissipation a strongly magnetized plasma, for example, in solar flares. We examine the problem of the plasma pressure limitations on the rapidity of flux pile-up reconnection. It is shown that for a two-dimensional stagnation point flow with nonzero vorticity the magnetic merging rate cannot exceed the Sweet-Parker scaling in a low-beta plasma, which is too slow to explain flares. Moreover, the solution has some undesireable properties such as a diffusion layer at the external boundary and the massively increasing inflow speed. The pressure limitation appears to be somewhat less restrictive for three-dimensional flux pile-up. This work was supported by NSF grant ATM-9813933.
X-ray spectroscopy around the pile-up region
Sharma, Gaurav; Kumar, Basu; Puri, Nitin Kumar; Nandi, Tapan
2015-01-01
We report a pile-up rejection technique based on X-ray absorption concept of Beer-Lambert law for measuring true events in the pile-up region. We have detected a four orders times weaker peak in the pile-up region. This technique also enables one to resolve the weak peaks adjacent to an intense peak provided the latter lies in the lower energy side, and the peaks are at least theoretically resolvable by the detector used. We have resolved such peaks by reducing the intensity ratios in our experiment. The technique allows us to obtain the actual intensities of the observed peaks to have been measured without any attenuator. The possible applications of this technique can be to study the physics of two electron one-photon transition as well as the properties of projectile-like or target-like ions.
Grouting Control for Deep-Water Jacket Skirt Pile
Institute of Scientific and Technical Information of China (English)
ZHANG Qing; ZHANG Jianxin; XU Lianjiang
2006-01-01
Deep-water jacket skirt pile grouting is a critical step in ocean platform construction. Because of the complexity of the skirt pile structure and grouting pipeline, the calculation of grouting pressure and the control of output pressure are involved. Beginning with the jacket skirt pile grouting construction scheme, grouting pressure is estimated on the basis of engineering fluid mechanics theory and variable frequency control technique. Programmable logic controller is the center of grouting pressure control system, which accomplishes the flow control of cement buffer tank water buffer tank, additive buffer tank, cement metering tank, water metering tank, additive metering tank, mixer and agitator. Based on PROFIBUS-DP network, the output pressure of the slurry pump is controlled by the inverter. This method has been applied successfully in JZ20-2 Nor. high spot jacket platform construction.
Identification of Defects in Piles Through Dynamic Testing
Liao, Shutao T.; Roesset, Jose M.
1997-04-01
The objective of this work was to evaluate the theoretical capabilities of the non-destructive impact-response method in detecting the existence of a single defect in a pile, its location and its length. The cross-section of the pile is assumed to be circular and the defects are assumed to be axisymmetric in geometry. As mentioned in the companion paper, special codes utilizing one-dimensional (1-D) and three-dimensional (3-D) axisymmetric finite element models were developed to simulate the responses of defective piles to an impact load. Extensive parametric studies were then performed. In each study, the results from the direct use of time histories of displacements or velocities and the mechanical admittance (or mobility) function were compared in order to assess their capabilities. The effects of the length and the width of a defect were also investigated using these methods. Int. J. Numer. Anal. Meth. Geomech., vol. 21, 277-291 (1997)
Testing of Laterally Loaded Rigid Piles with Applied Overburden Pressure
DEFF Research Database (Denmark)
Sørensen, Søren Peder Hyldal; Foglia, Aligi; Ibsen, Lars Bo
2012-01-01
Small-scale tests have been conducted for the purpose of investigating the quasi-static behaviour of laterally loaded, non-slender piles installed in cohesionless soil. For that purpose, a new and innovative test setup has been developed. The tests have been conducted in a pressure tank such that......Small-scale tests have been conducted for the purpose of investigating the quasi-static behaviour of laterally loaded, non-slender piles installed in cohesionless soil. For that purpose, a new and innovative test setup has been developed. The tests have been conducted in a pressure tank...... such that it was possible to apply an overburden pressure to the soil. Hereby, the traditional uncertainties related to low effective stresses for small-scale tests has been avoided. A scaling law for laterally loaded piles has been proposed based on dimensional analysis. The novel testing method has been validated against...
Design of Jetty Piles Using Artificial Neural Networks
Directory of Open Access Journals (Sweden)
Yongjei Lee
2014-01-01
Full Text Available To overcome the complication of jetty pile design process, artificial neural networks (ANN are adopted. To generate the training samples for training ANN, finite element (FE analysis was performed 50 times for 50 different design cases. The trained ANN was verified with another FE analysis case and then used as a structural analyzer. The multilayer neural network (MBPNN with two hidden layers was used for ANN. The framework of MBPNN was defined as the input with the lateral forces on the jetty structure and the type of piles and the output with the stress ratio of the piles. The results from the MBPNN agree well with those from FE analysis. Particularly for more complex modes with hundreds of different design cases, the MBPNN would possibly substitute parametric studies with FE analysis saving design time and cost.
Probabilistic Assessment for Seismic Performance of Pile-Supported Wharves
Directory of Open Access Journals (Sweden)
Hamid Heidary Torkamani
2013-03-01
Full Text Available The main objective of this study is to investigate the influence of uncertainties associated with the material properties on the seismic performance of pile-supported wharves. For this purpose a two-dimensional finite difference model, representing typical pile-supported wharf structures from western United States has been constructed using software FLAC2D. Incremental dynamic analysis has been applied to evaluate the response of wharf structure under different levels of seismic loading. The uncertainties at both structural and geotechnical parameters have been investigated using a tornado diagram and a ﬁrst-Order Second-Moment (FOSM analysis. It has been found that the uncertainties at the dead load of structure, friction angle of rock fill and the porosity of rock fill contribute most to the variability of the displacement ductility factor of the pile-supported wharf structures. Based on the results, design considerations have been provided.
Cryogenic Hybrid Magnetic Bearing
Meeks, Crawford R.; Dirusso, Eliseo; Brown, Gerald V.
1994-01-01
Cryogenic hybrid magnetic bearing is example of class of magnetic bearings in which permanent magnets and electromagnets used to suspend shafts. Electromagnets provide active control of position of shaft. Bearing operates at temperatures from -320 degrees F (-196 degrees C) to 650 degrees F (343 degrees C); designed for possible use in rocket-engine turbopumps, where effects of cryogenic environment and fluid severely limit lubrication of conventional ball bearings. This and similar bearings also suitable for terrestrial rotating machinery; for example, gas-turbine engines, high-vacuum pumps, canned pumps, precise gimbals that suspend sensors, and pumps that handle corrosive or gritty fluids.
TOPICAL REVIEW: Superconducting bearings
Hull, John R.
2000-02-01
The physics and technology of superconducting bearings is reviewed. Particular attention is given to the use of high-temperature superconductors (HTSs) in rotating bearings. The basic phenomenology of levitational forces is presented, followed by a brief discussion of the theoretical models that can be used for conceptual understanding and calculations. The merits of various HTS bearing designs are presented, and the behaviour of HTS bearings in typical situations is discussed. The article concludes with a brief survey of various proposed applications for HTS bearings.
Institute of Scientific and Technical Information of China (English)
Wang Teng; Wang Kuihua; Xie Kanghe
2001-01-01
The vibration problem of a pile of arbitrary segments with variable modulus under exciting force is established, in which the influence of the soil under pile toe and the surroundings is taken into account. With Laplace transforms, the transmit functions for velocity and displacement of pile are derived. Furthermore, in terms of the convolution theorem and inversed Laplace transform, an analytical solution for the time domain response of a pile subjected to a semi-sine impulse is developed,which is the theoretical basis of the sonic method in pile integrity testing. Based on the solution, the vibration properties of pile with sharp or continuous modulus are studied. The validity of this approach is verified through fidd dynamic tests on some engineering piles. It shows that the theoretical prediction and the response of the pile are in good agreement.
Numerical Analysis of Interaction Between Pile-Supported Pier and Bank Slope
Institute of Scientific and Technical Information of China (English)
王年香
2001-01-01
Two- and three-dimensional finite element analysis programs for pile-soil interaction are compiled. Duncan-Chang's Model is used. The construction sequence of the pier is modeled. The pile-soil interface element is used. The influence of the combination type of piles on the deformation of bank slope and pile behaviour is analyzed. Different designs of a pile-supported pier are compared thoroughly. Calculation results show that the stresses and displacements of the pile are directly related to the distance from the bank slope and the direction of inclination. An inclined prop pile set in the rear platform would remarkably reduce the stresses of piles and the displacement of the pier.
Cumulative Damage in Strength-Dominated Collisions of Rocky Asteroids: Rubble Piles and Brick Piles
Housen, Kevin
2009-01-01
Laboratory impact experiments were performed to investigate the conditions that produce large-scale damage in rock targets. Aluminum cylinders (6.3 mm diameter) impacted basalt cylinders (69 mm diameter) at speeds ranging from 0.7 to 2.0 km/s. Diagnostics included measurements of the largest fragment mass, velocities of the largest remnant and large fragments ejected from the periphery of the target, and X-ray computed tomography imaging to inspect some of the impacted targets for internal damage. Significant damage to the target occurred when the kinetic energy per unit target mass exceeded roughly 1/4 of the energy required for catastrophic shattering (where the target is reduced to one-half its original mass). Scaling laws based on a rate-dependent strength were developed that provide a basis for extrapolating the results to larger strength-dominated collisions. The threshold specific energy for widespread damage was found to scale with event size in the same manner as that for catastrophic shattering. Therefore, the factor of four difference between the two thresholds observed in the lab also applies to larger collisions. The scaling laws showed that for a sequence of collisions that are similar in that they produce the same ratio of largest fragment mass to original target mass, the fragment velocities decrease with increasing event size. As a result, rocky asteroids a couple hundred meters in diameter should retain their large ejecta fragments in a jumbled rubble-pile state. For somewhat larger bodies, the ejection velocities are sufficiently low that large fragments are essentially retained in place, possibly forming ordered "brick-pile" structures.
DEFF Research Database (Denmark)
van Leeuwen, Theo; Caldas-Coulthardt, Carmen
2014-01-01
This paper presents a semiotic analysis of a key cultural artefact, the teddy bear. After introducing the iconography of the teddy bear, it analyses different kinds of stories to show how teddy bears are endowed with meaning in everyday life: stories from children's books, reminiscenses by adults...... about their childhood teddy bears, and children's accounts of what they do with teddy bears, both written for school and told 'out of school', The chapter sees teddy bears as artefacts that provide a cultural channeling for the child's need of a transitional object and argues that the meanings of teddy...... bears have traditionally centred on interpersonal relations within the nuclear family, but have recently been institutionalized and commercialized....
Centrifuge modelling of a laterally cyclic loaded pile
DEFF Research Database (Denmark)
Klinkvort, Rasmus Tofte; Leth, Caspar Thrane; Hededal, Ole
2010-01-01
A total number of 9 static and 6 cyclic centrifuge tests on laterally loaded piles in very dense, dry sand was erformed. The prototype dimensions of the piles were 1 meter in diameter and penetration depths varying from 6 to 10 meters. The static tests were used to investigate the initial subgrade...... reaction modulus and as a reference for cyclic tests. For the cyclic tests the accumulation of deflections and the change in secant stiffness of the soil from repetitive loading were investigated. From all the tests carried out accumulations of deflections were seen. rom the centrifuge tests it was seen...
Testing of Laterally Loaded Rigid Piles with Applied Overburden Pressure
DEFF Research Database (Denmark)
Sørensen, Søren Peder Hyldal; Ibsen, Lars Bo; Foglia, Aligi
2015-01-01
Small-scale tests have been conducted to investigate the quasi-static behaviour of laterally loaded, non-slender piles installed in cohesionless soil. For that purpose, a new and innovative test setup has been developed. The tests have been conducted in a pressure tank such that it was possible...... to apply an overburden pressure to the soil. As a result of that, the traditional uncertainties related to low effective stresses for small-scale tests have been avoided. A normalisation criterion for laterally loaded piles has been proposed based on dimensional analysis. The test results using the novel...
Wave Run-up on Slender Piles in Design Conditions
DEFF Research Database (Denmark)
Andersen, Thomas Lykke; Frigaard, Peter; Damsgaard, M. L.;
2011-01-01
in the design of Horns Reef 1. As a consequence damage was observed on the platforms. This has been the situation for several sites and design tools for platform loads are lacking. As a consequence a physical model test study was initiated at Aalborg University to clarify wave run-up on cylindrical piles...... to the pile an empirical factor is included on the velocity head. The evaluation of the calculation model shows that an accurate design rule can be established even in breaking wave conditions. However, calibration of a load model showed that it was necessary to increase the run-up factor on the velocity head...
Experimental Investigations of Ice Rubble: Shear Box and Pile Testing
Astrup, Oda Skog
2012-01-01
The largest part of an ice ridge consists of unconsolidated ice rubble, whose material properties decide the load from ridges on ships and structures. Material resistance is attributed to the initial freeze-bonds and the friction and interlocking between blocks. The objective of the thesis was to investigate rubble behaviour by two tests: shear box test at NTNU and pile test at HSVA. The shear box test was aimed at investigating freeze-bond mechanisms in rubble. The pile test was aimed at sug...
Effects of Impulsive Pile-Driving Exposure on Fishes.
Casper, Brandon M; Carlson, Thomas J; Halvorsen, Michele B; Popper, Arthur N
2016-01-01
Six species of fishes were tested under aquatic far-field, plane-wave acoustic conditions to answer several key questions regarding the effects of exposure to impulsive pile driving. The issues addressed included which sound levels lead to the onset of barotrauma injuries, how these levels differ between fishes with different types of swim bladders, the recovery from barotrauma injuries, and the potential effects exposure might have on the auditory system. The results demonstrate that the current interim criteria for pile-driving sound exposures are 20 dB or more below the actual sound levels that result in the onset of physiological effects on fishes.
Dynamic Active Earth Pressures of the Retaining Piles with Anchors under Vehicle Loads
Hong-zhi Qiu; Ji-ming Kong; Ren-chao Wang
2016-01-01
The pile-anchor supporting structure is widely used in foundation pit engineering; then knowledge of active earth pressure on piles is very important for engineers. In this paper, based on the pseudodynamic method and considering the vehicle’s vibration characteristic, a method to calculate the earth pressure on piles under vehicle load is presented. At the same time, the constraint of anchor is simplified relation of lateral deformation of piles in present method. Effects of a wide range of ...
软土地区预应力管桩偏位原因分析及处理%Cause Analysis and Treatment of Deviated Prestressed Pipe Piles in Soft Soil
Institute of Scientific and Technical Information of China (English)
吴映栋; 党姣梅; 颜潇潇
2014-01-01
预应力管桩成桩质量好，承载力高，基础造价低，在江浙地区应用广泛。但在复杂地质情况下，特别是宁波软土地区，极易出现管桩偏位、断桩、斜桩等现象。结合工程实例，分析了预应力管桩产生偏位的原因，介绍了预应力管桩偏位的处理方法：准确测量偏位情况、低应变动测确定桩身损伤情况、根据管桩偏位及损伤情况采用针对性的处理措施如管桩内芯放钢筋笼灌芯加固处理以及承台地梁加强和补桩等。%The prestressed pipe pile has a variety of desired characteristics such as high bearing capacity, low cost and good quality, and has an extensive use in Jiangsu and Zhejiang area. But in the most case of complex ground, especially if it’ s in the soft soil of Ningbo, the concrete pile has the tendency to being deviated, broken and sloped when hammered. Based on an engineering example, the reason of sloping prestressed pipe piles and the treatment measures are given. First of all, the sloping condition of each pile should be made clearly, then the damaged position of each pile is found out using low strain dynamic tests, and finally treatment measures are put forward, such as placing reinforcement cage and pouring concrete in the cores of piles, strengthening through cushion caps and grade beams and adding bored piles.
Institute of Scientific and Technical Information of China (English)
孙友义; 侯金林; 刘明
2014-01-01
Wellhead platforms with 4 legs and 8 skirt piles can be classified as three forms inclu-ding single-batter type,double-batter type and batter-to-vertical type according to the jacket leg batter.The pile foundation mechanical characteristic is an important performance of the platform. Pile foundation mechanical characteristics for the three types of platforms were studied,using SACS software,based on nonlinear soil-pile-structure interaction analysis.Influence factor analy-sis on pile foundation mechanical characteristics was performed,and measures for improving the pile foundation bearing capacities were discussed.The results can provide a reference for jacket and pile foundation design for these types of platforms.%4腿8裙桩井口平台按导管架腿斜度可分为单斜式、双斜式与斜变直式3种形式。桩基受力特性是平台的重要性能。以 SACS 程序为分析工具，基于非线性土壤/桩基/结构交互分析，研究了这3种形式平台的桩基受力特性。通过桩基受力影响因素分析，提出了改善桩基受力的措施，可为该类平台的导管架与桩基设计提供参考。
能源桩的荷载－温度联合测试技术∗%IN-SITU MECHANICAL-THERMO COMBINED TESTING TECHNIQUE OF GEOTHERMAL ENERGY PILES
Institute of Scientific and Technical Information of China (English)
王昊; 路宏伟; 洪鑫; 史春乐; 龚红卫; 蒋刚
2016-01-01
Energy pile is a new artifical foundation technology with which pipe loops are incorporated in the pile foundation for ground⁃source heat⁃pump systems, but there have been little information regarding the researching and testing of bearing behavior of energy piles under the pile⁃soil heat exchange. Combined with the conventional static load test and the ground thermal response test, established the methods and requirements for the testing technique of energy piles under the mechanical thermo coupling effect were established, the testing scheme was determined by load level of energy piles and the operating of pile⁃soil heat exchange. It was suggested the testing items, contents, equipment selection and the point of testing. Combined with an engineering example of energy piles, it was introduced the scheme, contents and heat exchange equipment of the field testing, combined with the characteristics of soil in layers,the layout of the temperature and stress sensors on energy piles were also introduced. According to the testing process, the pile top settlement and the axial stresses of energy piles with the change of the temperature of pile shaft were presented.%能源桩是在桩基中埋设地源热泵换热器的新型桩基础。但目前对能源桩因桩－土热交换引起的桩身承载性状变化的研究和测试却极为有限。结合常规桩基静荷载试验和岩土热响应试验，建立了荷载－温度作用下能源桩的联合测试技术方法，提出以能源桩荷载水平和桩－土热交换工况等因素作用来确定荷载－温度联合测试方案，建议了相应的测试项目和内容、测试设备的选择及测试要点。结合某能源桩工程实例，介绍能源桩荷载－温度现场测试方案、内容及热交换设备；结合土层分布特征，介绍了桩身温度、应力传感器的布置的设计，并给出与桩身温度相关的桩顶沉降、桩身应力等数据。
Institute of Scientific and Technical Information of China (English)
顾寄平
2000-01-01
It introduces the calculation principle for the structures of three 50, 000 dwtcontainer terminals of Yantian Port 2nd-phase Project, types of foundation piles and the structural types, piling control standard, as well as the construction machinery and construction method for embedded piles, anchor piles and embedded-anchor piles. It also gives an introduction to the actural bearing capacity testing by combining high-strain dynamic test with static load test.%介绍盐田港二期3个5万吨级集装箱码头结构的计算原则，基桩类型及其结构型式，沉桩控制标准及嵌岩桩、锚定桩、锚定嵌桩的施工机具和施工方法，还介绍了采用高应变动力试验与静载试验相结合的方法验证工程桩实际承载力的情况。
单桩承载力预测的PSO-Gompertz模型研究%The PSO-Gompertz Model Study for Single Pile Capacity Prediction
Institute of Scientific and Technical Information of China (English)
杜勇立
2012-01-01
在对桩的荷载传递规律进行分析的基础上,运用生物生长观点将Gompertz函数模型用于单桩极限荷载的预测中,给出模型参数估计的粒子群(PSO)方法,并在实例分析的基础上将PSO-Gompertz模型与常用预测模型进行了对比.结果表明:在桩顶静荷载作用下,单桩承载力的发展经历了发生、发展、成熟并趋于饱和的生长过程；桩的荷载Q-沉降s曲线可用logistic函数描述；提出的PSO-Gompertz模型比双曲线模型、指数模型有更高的预测精度.%According to the biological growth law, the Gompertz function model was used to the forecast of single-pile ultimate load after the load transmission mechanism of piles was analyzed, the Particle Swarm Optimization for parameter estimation of the model was provided, the prediction effects of PSO-Gompertz model and double common forecast models were compared with each other based on case-study. The results show that the growth process of pile bearing capacity usually experience the stages of begin, development, maturity and saturation; the load-settlement (Q-s) curve of piles under static load can be described by the Gompertz function; PSO-Gompertz model works better than the hyperbola and index ones in the forecast of single-pile ultimate load.
Influence of Circulation Fluid on the Property of Energy Pile%循环液对能量桩性能的影响
Institute of Scientific and Technical Information of China (English)
李飞跃; 郑秀华
2013-01-01
能量桩大大降低了地源热泵的初始投资，节约地表面积，引起了人们的极大关注。目前，能量桩在我国还处于理论研究阶段，绝大部分关注的是能量桩的热效率，关于循环液对能量桩工程性质影响的文献资料还是空白。通过对英国朗伯斯(Lambeth)学院关于能量桩的试验进行分析，探索循环液对能量桩的承载力、荷载分布等性质的影响，优化能量桩的设计，为国内能量桩的设计提供借鉴。%Energy pile has attracted great attention as it can greatly reduce the initial investment of ground source heat pump as well as save its occupied area of the earth’s surface. At present, the study of energy pile is still in the theoretical phase, with most attention fixed on its thermal efficiency, while there is barely any relevant bibliographic data concerning the influence of circulation fluid on the properties of energy pile. This paper is aimed at analyzing the experiment of energy pile carried out in Lambeth, in order to explore the influence of circu-lation fluid on the properties of energy pile, such as its bearing capacity, load distribution, etc. and to optimize its design.
Finite Element Investigations on the Interaction between a Pile and Swelling Clay
DEFF Research Database (Denmark)
Kaufmann, Kristine Lee; Nielsen, Benjaminn Nordahl; Augustesen, Anders Hust
. For the investigated case study, the influence of the pile is observed in a radius of approximately 3 pile diameters from the pile centre creating a weak zone inside this radius. The maximum heave of the excavation level inside this radius decreases polynomially with increasing interface strength. The swelling...
Jansen, H.W.; Jong, C.A.F. de; Jung, B.
2012-01-01
Because of the concern about potential effects on marine pile driving, the industry is developing silent marine pile driving concepts. One of the new concepts, which has been engineered by IHC Hydrohammer in the Netherlands, is the application of a steel Noise Mitigation Screen (NMS) around the pile
The effect of the timing of pile mixing on greenhouse gas (GHG) emissions during dairy manure composting was determined using large flux chambers designed to completely cover replicate pilot-scale compost piles. GHG emissions from compost piles that were mixed at 2, 3, 4, or 5 weeks after initial c...
The Underwater Sound Field from Impact Pile Driving and Its Potential Effects on Marine Life
Dahl, P.H.; Jong, C.A.F. de; Popper, A.N.
2015-01-01
Impact pile driving is a method used to install piles for marine and inland water construction projects using high-energy impact hammers. The installation of hollow steel piles in this manner can produce extremely high sound levels in the surrounding waters (as well as in the air). Given the large-
30 CFR 57.16002 - Bins, hoppers, silos, tanks, and surge piles.
2010-07-01
... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Bins, hoppers, silos, tanks, and surge piles... NONMETAL MINES Materials Storage and Handling § 57.16002 Bins, hoppers, silos, tanks, and surge piles. (a) Bins, hoppers, silos, tanks, and surge piles, where loose unconsolidated materials are stored,...
16 CFR 300.26 - Pile fabrics and products composed thereof.
2010-01-01
... 16 Commercial Practices 1 2010-01-01 2010-01-01 false Pile fabrics and products composed thereof... CONGRESS RULES AND REGULATIONS UNDER THE WOOL PRODUCTS LABELING ACT OF 1939 Labeling § 300.26 Pile fabrics and products composed thereof. The fiber content of pile fabrics or products made thereof may...
Bending behavior of double-row stabilizing piles with constructional time delay
Institute of Scientific and Technical Information of China (English)
Yang YU; Yue-quan SHANG; Hong-yue SUN
2012-01-01
The bending behavior of double-row stabilizing plies is associated with the constructional time delay (CTD),which can be defined as the time interval between the installations of the front stabilizing pile and the rear stabilizing pile.This paper investigates the effect of CTD on the bending moments of double-row stabilizing piles and a method for determining the optimal CTD is proposed.The stabilizing pile is modeled as a cantilever pile embedded in the Winkler elastic foundation.A triangular distributed earth pressure is assumed on the pile segment in the sliding layer.The front stabilizing pile and the rear stabilizing pile are connected by a beam with pinned joints.The analytical solutions of bending moments on the front and the rear stabilizing piles are derived and the accuracy of bending moment solutions is validated by comparing the tensile strain measured from the Hongyan landslide project,Taizhou,Zhejiang,China.It is concluded that CTD has a significant influence on the bending moments of double-row stabilizing piles.An optimal CTD can be obtained when the maximum tensile stress in the front stabilizing pile is equal to that in the rear stabilizing pile,which is 1.4 months for the Hongyan landslide project.
Centrifuge modeling of rapid load tests with open-ended piles
Nguyen, T.C.; Van Lottum, H.; Holscher, P.; Van Tol, A.F.
2012-01-01
Rapid and static load tests were conducted on open-ended and close-ended piles in the Deltares GeoCentriflige. hi flight, a pile was driven into the soil. Both fme-grained sand and silt beds were tested. Both the rapid and static soil resistances o f a close-ended pile were higher than the soil resi
Institute of Scientific and Technical Information of China (English)
无
2002-01-01
Two full-scale experiments using controlled blasting were conducted in the Port of Tokachi on Hokkaido Island,Japan, to assess the behavior of piles and pipelines subjected to lateral spreading. Test specimens were extensively instrumented with strain gauges to measure the distribution of moment during lateral spreading. This allowed us to compute the loading condition, as well as to conduct damage and performance assessments on the piles and pipelines. This paper presents the test results and discussions on the response of single piles and pipelines observed from the full-scale experiments. Based on the test results, it can be concluded that using controlled blasting successfully liquefied the soil, and subsequently induced lateral spreading. The movements of the single pile, as well as the transverse pipelines, were approximately the same as the free field soil movement. Observed moment distribution of the single pile indicated that global translation of the liquefied soil layer provided insignificant force to the pile. In addition, the degree of fixity at the pile tip significantly affected the moment along the pile as well as the pile head displacement. The pile with a higher degree of fixity at the pile tip had smaller pile head displacement but larger maximum moment.
30 CFR 56.16002 - Bins, hoppers, silos, tanks, and surge piles.
2010-07-01
... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Bins, hoppers, silos, tanks, and surge piles... MINES Materials Storage and Handling § 56.16002 Bins, hoppers, silos, tanks, and surge piles. (a) Bins, hoppers, silos, tanks, and surge piles, where loose unconsolidated materials are stored, handled...
16 CFR 303.24 - Pile fabrics and products composed thereof.
2010-01-01
... 16 Commercial Practices 1 2010-01-01 2010-01-01 false Pile fabrics and products composed thereof... CONGRESS RULES AND REGULATIONS UNDER THE TEXTILE FIBER PRODUCTS IDENTIFICATION ACT § 303.24 Pile fabrics and products composed thereof. The fiber content of pile fabrics or products composed thereof may...
New method of designing anti-slide piles-the strength reduction FEM
Institute of Scientific and Technical Information of China (English)
Zheng Yingren; Zhao Shangyi; Lei Wenjie; Tang Xiaosong
2010-01-01
At present,the thrust of an anti-slide pile can be worked out with some calculation methods.However,the resistance in front of the pile,the distributions of resistance and thrust,and appropriate pile length cannot be easily obtained.In this paper,the authors applied the strength-reduction finite element method(FEM)to several design cases of anti-slide piles.Using this method,it is possible to take the pile-soil interactions into consideration,obtain reasonable resistance in front of pile and the distributions of thrust and resistance,and reasonable lengths of anti-slide piles.In particular,the thrust and resistance imposed on embedded anti-slide piles can be calculated and composite anti-slide pile structures such as anchored piles and braced piles can be optimized.It is proved through the calculation examples that this method is more reliable and economical in the design of anti-slide pile.
Institute of Scientific and Technical Information of China (English)
李颖; 贡金鑫
2011-01-01
为清楚了解斜桩在地震中的性能,采用非线性有限元软件ABAQUS对全直桩码头和斜桩码头分别进行了弹塑性时程分析.全直桩码头为全部采用直桩的码头,有斜桩码头分2种情况,一种是1根直桩顶部另设置1对斜桩,其余直桩全部与全直桩码头相同,另一种是将直桩截面尺寸和配筋减小后设置1对斜桩使其荷载-变形特性与全直桩码头相近.研究表明,有斜桩码头的刚度较大,水平位移、直桩桩端弯矩和水平力均较小,但残余位移较大.当地震作用较强时,由于斜桩变形能力较差,混凝土容易压碎,丧失水平承载力.计算分析也同时表明,近陆侧直桩比斜桩承受更大的地震弯矩和水平侧向力.%Recent experiences have demonstrated that earthquake-induced damage to wharf structure is highly susceptible to batter piles. In the United States, wharf structures without batter piles attached are commonly constructed in seismically active regions, however, batter piles are still being advocated in new wharf designs in China. In order to better understand seismic performance of batter piles, elastic-plastic time history analysis is implemented for two cases using ABAQUS. The first case analysis is carried out with and without the batter piles attached at identical input accelerations. The second case focuses on the wharf which has a similar load-displacement curve with vertical pile-supported structure. The evaluation of model behavior is summarized: ( 1 )batter piles attract less lateral load and moment than surrounding vertical piles; (2)horizontal displacements increase where batter piles are detached due to less stiffness; (3)significant increases in residual displacement are observed when the batter piles are attached; (4) the deformability of batter piles is weak, resulting in concrete cracks and bearing capacity loss; (5) the onshore vertical pile attracts more load than the offshore vertical pile which has a greater
上海中心大厦桩基础变刚度调平设计%Variable rigidity design in the pile foundation of Shanghai Tower
Institute of Scientific and Technical Information of China (English)
姜文辉; 巢斯
2012-01-01
How to control the settlement and differential settlements of buildings in Shanghai is important. Variable rigidity design is based on the settlement control and is efficient in differential-settlement control of high-rise buildings with piles group and soft bed. Large-diameter post-grouting bored piles are adopted in the foundation of Shanghai Tower. The foundation of Shanghai Tower was designed according to the variable rigidity conception. By selecting length and distance of piles properly, the differential settlements of plate at centre and edges were controlled within the reasonable range, which can optimize the plate design. Pile tests show that post-grouting technique can increase the bearing capacity of the single pile as well as decrease differences among bearing capacities of different piles.%对于上海地区的超厚软弱土层,如何控制建筑沉降和差异沉降是设计的重点。变刚度调平设计是基于沉降控制的基础设计方法,对于群桩基础和软土地基的高层建筑沉降差异控制有显著的效果。介绍了上海中心大厦大直径后注浆钻孔灌注桩基础设计中按照变刚度调平概念,通过合理选择桩长和桩距,使得主楼底板中心和边缘的计算差异沉降控制在合理的范围,优化了底板的设计。经过试桩,认为后注浆的桩端注浆方法能有效提高单桩承载力和减小不同桩承载力间的变异值。
Sources of salinity near a coal mine spoil pile, north-central Colorado.
Zielinski, R A; Otton, J K; Johnson, C A
2001-01-01
A small (1 km2) salt-affected stream drainage on the High Plains north of Denver, Colorado was sampled to determine the near-surface dispersion of soluble salts and metals from low-sulfur coal mining waste (spoil). Surface waters collected along the 0.8-km stream reach, and aqueous leachates of spoil and naturally saline local soil, were analyzed for chemical constituents and sulfur isotopes. In this semiarid setting with abundant carbonate-bearing surficial sediments, the limited, mildly acidic drainage from the spoil pile is quickly neutralized, restricting the mobility of many elements. However, some spoil-derived constituents were clearly traceable within the upper 0.4 km of the stream reach. Spoil leachates and surface water near the spoil pile have distinctive compositions of major anions and cations, and elevated levels of dissolved nitrate compared with downstream waters. Spoil-derived sulfate was traceable because it has generally positive values of delta34S that contrasted with generally negative values of delta34S in soil leachates and evaporite salts from the surrounding area. Spatial-chemical sampling of surface water showed an abrupt increase in dissolved U, Se, B, Li, and Mn in the lower 0.4 km of the stream reach where shallow ground water from surrounding irrigated fields contributed to surface flow. The downstream evolution of surface water chemistry and sulfur isotopic composition is consistent with mixing between spoil-affected upstream water and irrigation-return water. The methods described should be applicable at other sites in similar settings where the environmental effect of low-sulfur coal mining waste must be assessed and where access to samples of shallow ground water is limited.
Institute of Scientific and Technical Information of China (English)
付强; 刘汉龙; 丁选明; 郑长杰
2015-01-01
A three-dimensional dynamic finite element model of track-ballast-embankment and piled raft foundation system is established. Dynamic response of a railway embankment to a high-speed train is simulated for two cases: soft ground improved by piled raft foundation, and untreated soft ground. The obtained results are compared both in time domain and frequency domain to evaluate the effectiveness of the ground improvement in mitigating the embankment vibrations induced by high-speed trains. The results show that ground improving methods can significantly reduce the embankment vibrations at all considered train speeds(36-432 km/h). The ground response to a moving load is dictated largely by the relationship between load speed and characteristic value of wave velocities of the ground medium. At low speeds, the ground response from a moving load is essentially quasi-static. That is, the displacements fields are essential the static fields under the load simply moving with it. For the soft ground, the displacement on the ballast surface is large at all observed train speeds. For the model case where the ground is improved by piled raft foundation, the peak displacement is reduced at all considered train speeds compared with the case without ground improvement. Based on the effect of energy-dissipating of ballast-embankment-ground system with damping, the train-induced vibration waves moving in ballast and embankment are trapped and dissipated, and thus the vibration amplitudes of dynamic displacement outside the embankment are significantly reduced. But for the vibration amplitude of dynamic velocity, the vibration waves in embankment are absorbed or reflected back, and the velocity amplitudes at the ballast and embankment surface are enhanced. For the change of the vibration character of embankment and ballast, the bearing capacity and dynamic character are improved. Therefore, both of the static and dynamic displacements are reduced by ground improvement; the dynamic
Institute of Scientific and Technical Information of China (English)
付强; 刘汉龙; 丁选明; 郑长杰
2015-01-01
A three-dimensional dynamic finite element model of track-ballast-embankment and piled raft foundation system is established. Dynamic response of a railway embankment to a high-speed train is simulated for two cases: soft ground improved by piled raft foundation, and untreated soft ground. The obtained results are compared both in time domain and frequency domain to evaluate the effectiveness of the ground improvement in mitigating the embankment vibrations induced by high-speed trains. The results show that ground improving methods can significantly reduce the embankment vibrations at all considered train speeds (36− 432 km/h). The ground response to a moving load is dictated largely by the relationship between load speed and characteristic value of wave velocities of the ground medium. At low speeds, the ground response from a moving load is essentially quasi-static. That is, the displacements fields are essential the static fields under the load simply moving with it. For the soft ground, the displacement on the ballast surface is large at all observed train speeds. For the model case where the ground is improved by piled raft foundation, the peak displacement is reduced at all considered train speeds compared with the case without ground improvement. Based on the effect of energy-dissipating of ballast-embankment-ground system with damping, the train-induced vibration waves moving in ballast and embankment are trapped and dissipated, and thus the vibration amplitudes of dynamic displacement outside the embankment are significantly reduced. But for the vibration amplitude of dynamic velocity, the vibration waves in embankment are absorbed or reflected back, and the velocity amplitudes at the ballast and embankment surface are enhanced. For the change of the vibration character of embankment and ballast, the bearing capacity and dynamic character are improved. Therefore, both of the static and dynamic displacements are reduced by ground improvement; the dynamic
Institute of Scientific and Technical Information of China (English)
刘汉龙; 王成龙; 孔纲强; 吴宏伟; 吴迪
2016-01-01
Energy pile is an emerging technology incorporating heat-exchange elements.It provides necessary support for buildings and acts as heat exchanger units to obtain geothermal energy.However,the research focused on the thermal-mechanical behavior between the pile and soil is limited.Based on the model test,the thermal-mechanical behavior and bearing character were studied through tamping and pluvial deposition methods on saturated sand.The temperature of the pile and surrounding soil,horizontal soil pressure,thermal strain,thermal stress,and the pile head settlement were monitored.The results indicated that horizontal soil pressure increased when the pile was heated.The thermal stress and pile heave were also produced.In addition,the larger the compaction degree,the larger was the horizontal soil pressure and the thermal stress with heating.However,the pile heave would be smaller as the degree of compaction was increased.%能量桩是1种新型桩基埋管地源热泵技术，在传递上部荷载的同时获取地热能源；但是目前对于桩土之间的相互作用以及桩体的热力学效应却研究较少。基于模型试验方法，采用打夯法和砂雨法，对饱和砂土中不同压实度下的桩体热力学效应和承载特性进行对比研究。试验测得桩体和桩周土体温度变化、桩周土体水平压力变化、桩体应变应力以及桩顶位移。结果表明，加热时，桩周土体会有水平土压力的增大，桩体内部会有压应力的产生，桩顶会产生向上的位移，并且压实度越大，桩周水平土压力越大，桩体应力越大，桩顶位移变化越小。
Behavior of Pile Group with Elevated Cap Subjected to Cyclic Lateral Loads
Institute of Scientific and Technical Information of China (English)
陈云敏; 顾明; 陈仁朋; 孔令刚; 张浙杭; 边学成
2015-01-01
The pile group with elevated cap is widely used as foundation of offshore structures such as turbines, power transmission towers and bridge piers, and understanding its behavior under cyclic lateral loads induced by waves, tide water and winds, is of great importance to designing. A large-scale model test on 3×3 pile group with elevated cap subjected to cyclic lateral loads was performed in saturated silts. The preparation and implementation of the test is presented. Steel pipes with the outer diameter of 114 mm, thickness of 4.5 mm, and length of 6 m were employed as model piles. The pile group was cyclic loaded in a multi-stage sequence with the lateral displacement controlled. In addition, a single pile test was also conducted at the same site for comparison. The displacement of the pile cap, the internal forces of individual piles, and the horizontal stiffness of the pile group are presented and discussed in detail. The results indicate that the lateral cyclic loads have a greater impact on pile group than that on a single pile, and give rise to the significant plastic strain in the soil around piles. The lateral loads carried by each row of piles within the group would be redistributed with loading cycles. The lateral stiffness of the pile group decreases gradually with cycles and broadly presents three different degradation patterns in the test. Significant axial forces were measured out in some piles within the group, owing to the strong restraint provided by the cap, and finally lead to a large settlement of the pile group. These findings can be referred for foundation designing of offshore structures.
Behavior of pile group with elevated cap subjected to cyclic lateral loads
Chen, Yun-min; Gu, Ming; Chen, Ren-peng; Kong, Ling-gang; Zhang, Zhe-hang; Bian, Xue-cheng
2015-06-01
The pile group with elevated cap is widely used as foundation of offshore structures such as turbines, power transmission towers and bridge piers, and understanding its behavior under cyclic lateral loads induced by waves, tide water and winds, is of great importance to designing. A large-scale model test on 3×3 pile group with elevated cap subjected to cyclic lateral loads was performed in saturated silts. The preparation and implementation of the test is presented. Steel pipes with the outer diameter of 114 mm, thickness of 4.5 mm, and length of 6 m were employed as model piles. The pile group was cyclic loaded in a multi-stage sequence with the lateral displacement controlled. In addition, a single pile test was also conducted at the same site for comparison. The displacement of the pile cap, the internal forces of individual piles, and the horizontal stiffness of the pile group are presented and discussed in detail. The results indicate that the lateral cyclic loads have a greater impact on pile group than that on a single pile, and give rise to the significant plastic strain in the soil around piles. The lateral loads carried by each row of piles within the group would be redistributed with loading cycles. The lateral stiffness of the pile group decreases gradually with cycles and broadly presents three different degradation patterns in the test. Significant axial forces were measured out in some piles within the group, owing to the strong restraint provided by the cap, and finally lead to a large settlement of the pile group. These findings can be referred for foundation designing of offshore structures.
Effect of sediment on vertical dynamic impedance of rock-socketed pile with large diameter
Institute of Scientific and Technical Information of China (English)
俞缙; 蔡燕燕; 吴文兵
2013-01-01
Based on the fictitious soil pile model, the effect of sediment on the vertical dynamic impedance of rock-socketed pile with large diameter was theoretically studied by means of Laplace transform technique and impedance function transfer method. Firstly, the sediment under rock-socketed pile was assumed to be fictitious soil pile with the same sectional area. The Rayleigh-Love rode model was used to simulate the rock-socketed pile and the fictitious soil pile with the consideration of the lateral inertial effect of large-diameter pile. The layered surrounding soils and bedrock were modeled by the plane strain model. Then, by virtue of the initial conditions and boundary conditions of the soil pile system, the analytical solution of the vertical dynamic impedance at the head of rock-socketed pile was derived for the arbitrary excitation acting on the pile head. Lastly, based on the presented analytical solution, the effect of sediment properties, bedrock property and lateral inertial effect on the vertical dynamic impedance at rock-socketed pile head were investigated in detail. It is shown that the sediment properties have significant effect on the vertical dynamic impedance at the rock-socketed pile head. The ability of soil-pile system to resist dynamic vertical deformation is weakened with the increase of sediment thickness, but amplified with the increase of shear wave velocity of sediment. The ability of soil pile system to resist dynamic vertical deformation is amplified with the bedrock property improving, but the ability of soil-pile system to resist vertical vibration is weakened with the improvement of bedrock property.
Rapid pile load tests in the geotechnical centrifuge
Holscher, P.; Van Tol, A.F.; Huy, N.Q.
2012-01-01
Centrifiige experiments were carried out to gain insight into the factors that affect the mobilized resistance during rapid load testing on piles in sand. The influence of generated pore water pressure during rapid load tests is shidied, and its effect on the commonly used unloadmg point method to d
The impact of wind energy turbine piles on ocean dynamics
Grashorn, Sebastian; Stanev, Emil V.
2016-04-01
The small- and meso-scale ocean response to wind parks has not been investigated in the southern North Sea until now with the help of high-resolution numerical modelling. Obstacles such as e.g. wind turbine piles may influence the ocean current system and produce turbulent kinetic energy which could affect sediment dynamics in the surrounding area. Two setups of the unstructured-grid model SCHISM (Semi-implicit Cross-scale Hydroscience Integrated System Model) have been developed for an idealized channel including a surface piercing cylindrical obstacle representing the pile and a more realistic test case including four exemplary piles. Experiments using a constant flow around the obstacles and a rotating M2 tidal wave are carried out. The resulting current and turbulence patterns are investigated to estimate the influence of the obstacles on the surrounding ocean dynamics. We demonstrate that using an unstructured ocean model provides the opportunity to embed a high-resolution representation of a wind park turbine pile system into a coarser North Sea setup, which is needed in order to perform a seamless investigation of the resulting geophysical processes.
20051655 - Petronas, Capacity of Driven Piles Offshore Malaysia
DEFF Research Database (Denmark)
Augustesen, Anders
This report presents the results of work carried out by Aalborg Univesity for NGI related to the effects of ageing on the axial capacity of piles in clay and sand. The document is the fourth of four notes regarding the subject and it includes a recommended approach to account for ageing effects...
Aerial sampling of emissions from biomass pile burns in Oregon
Emissions from burning piles of post-harvest timber slash in Grande Ronde, Oregon were sampled using an instrument platform lofted into the plume using a tether-controlled aerostat or balloon. Emissions of carbon monoxide, carbon dioxide, methane, particulate matter (PM2.5 µm), ...
Dynamic Response of Intact Piles to Impulse Loads
Liao, Shutao T.; Roesset, Jose M.
1997-04-01
The objective of this work was to evaluate the theoretical capabilities of the non-destructive impact-response method in estimating the length and cross-sectional area of intact piles. Three-dimensional (3-D) axisymmetric finite element models were developed to simulate the testing. The results obtained were compared to one-dimensional solutions to evaluate the importance of 3-D effects. Extensive parametric studies were then performed on piles without defects. In each parametric study, the results from the direct use of time histories of displacements or velocities, the mobility function and the Fourier transform of the recorded displacements (impact-echo method) were compared in order to assess their relative advantages and disadvantages. The effects of the relative stiffness of the surrounding soil to that of the pile and of the embedment depth were also investigated for all three methods. In a companion paper the use of these procedures to detect defects such as bulbs (increases in the cross-sectional area of the pile) or necks (decreases in area) is studied. Int. J. Numer. Anal. Meth. Geomech., vol. 21, 255-275 (1997)
Numerical experiments with rubble piles : equilibrium shapes and spins
Richardson, Derek C.; Elankumaran, Pradeep; Sanderson, Robyn E.
2005-01-01
We present numerical experiments investigating the shape and spin limits of self-gravitating "perfect" rubble piles that consist of identical, smooth, rigid, spherical particles with configurable normal coefficient of restitution and no sliding friction. Such constructs are currently employed in a v
Centrifuge modelling of rigid piles in soft clay
DEFF Research Database (Denmark)
Klinkvort, R.T.; Poder, M.; Truong, P.;
2016-01-01
of this study is to employ centrifuge modelling in order to derive experimental p-y curves for rigid piles embedded in over-consolidated soft clay. A kaolin clay sample was prepared and pre-consolidated by applying a constant pressure at the soil surface, while different over-consolidation ratios were achieved...
20051655 - Petronas, Capacity of Driven Piles Offshore Malaysia
DEFF Research Database (Denmark)
Augustesen, Anders
This document is one of four notes concerning the effects of time (in this case ageing) on the vertical capacity of piles. It includes summaries of relevant publications related to the topic. Further, focus has been paid to publications that deal with quantification of setup and not the mechanisms...
30 CFR 816.83 - Coal mine waste: Refuse piles.
2010-07-01
.... Critical construction periods shall include at a minimum: (i) Foundation preparation including the removal... revegetated upon completion of construction. (c) Placement. (1) All vegetative and organic materials shall be... professional engineer, shall inspect the refuse pile during construction. The professional engineer...
30 CFR 817.83 - Coal mine waste: Refuse piles.
2010-07-01
.... Critical construction periods shall include at a minimum: (i) Foundation preparation including the removal... revegetated upon completion of construction. (c) Placement. (1) All vegetative and organic materials shall be... professional engineer, shall inspect the refuse pile during construction. The professional engineer...
Assessment of Cumulative Sound Exposure Levels for Marine Piling Events
Lepper, P.A.; Robinson, S.P.; Ainslie, M.A.; Theobald, P.D.; Jong, C.A.F. de
2012-01-01
The installation of offshore wind farms in European waters and the scale of the planned activity have led to concern over the generation of noise and its potential impact on marine life. Much of this concern is centered around the noise generated by pile driving, which is used for the installation o
Testing of Laterally Loaded Rigid Piles with Applied Overburden Pressure
DEFF Research Database (Denmark)
Sørensen, Søren Peder Hyldal; Ibsen, Lars Bo; Foglia, Aligi
2015-01-01
to apply an overburden pressure to the soil. As a result of that, the traditional uncertainties related to low effective stresses for small-scale tests have been avoided. A normalisation criterion for laterally loaded piles has been proposed based on dimensional analysis. The test results using the novel...
Enhanced mixing downstream of a pile in an estuarine flow
Lass, H. U.; Mohrholz, V.; Knoll, M.; Prandke, H.
2008-11-01
We studied the impact on stratification and mixing of a bridge pile in a stratified shear flow at the Western Bridge of the Great Belt Fixed Link, Denmark, in January and April 2006. Stratification was measured with high horizontal resolution by towed CTD chains and dissipation of turbulent kinetic energy was measured by a free-falling MSS 90 microstructure profiler equipped with shear probes. Background stratification and current were measured by standard CTD and a bottom-mounted ADCP, respectively. The spatial and temporal variability of the flow field close behind a single pile was measured by an ADCP mounted on a small catamaran tethered to this pile. A shear background flow of varying strength was observed with an inflow of up to 80 cm s - 1 in the surface layer and an outflow of 10 cm s - 1 in the bottom layer. The brackish surface layer was separated from the saline Kattegat water in the bottom layer by an intermediate layer resulting in a Brunt-Väisälä frequency of up to 100 cycles per hour (cph). The maximum Reynolds number ( Re) and internal Froude number ( Fr) were 4.6 × 10 6 and 1.3, respectively. Eddies occurred downstream of a pile with a characteristic diameter of the pile and a frequency corresponding to a von Kármán vortex street when near-surface Fr > 0.7. Enhanced mixing was observed in the von Kármán vortex streets, which caused an increase in salinity by a few psu in the surface mixed layer of the eddy up to 400 m downstream of the piles. Differential advection by cross-channel circulation smeared out laterally from the wakes' salinity anomalies and turbulence. The dissipation of turbulent kinetic energy in the intermediate layer increased by an order of magnitude downstream of the piles as a function of Fr when Fr > 0.7. This enhanced mixing reduced the mean potential energy anomaly downstream by some 10 Jm - 3 in the upper 15 m depth and caused an upstream-directed baroclinic pressure gradient of the same order as the barotropic
DEFF Research Database (Denmark)
Nielsen, Nick; Pedersen, Sandra Bleuenn; Sørensen, Jens Ager
2015-01-01
In this paper, we introduce the EcoBears concept that aims to augment household appliances with functional and aesthetic features to promote their "use'' and "longevity of use'' to prevent their disposal. The EcoBears also aim to support the communication of environmental issues in the home setting....... We present our initial design and implementation of the EcoBears that consist of two bear modules (a mother and her cub). We also present our preliminary concept validations and lessons learned to be considered for future directions....
Experimental Research on Large Diameter Cast-in-Place Piles Embedded in Rock
Institute of Scientific and Technical Information of China (English)
衡朝阳; 何满潮; 姚爱军
2001-01-01
This paper expatiated the field test of large diameter cast-in-place piles embedded in soft rock, including static loading test, high or low strain dynamic test, measurement of stresses and strains of pile body, and pressure measurements between pile tip and soft rock. The relative in-situ test problems are discussed. Based on the limit equilibrium theory and the load transfer equation, a synthesis method of analyzing the ultimate carrying capacity of single large diameter pile is put forward. The research results show that the key to determining the ultimate carrying capacity of single pile with a large diameter is the analysis of the intensity of soft rock.
Li, Jin; Correia, Ricardo P.; Chehura, Edmon; Staines, Stephen; James, Stephen W.; Tatam, Ralph; Butcher, Antony P.; Fuentes, Raul
2009-10-01
Pile loading test plays an important role in the field of piling engineering. In order to gain further insight into the load transfer mechanism, strain gauges are often used to measure local strains along the piles. This paper reports a case whereby FBG strain sensors was employed in a field trial conducted on three different types of pile loading tests in a glacial till. The instrumentation systems were configured to suit the specific characteristic of each type of test. Typical test results are presented. The great potential of using FBG sensors for pile testing is shown.
Energy Technology Data Exchange (ETDEWEB)
Furet, J. [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires
1962-07-01
A brief survey is first given of the general theorems of Boodle's algebra and of sequence systems using D.A. Huffmans theory. Some indications are then given concerning the setting-up and the operation of digital computers and also of the principal codes used in digital techniques. It is then shown how digitalisation in atomic pile control makes it possible to use new techniques having the following advantages in particular: greater working safety, a higher degree of centralisation, and suppression of the linear elements. A few examples are given of the application of these techniques to control, particularly with respect to the measurement of the neutronic power and of the period and also of course, to the treatment of the data and the sequence automatisms. The advantage of using digital techniques in the shutdown channels is also examined. Finally a review is given of the technology and the viability of the control devices used. (author) [French] On rappelle d'abord ici les theoremes generaux de l'algebre de Boole et des systemes a sequences en s'appuyant sur la theorie de D.A. Huffmann. On donne ensuite quelques indications sur l'agencement et le fonctionnement des calculateurs digitaux ainsi que les principaux codes utilises dans les techniques digitales. On montre alors comment la digitalisation dans le controle des piles atomiques permet d'utiliser de nouvelles techniques presentant principalement les avantages suivants: securite de fonctionnement plus grande, centralisation plus elevee et suppression des elements lineaires. Un certain nombre d'exemples sont donnes sur l'application de ces techniques au controle, particulierement en ce qui concerne la mesure de la puissance neutronique, de la periode et aussi bien entendu du traitement des informations et des automatismes a sequences. On analyse aussi l'avantage de l'utilisation des techniques digitales dans les chaines de securite. Enfin, un apercu est donne
Bending Moment Calculations for Piles Based on the Finite Element Method
Directory of Open Access Journals (Sweden)
Yu-xin Jie
2013-01-01
Full Text Available Using the finite element analysis program ABAQUS, a series of calculations on a cantilever beam, pile, and sheet pile wall were made to investigate the bending moment computational methods. The analyses demonstrated that the shear locking is not significant for the passive pile embedded in soil. Therefore, higher-order elements are not always necessary in the computation. The number of grids across the pile section is important for bending moment calculated with stress and less significant for that calculated with displacement. Although computing bending moment with displacement requires fewer grid numbers across the pile section, it sometimes results in variation of the results. For displacement calculation, a pile row can be suitably represented by an equivalent sheet pile wall, whereas the resulting bending moments may be different. Calculated results of bending moment may differ greatly with different grid partitions and computational methods. Therefore, a comparison of results is necessary when performing the analysis.
Nonlinear analysis of pile load-settlement behavior in layered soil
Institute of Scientific and Technical Information of China (English)
吕述晖; 王奎华; 张鹏; C. J. LEO3
2015-01-01
A simplified approach is presented to analyze the single pile settlement in multilayered soil. First, a fictitious soil−pile model is employed to consider the effect of layered soil beneath pile toe on pile settlement behavior. Two approximation methods are proposed to simplify the nonlinear load transfer function and simulate the nonlinear compression of fictitious soil−pile, respectively. On this basis, an efficient program is developed. The procedures for determining the main parameters of mathematical model are discussed. Comparisons with two well-documented field experimental pile loading tests are conducted to verify the rationality of the present method. Further studies are also made to evaluate the practicability of the proposed approach when a soft substratum exists, and the results suggest that the proposed method can provide a constructive means for assessing the settlement of a single pile for use in engineering design.
Elrod, David A.
1990-01-01
High side loads reduce the life of the Space Shuttle Main Engine (SSME) High Pressure Oxygen Turbopump (HPOTP) bearings. High stiffness damper seals were recommended to reduce the loads on the pump and turbine end bearings in the HPOTP. The seals designed for use on the pump end are expected to adequately reduce the bearing loads; the predicted performance of the planned turbine end seal is marginal. An alternative to the suggested turbine end seal design is a damper bearing with radial holes from the pressurized center of the turbopump rotor, feeding a smooth land region between two rough-stator/smooth-rotor annular seals. An analysis was prepared to predict the leakage and rotor dynamic coefficients (stiffness, damping, and added mass) of the damper bearing. Governing equations of the seal analysis modified to model the damper bearing; differences between the upstream conditions of the damper bearing and a typical annular seal; prediction of the damper bearing analysis; and assumptions of the analysis which require further investigation are described.
Institute of Scientific and Technical Information of China (English)
焦占生; 雷洋
2014-01-01
Taking a project in Caofeidian manufacturing district as an example, the difficulties of soft ground treatment for blowing and filling, the complex use of gravel pile and plain concrete pile are analyzed in this thesis. Not only can it improve the bearing capacity, but also eliminate liquefaction. It is very economical and applicable.%以曹妃甸工业区某项目为例，分析了吹填土软弱地基处理的难点，提出砂石桩与素混凝土桩复合使用，不仅提高承载力，消除液化，又经济适用。
Picking up Clues from the Discard Pile (Stereo)
2008-01-01
As NASA's Phoenix Mars Lander excavates trenches, it also builds piles with most of the material scooped from the holes. The piles, like this one called 'Caterpillar,' provide researchers some information about the soil. On Aug. 24, 2008, during the late afternoon of the 88th Martian day after landing, Phoenix's Surface Stereo Imager took separate exposures through its left eye and right eye that have been combined into this stereo view. The image appears three dimensional when seen through red-blue glasses. This conical pile of soil is about 10 centimeters (4 inches) tall. The sources of material that the robotic arm has dropped onto the Caterpillar pile have included the 'Dodo' and ''Upper Cupboard' trenches and, more recently, the deeper 'Stone Soup' trench. Observations of the pile provide information, such as the slope of the cone and the textures of the soil, that helps scientists understand properties of material excavated from the trenches. For the Stone Soup trench in particular, which is about 18 centimeters (7 inches) deep, the bottom of the trench is in shadow and more difficult to observe than other trenches that Phoenix has dug. The Phoenix team obtained spectral clues about the composition of material from the bottom of Stone Soup by photographing Caterpillar through 15 different filters of the Surface Stereo Imager when the pile was covered in freshly excavated material from the trench. The spectral observation did not produce any sign of water-ice, just typical soil for the site. However, the bigger clumps do show a platy texture that could be consistent with elevated concentration of salts in the soil from deep in Stone Soup. The team chose that location as the source for a soil sample to be analyzed in the lander's wet chemistry laboratory, which can identify soluble salts in the soil. The Phoenix Mission is led by the University of Arizona, Tucson, on behalf of NASA. Project management of the mission is by NASA's Jet Propulsion Laboratory
Institute of Scientific and Technical Information of China (English)
李飒; 王耀存; 蒲玉成; 孙振平; 樊之夏; 韩亮
2014-01-01
打桩过程中突然快速的溜桩可能造成脱锤，桩体破坏，引发安全事故。由于溜桩的产生往往造成打桩锤击数的预测值与实测值具有较大的偏差，此时准确评价溜桩后桩基承载力就成为实际工程中非常关注的问题。本文选择我国东海两个工程实例，根据现场高应变动测试验和打桩记录，研究了溜桩对桩基承载力的影响。计算分析显示，溜桩的产生会导致打桩总能量的明显降低；现场动测试验结果显示，溜桩发生后在发生溜桩的土层的桩体侧摩阻力接近于零，而桩端阻力没有明显的异常，说明溜桩导致的承载力降低主要来自于侧摩阻力的减小。在本文的实例中，溜桩导致的桩基承载力的降低最大可以达到桩基承载力计算值的17%。%Pile sinking during pile driving is common.A sudden drop of a pile after a strike from the hammer may cause a serious accident,such as the pile falling out of the drive cap or damage to the pile from high tension stress.Pile sinking also often causes a large deviation between the drivabili-ty prediction and the measured blow count.Therefore,an accurate assessment of pile capacity af-ter pile sinking becomes an important problem to address in practice.In this paper,two projects in the East China Sea are chosen to analyze.Based on the results of dynamic load tests in the field and pile driving records,the influence of pile sinking on pile capacity at the end of driving (EOD) is studied.The analysis results show that pile sinking will lead to a significant decrease in the total energy used in pile driving.The results from CAPWAP show that the unit friction of a soil layer where piles run off is close to zero,while the pile end resistance shows no obvious abnormalities. This indicates that the decrease in pile capacity caused by pile sinking is mainly from friction re-duction.In this instance,the pile capacity reduction resulting from pile sinking
Institute of Scientific and Technical Information of China (English)
顾长存; 洪昌地; 马文彬; 李雪平
2008-01-01
Grouting pile is a new soft soil foundation treatment method with characteristics such as no vibration, no noise, no soil compaction, light construction machines and quick construction velocity and so on. At present, study on reinforcement mechanism and design calculation method of composite foundation of grouting pile is initially started without design specifications, so it is usually required to draw on design specifications of stump pile when designing composite foundation of grouting pile while grouting pile has its characteristics and difference although reinforcement mechanisms and construction processes of two types of piles are similar. Sedimentation formula of composite foundation of grouting pile with cover plate is educed and a suitable deformation mode is proposed by aiming to deformation characteristics of composite foundation of grouting pile with cover plate under embankment load on basis of relevant sedimentation theories of composite foundation by combination of characteristics of composite foundation of grouting pile. The sedimentation calculation formula of grouting pile with cover plate under embankment load is educed according to balance relation of force and displacement coordination conditions by elastic theory and sedimentation calculation model established is validated by sedimentation monitoring documents of one expressway in China.
New Analysis Techniques for Avalanches in a Conical Bead Pile with Cohesion
Tieman, Catherine; Lehman, Susan
2015-03-01
Avalanche statistics and pile geometry for 3 mm steel spheres dropped on a conical bead pile were studied at different drop heights and different cohesion strengths. The pile is initially built on a circular base and is subsequently slowly driven by adding one bead at a time to the apex of the pile. We investigate the dynamic response of the pile by recording avalanches off the pile over the course of tens of thousands of bead drops. The level of cohesion is tuned through use of an applied uniform magnetic field. Changes in the pile mass and geometry were investigated to determine the effect of cohesion and drop height on the angle of repose. The angle of repose increased with cohesion strength, and decreased somewhat for higher drop heights. The packing density of beads is expected to decrease as magnetic cohesion increases, but for our 20 000-bead pile, this effect has not been observed. The proportion of beads removed from the pile by different avalanche sizes was also calculated. Although larger avalanches are much rarer occurrences, they carry away a larger fraction of the total avalanched mass than small avalanches. As the pile cohesion increases, the number of small and medium avalanches decreases so that this mass loss distribution shifts more strongly to large sizes.
CONSTRUCTION TECHNOLOGY OF ROTARY DRILLING HOLE DRY IN BORED FILLING PILE%钻孔灌注桩旋挖干取土成孔施工技术
Institute of Scientific and Technical Information of China (English)
王玮
2012-01-01
According to the different strata and ground water level,construction of rotary drilling hole may using process with drilling pile dry and mud. Drilling pile dry without mud, hole wall do not produce sludge, thickness of waste in hole bottom is small,conducive to play the bearing capacity of pile. Meanwhile,high construction efficiency, mud - free emission,pollution of small,especially suitable for construction of urban construction foundation.%根据不同的地层及地下水位情况，旋挖钻成孔灌注桩可采用干取土成孔和泥浆护壁成孔工艺。干取土成孔工艺不需泥浆护壁，孔壁不产生泥皮，孔底渣土厚度小，利于桩基承载力的发挥。同时，施丁效率高，无泥浆排放，对环境污染小，尤其适合于城市建设基础的施工。
Resolution of Identity Crisis of Events in Pile-up
Deshpande, Avinash A
2012-01-01
Mutually uncorrelated random discrete events, manifesting a common basic process, are examined often in terms of their occurrence rate as a function of one or more of their distinguishing attributes, such as measurements of photon spectrum as a function of energy. Such rate distributions obtained from the observed attribute values for an ensemble of events will correspond to the "true" distribution only if the event occurrence were {\\it mutually exclusive}. However, due to finite resolution in such measurements, the problem of event {\\it pile-up} is not only unavoidable, but also increases with event rate. Although extensive simulations to estimate the distortion due to pile-up in the observed rate distribution are available, no restoration procedure has yet been suggested. Here we present an elegant analytical solution to recover the underlying {\\it true} distribution. Our method, based on Poisson statistics and Fourier transforms, is shown to perform as desired even when applied to distributions that are si...
Probability distributions for Poisson processes with pile-up
Sevilla, Diego J R
2013-01-01
In this paper, two parametric probability distributions capable to describe the statistics of X-ray photon detection by a CCD are presented. They are formulated from simple models that account for the pile-up phenomenon, in which two or more photons are counted as one. These models are based on the Poisson process, but they have an extra parameter which includes all the detailed mechanisms of the pile-up process that must be fitted to the data statistics simultaneously with the rate parameter. The new probability distributions, one for number of counts per time bins (Poisson-like), and the other for waiting times (exponential-like) are tested fitting them to statistics of real data, and between them through numerical simulations, and their results are analyzed and compared. The probability distributions presented here can be used as background statistical models to derive likelihood functions for statistical methods in signal analysis.
The Supercritical Pile Model: Prompt Emission Across the Electromagnetic Spectrum
Kazanas, Demos; Mastichiadis, A.
2008-01-01
The "Supercritical Pile" GRB model is an economical model that provides the dissipation necessary to convert explosively the energy stored in relativistic protons in the blast wave of a GRB into radiation; at the same time it produces spectra whose luminosity peaks at 1 MeV in the lab frame, the result of the kinematics of the proton-photon - pair production reaction that effects the conversion of proton energy to radiation. We outline the fundamental notions behind the "Supercritical Pile" model and discuss the resulting spectra of the prompt emission from optical to gamma-ray energies of order Gamma^2 m_ec^2, (Gamma is the Lorentz factor of the blast wave) present even in the absence of an accelerated particle distribution and compare our results to bursts that cover this entire energy range. Particular emphasis is given on the emission at the GLAST energy range both in the prompt and the afterglow stages of the burst.
The Pressure Limitations on Flux Pile-up Reconnection
Litvinenko, Yuri E.
1999-05-01
The problem of the plasma pressure limitations on the rapidity of flux pile-up magnetic reconnection is re-examined, following the claim made by Jardine and Allen (1998) that the limitations can be removed by relaxing the assumption of zero-vorticity two-dimensional plasma flows. It is shown that for a two-dimensional stagnation point flow with nonzero vorticity the magnetic merging rate cannot exceed the Sweet-Parker scaling in a low-beta plasma. The pressure limitation appears to be much less restrictive for weak three-dimensional flux pile-up, provided the perturbation length scale in the third dimension is much less than the global length scale. The actual reconnection rate in the latter case, however, is much lower than this upper estimate unless the current sheet width is also much less than the global scale.
ESTIMATION OF SCOUR HOLE PROPERTIES AROUND VERTICAL PILE USING ANNs
Institute of Scientific and Technical Information of China (English)
A.KHOSRONEJAD; G. A. MONTAZER; M. GHODSIAN
2003-01-01
Correct estimation of the scour around vertical piles in the field exposed to oscillatory waves is very important for many offshore structures and coastal engineering projects. Conventional predictive formulas for the geometric properties of scour hole, however, are not able to provide sufficiently accurate results. Artificial Neural Networks (ANNs) are simplified mathematical representation of the human brain. Three-layer normal feed-forward ANN is a powerful tool for input-output mapping and has been widely used in civil engineering problems. In this article the ANNs approach is used to predict the geometric properties of the scour around vertical pile. Two different ANNs including multilayer perceptron (with four different learning rules) and radial basis functions neural networks are used for this purpose. The results show that a three-layer normal feed-forward multilayer perceptron with quick propagation (QP) learning rule can predict the scour hole properties successfully.
Piles, Tabs and Overlaps in Navigation among Documents
DEFF Research Database (Denmark)
Jakobsen, Mikkel Rønne; Hornbæk, Kasper Anders Søren
2010-01-01
documents worked well for tasks that involved visual features of the documents, but the utility of recency or stable ordering of documents was task dependent. Based on the results, we discuss the effects of spatial arrangement, visibility, and task-dependency, and suggest areas for future research......Navigation among documents is a frequent, but ill supported activity. Overlapping or tabbed documents are widespread, but they offer limited visibility of their content. We explore variations on navigation support: arranging documents with tabs, as overlapping windows, and in piles....... In an experiment we compared 11 participants’ navigation with these variations and found strong task effects. Overall, overlapping windows were preferred and their structured layout worked well with some tasks. Surprisingly, tabbed documents were efficient in tasks requiring simply finding a document. Piled...
Wardle, F
2015-01-01
Ultra-precision bearings can achieve extreme accuracy of rotation, making them ideal for use in numerous applications across a variety of fields, including hard disk drives, roundness measuring machines and optical scanners. Ultraprecision Bearings provides a detailed review of the different types of bearing and their properties, as well as an analysis of the factors that influence motion error, stiffness and damping. Following an introduction to basic principles of motion error, each chapter of the book is then devoted to the basic principles and properties of a specific type of bearin
CFG Pile Quality Investigation and Production of Pile-cutting Equipment%CFG桩头质量调查及截桩设备的制作
Institute of Scientific and Technical Information of China (English)
刘红峰
2013-01-01
本文在总结钻孔桩桩头超灌高度的基础上，通过试验，提出CFG桩超灌高度为0.5m以上，制作并使用特制截桩设备大大减小了截桩对CFG桩的扰动，此外还对桩间土的开挖进行了详细论述。%Based on the summary of extra filling height of bored pile, through experiment, the paper points out the extra filling height of CFG pile is above 0.5m. The special pile-cutting equipment greatly reduced the disturbance of CFG pile. Additionally, it describes the excavation of soil between piles in detail.
Chestnut Ridge Borrow Area Waste Pile work plan
Energy Technology Data Exchange (ETDEWEB)
Johnson, R. (Oak Ridge Y-12 Plant, TN (United States))
1991-08-01
The US Department of Energy (DOE), through its contractor Martin Marietta Energy Systems, Inc., has constructed a storage facility, the Chestnut Ridge Borrow Area Waste Pile (CRBAWP), for mercury-contaminated soil excavated from the Oak Ridge Civic Center properties and the Oak Ridge Sewer Line Beltway. Excavation of the soil from the Civic Center began in September 1984 and was completed in early 1985. Similar soils from other areas of the city were added to the pile until 1987. Approximately 3000 yd{sup 3} are stored at the present time. An Interim Status RCRA permit was initially sought for this facility. Samples from the waste pile passed the Extraction Procedure Toxicity Test (EP Tox). The Tennessee Department of Health and Environment (now the Tennessee Department of Conservation-TDC) denied the permit based on their conclusion that the waste was not a RCRA-regulated waste. On September 25, 1990 the Toxicity Characteristic Leaching Procedure (TCLP) superseded the EP Tox test. TCLP tests are not proposed to satisfy a request by TDC and to make a final determination of the nature of the soils in order to close the CRBAWP as a solid waste disposal facility under Tennessee State rule 1200-1-7-.04. The objectives of this work are to summarize existing site information and detail actions necessary to sample and characterize soils from the waste pile as hazardous or nonhazardous per the Toxicity Characteristic Leaching Procedure (TCLP). Within the scope of this plan, a site investigation will be discussed; a field sampling plan will be described in terms of sampling locations, procedures, and quality assurance; and ancillary activities such as waste management, data management, and health and safety will be outlines. 15 refs., 7 figs., 2 tabs.
Collapse mechanisms and strength prediction of reinforced concrete pile caps
DEFF Research Database (Denmark)
Jensen, Uffe G.; Hoang, Linh Cao
2012-01-01
This paper describes an upper bound plasticity approach for strength prediction of reinforced concrete pile caps. A number of collapse mechanisms are identified and analysed. The procedure leads to an estimate of the load-carrying capacity and an identification of the critical collapse mechanism....... It is argued that the upper bound approach may be a useful complement to the widely used lower bound strut-and-tie method. Especially when dealing with strength assessment of existing structures....
Enhanced in-pile instrumentation at the advanced test reactor
Energy Technology Data Exchange (ETDEWEB)
Rempe, J. L.; Knudson, D. L.; Daw, J. E.; Unruh, T.; Chase, B. M.; Palmer, J.; Condie, K. G.; Davis, K. L. [Idaho National Laboratory, MS 3840, P.O. Box 1625, Idaho Falls, ID 83415 (United States)
2011-07-01
Many of the sensors deployed at materials and test reactors cannot withstand the high flux/high temperature test conditions often requested by users at U.S. test reactors, such as the Advanced Test Reactor (ATR) at the Idaho National Laboratory. To address this issue, an instrumentation development effort was initiated as part of the ATR National Scientific User Facility in 2007 to support the development and deployment of enhanced in-pile sensors. This paper reports results from this effort. Specifically, this paper identifies the types of sensors currently available to support in-pile irradiations and those sensors currently available to ATR users. Accomplishments from new sensor technology deployment efforts are highlighted by describing new temperature and thermal conductivity sensors now available to ATR users. Efforts to deploy enhanced in-pile sensors for detecting elongation and realtime flux detectors are also reported, and recently-initiated research to evaluate the viability of advanced technologies to provide enhanced accuracy for measuring key parameters during irradiation testing are noted. (authors)
Cost analysis of continuous flight auger piles construction in Egypt
Directory of Open Access Journals (Sweden)
Hossam E. Hosny
2016-09-01
Full Text Available Continuous Flight Auger (CFA piling is widely used in the Egyptian construction industry. There is a dramatic fluctuation in pricing of executing this work package within short periods as a result of unsteady changes in supply-demand equilibrium. Consequently, there is an urgent need for the use of a scientific approach in estimating construction costs. Accordingly, it is crucial to consider the different cost elements of CFA piling construction as a step to reach an accurate and realistic cost estimate to be used by contractors in tendering. This research aims to study these cost elements based on an expert judgment, site observations and statistical analysis in order to develop an effective tool to estimate the total construction cost of the CFA piles in any future project. Expert survey was performed to draw detailed information to construct a cost breakdown structure (CBS that was used as a basis for developing the proposed cost model. The developed cost model is then validated through the application on fifty two projects. Such projects were carefully selected in different sizes, purposes and locations. Then the collected data were exposed to statistical analysis techniques. An average percentage error of 4.1% was observed upon comparing the estimated costs with the actual costs of these projects. A sensitivity analysis was then performed to recognize the most effective cost factors. The developed recommended model was used by some experienced contractors in the Egyptian market who expressed their satisfaction with the model.
NEET In-Pile Ultrasonic Sensor Enablement-Final Report
Energy Technology Data Exchange (ETDEWEB)
J. Daw; J. Rempe; J. Palmer; P. Ramuhalli; R. Montgomery; H.T. Chien; B. Tittmann; B. Reinhardt; P. Keller
2014-09-01
Ultrasonic technologies offer the potential to measure a range of parameters during irradiation of fuels and materials, including geometry changes, temperature, crack initiation and growth, gas pressure and composition, and microstructural changes under harsh irradiation test conditions. There are two primary issues that currently limit in-pile deployment of ultrasonic sensors. The first is transducer survivability. The ability of ultrasonic transducer materials to maintain their useful properties during an irradiation must be demonstrated. The second issue is signal processing. Ultrasonic testing is typically performed in a lab or field environment, where the sensor and sample are accessible. The harsh nature of in-pile testing and the variety of desired measurements demand that an enhanced signal processing capability be developed to make in-pile ultrasonic sensors viable. To address these issues, the NEET ASI program funded a three year Ultrasonic Transducer Irradiation and Signal Processing Enhancements project, which is a collaborative effort between the Idaho National Laboratory, the Pacific Northwest National Laboratory, the Argonne National Laboratory, and the Pennsylvania State University. The objective of this report is to document the objectives and accomplishments from this three year project. As summarized within this document, significant work has been accomplished during this three year project.
Radiocarbon from Pile Graphite; Chemical Methods for Its Concentrations
Arnold, J. R.; Libby, W. F.
1946-10-10
Samples of pile graphite, irradiated in a test-hole at Hanford for 15 months, have been assayed for radioactive C{sup 14} yielding 0.38 ± 0.04 microcuries per gram. At this level of activity, the pile graphite contains very valuable amounts of C{sup14}. The relation between the above assay and the probable average assay of pile graphite is discussed, and it is concluded that the latter is almost certainly above 0.3 microcuries/gram. Controlled oxidation of this graphite, either with oxygen at ~750ºC, or with chromic acid "cleaning solution" at room temperature, yields early fractions which are highly enriched in C{sup 14}. Concentrations of 5-fold with oxygen, and 50-fold with CrO{sub 3}, have been observed. The relation between the observed enrichment and the Wigner effect is discussed, and a mechanism accounting for the observations put forward. According to this, about 25% of the stable carbon atoms in the lattice have been displaced by Wigner effect, a large fraction of which have healed by migrating to crystal edges. All the C{sup 14} atoms have been displaced, and the same fraction of these migrate to the edges. The enrichment then results from surface oxidation, in the oxygen case. Predictions are made on the basis of this hypothesis. A technique of counting radioactive CO{sub 2} in the gas phase is described.
CENTRIFUGAL MODEL TEST OF SLOPE REINFORCED BY SMALL-DIAMETER STEEL PIPE ROW PILES%小直径钢管排桩加固边坡的离心模型试验
Institute of Scientific and Technical Information of China (English)
向波; 马建林; 何云勇; 朱林; 张正义
2012-01-01
As a new retaining structure, the small-diameter steel pipe anti-sliding pile is used extensively for slope reinforcement and landslide control, but its some behaviors, such as anti-sliding characteristics, force mechanism and failure mode, etc., need to be further studied. Combining with a specific engineering, centrifugal model tests of small- diameter steel pipe row piles are used to investigate the effects of slope failure mode, stress condition, pile spacing and connection beams on slope anti-sliding capacity. The results show that the model slope in each group suffers overall structure failure, and sliding surface can be observed clearly only in slopes without reinforcement. The anti-sliding mechanism of this kind of structures represents the geological improvement by high-pressure grouting and cooperative anti-sliding activity by piles and rock-soil composite structure. The main failure mode of this kind of structure is overall instability caused by axial tension and compression. The anti-sliding capacity of row piles is affected dramatically by pile spacing. The relationship between the ratio of pile spacing to pile diameter(L/φ) and factor of safety of slope is apower function, and the value of L/φ of this type of row piles is recommended to be 6 - 12. Soil pressures behind piles increase with the increasing depth first and then decrease, and they approximately present a triangular distribution above the sliding surface. For the triple-row pile structure with connection beams, the bearing capacity of pile B decreases with the increase of acceleration, while that of pile C is on the contrary. The factor of safety of slope increases by 38.3% under the action of connection beams.%小直径钢管抗滑桩作为一种新型支挡结构广泛应用于边坡加固和滑坡治理中,但其抗滑特性、受力机制及破坏模式等还有待于深入研究.结合工程背景,开展小直径钢管排桩离心模型试验,研究排桩加固边坡破坏模式、
Response of carrying capacity of piles induced by adjacent Metro tunneling
Institute of Scientific and Technical Information of China (English)
YANG Xiao-jie; DENG Fei-huang; WU Jia-jia; LIU Jian; WANG Fu-qiang
2009-01-01
Construction of tunnels in urban areas requires assessment of the impact of tunneling on the stability and integrity of existing pile foundations. We have focused our attention to the analysis of the carrying capacity of pile foundations provided by the impact of construction of urban tunnels on adjacent pile foundations, under the engineering background of the construction of the # 2 Line of the Guangzhou subway. It is carried out using a fast Lagrangian analysis of a continuum in a 3D numerical code, which is an elastoplastic three-dimensional finite difference model, to simulate the response of piles under the entire process of metro tun-neling (deactivation of soil element and activation of the lining). The adjacent stratum around the tunnel is classified into three re-gions: Zone Ⅰ(upper adjacent stratum of tunnel), Zone Ⅱ (45°-upper-lateral adjacent stratum of tunnel) and Zone Ⅲ (lateral adjacent stratum of tunnel). In each region one typical pile is chosen to be calculated and analyzed in detail. Numerical simulations are mainly conducted at three points of each pile shaft: the side-friction force of the pile, the tip resistance of the pile and the axial loading of the pile. A contrasting analysis has been conducted both in the response of typical piles in different regions and from computer calculated values with site monitoring values. The results of numerical simulations show that the impact on carrying ca-pacity of the piles lies mainly in the impact of construction of urban tunnels on the side-friction forces and the tip resistance of piles. The impact differs considerably among the different strata zones where the pile tips are located. The complicated rules of side-friction force and tip resistance of piles has resulted in complicated rules of pile axial loading thus, in the end, it impacts the carrying capacity of pile-foundations. It is necessary to take positive measures, such as stratum grouting stabilization or foundation underpinning, ete
Institute of Scientific and Technical Information of China (English)
王铁成; 杨志坚; 赵海龙; 王文进
2015-01-01
Based on the results of four prestressed high strength concrete(PHC)pile-pile cap connections under cyclic loading,the failure patterns and the mode of the specimens are described. The strain of pile,anchor bars and carbon fiber-reinforced polymer(CFRP),hysteretic curve,bearing capacity and displacement ductility of connections are analyzed. The test results show that the cap of specimens appeared to be a squeezing failure. The anchor bars lost con-straint,and formed a hinge joint that resulted in the connection rotation being unrestricted and the rotation capacity of connection being increased. PHC pile reinforced by steel fiber and non-prestressed steel bars can improve the dis-placement ductility of connections. The connections should be designed with enough rotating capacity,which ensures that the cap will not be damaged by squeezing or prying due to the rotating of the pile end. The finite element software OpenSees was used to simulate the nonlinear behavior of pile-cap connections under cyclic loading. Comparison be-tween analytical and experimental results shows that the proposed modeling technique is capable of accurately describ-ing the cyclic behavior of the connections.%对4个预应力高强混凝土(PHC)管桩与承台连接节点进行了低周往复荷载试验，描述了试件的破坏过程和形态，分析了桩身混凝土、锚固钢筋以及碳纤维约束预应力混凝土管桩(CFRP)的应变，对构件的滞回曲线、承载力和位移延性等进行了研究。试验结果表明，在弯矩作用下，节点区域混凝土被压碎，节点区锚固钢筋约束减弱，形成铰接点，节点转动能力变大；在桩身混凝土中掺入钢纤维以及配置非预应力筋可以提高节点的位移延性；在进行节点设计时，应保证承台不会由于桩端转动时产生的挤压力或撬力作用过早地发生破坏。采用有限元分析软件OpenSees对节点在往复荷载作用下的受力性能进行了模拟分
Weinberg, Brian (Inventor); Mavroidis, Constantinos (Inventor); Vranish, John M. (Inventor)
2011-01-01
A gear bearing drive provides a compact mechanism that operates as an actuator providing torque and as a joint providing support. The drive includes a gear arrangement integrating an external rotor DC motor within a sun gear. Locking surfaces maintain the components of the drive in alignment and provide support for axial loads and moments. The gear bearing drive has a variety of applications, including as a joint in robotic arms and prosthetic limbs.
Harris, Tedric A
2001-01-01
One of the most well-known experts in the field brings cutting-edge research to practitioners in the new edition of this important reference. Covers the improved mathematical calculations for rolling bearing endurance developed by the American Society of Mechanical Engineers and the Society of Lubrication and Tribology Engineers. Updated with new material on Condition-Based Maintenance, new testing methods, and new bearing materials.
Institute of Scientific and Technical Information of China (English)
钱佳楠
2005-01-01
@@ As Valentine's Day came closer,every shop was full of colourful gifts such as cookies in the shape of heart, chocolates,Teddy Bears and so on.When I step into a shop on February 14th,I felt most lonely as I was alone.With mv eves fixed on a lovely Teddy Bear, I wished that someone could send me this stuffed toy.
EURIPIDES, load tests on large driven piles in dense silica sands
Energy Technology Data Exchange (ETDEWEB)
Zuidberg, H.M.; Vergobbi, P.
1996-12-31
In 1995 an extensive load testing program was conducted on 30 inch pipe piles in dense silica sands similar to those found in the southern North Sea. A highly instrumented pile was driven at one location, extracted and redriven at a second location. A total of twelve static compression and tension load tests were performed at three penetration depths between 30 and 47 meters. Test objectives included acquiring reliable data on capacity of offshore type piles in sands which hitherto were hardly available and to understand the failure mechanisms in order to improve current foundation design. The paper describes the design of the testing program and project organization and funding. Details of the test pile and instrumentation to measure the loads in the pile and the pile-sand interaction are highlighted with an emphasis on quality of the measurements. The field-work and innovative testing facilities are also described.
Case Study of CPT-based Design Methods for Axial Capacity of Driven Piles in Sand
DEFF Research Database (Denmark)
Thomassen, Kristina; Ibsen, Lars Bo; Andersen, Lars Vabbersgaard
2012-01-01
Today the design of onshore axially loaded driven piles in cohesionless soil is commonly made on basis of CPT-based methods because field investigations have shown strong correlation between the local shaft friction and the CPT cone resistance. However, the recommended design method for axially....... Thus, several CPT-based methods have been proposed for the design of offshore driven piles in cohesionless soil such as the UWA-05, ICP-05, and NGI-99 methods. This article treats a case study where the API-method as well as the UWA-05 and NGI-99 methods are compared using CPT-data from an offshore...... location with dense to very dense sand. The design of the piles in the jacket foundation shows that API-00 for both the tension and the compression loads predicted much longer piles than the CPT-based methods. Variation of the pile length and pile diameter shows that NGI-99 and UWA-05 predicts almost...
The Shielding Effect of Multi-Pile Structures on Ice Force
Institute of Scientific and Technical Information of China (English)
史庆增; 黄焱; 宋安
2004-01-01
The shielding effect of the front pile-row on the ice force acting on the back pile-row is studied by ice force model tests. In the tests, the front pile-row is designed to model jacket legs and the back pile-row to model the water resisting pipe-phalanx within the jacket. The shielding factor for ice force corresponding to different conditions are given in this paper. The research indicates that there are many factors, including the longitudinal and lateral spacing between the front and back pile-row, ice attacking angle and the ratio of pile diameter to ice thickness, that influence the shielding effect on ice force.
Mechanical response of bridge piles in high-steep slopes and sensitivity study
Institute of Scientific and Technical Information of China (English)
赵衡; 尹平保; 李夕兵
2015-01-01
The bridge piles located in high-steep slopes not only endure the loads from superstructure, but also the residual sliding force as well as the resistance from the slope. By introducing the Winkler foundation theory, the mechanical model of piles−soils−slopes system was established, and the equilibrium differential equations of pile were derived. Moreover, an analytic solution for identifying the model parameters was provided by means of power series method. A project with field measurement was compared with the proposed method. It is indicated that the lateral loads have great influences on the pile, the steep slope effect is indispensable, and reasonable diameter of the pile could enhance the bending ability. The internal force and displacements of pile are largely based upon the horizontal loads applied on pile, especially in upper part.
Numerical Simulations of Pile Supported Protective System Subjected to Ship Impact
Institute of Scientific and Technical Information of China (English)
SUN Zhen; WANG Junjie
2006-01-01
The head-on collision process between ship and concrete pile supported protective system is simulated by software LS-DYNA.The influences of pile non-linearity and soil non-linearity on impact force,ship crush depth and the cap displacement of pile supported protective system are discussed.It's shown that for both severe impact case and non-severe impact case,the non-linearity of pile material influence the impact force history,ship crush depth.The non-linearity of pile material and soil has remarkable influence on the cap displacement especially for severe impact case.These issues should not be ignored in the analysis of pile supported protective system subjected to ship impact.
我国北方某热电厂桩载试验研究%COMPARISONS OF TWO PILE LOAD TESTING METHODS AT HEAT AND POWER PLANT IN NORTH CHINA
Institute of Scientific and Technical Information of China (English)
许鹏; 王清; 齐迪; 鲍硕超
2012-01-01
高应变动测法目前得到了越来越广泛的应用,研究其测试结果的可靠性对实际工程具有重要意义.对PHC桩应用高应变法、竖向静载方法进行试验,以确定桩基的单桩极限承载力.首先对2组不同直径的6根试桩进行高应变测试,采用国际上推荐的GOBLE-CAPWAPC-CASE方法,得到试桩的单桩极限承载力；然后按慢速维持荷载法进行竖向抗压静载试验,将所得极限承载力与高应变法所得结果进行对比,高应变法所得结果高于静载试验的结果,2种方法结果不同是由于2种方法的测试原理、计算方法、影响因素等不同所致.高应变法的理想化桩-土体系以及主要参数的设定对结果都有很大的影响,实际试验中应充分考虑如何取值.%High strain dynamic testing method has been more widely used now. It is important to study the reliability of test results for projects. In this paper,the ultimate bearing capacity of single PHC pile is determined by static loading test and high strain test. There are two different diameters of the six test piles. At first,the six piles are tested with the high strain method. The results are obtained with the GOBLE-CAPWAPC-CASE method. Then the piles are tested with the static vertical load testing and slow maintenance loading method. Comparing the results of the two methods, the bearing capacity of the piles by the high strain dynamic testing method is higher than that of the piles tested by the static loading test. The differences are relative with the testing principles, calculating methods and different affecting factors of the two methods. The idealized pile-soil system and how to set the main parameters of high strain method have great influence on the results. How to use the values should be fully considered in testing.
Numerical modeling of Thermal Response Tests in Energy Piles
Franco, A.; Toledo, M.; Moffat, R.; Herrera, P. A.
2013-05-01
Nowadays, thermal response tests (TRT) are used as the main tools for the evaluation of low enthalpy geothermal systems such as heat exchangers. The results of TRT are used for estimating thermal conductivity and thermal resistance values of those systems. We present results of synthetic TRT simulations that model the behavior observed in an experimental energy pile system, which was installed at the new building of the Faculty of Engineering of Universidad de Chile. Moreover, we also present a parametric study to identify the most influent parameters in the performance of this type of tests. The modeling was developed using the finite element software COMSOL Multiphysics, which allows the incorporation of flow and heat transport processes. The modeled system consists on a concrete pile with 1 m diameter and 28 m deep, which contains a 28 mm diameter PEX pipe arranged in a closed circuit. Three configurations were analyzed: a U pipe, a triple U and a helicoid shape implemented at the experimental site. All simulations were run considering transient response in a three-dimensional domain. The simulation results provided the temperature distribution on the pile for a set of different geometry and physical properties of the materials. These results were compared with analytical solutions which are commonly used to interpret TRT data. This analysis demonstrated that there are several parameters that affect the system response in a synthetic TRT. For example, the diameter of the simulated pile affects the estimated effective thermal conductivity of the system. Moreover, the simulation results show that the estimated thermal conductivity for a 1 m diameter pile did not stabilize even after 100 hours since the beginning of the test, when it reached a value 30% below value used to set up the material properties in the simulation. Furthermore, we observed different behaviors depending on the thermal properties of concrete and soil. According to the simulations, the thermal
Influence of axial load on the lateral pile groups response in cohesionless and cohesive soil
Institute of Scientific and Technical Information of China (English)
Jasim M. ABBASA[1; Zamri CHIK[2; Mohd Raihan TAHA[2
2015-01-01
The lateral response of single and group of piles under simultaneous vertical and lateral loads has been analyzed using a 3D finite element approach. The response in this assessment considered lateral pile displacement and lateral soil resistance and corresponding p-y curve. As a result, modified p-y curves for lateral single pile response were improved with respect to the influence of increasing axial load intensities. The improved plots can be used for lateral loaded pile design and to produce the group action design p-multiplier curves and equations. The effect of load combination on the lateral pile group response was performed on three pile group configurations （i.e., 2 × 1, 2 × 2 and 3 × 2） with four pile spacings （i.e., s = 2D, 4D, 6D and 8D）. As a result, design curves were developed and applied on the actual case studies and similar expected cases for assessment of pile group behavior using improved p-multiplier. A design equation was derived from predicted design curves to be used in the evaluation of the lateral pile group action taking into account the effect of axial load intensities. It was found that the group interaction effect led to reduced lateral resistance for the pile in the group relative to that for the single pile in case of pure lateral load. While, in case of simultaneous combined loads, large axial load intensities （i.e., more than 6H, where H is lateral load values） will have an increase inp-multiplier by approximately 100% and will consequently contribute to greater group piles capacities.
INDOT/Purdue Pile Driving Method for Estimation of Axial Capacity
Zaheer, Mir A; Salgado, Rodrigo; Prezzi, Monica; Han, Fei
2015-01-01
This presentation discusses the new pile driving analysis method. Models for both base and shaft dynamic resistances that account for soil nonlinearity, both radiation and hysteric damping, and rate effects on soil strength will be presented. The analysis is validated through well-documented field tests on instrumented piles. The predictions from the proposed formulas will be compared with the results from static load tests and dynamic load test. Driven pile capacity results from two projects...
Comparison between static and dynamic pile load test in marsh soil
Erbežnik, Miha
2012-01-01
Construction of buildings has increased markedly over the past decades in areas of poor foundation soil, which led to increased need for construction of piles. In accordance with European standards, quality control of installed piles has to be done. Quickest and simplest test is low strain intergity test, but in cases of complex structures a static or dynamic pile load test must be made. Execution of tests and analysis of the results are very different, but the final results are the same. In...
Institute of Scientific and Technical Information of China (English)
石北啸; 杨燕伟; 谢荣星; 吴辛
2013-01-01
Considering the annular drainage section of concrete-cored sand-gravel pile composite foundation, both radial and vertical flows within the sand-gravel pile and soil construction disturbance, using the initial condition of load beared by soil and pile, the governing equations of consolidation problem of composite foundation with concrete-cored sand-gravel piles are derived; the analytical solution to the governing equations is obtained;the overall average degree of consolidation defined in terms of stress and deformation is given;and the influences of several factors, such as the permeability coefficient of sand-gravel piles, diameter ratio of concrete-cored pile and sand-gravel pile on the consolidation of composite foundation are analyzed. The results show that the solution of overall average degree of consolidation in terms of stress is not equal to that in terms of deformation;the greater the permeability coefficient of sand-gravel piles is, the faster the consolidation rate is;under the condition of a certain diameter size of sand-gravel piles, with diameter of concrete-cored pile increasing, the consolidation rate is increased at first and then decreased. Finally, a comparison between the present solution and two previous solutions is made. Compared with two previous solutions,the present solution considers the influences of annular drainage section and load beared by soil and pile together, the overall average degree of consolidation calculated by the present solution is between two previous solutions.%考虑了混凝土芯砂石桩复合地基中砂石桩的环形排水通道、砂石桩体内的径、竖向渗流和土体施工扰动，并采用桩土共同分担荷载的初始条件，得到了混凝土芯砂石桩复合地基固结问题的控制方程，给出了控制方程的解答；并分别给出了复合地基按应力和按变形定义的总平均固结度，分析了砂石桩桩体渗透系数、芯桩与砂石桩直径比对地基固结性状
能量桩桩-土接触面力学特性室内试验研究%Laboratory Experimental on Interface Mechanical Properties of Energy Pile-soil
Institute of Scientific and Technical Information of China (English)
李春红; 孔纲强; 车平; 孙学谨
2016-01-01
Energy pile, which is based on ground source heat pump technology, is gradually applied on engineering. However, there is relative little studies focused on the bearing behaviors of energy pile influence by energy exchange, especially little researches focused on the energy pile-soil interface friction. Based on laboratory experiments and three typical Nanjing soil samples, the energy pile -soil interface friction behaviors influenced by temperature and water content were focused and analyzed. The test results show that temperature effect of energy pile-clay interface friction is larger than that of energy pile-silt and energy pile-sand interface friction with the same water content. The behaviors of energy pile-clay interface friction influenced by water content is larger than those of energy pile-silt and energy pile-sand interface friction. The research results can be provided a frame of reference to the design and calculation of the bearing capacity of energy piles.%基于地源热泵桩埋管形式的能量桩技术逐渐在工程中得到推广应用；但是，针对冷热交换影响下能量桩的承载力特性研究相对较少，尤其针对能量桩-土接触面的摩擦力学特性研究相对更少。基于室内土工试验和南京地区3种具有代表性的典型土样，针对能量桩-黏土、能量桩-粉土和能量桩-砂土接触面的摩擦力学特性进行室内土工直剪试验；着重分析不同桩体温度和桩周土体含水率等情况下能量桩-土接触面力学特性。研究结果表明，相同含水率情况下，能量桩-黏土接触面的温度效应最明显、能量桩-粉土接触面的温度效应次之、能量桩-砂土接触面的温度效应最小；相同桩体温度情况下，桩周土体含水率的大小对能量桩-黏土接触面力学特性的影响最明显、对能量桩-砂土接触面力学特性的影响最小；相关研究成果为能量桩承载力的设计与计算提供一定的参考依据。
Comparative Model Tests of SDP and CFA Pile Groups in Non-Cohesive Soil
Krasiński, Adam; Kusio, Tomasz
2015-02-01
The research topic relates to the subject of deep foundations supported on continuous flight auger (CFA) piles and screw displacement piles (SDP). The authors have decided to conduct model tests of foundations supported on the group of piles mentioned above and also the tests of the same piles working as a single. The tests are ongoing in Geotechnical Laboratory of Gdaňsk University of Technology. The description of test procedure, interpretation and analysis of the preliminary testing series results are presented in the paper.
Design of anti-slide piles for slope stabilization in Wanzhou city, Three Gorges Area, China
Zhou, Chunmei; van Westen, Cees
2013-04-01
This study is related to the design of anti-slide piles for several landslides in Wanzhou city located in the Three Gorges area. Due to the construction of the Three Gorges Reservoir the hydro-geological conditions in this area have deteriorated significantly, leading to larger instability problems. China has invested a lot of money in slope stabilization measures for the treatment of landslides in the Three Gorges area. One of the methods for the stabilization of large landslides is the design of anti-sliding piles. This paper focuses on extensive slope stability analysis and modeling of the mechanical behavior of the landslide masses, and the parameters required for designing the number, size and dimensions of reinforced concrete stabilization piles. The study focuses on determining the rock parameters, anchor depth, and the pile and soil interaction coefficient. The study aims to provide guidelines for anti-slide pile stabilization works for landslides in the Wanzhou area. The research work contains a number of aspects. First a study is carried out on the distribution of pressures expected on the piles, using two different methods that take into account the expected pore water pressure and seismic acceleration. For the Ercengyan landslide , the Limit Equilibrium Method and Strength Reduction Method of FEM are compared through the results of the landslide pressure distributions on the piles and stress fields in the piles. The second component is the study of the required anchor depth of antislide piles, which is carried out using a statistical analysis with data from 20 landslides that have been controlled with anti-sliding piles. The rock characteristics of the anchor locations were obtained using laboratory tests, and a classification of rock mass quality is made for the anchors of antislide piles. The relationship between the critical anchor height and the angle of the landslide slip surface is determined. Two different methods are presented for the length
Institute of Scientific and Technical Information of China (English)
邹新军; 杨眉; 赵明华; 杨小礼
2008-01-01
To discuss the soil arching effect on the load transferring model and sharing ratios by the piles and inter-pile subsoil in the bidirectionally reinforced composite ground, the forming mechanism, mechanical behavior and its effect factors were discussed in detail. Then, the unified strength theory was introduced to set up the elastoplastic equilibrium differential equation of the subsoil under the limit equilibrium state. And from the equation, the solutions were derived with the corresponding formulas presented to calculate the earth pressure over and beneath the horizontal reinforced cushion or pillow, the stress of inter-pile subsoil and the pile-soil stress ratio. Based on the obtained solutions and measured data from an engineering project, the influence rules by the soil property parameters (i.e., the cohesion c and internal friction angle φ) and pile spacing on the pile-soil stress ratio n were discussed respectively. The results show that to improve the load sharing ratio by the piles, the more effective means for filling materials with a larger value of φ is to increase the ratio of pile cap size to spacing, while to reduce the pile spacing properly and increase the value of cohesion c is advisable for those filling materials with a smaller value of φ.
Multifield coupling model and its applications for pile foundation in permafrost
Institute of Scientific and Technical Information of China (English)
WU; Yaping; ZHU; Yuanlin; GUO; Chunxiang; SU; Qiang; MA; We
2005-01-01
Importing the interface element which links the frozen soil base with concrete piles and considering the couplings of stress field, temperature field and moisture field, this paper establishes the nonlinear visco-elastic plastic finite element model of pile-soil. For a practical bridge structure the stress field and displacement field of single pile in freezing process are calculated.This paper emphatically studies the process of the tangential frost heave stress field, freezing stress field and displacement field varying with time, and ulteriorly studies time variation process of single pile carrying capacity in freezing process.
Optimal Pile Arrangement for Minimizing Excess Pore Water Pressure Build-Up
DEFF Research Database (Denmark)
Barari, Amin; Saadati, Meysam; Ibsen, Lars Bo
2013-01-01
Numerical analysis of pile group in a liquefiable soil was considered to investigate the influence of pile spacing on excess pore pressure distribution and liquefaction potential. The analysis is conducted using a two-dimensional plain strain finite difference program considering a nonlinear...... constitutive model for sandy soil, strength and stiffness reduction, and pile-soil interaction. The Mohr-Coulomb constitutive model coupled with Byrne pore pressure build-up model have been employed in the analysis. Numerical analysis results show that pile groups have significant influence on the dynamic...... response of sandy soil as they reduce the amount of excess pore pressure development during seismic shaking and may even prevent liquefaction....
Reduction Rate of Dragload and Downdrag of Piles by Taper Angles
Institute of Scientific and Technical Information of China (English)
孔纲强; 周立朵; 彭怀风; 顾红伟
2016-01-01
Taper angle is one of the effective methods to reduce the dragload and downdrag of piles under the surcharge load. The model tests on the tapered pile and uniform cross-section pile embedded in sand were carried out under the surcharge load. The values of dragload and downdrag of piles versus the surcharge loads were meas-ured. Based on the concentric cylinder shearing theory, a simplified theoretical model for calculating the dragload and downdrag of tapered piles with small taper angles under the surcharge load was proposed considering the angle effect. The correctness of the developed theoretical model was validated through comparing with the model test results obtained in this study and previous literature. Then the parametric studies of the taper angle, surcharge, strength and modulus of soil were discussed. It is shown that the tapered pile with the taper angle of 3° can reduce approximately 65% of the maximum dragload value and 30% of the downdrag value compared with a uniform cross-section pile. The value of downdrag can be decreased by approximately 50% compared with a uniform cross-section pile in the same average pile diameter.
Control of floor heaves with steel pile in gob-side entry retaining
Institute of Scientific and Technical Information of China (English)
Xu Ying; Chen Jin; Bai Jianbiao
2016-01-01
A new approach named as steel pile method is innovatively proposed in this study to control severe floor heaves in gob-side entry retaining. It is required that the steel piles be installed in the floor corners with a certain interval before the influence of the dynamic pressure induced by current panel extraction. Using numerical simulation and theoretical analysis, this study investigated the interaction between the steel piles and the floor rocks during the service life of the steel piles, and revealed the mechanism of the steel piles in controlling floor heaves. The effect of the steel pile parameters on the control of floor heaves was presented and elaborated. It is found that the effectiveness of the steel piles in controlling floor heaves can be enhanced with greater installed dip angle, longer length and smaller interval of the steel piles. Compared with traditional methods, e.g., using floor anchor bolts and floor restoration, the advantages using steel pile were successfully defined in terms of controlling effect and economic benefits. It is hoped that the proposed method can contribute to the development of gob-side entry retaining technique.
Estimate of the residual loads obtained in the end of piles driven in porous soils
Directory of Open Access Journals (Sweden)
David de Carvalho
2005-02-01
Full Text Available In the geotechnical engineering the study about the quantification of the residual loads in the pile end, after the end of the first loading of the load test attempt, highlighted some works on its interpretation in the curve load versus pile settlement. The construction of a mathematical model to study such a phenomenon is based on the Relations of Cambefort Precast-concrete piles were specially built for this research. They have special elements installed all along their length where the residual loads inlaid in the pile end region could be measured by means of deformation strain gauges.
Magnetic Bearing Consumes Low Power
Studer, P. A.
1982-01-01
Energy-efficient linear magnetic bearing maintains a precise small separation between its moving and stationary parts. Originally designed for cryogenic compressors on spacecraft, proposed magnetic bearing offers an alternative to roller or gas bearing in linear motion system. Linear noncontacting bearing operates in environments where lubricants cannot be used.
Tribology of alternative bearings.
Fisher, John; Jin, Zhongmin; Tipper, Joanne; Stone, Martin; Ingham, Eileen
2006-12-01
The tribological performance and biological activity of the wear debris produced has been compared for highly cross-linked polyethylene, ceramic-on-ceramic, metal-on-metal, and modified metal bearings in a series of in vitro studies from a single laboratory. The functional lifetime demand of young and active patients is 10-fold greater than the estimated functional lifetime of traditional polyethylene. There is considerable interest in using larger diameter heads in these high demand patients. Highly cross-linked polyethylene show a four-fold reduction in functional biological activity. Ceramic-on-ceramic bearings have the lowest wear rates and least reactive wear debris. The functional biological activity is 20-fold lower than with highly cross-linked polyethylene. Hence, ceramic-on-ceramic bearings address the tribological lifetime demand of highly active patients. Metal-on-metal bearings have substantially lower wear rates than highly cross-linked polyethylene and wear decreases with head diameter. Bedding in wear is also lower with reduced radial clearance. Differential hardness ceramic-on-metal bearings and the application of ceramic-like coatings reduce metal wear and ion levels.
Effects of pile driving by high frequency hammers on adjacent piles%高频振动打桩对邻近基桩影响分析
Institute of Scientific and Technical Information of China (English)
杨祁; 陈福全; 刘建鹏
2014-01-01
The stress waves caused by pile driving will disturb surrounding buildings and affect the normal serv-ice of underground facilities. The technique of high frequency hydraulic vibratory pile driving has been widely ap-plied to solve this problem. The effects of pile driving on adjacent piles are investigated by numerical analysis meth-od using software package ABAQUS. A 1. 0 mm radius rigid tube is modeled along the axis of penetration. At the beginning of the analysis this tube is in frictionless contact with the surrounding soils. During pile penetration the pile slides over the tube and the soil separates from the tube to establish the contact between the penetrating pile and the surrounding soil. The driven pile and the tube are simulated with rigid body,and the soils with Mohr-Cou-lomb model. Then the three-dimensional model of high frequency hydraulic vibratory pile driving is established. Tn this way,a numerical analysis for the effects of the full process of pile driving by using high frequency hammers on the adjacent piles are performed. The numerical simulation analysis of pile penetration process shows that the stress concentration occurred around the pile tip. The effect on existing piles is smaller with the larger distance from the driven pile. The analysis also shows the high frequency vibratory pile driving has small effect on adjacent piles.%为解决在城市里桩基施工引起的环境问题，国外开发并推广应用了高频液压振动锤技术。通过有限元软件Abaqus对高频振动打桩对邻近桩基影响进行模拟。模拟中桩轴线处建立半径为1mm的管，管土接触设为光滑，打桩时土管分离，桩随着管向下贯入，形成打入桩和周围土体之间的接触关系。打入桩和圆管采用刚体模拟，土体单元则采用摩尔库伦本构模型，建立高频打桩的三维模型，很好的实现高频液压振动沉桩整个过程的数值分析。贯入模拟过程表明打入桩桩尖深度
Radial Halbach Magnetic Bearings
Eichenberg, Dennis J.; Gallo, Christopher A.; Thompson, William K.
2009-01-01
Radial Halbach magnetic bearings have been investigated as part of an effort to develop increasingly reliable noncontact bearings for future high-speed rotary machines that may be used in such applications as aircraft, industrial, and land-vehicle power systems and in some medical and scientific instrumentation systems. Radial Halbach magnetic bearings are based on the same principle as that of axial Halbach magnetic bearings, differing in geometry as the names of these two types of bearings suggest. Both radial and axial Halbach magnetic bearings are passive in the sense that unlike most other magnetic bearings that have been developed in recent years, they effect stable magnetic levitation without need for complex active control. Axial Halbach magnetic bearings were described in Axial Halbach Magnetic Bearings (LEW-18066-1), NASA Tech Briefs, Vol. 32, No. 7 (July 2008), page 85. In the remainder of this article, the description of the principle of operation from the cited prior article is recapitulated and updated to incorporate the present radial geometry. In simplest terms, the basic principle of levitation in an axial or radial Halbach magnetic bearing is that of the repulsive electromagnetic force between (1) a moving permanent magnet and (2) an electric current induced in a stationary electrical conductor by the motion of the magnetic field. An axial or radial Halbach bearing includes multiple permanent magnets arranged in a Halbach array ("Halbach array" is defined below) in a rotor and multiple conductors in the form of wire coils in a stator, all arranged so the rotary motion produces an axial or radial repulsion that is sufficient to levitate the rotor. A basic Halbach array (see Figure 1) consists of a row of permanent magnets, each oriented so that its magnetic field is at a right angle to that of the adjacent magnet, and the right-angle turns are sequenced so as to maximize the magnitude of the magnetic flux density on one side of the row while
Vranish, John M. (Inventor)
2010-01-01
A partial gear bearing including an upper half, comprising peak partial teeth, and a lower, or bottom, half, comprising valley partial teeth. The upper half also has an integrated roller section between each of the peak partial teeth with a radius equal to the gear pitch radius of the radially outwardly extending peak partial teeth. Conversely, the lower half has an integrated roller section between each of the valley half teeth with a radius also equal to the gear pitch radius of the peak partial teeth. The valley partial teeth extend radially inwardly from its roller section. The peak and valley partial teeth are exactly out of phase with each other, as are the roller sections of the upper and lower halves. Essentially, the end roller bearing of the typical gear bearing has been integrated into the normal gear tooth pattern.
Pile-Up Discrimination Algorithms for the HOLMES Experiment
Ferri, E.; Alpert, B.; Bennett, D.; Faverzani, M.; Fowler, J.; Giachero, A.; Hays-Wehle, J.; Maino, M.; Nucciotti, A.; Puiu, A.; Ullom, J.
2016-07-01
The HOLMES experiment is a new large-scale experiment for the electron neutrino mass determination by means of the electron capture decay of ^{163}Ho. In such an experiment, random coincidence events are one of the main sources of background which impair the ability to identify the effect of a non-vanishing neutrino mass. In order to resolve these spurious events, detectors characterized by a fast response are needed as well as pile-up recognition algorithms. For that reason, we have developed a code for testing the discrimination efficiency of various algorithms in recognizing pile up events in dependence of the time separation between two pulses. The tests are performed on simulated realistic TES signals and noise. Indeed, the pulse profile is obtained by solving the two coupled differential equations which describe the response of the TES according to the Irwin-Hilton model. To these pulses, a noise waveform which takes into account all the noise sources regularly present in a real TES is added. The amplitude of the generated pulses is distributed as the ^{163}Ho calorimetric spectrum. Furthermore, the rise time of these pulses has been chosen taking into account the constraints given by both the bandwidth of the microwave multiplexing read out with a flux ramp demodulation and the bandwidth of the ADC boards currently available for ROACH2. Among the different rejection techniques evaluated, the Wiener Filter technique, a digital filter to gain time resolution, has shown an excellent pile-up rejection efficiency. The obtained time resolution closely matches the baseline specifications of the HOLMES experiment. We report here a description of our simulation code and a comparison of the different rejection techniques.
OPAL Cold Neutron Guide In-Pile Replacement
Energy Technology Data Exchange (ETDEWEB)
Rownes, T.; Eltobaji, A.; Bell, M.; Klose, F. [Nuclear Operations, Baitain (Australia)
2013-07-01
The 20 MW{sub th} OPAL research reactor has five neutron beam assemblies. These provide cold and thermal neutrons to various neutron guides and associated neutron beam instruments. In 2010 a project was initiated to install a new cold neutron guide, CG2, in one of the assemblies. This installation would allow up to four new neutron beam instruments to be built, significantly expanding the reactor's capabilities. The project concluded in December 2012 with the successful installation of CG2. Each neutron beam assembly has an in-pile plug, a primary shutter and a front cover. Together these constitute the neutron guide's in-pile components, with a total mass of over 12 tonnes. The CG2 installation required the complete replacement of the existing components. This replacement was scheduled to coincide with OPAL's first major shutdown. With a budget of $2.3 million and an expected dose of 50 man.mSv, the CG2 installation was a large and complex task. Work during the shutdown involved over 40 ANSTO personnel and radiation fields approached 1 Sv/h in some areas. Despite this, the installation team received a collective dose of only 10 man.mSv, and the project was completed to budget and within schedule. This paper will outline the details of the project, focusing on lessons learned and recommended practices. Each OPAL in-pile plug has a design life of 10 years at full power operation, and similar replacements will be performed regularly as the reactor ages. It is hoped that this information will be useful for other research reactors planning large capital engineering projects.
Institute of Scientific and Technical Information of China (English)
林战峰; 乐伟国
2007-01-01
@@ 一、故事内容 A little bear has a magic stick.It can make his wishes come true. One day,the little bear is walking in the forest.He sees a bird.It is flying in the sky.It has two beautiful wings."I want two beautiful wings.I wish I can fly like a bird,"he says to the magic stick.Two beautiful wings come out from his back and he can fly like a bird now.He is very happy.
Vranish, John M. (Inventor)
2009-01-01
A gearing system using modular gear bearing components. Each component is composed of a core, one or more modules attached to the core and two or more fastening modules rigidly attaching the modules to the core. The modules, which are attached to the core, may consist of gears, rollers or gear bearing components. The core orientation affects the orientation of the modules attached to the core. This is achieved via the keying arrangement of the core and the component modules that attach to the core. Such an arrangement will also facilitate the phase tuning of gear modules with respect to the core and other gear modules attached to the core.
Method and apparatus for analog pulse pile-up rejection
De Geronimo, Gianluigi
2013-12-31
A method and apparatus for pulse pile-up rejection are disclosed. The apparatus comprises a delay value application constituent configured to receive a threshold-crossing time value, and provide an adjustable value according to a delay value and the threshold-crossing time value; and a comparison constituent configured to receive a peak-occurrence time value and the adjustable value, compare the peak-occurrence time value with the adjustable value, indicate pulse acceptance if the peak-occurrence time value is less than or equal to the adjustable value, and indicate pulse rejection if the peak-occurrence time value is greater than the adjustable value.
Dislocation Pile-Ups, Material Strength Levels, and Thermal Activation
Armstrong, Ronald W.
2016-12-01
A review dedicated to James C.M. Li is given of dislocation pile-ups and their connection to the Hall-Petch dependence of polycrystalline strength and fracture mechanics properties on an inverse square root of grain size basis, with such grain size dependence now very importantly extended to nanopolycrystalline material behaviors. An analogous H-P dependence is described for the inverse activation volume parameter obtained from the strain rate (and thermal) dependencies contained in the model dislocation thermal activation-strain rate analysis, also relating to pioneering contributions of Li to the topic of thermally activated dislocation dynamics.
2012-06-04
... piles' strength. Vibratory and impact pile driving may result in anticipated hydroacoustic levels... range-finder) in order to determine if animals have entered into the exclusion zone or Level...
Okajima, Kenji; Imai, Junichi; Tanaka, Tadatsugu; Iida, Toshiaki
Damage to piles in the liquefied ground is frequently reported. Buckling by the excess vertical load could be one of the causes of the pile damage, as well as the lateral flow of the ground and the lateral load at the pile head. The buckling mechanism is described as a complicated interaction between the pile deformation by the vertical load and the earth pressure change cased by the pile deformation. In this study, series of static buckling model tests of a pile were carried out in dried sand ground with various thickness of the layer. Finite element analysis was applied to the test results to verify the effectiveness of the elasto-plastic finite element analysis combining the implicit-explicit mixed type dynamic relaxation method with the return mapping method to the pile buckling problems. The test results and the analysis indicated the possibility that the buckling load of a pile decreases greatly where the thickness of the layer increases.
Study on the squeezing effect of open-ended pipe piles
Institute of Scientific and Technical Information of China (English)
Yan-er Lu; Jun-jie Zheng; Jian-hua Yin
2009-01-01
During the installation of a pipe pile, the soil around the pile will be squeezed out. This paper deals with this squeezing effect of open-ended pipe piles using the cylindrical cavity expansion theory. The characteristics of soil with different tension and compression modnli and dilation are involved by applying the elastic theory with different moduli and logarithmic strain. The closed-form solutions of the radius of the plastic region, the displacement of the boundary between the plastic region and the elastic region and the expansion pressure on the external surface of the pipe piles are obtained. When obtaining these solutions, the soil ping in the open-ended pipe pile is considered by employing an incremental filling ratio to quantify the degree of soil plugging. Moreover, the effects of the ratio of tension and compression moduli, angle of dilation and incremental filling ratio on the radius of the plastic region and the expansion pressure on the external surface of the pipe pile are investigated. The parametric analyses show that it is necessary and important to consider the difference between the tension modulus and compression modulus, dilation angle and incremental filling ratio for studying the squeezing effect of open-ended pipe pile installation. It is concluded that the analytical solutions presented in this paper are suitable for studying the squeezing effect of open-ended pipe piles.
2012-03-14
... Specified Activities; Pile Placement for ORPC Maine's Cobscook Bay Tidal Energy Pilot Project AGENCY...\\) during pile placement. While the foundation frame will take up a limited amount of space on the seafloor...-finder as well as a digital SLR camera with telephoto lens and video capability) in order to determine...
Behaviour of Single Pile in Reinforced Slope Subjected to Inclined Load
Directory of Open Access Journals (Sweden)
Dr. A. I. Dhatrak
2016-09-01
Full Text Available Deep foundations, including driven piles, are used to support vertical loads of structures and lateral forces. Typical structures subjected to lateral loads include bridge abutments, transmission tower, sand offshore platforms. Traffic, wind, wave, and seismic forces are common types of lateral loads subjected to pile foundations. The present work is focused on understanding the lateral load capacity of vertical piles located near crest of the slope and subjected to the lateral and inclined loads. The experimental investigation was carried out to study the effect of reinforcing an earth slope on the inclined loading behavior of a single vertical pile located near the slope. Layers of geogrid were used to reinforce a sandy slope of 1V:2H. The parametric studies were performed by varying the length of pile(L, angle of inclination of load (θ, number of geogrid reinforcement (Nr and crest distance. It was observed that the lateral load capacity of pile depends upon these parameters. The lateral load capacity of pile increases with increase in inclination of load, length of pile(L, number of geogrid reinforcement (Nr and crest distance.
Effect of relative pile’s stiffness on lateral pile response under loading of large eccentricity
DEFF Research Database (Denmark)
Zania, Varvara; Hededal, Ole; Klinkvort, R.T.
2015-01-01
of the relative pile’s stiffness, when it is subjected to lateral load of large eccentricity. Employing centrifuge experiments, a hollow steel pile well instrumented with strain gauge pairs has been subjected to lateral load. The bending moment distribution of the model pile embedded in uniform, dense, dry sand...
A performance case study of energy pile foundation at Rosborg Gymnasium (Denmark)
DEFF Research Database (Denmark)
Pagola, Maria Alberdi; Jensen, Rasmus Lund; Poulsen, Søren Erbs
2016-01-01
The Rosborg Gymnasium building in Vejle (Denmark) is partially founded on 200 foundation pile heat exchangers (energy piles). The thermo-active foundation has supplemented the heating and free cooling needs of the building since 2011 (4,000 m2 living area). Operational data from the ground source...
Response of stiff piles in sand to long-term cyclic lateral loading
DEFF Research Database (Denmark)
Bakmar, Christian LeBlanc; Houlsby, Guy T.; Byrne, Byron W.
2010-01-01
and loading ranges were realistic. A complete non-dimensional framework for stiff piles in sand is presented and applied to interpret the test results. The accumulated rotation was found to be dependent on relative density and was strongly affected by the characteristics of the applied cyclic load. The pile...
Small-Scale Cyclic Tests on Nonslender Piles Situated in Sand
DEFF Research Database (Denmark)
Sørensen, Søren Peder Hyldal; Ibsen, Lars Bo
In the period from August 2011 till October 2011 a series of small-scale tests on pile foundations has been conducted at Aalborg University. In all the tests, the piles have been exposed to cyclic loading consisting of 20-25 load cycles and all the tests have been conducted in a pressure tank...
Small-Scale Quasi-Static Tests on Non-Slender Piles Situated in Sand
DEFF Research Database (Denmark)
Sørensen, Søren Peder Hyldal; Ibsen, Lars Bo
In the period from February 2009 till March 2011 a series of small-scale tests on pile foundations has been conducted at Aalborg University. In all the tests the piles have been exposed to quasi-static loading and all the tests have been conducted in a pressure tank. The objective of the tests has...
Pile-up corrections in laser-driven pulsed x-ray sources
Hernández, Guillermo
2016-01-01
A formalism for treating the pile-up produced in laser-driven pulsed x-ray sources has been developed. It allows the direct use of x-ray spectroscopy without artificially decreasing the number of counts in the detector. The influence of the pile-up on the overestimation of temperature parameters is shown up.
In-situ grouting of uranium-mill-tailings piles: an assessment
Energy Technology Data Exchange (ETDEWEB)
Tamura, T.; Boegly, W.J. Jr.
1983-05-01
Passage in 1978 of the Uranium Mill Tailings Radiation Control Act (UMTRCA) initiated a program of remedial action for 22 existing mill tailings piles generated in the period 1940 to 1970 as part of the nation's defense and nuclear power programs. The presence of these piles poses potential health and environmental contamination concerns. Possible remedial actions proposed include multilayer covers over the piles to reduce water infiltration, reduce radon gas releases, and reduce airborne transport of tailings fines. In addition, suggested remedial actions include (1) the use of liners to prevent groundwater contamination by leachates from the piles and (2) chemical stabilization of the tailings to retain the radioactive and nonradioactive sources of contamination. Lining of the piles would normally be applicable only to piles that are to be moved from their present location such that the liner could be placed between the tailings and the groundwater. However, by using civil engineering techniques developed for grouting rocks and soils for strength and water control, it may be possible to produce an in situ liner for piles that are not to be relocated. The Department of Energy (DOE) Uranium Mill Tailings Remedial Action Project Office requested that ORNL assess the potential application of grouting as a remedial action. This report examines the types of grouts, the equipment available, and the costs, and assesses the possibility of applying grouting technology as a remedial action alternative for uranium mill tailings piles.
Time scale of scour around a pile in combined waves and current
DEFF Research Database (Denmark)
Petersen, Thor Ugelvig; Sumer, B. Mutlu; Fredsøe, Jørgen
The time scale of the scour process around a circular vertical pile is studied in combined waves and current. A series of tests were carried out in a flume with pile diameters 40 mm and 75 mm, in both steady current, waves and combined waves and current. In the combined wave and current flow regime...
In-Situ Test and Numerical Analysis of Bore Pressure on Sheet-Pile Groin
Institute of Scientific and Technical Information of China (English)
XU Chang-jie; CAI Yuan-qiang; XUAN Wei-li; CHEN Hai-jun; SONG Yang
2006-01-01
An in-situ test of bore pressure on a sheet-pile groin is carried out to investigate the characteristics of the bore pressure of tide in the Qian-tang River. The histories of bore pressure and the rule of the distribution of bore pressure on the sheet-pile groin are obtained through the test, which shows that the bore pressure on the sheet-pile groin are varies with time and space. The peak value of bore pressure on sheet-pile groin at different heights occurs almost at the same time. The vertical distribution of bore pressure on the sheet-pile groin is linear above the still water level. The maximum bore pressure on the sheet-pile groin occurs at the still water level. Then a numerical method is also used to further study the characteristics of bore pressure. The standard κ-ε turbulence model and VOF (volume of fluid) method for surface tracking are used to simulate the bore against the sheet-pile groin. The numerical results show flow fields, the position of free surface and time history and spatial distribution of bore pressure on the sheet-pile groin. The numerical and test results show good agreement.
Effect of Welding Methods on the Structure and Mechanical Properties of Welded Joints of Screw Piles
Golikov, N. I.; Sidorov, M. M.; Stepanova, K. V.
2016-11-01
Mechanical properties and characteristics of the structure of welded joints of screw piles are studied. It is shown that cast tips from steel 25L do not meet the performance specifications for operation in the Northern climatic zone. Quality welded joints of screw piles can be obtained by semiautomatic welding in an environment of CO2 with Sv-08G2S welding wire.
Influences of Family Management and Spousal Perceptions on Stressor Pile-up.
Imig, David R.; Imig, Gail L.
1986-01-01
Describes the contingent influence of family managerial efficacy and related spousal perceptions on the relationship between stressor pile-up and family cohesion. Perceived loss of managerial efficacy in conjunction with discrepant spousal perceptions of such change substantially increased the family's vulnerability to stressor pile-up. A…
Kastelein, R.A.; Hoek, L.; Gransier, R.; Jong, C.A.F. de
2013-01-01
Pile driving is presently the most common method used to attach wind turbines to the sea bed. To assess the impact of pile driving sounds on harbor porpoises, it is important to know at what distance these sounds can be detected. Using a psychophysical technique, a male porpoise’s hearing thresholds
An efficient model for prediction of underwater noise due to pile driving at large ranges
Nijhof, M.J.J.; Binnerts, B.; Jong, C.A.F. de; Ainslie, M.A.
2014-01-01
Modelling the sound levels in the water column due to pile driving operations nearby and out to large distances from the pile is crucial in assessing the likely impact on marine life. Standard numerical techniques for modelling the sound radiation from mechanical structures such as the finite elemen
2012-07-24
... Specified Activities; Pile Driving for Honolulu Seawater Air Conditioning Project AGENCY: National Marine... Harassment Authorization (IHA) to take marine mammals, by harassment, incidental to pile driving offshore... for the take, by Level B harassment, of small numbers of 17 marine mammal species incidental to...
40 CFR 411.30 - Applicability; description of the materials storage piles runoff subcategory.
2010-07-01
... runoff of rainfall which derives from the storage of materials including raw materials, intermediate... materials storage piles runoff subcategory. 411.30 Section 411.30 Protection of Environment ENVIRONMENTAL... Materials Storage Piles Runoff Subcategory § 411.30 Applicability; description of the materials...
Formation and remediation of drill-cutting piles in the North Sea
Eames, I.; de Leeuw, B.; Conniff, P.
2002-01-01
Drill cuttings generated during borehole excavation have been routinely dumped into the North Sea, where they now represent a significant environmental hazard owing to contamination by oil residues and heavy metals. In-situ measurements of the structure of drill-cutting piles are relatively poor owing to the difficulty of accessing water depths of 60-180 m. In an effort to understand how drill-cutting piles are formed, laboratory-scale experiments were undertaken to investigate how granular material, poured into a tank of water, spreads along a rigid horizontal wall. The laboratory study examined how the pile radius varied as a function of particle size (90 µm to 3 mm), source height above the wall, particle volume flux and volume deposited. A model of drill-cutting pile formation is developed by combining descriptions of descent as a plume and propagation along the wall as a gravity current. Satisfactory agreement is obtained between experimental measurements and model predictions, which are applied to interpret available field data. The implications of this research for drill-cutting pile remediation are discussed. The model indicates that when natural bioremediation has broken down a 5-cm layer of a drill-cutting pile, only 50-100% of the pile area (or 75-95% of the pile volume) requires treatment.
Institute of Scientific and Technical Information of China (English)
LIU YUNYUN
2010-01-01
@@ Chinese director Wang Quan'an won the Silver Bear Prize at the 60th Berlin International Film Festival that lasted during February 11 to 21 tor the best screenplay for his movie Apart Together.The film also opened the festival.
Hybrid superconductor magnet bearings
Chu, Wei-Kan
1995-01-01
Hybrid superconductor magnet bearings (HSMB's) utilize high temperature superconductors (HTS's) together with permanent magnets to form a frictionless interface between relatively rotating parts. They are low mass, stable, and do not incur expenditure of energy during normal operation. There is no direct physical contact between rotor and stator, and hence there is no wear and tear. However, just as any other applications of HTS's, it requires a very cold temperature to function. Whereas this might be perceived as a disadvantage on earth, it is of no great concern in space or on the moon. To astronomers, the moon is an excellent site for an observatory, but the cold and dusty vacuum environment on the moon precludes the use of mechanical bearings on the telescope mounts. Furthermore, drive mechanisms with very fine steps, and hence bearings with extremely low friction are needed to track a star from the moon, because the moon rotates very slowly. All aspects considered, the HSMB is about the only candidate that fits in naturally. Here, we present a design for one such bearing, capable of supporting a telescope that weighs about 3 lbs on Earth.
In-pile and out-of-pile testing of a molybdenum-uranium dioxide cermet fueled themionic diode
Diianni, D. C.
1972-01-01
The behavior of Mo-UO2 cermet fuel in a diode for thermionic reactor application was studied. The diode had a Mo-0.5 Ti emitter and niobium collector. Output power ranged from 1.4 to 2.8 W/cm squared at emitter and collector temperatures of 1500 deg and 540 C. Thermionic performance was stable within the limits of the instrumentation sensitivity. Through 1000 hours of in-pile operation the emitter was dimensionally stable. However, some fission gases (15 percent) leaked through an inner clad imperfection that occurred during fuel fabrication.
Magnetic bearings for cryogenic turbomachines
Iannello, Victor; Sixsmith, Herbert
1991-01-01
Magnetic bearings offer a number of advantages over gas bearings for the support of rotors in cryogenic turboexpanders and compressors. Their performance is relatively independent of the temperature or pressure of the process gas for a large range of conditions. Active magnetic bearing systems that use capacitive sensors have been developed for high speed compressors for use in cryogenic refrigerators. Here, the development of a magnetic bearing system for a miniature ultra high speed compressor is discussed. The magnetic bearing has demonstrated stability at rotational speeds exceeding 250,000 rpm. This paper describes the important features of the magnetic bearing and presents test results demonstrating its performance characteristics.
A numerical study of the effect of groundwater on spiral coil energy piles
Kim, Seong-Kyun; Lee, Youngmin
2016-04-01
Numerical simulations were performed to investigate effects of groundwater on the thermal performance of the geothermal energy pile. Energy piles, a part of the closed-loop geothermal heat pump systems, are used to exchange heat between the ground and the heat pump. A heat-carrying fluid circulates the ground through a coiled pipe installed in pile foundations. The COMSOL multiphysics was used as a simulator, which can solve the equations for the temperature and fluid flow in the pipe system, as well as those in the ground. Water temperatures at the pipe outlet after 90-day injection of warm water (30℃) were calculated from following cases: (1) one energy pile installed at the fully saturated medium with regional groundwater flow (100 m/year), (2) one energy pile installed at the partially saturated medium (water table is located 13.5 m below the ground surface) with regional groundwater flow (1,000 m/year), (3) one energy pile installed at the fully saturated medium with no regional groundwater flow, (4) one energy pile installed at the partially saturated medium with no regional groundwater flow, (5), (6), (7) four energy piles (distance between energy piles is 10, 5 ,2 m) installed at the fully saturated medium with regional groundwater flow, and (8), (9), (10) four energy piles installed at the partially saturated medium with regional groundwater flow. The outlet temperature of each case is (1) 28.11℃, (2) 28.84℃, (3) 28.97℃, (4) 29.09℃, (5) 28.19℃ (mean value), (6) 28.24℃ (mean value), (7) 28.33℃ (mean value), (8) 28.84℃ (mean value), (9) 28.90℃ (mean value), and (10) 29.10℃ (mean value), respectively. The thermal power ratio of the energy pile of each case (standard case is case 1) is (1) 0%, (2) -46%, (3) -39%, (4) -52%, (5) -4%, (6) -7%, (7) -12%, (8) -39%, (9) -42%, and (10) -53%, respectively. Numerical results show that the performance of the energy pile installed at the fully saturated medium with regional groundwater flow (case 1
Free vibration of semi-rigid connected Reddy–Bickford piles embedded in elastic soil
Indian Academy of Sciences (India)
Yusuf Yesilce; Hikmet H Catal
2008-12-01
The literature on free vibration analysis of Bernoulli–Euler and timoshenko piles embedded in elastic soil is plenty, but that of Reddy–Bickford piles partially embedded in elastic soil with/without axial force effect is fewer. The soil that the pile partially embedded in is idealized by Winkler model and is assumed to be two-layered. The pile part above the soil is called the ﬁrst region and the parts embedded in the soil are called the second and the third region, respectively. It is assumed that the behaviour of the material is linear-elastic, that axial force along the pile length to be constant and the upper end of the pile that is semi-rigid supported against rotation is modelled by an elastic spring. The governing differential equations of motion of the rectangular pile in free vibration are derived using Hamilton’s principle and Winkler hypothesis. The terms are found directly from the solutions of the differential equations that describe the deformations of the cross-section according to the high-order theory. The models have six degrees of freedom at the two ends, one transverse displacement and two rotations, and the end forces are a shear force and two end moments. Natural frequencies of the pile are calculated using transfer matrix and the secant method for non-trivial solution of linear homogeneous system of equations obtained due to values of axial forces acting on the pile, total and embedded lengths of the pile, the linear-elastic rotational restraining stiffness at the upper end of the pile and to the boundary conditions of the pile. Two different boundary conditions are considered in the study. For the ﬁrst boundary condition, the pile’s end at the ﬁrst region is semi-rigid connected and not restricted for horizontal displacement and the end at the third region is free and for the second boundary condition, the pile’s end at the ﬁrst region is semi-rigid connected and restricted for horizontal displacement and the end at the
Experimental study on settlement of model piles in frozen soil under dynamic loading
Institute of Scientific and Technical Information of China (English)
张建明; 朱元林; 张家懿
1999-01-01
Test results show that the settlement process of model piles is mainly the rheological process of frozen soil under shear loading. The settlement rate of model piles increases with increasing temperature of frozen soil, decreasing roughness of pile surface and increasing rigidity of pile foundation. As the water content of frozen soil reaches its saturation value, the settlement rate is the least. When the level of loading is higher, the settlement rate under dynamic loading is less than that under static loading. With the level of loading lowering, the effect between dynamic and static loading on the settlement rate becomes close gradually. Under the present test conditions, the settlement rate of model piles is independent of the frequency of dynamic loads.
Dynamic soil-pile-interaction effects on eigenfrequency and damping of slender structures
DEFF Research Database (Denmark)
Zania, Varvara
2014-01-01
of the dynamic soil-pile-interaction on the natural vibration characteristics of the flexibly supported structure. For this purpose a two-step iterative procedure has been developed based on two analytical solutions. The frequency dependent dynamic stiffness and damping coefficients are taken into consideration...... after a rigorous solution of horizontal soil – pile vibration, while the modified SSI eigenperiod and damping are calculated accounting for the cross coupling stiffness and damping terms of the soil – pile system. Disregarding the off diagonal terms is considered inappropriate since it results to non......-conservative overestimation of the eigenfrequency and underestimation of damping especially for small slenderness ratios and high flexibility factor of the soil – pile system (short, rigid piles). The observed trends become even more prominent as the height of the slender structure increases. The effect of the monopile...
Performance of pile-up mitigation techniques for jets in pp collisions with the ATLAS detector
Energy Technology Data Exchange (ETDEWEB)
Testa, M., E-mail: marianna.testa@lnf.infn.it
2016-07-11
The large rate of multiple simultaneous proton–proton interactions, or pile-up, generated by the Large Hadron Collider in Run 1 required the development of many new techniques to mitigate the adverse effects of these conditions. The methods employed to correct for the impact of pile-up on jet energy, shapes and multiplicity with the ATLAS detector are presented here. They include energy correction techniques based on estimates of the average pile-up energy density and jet-to-vertex association techniques. Extensions of these methods to reduce the impact of pile-up on jet shapes use both subtraction and grooming procedures. Prospects for pile-up suppression at the HL-LHC are also shown.
Performance of pile-up mitigation techniques for jets in pp collisions with the ATLAS detector
Testa, Marianna; The ATLAS collaboration
2015-01-01
The large rate of multiple simultaneous proton-proton interactions, or pile-up, generated by the Large Hadron Collider in Run I required the development of many new techniques to mitigate the adverse effects of these conditions. This presentation shows the methods employed to correct for the impact of pile-up on jet energy, jet shapes, and even spurious additional jets. Energy correction techniques that incorporate sophisticated estimates of the average pile-up energy density and tracking information are described in detail. Jet-to-vertex association techniques are also presented. We also describe the extension of these techniques to ameliorate the effect of pile-up on jet shapes using both subtraction and grooming procedures. Prospects for pile-up suppression at the HL-LHC will be also discussed.
Performance of pile-up mitigation techniques for jets in pp collisions with the ATLAS detector
Testa, Marianna; The ATLAS collaboration
2015-01-01
The large rate of multiple simultaneous proton-proton interactions, or pile-up, generated by the Large Hadron Collider in Run I required the development of many new techniques to mitigate the adverse effects of these conditions. The methods employed to correct for the impact of pile-up on jet energy, shapes and multiplicity with the ATLAS detector are here presented. They include energy correction techniques based on estimates of the average pile-up energy density and jet-to-vertex association techniques. Extensions of these methods to reduce the impact of pile-up on jet shapes use both subtraction and grooming procedures. Prospects for pile-up suppression at the HL-LHC are also shown.
Performance of pile-up mitigation techniques for jets in pp collisions with the ATLAS detector
Testa, M.
2016-07-01
The large rate of multiple simultaneous proton-proton interactions, or pile-up, generated by the Large Hadron Collider in Run 1 required the development of many new techniques to mitigate the adverse effects of these conditions. The methods employed to correct for the impact of pile-up on jet energy, shapes and multiplicity with the ATLAS detector are presented here. They include energy correction techniques based on estimates of the average pile-up energy density and jet-to-vertex association techniques. Extensions of these methods to reduce the impact of pile-up on jet shapes use both subtraction and grooming procedures. Prospects for pile-up suppression at the HL-LHC are also shown.
Catastrophic model for stability analysis of high pile-column bridge pier
Institute of Scientific and Technical Information of China (English)
无
2007-01-01
According to the engineering features of higher pile-column bridge pier in mountainous area, a clamped beam mechanical model was set up by synthetically analyzing the higher pile-column bridge pier buckling mechanism. Based on the catastrophe theory, the cusp catastrophe model of higher pile-column bridge pier was established by the determination of its potential function and bifurcation set equation, the necessary instability conditions of high pile-column bridge pier were deduced, and the determination method for column-buckling and lateral displacement of high pile-column bridge pier was derived. The comparison between the experimental and calculated results show that the calculated curves agree with testing curves and the method is reasonable and effective.
Coupled 3D discrete-continuum numerical modeling of pile penetration in sand
Institute of Scientific and Technical Information of China (English)
Jian ZHOU; Qi-wei JIAN; Jiao ZHANG; Jian-jun GUO
2012-01-01
A coupled discrete-continuum simulation incorporating a 3D aspect and non-circular particles was performed to analyze soil-pile interactions during pile penetration in sand.A self-developed non-circular particle numerical simulation program was used which considered sand near the pile as interacted particles using a discrete element method; the sand away from the pile was simulated as a continuous medium exhibiting linear elastic behaviors.The domain analyzed was divided into two zones.Contact forces at the interface between the two zones were obtained from a discrete zone and applied to the continuum boundaries as nodal forces,while the interface velocities were obtained from the continuum zone and applied to the discrete boundaries.We show that the coupled discrete-continuum simulation can give a microscopic description of the pile penetration process without losing the discrete nature of the zone concerned,and may significantly improve computational efticiency.
Comparative Analysis of Seismic Response Characteristics of Pile-Soil-Structure Interaction System
Institute of Scientific and Technical Information of China (English)
无
2006-01-01
The study on the earthquake-resistant performance of a pile-soil-structure interaction system is a relatively complicated and primarily important issue in civil engineering practice. In this paper, a computational model and computation procedures for pile-supported structures, which can duly consider the pile-soil interaction effect, are established by the finite element method. Numerical implementation is made in the time domain. A simplified approximation for the seismic response analysis of pile-soil-structure systems is briefly presented. Then a comparative study is performed for an engineering example with numerical results computed respectively by the finite element method and the simplified method. Through comparative analysis, it is shown that the results obtained by the simplified method well agree with those achieved by the finite element method. The numerical results and findings will offer instructive guidelines for earthquake-resistant analysis and design of pile-supported structures.
Evaluation of Candidate In-Pile Thermal Conductivity Techniques
Energy Technology Data Exchange (ETDEWEB)
B. Fox; H. Ban; J. Daw; K. Condie; D. Knudson; J. Rempe
2009-05-01
Thermophysical properties of materials must be known for proper design, test, and application of new fuels and structural properties in nuclear reactors. In the case of nuclear fuels during irradiation, the physical structure and chemical composition change as a function of time and position within the rod. Typically, thermal conductivity changes, as well as other thermophysical properties being evaluated during irradiation in a materials and test reactor, are measured out-of-pile in “hot-cells.” Repeatedly removing samples from a test reactor to make out-of-pile measurements is expensive, has the potential to disturb phenomena of interest, and only provide understanding of the sample's end state at the time each measurement is made. There are also limited thermophysical property data for advanced fuels. Such data are needed for the development of next generation reactors and advanced fuels for existing nuclear plants. Having the capacity to effectively and quickly characterize fuels and material properties during irradiation has the potential to improve the fidelity of nuclear fuel data and reduce irradiation testing costs.
UNMANNED AERIAL VEHICLE USE FOR WOOD CHIPS PILE VOLUME ESTIMATION
Directory of Open Access Journals (Sweden)
M. Mokroš
2016-06-01
Full Text Available The rapid development of unmanned aerial vehicles is a challenge for applied research. Many technologies are developed and then researcher are looking up for their application in different sectors. Therefore, we decided to verify the use of the unmanned aerial vehicle for wood chips pile monitoring. We compared the use of GNSS device and unmanned aerial vehicle for volume estimation of four wood chips piles. We used DJI Phantom 3 Professional with the built-in camera and GNSS device (geoexplorer 6000. We used Agisoft photoscan for processing photos and ArcGIS for processing points. Volumes calculated from pictures were not statistically significantly different from amounts calculated from GNSS data and high correlation between them was found (p = 0.9993. We conclude that the use of unmanned aerial vehicle instead of the GNSS device does not lead to significantly different results. Tthe data collection consumed from almost 12 to 20 times less time with the use of UAV. Additionally, UAV provides documentation trough orthomosaic.
In-Pile Thermal Conductivity Measurement Method for Nuclear Fuels
Energy Technology Data Exchange (ETDEWEB)
Joy L. Rempe; Brandon Fox; Heng Ban; Joshua E. Daw; Darrell L. Knudson; Keith G. Condie
2009-08-01
Thermophysical properties of advanced nuclear fuels and materials during irradiation must be known prior to their use in existing, advanced, or next generation reactors. Thermal conductivity is one of the most important properties for predicting fuel and material performance. A joint Utah State University (USU) / Idaho National Laboratory (INL) project, which is being conducted with assistance from the Institute for Energy Technology at the Norway Halden Reactor Project, is investigating in-pile fuel thermal conductivity measurement methods. This paper focuses on one of these methods – a multiple thermocouple method. This two-thermocouple method uses a surrogate fuel rod with Joule heating to simulate volumetric heat generation to gain insights about in-pile detection of thermal conductivity. Preliminary results indicated that this method can measure thermal conductivity over a specific temperature range. This paper reports the thermal conductivity values obtained by this technique and compares these values with thermal property data obtained from standard thermal property measurement techniques available at INL’s High Test Temperature Laboratory. Experimental results and material properties data are also compared to finite element analysis results.
Unmanned Aerial Vehicle Use for Wood Chips Pile Volume Estimation
Mokroš, M.; Tabačák, M.; Lieskovský, M.; Fabrika, M.
2016-06-01
The rapid development of unmanned aerial vehicles is a challenge for applied research. Many technologies are developed and then researcher are looking up for their application in different sectors. Therefore, we decided to verify the use of the unmanned aerial vehicle for wood chips pile monitoring. We compared the use of GNSS device and unmanned aerial vehicle for volume estimation of four wood chips piles. We used DJI Phantom 3 Professional with the built-in camera and GNSS device (geoexplorer 6000). We used Agisoft photoscan for processing photos and ArcGIS for processing points. Volumes calculated from pictures were not statistically significantly different from amounts calculated from GNSS data and high correlation between them was found (p = 0.9993). We conclude that the use of unmanned aerial vehicle instead of the GNSS device does not lead to significantly different results. Tthe data collection consumed from almost 12 to 20 times less time with the use of UAV. Additionally, UAV provides documentation trough orthomosaic.
Institute of Scientific and Technical Information of China (English)
毛正君; 陶志怀; 魏荣誉; 韩小明
2016-01-01
由于垃圾填埋场地具有性质复杂、厚度变化大、强度较低、压缩系数大、腐蚀性和污染性强等特点，在服务期内和封顶后都会产生大幅度的沉降。结合西安某垃圾填埋场实例，探讨了孔内深层超强夯桩（ SDDC桩）结合灌注桩在垃圾填埋场地基处理中的施工技术。实践证明，采用该技术在满足地基承载力的基础上，降低了工程造价、提高了工程质量，取得了良好的社会经济效益。%Due to some characteristics of the landfill such as the complex properties, big change in thickness, low strength, large compressibility, strong corrosion resistance and polluting, it will generate settlement by a large margin during the service period and after capping. This paper cites an example of a landfill site in Xi’ an, probing into the foundation treatment construction technology of landfill by super down hole dynamic compaction pile combined with bored pile. It has been proved in practice that using this technique can meet the bearing capacity of foundation soil, at the same time, it also can reduce the engineering cost, improve the engineering quality and achieve good social and economic benefits.
Institute of Scientific and Technical Information of China (English)
李亭; 温发明
2011-01-01
Research purposes: Some special engineering measures must be taken for satisfying requirements of operation safety when the railway passes through the area with unfavorable geological condition. This paper discusses the problem of reinforcing the railway foundation in mining area, compares the reinforcing program of high - pressure jet grouting pile with the reinforcing program of cement fly - ash gravel pile ( CFG pile) , and analyzes the advantages of CFG pile of reinforcing the railway subgrade in mining subsidence area for providing the reference to the similar works. Research conclusions: Taking a special railway track in the coal mine as an example, on the basis of stability analysis, the limit height of soft soil embankment is obtained. In the case that the heightening requirements of the embankment under mining subsidence can not be met, the CFG pile can be used for reinforcing the subgrade. And based on the theoretical checking - calculation of the bearing capability of the composite subgrade, the comparative analysis of the settlement with finite - element method and the comparison with the reinforcing program of high - pressure jet grouting pile, the feasibility and safety of CFG pile for reinforcing soft foundation are tested and verified. The result shows the CFG pile is better for reinforcing soft foundation than the high - pressure jet grouting pile under the same conditions. According to the relative codes, the reinforcement design requirement with CFG pile is presented. The wide application CFG pile has the positive effect on making use of the wastes, saving the cost and protecting environment.%铁路穿越不良地基时,要采取一些特殊的工程措施加以解决,以满足铁路运行要求.本文针对采动区铁路地基加固问题,对采用高压旋喷桩和水泥粉煤灰碎石桩(CFG桩)加固方案进行对比,分析CFG桩加固采动区铁路路基的优越性,为类似地基加固提供借鉴.研究结论:以某煤矿铁路专用
Magnetic bearings grow more attractive
1993-10-01
Advances in materials and electronics have enabled designers to devise simpler, smaller magnetic bearings. As a result, costs have dropped, widening the applications for these very-low-friction devices. Avcon (Advanced Controls Technology) has patented a permanent-magnet bias actively controlled bearing. Here high-energy rare earth permanent-magnet materials supply the basic bearing load levitation, while servo-driven electromagnets generate stabilization and centering forces for motion contol. Previous heavy-duty magnetic bearings used electromagnets entirely for suspension and control, which led to large bearings and control systems with higher power requirements. Avcon has developed several types of permanent-magnet bias bearings. The simplest is the radial repulsion bearing. Avcon's homopolar permanent-magnet bias active bearing is the most versatile of the company's designs.
Centrifugally decoupling touchdown bearings
Post, Richard F
2014-06-24
Centrifugally decoupling mechanical bearing systems provide thin tensioned metallic ribbons contained in a support structure. This assembly rotates around a stationary shaft being centered at low speeds by the action of the metal ribbons. Tension springs are connected on one end to the ribbons and on the other end to the support structure. The ribbons pass through slots in the inner ring of the support structure. The spring preloading thus insures contact (or near-contact) between the ribbons and the shaft at rotation speeds below the transition speed. Above this speed, however, the centrifugal force on the ribbons produces a tensile force on them that exceeds the spring tensile force so that the ribbons curve outward, effectively decoupling them from mechanical contact with the shaft. They still remain, however, in position to act as a touchdown bearing in case of abnormally high transverse accelerations.
1993-01-01
The u.s. government bulks large in the nation's financial markets. The huge volume of government-issued and -sponsored debt affects the pricing and volume ofprivate debt and, consequently, resource allocation between competing alternatives. What is often not fully appreciated is the substantial influence the federal government wields overresource allocation through its provisionofcreditandrisk-bearing services to the private economy. Because peopleand firms generally seekto avoid risk, atsomeprice they are willing to pay another party to assume the risk they would otherwise face. Insurance companies are a class of private-sector firms one commonly thinks of as providing these services. As the federal government has expanded its presence in the U.S. economy during this century, it has increasingly developed programs aimed at bearing risks that the private sector either would not take on at any price, or would take on but atapricethoughtto besogreatthatmostpotentialbeneficiarieswouldnotpurchase the coverage. To...
Pinkus, O.; Etsion, I.
1976-01-01
A new concept of a journal bearing is developed which prevents side leakage of the lubricant, thus eliminating the need for sealing and collecting this leakage. The cooling of the bearing is accomplished by the prevailing circumferential flow. An analysis is performed and solutions are given for the bearing geometries and inlet pressures required to achieve the above purpose.
桩帽垫层对锤击沉桩的影响数值分析%Numerical Analysis of Influence of Pile Cap Cushion on Driving Pile
Institute of Scientific and Technical Information of China (English)
王继成; 倪占东; 柳爱; 周向阳
2011-01-01
Elastic pile cap cushion and hardwood cushion are simulated by ABAQUS, the famous finite element software, in order to study the influence of pile cap cushion on driving pile in this paper. It is discovered that elastic cushion can reduce the stress of the driven pile evidently during the driving process,but the capacity of reducing the pile stress of hardwood is poor. The penetration can be increased greatly with suitable thickness and stiffness of the cushion. There is certain relationship among hammering energy, thickness and stiffness of the cushion. A certain stiffness corresponds to an optimal thickness, the optimal thickness and the range of optimal thickness is enlarged with the increase of stiffness. Much better effectiveness of driving pile with thicker and suitable pile cap cushion can be obtained.%为了研究桩帽垫层对锤击沉桩效果的影响,采用有限元软件ABAQUS对弹性桩帽垫层和硬木垫层进行了模拟,发现弹性垫层在锤击过程中可显著降低桩身应力,而硬木板降低桩身应力的能力有限.采用合适厚度、刚度的垫层时,可显著增加贯人度.锤击能、垫层厚度、垫层刚度之间存在一定关系.对于某一垫层刚度,存在一最优垫层厚度,垫层刚度增加,最优垫层厚度范围也增加了.厚度较厚、刚度稍大的垫层能取得较好的沉桩效果.
Directory of Open Access Journals (Sweden)
Mohammad A. Assareh
2008-01-01
Full Text Available The operation for offshore oil has become an important issue in the recent years. Offshore platforms are some of those structures which are built to withstand environmental and accidental loads during oil exploitation operation. One of the most usual types of these platforms is the Jacket Type Offshore Platform (JTOP which can be divided into three important parts, which are Deck, Jacket and piles. In order to increase the safety, particular attention should be paid to earthquake excitations which are directly applied to the piles of these structures. Nonlinearity in piles and buckling of the struts are important issues which have to be considered by the designers of offshore platforms. The case of nonlinearity in piles and failure capture in these members has not effectively been covered by researchers. Incremental Dynamic Analysis (IDA is a powerful tool to assess the capacity of a structure upon seismic loads. In this paper incremental dynamic analysis has been implemented on single piles considering soil-pile interactions and free field site response. The use of nonlinear materials and lateral load resisting elements in the incremental dynamic analysis done in this paper has made it possible to get promising insights for incorporation of appropriate limit states and applications of performance based engineering. Special Engineering Demand Parameters (EDP and Intensity Measures (IM have been introduced for the single pile dynamic analysis in jacket type offshore platforms.
Crack initiation ahead of piled-up of dislocations emitted from a mode Ⅱ blunt crack
Institute of Scientific and Technical Information of China (English)
无
2002-01-01
In situ tensile tests in a transmission electron microscope (TEM) show that dislocations emitted from a mode II crack tip will form a inverse piled-up group after equilibrium or a double piled-up group when they meet a obstruction, e.g., grain boundary or second phase. A microcrack can initiates in front of the piled-up group of dislocations. Micromechanics analysis shows that dislocations emitted from a mode II blunt crack tip can form a inverse piled-up or double piled-up group, depending upon the applied stress intensity factor KIIa, latticefriction stress and the distance of the obstruction from the crack tip L. The maximum normal stress in front of the double piled-up group which is located at the direction of €? Increases with the increase in the stress intensity KIIa and the obstruction site L, and the decrease in the friction stress . When it increases to equate the cohesive strength, a microcrack will initiate in front of the piled-up group.
Refreezing of cast-in-place piles under various engineering conditions
Institute of Scientific and Technical Information of China (English)
Lei Guo; QiHao Yu; XiaoNing Li; XinBin Wang; YongYu Yue
2015-01-01
In the construction of the Qinghai-Tibet Power Transmission Line (QTPTL), cast-in-place piles (CIPPs) are widely applied in areas with unfavorable geological conditions. The thermal regime around piles in permafrost regions greatly affects the stability of the towers as well as the operation of the QTPTL. The casting of piles will markedly affect the thermal regime of the surrounding permafrost because of the casting temperature and the hydration heat of cement. Based on the typical geological and engineering conditions along the QTPTL, thermal disturbance of a CIPP to surrounding permafrost under different casting seasons, pile depths, and casting temperatures were simulated. The results show that the casting season (summer versus winter) can influence the refreezing process of CIPPs, within the first 6 m of pile depth. Sixty days after being cast, CIPPs greater than 6 m in depth can be frozen regardless of which season they were cast, and the foundation could be refrozen after a cold season. Comparing the refreezing characteristics of CIPPs cast in different seasons also showed that, without considering the ground surface conditions, warm seasons are more suitable for casting piles. With the increase of pile depth, the thermal effect of a CIPP on the surrounding soil mainly expands vertically, while the lateral heat disturbance changes little. Deeper, longer CIPPs have better stability. The casting temperature clearly affects the thermal disturbance, and the radius of the melting circle increases with rising casting temperature. The optimal casting temperature is between 2 °C and 9 °C.
Analytical method of load-transfer of single pile under expansive soil swelling
Institute of Scientific and Technical Information of China (English)
FAN Zhen-hui; WANG Yong-he; XIAO Hong-bin; ZHANG Chun-shun
2007-01-01
The elastic differential equations of load-transfer of single pile either with applied loads on pile-top or only under the soil swelling were established, respectively, based on the theory of pile-soil interaction and the shear-deformation method. The derivation of analytic solution to load-transfer for single pile in expansive soil could hereby be obtained by means of superposition principle under expansive soils swelling. The comparison of two engineering examples was made to prove the credibility of the suggested method. The analyzed results show that this analytic solution can achieve high precision with few parameters required, indicating its' simplicity and practicability in engineering application. The employed method can contribute to determining the greatest tension along pile shaft resulting from expansive soils swelling and provide reliable bases for engineering design. The method can be employed to obtain various distributive curves of axial force, settlements and skin friction along the pile shaft with the changes of active depth, vertical movements of the surface and loads of pile-top.
Simulating pile load-settlement behavior from CPT data using intelligent computing
Alkroosh, I.; Nikraz, H.
2011-09-01
Analysis of pile load-settlement behavior is a complex problem due to the participation of many factors involved. This paper presents a new procedure based on artificial neural networks (ANNs) for simulating the load-settlement behavior of pile foundations embedded in sand and mixed soils (subjected to axial loads). Three ANN models have been developed, a model for bored piles and two other models for driven piles (a model for each of concrete and steel piles). The data used for development of the ANN models is collected from the literature and comprise a series of in-situ piles load tests as well as cone penetration test (CPT) results. The data of each model is divided into two subsets: Training set for model calibration and independent validation set for model verification. Predictions from the ANN models are compared with the results of experimental data and with predictions of number of currently adopted load-transfer methods. Statistical analysis is used to verify the performance of the models. The results indicate that the ANN model performs very well and able to predict the pile load-settlement behaviour accurately.
Effects of Cohesion On the Dynamic Response of A Conical Bead Pile
Palchoudhuri, Paroma; Lehman, Susan; Jacobs, D. T.
2014-03-01
We investigate the critical behavior of a 3D conical bead pile built from uniform 3 mm steel spheres. The pile is initially built on a circular base and is subsequently slowly driven through the addition of one bead at a time to the apex of the pile. We investigate the dynamic response of the pile by recording avalanches from the pile over the course of tens of thousands of bead drops, and determining the resulting distribution of avalanche size. In previous work, we have shown that dropping the beads onto the pile from a greater height causes the distribution to deviate from a simple power law due to a stark reduction in number of the largest avalanches. By placing the pile in a uniform magnetic field, we are now observing changes in the avalanche size distribution due to cohesion. When there is cohesion between beads, we find an increase in probability for the largest avalanches and a strong decrease in the probability of medium-sized avalanches. We also observe an increase in the time between avalanches as the cohesion of the system increases. Preliminary results on the effect of simultaneously increasing cohesion, which tends to make large avalanches more probable, and increasing drop height, which tends to make large avalanches less probable, will also be presented.
Vranish, John M. (Inventor)
2009-01-01
A gear bearing having a first gear and a second gear, each having a plurality of teeth. Each gear operates on two non-parallel surfaces of the opposing gear teeth to perform both gear and bearing functions simultaneously. The gears are moving at substantially the same speed at their contact points. The gears may be roller gear bearings or phase-shifted gear bearings, and may be arranged in a planet/sun system or used as a transmission. One preferred embodiment discloses and describes an anti-backlash feature to counter ''dead zones'' in the gear bearing movement.
Catalyse électro-microbienne dans les piles à combustible
Dumas, Claire
2007-01-01
Les piles à combustible microbiennes (PACM) sont des systèmes qui assurent la conversion directe de matières organiques en énergie électrique en utilisant des biofilms bactériens comme catalyseur des réactions électrochimiques. Cette étude vise à améliorer la compréhension des mécanismes de transfert électronique entre les bactéries adhérées et les électrodes, ainsi qu'à optimiser la production électrique des PACMs en explorant et caractérisant différents matériaux d'électrodes. Les expérienc...
Full Wave Solution for Hydrodynamic Behaviors of Pile Breakwater
Institute of Scientific and Technical Information of China (English)
ZHU Da-tong
2013-01-01
Rayleigh expansion is used to study the water-wave interaction with a row of pile breakwater in finite water depth.Evanescent waves,the wave energy dissipated on the fluid resistance and the thickness of the breakwater are totally included in the model.The formulae of wave reflection and transmission coefficients are obtained.The accuracy of the present model is verified by a comparison with existing results.It is found that the predicted wave reflection and transmission coefficients for the zero order are all highly consistent with the experimental data (Hagiwara,1984;Isaacson et al.,1998) and plane wave solutions (Zhu,2011).The losses of the wave energy for the fluid passing through slits play an important role,which removes the phenomena of enhanced wave transmission.
Prehistoric Packrats Piled Up Clues to Climate Change
Cole, Kenneth L.
2008-01-01
Scientists from the U.S. Geological Survey and Northern Arizona University studying climate change in the Southwestern United States are getting a helping hand?or would that be paw??from prehistoric packrats. By hoarding parts of animals and plants, including seeds and leaves, in garbage piles or ?middens,? these bushy-tailed rodents preserved crucial ecological and environmental information about the past. From these middens, scientists are able to reconstruct plant communities and natural systems from as long ago as 50,000 years. The contents of middens allow scientists to understand how ecosystems responded to rapid, large-scale climate changes of the past. The insights gained from midden research could offer clues to future changes driven by rapid climate shifts.
Elbetti, C; Giani, I; Novelli, E; Fucini, C; Martellucci, Jacopo
2015-12-01
The purpose of the paper is to compare Goligher Classification with the Single Pile Hemorrhoid Classification (SPHC) to show the possible bias and limits of Goligher's use and the possible advantage with the employment of the new classification. SPHC considers the number of pathological piles(N), the characteristics of each internal pile and the characteristics of each external pile, reporting the presence of a fibrous inelastic redundant pile(F), the presence of the subversion of dentate line or the congestion of the external pile(E) and the presence of not tolerated skin tags(S). From September 2010 to December 2012, 197 consecutive patients were analysed according to both classifications. Considering pathological piles, I and II Goligher patients showed a complete agreement between pathological pile and grade, III Goligher patients had 80.5 % of pathological piles of III grade while IV Goligher patients had only 44.3 % of IV grade pathological piles (p < 0.001). Regarding the distribution of the other anatomical variables: F, E, S described in SPHC, the results showed that F was present in 18.3 % while ES was present in 46.2 %. Goligher's Classification has showed to be an inadequate tool to overview surgical outcome or to compare surgical procedure, particularly for high grades, while SPHC showed to be a feasible instrument both to describe and to compare patients affected by hemorrhoid disease.
Laboratory testing of cyclic laterally loaded pile in cohesionless soil. [MONOPILES
Energy Technology Data Exchange (ETDEWEB)
Hansen, Mette; Kirk Wolf, T. [COWI, Kgs. Lyngby (Denmark); Lange Rasmussen, K. [Niras, Aalborg (Denmark); Ravn Roesen, H.; Ibsen, L.B. [Aalborg Univ.. Dept. of Civil Engineering, Aalborg (Denmark)
2013-06-15
Offshore wind turbines are placed in a rough environment, subjected to variable lateral loads, mostly from wind and waves. A long-term lateral loading may create rotation (tilt) of the pile by change in the soil-pile system which is critical in the serviceability limit state. The accumulated rotation due to long-term lateral loading is therefore a current issue of interest as today's design guidances have little knowledge in this area. The cost of large-scale testing is extensive which make small-scale testing desirable as a tool for describing the behaviour of a soil-pile system subjected to lateral load. In this paper small-scale testing of a pile subjected to cyclic, lateral loading is treated in order to investigate the effect of cyclic loading. The test pile has a diameter of 100 mm and is 600 mm high, making the slenderness ratio 6, which resembles the ratio of offshore wind turbines today. The test pile is placed in saturated dense sand. A monotonic test is conducted to define the ultimate lateral capacity. Afterwards a cyclic test is conducted to investigate the accumulation of rotation when the pile is subjected to cyclic lateral load. Force and displacement during both tests are recorded to determine the deformation of the pile. Comparing the responses of the monotonic and the cyclic test, the cyclic test shows a stiffer response. During the cyclic test, the rotation of the pile accumulates with decreasing rotation increments. However, no stabilised situation occurs. The measured data is compared to theories on degradation, agreeing that the accumulated rotation as an estimate can be express by both a logarithmic and exponential expression. Comparing the results from the cyclic test with results from other recent small-scale tests shows agreement in the accumulation of rotation with decreasing rotation increments with no stabilising situation. (Author)
Institute of Scientific and Technical Information of China (English)
Wengang Zhang; Anthony T.C. Goh
2016-01-01
Piles are long, slender structural elements used to transfer the loads from the superstructure through weak strata onto stiffer soils or rocks. For driven piles, the impact of the piling hammer induces compression and tension stresses in the piles. Hence, an important design consideration is to check that the strength of the pile is sufficient to resist the stresses caused by the impact of the pile hammer. Due to its complexity, pile drivability lacks a precise analytical solution with regard to the phenomena involved. In situations where measured data or numerical hypothetical results are available, neural networks stand out in mapping the nonlinear interactions and relationships between the system’s predictors and dependent responses. In addition, unlike most computational tools, no mathematical relationship assumption between the dependent and independent variables has to be made. Nevertheless, neural networks have been criticized for their long trial-and-error training process since the optimal configu-ration is not known a priori. This paper investigates the use of a fairly simple nonparametric regression algorithm known as multivariate adaptive regression splines (MARS), as an alternative to neural net-works, to approximate the relationship between the inputs and dependent response, and to mathe-matically interpret the relationship between the various parameters. In this paper, the Back propagation neural network (BPNN) and MARS models are developed for assessing pile drivability in relation to the prediction of the Maximum compressive stresses (MCS), Maximum tensile stresses (MTS), and Blow per foot (BPF). A database of more than four thousand piles is utilized for model development and comparative performance between BPNN and MARS predictions.
Institute of Scientific and Technical Information of China (English)
张睿
2016-01-01
Through the design analysis of a bridge project pile,the cast-in-place piles with expanded branches and bells by 3-way extruding arms in the basic principle and design method are described in this paper and their vertical bearing capacity are calculated.The economic advantage and vertical bear-ing capacity advantage are verified,and the problems of its application in bridge engineering design are presented.%通过对某桥梁项目灌注桩的设计分析，阐述了三岔双向挤扩灌注桩的基本原理和设计方法，分别计算了三岔双向挤扩灌注桩与普通钻孔灌注桩的单桩竖向承载力，验证了三岔双向挤扩灌注桩在经济性及桩基竖向承载力等方面的优势，并提出了该桩基在桥梁工程设计中需要注意的问题。
Damping Bearings In High-Speed Turbomachines
Von Pragenau, George L.
1994-01-01
Paper presents comparison of damping bearings with traditional ball, roller, and hydrostatic bearings in high-speed cryogenic turbopumps. Concept of damping bearings described in "Damping Seals and Bearings for a Turbomachine" (MFS-28345).
Krebs, Justin; Jacobs, Fred; Conway, Robert; Popper, Arthur N; Moese, Mark; Rollino, John; Racca, Roberto; Martin, Bruce; MacGillivray, Alexander
2016-01-01
The potential impacts of pile-driving noise on Hudson River sturgeon during construction of the New NY Bridge were predicted. Abundance data for shortnose and Atlantic sturgeon derived from fisheries sampling were combined with data about the spatial extent of pile-driving noise. This approach was used to calculate the number of sturgeon that could occur within sound level isopleths exceeding peak and cumulative noise criteria used by the National Marine Fisheries Service to determine the incidental take of sturgeon. The number of sturgeon subject to the potential onset of physiological effects during pile driving was predicted to be 35-41 fish for each species.
Treating jet correlations in high pile-up at hadron colliders
Directory of Open Access Journals (Sweden)
F. Hautmann
2016-03-01
Full Text Available Experiments in the high-luminosity runs at the Large Hadron Collider face the challenges of very large pile-up. Primary techniques to deal with this are based on precise vertex and track reconstruction. Outside tracker acceptances, however, lie regions of interest for many aspects of the LHC physics program. We explore complementary approaches to pile-up treatment and propose a data-driven jet-mixing method which can be used outside tracker acceptances without depending on Monte Carlo generators. The method can be applied to treat correlation observables and take into account, besides the jet transverse momentum pedestal, effects of hard jets from pile-up.
Evaluation of the Load-Displacement Relationships for Large-Diameter Piles in Sand
DEFF Research Database (Denmark)
Sørensen, Søren Peder Hyldal; Brodbaek, K. T.; Moller, M.;
2009-01-01
was developed for slender piles with diameters much less than 6 m and it is based on a limited number of tests. The aim of the present work is to extend the p-y curve method to large-diameter non-slender piles by considering the effects of the pile diameter on the soil response. The main focus is the initial...... stiffness of the p-y curves. The evaluation is based on experimental work as well as three-dimensional numerical analyses in the commercial programme FLAC3D....
Backfilling of a Scour Hole around a Pile in Waves and Current
DEFF Research Database (Denmark)
Sumer, B. Mutlu; Petersen, Thor Ugelvig; Locatelli, Luca;
2013-01-01
This paper presents the results of an experimental investigation of the backfilling of scour holes around circular piles. Scour holes around a pile are generated either by a current or a wave. Subsequently, the flow climate is changed from current to wave, combined waves and current, or wave...... around the pile for the same wave (or combined waves and current) climate. The time scale of backfilling has been determined as a function of three parameters, namely, (1) the Keulegan-Carpenter number of the initial wave or current (which generates the initial scour hole); (2) that of the subsequent...
Study on the squeezing effect of open-ended pipe piles
Institute of Scientific and Technical Information of China (English)
无
2009-01-01
During the installation of a pipe pile,the soil around the pile will be squeezed out. This paper deals with this squeezing effect of open-ended pipe piles using the cylindrical cavity expansion theory. The characteristics of soil with different tension and compression moduli and dilation are involved by applying the elastic theory with different moduli and logarithmic strain. The closed-form solutions of the radius of the plastic region,the displacement of the boundary between the plastic region and the ela...
Analysis and treatment of quality problem of boulder in foundation pile project%基桩遇孤石质量问题的分析与处理
Institute of Scientific and Technical Information of China (English)
杨文武
2015-01-01
基于地基与基础等强置换、地基压力扩散原理及复合地基理论，以孤石加固法、结构加固法、复合地基与基础加固法及等强补桩法比较，分析了某建筑主体结构已施工基桩遇孤石的承载力、沉降量不能全部满足要求的处理方案，探讨复合地基加固法和等强补桩法的应用。提高土层压缩模量是复合地基加固的重要途径，合理、有效地确定地基处理范围是复合地基加固的重要环节。%Based on the equal strength displacement theory of foundation and foundation, ground pressure diffusion principle and the theory of composite foundation, comparisons of boulder reinforcement method, the structure reinforcement method, composite foundation and pile foundation reinforcement method and equal strength reinforcement method were made.The treatment plan for bearing capacity and settle-ment under requirements due to boulder encountered in a foundation pile which main structure has been built was analyzed.Application of composite foundation reinforcement method and equal strength pile reinforcement method were discussed.Improvement of the soil compres-sion modulus is the important way of compound foundation reinforcement, reasonable and effective determination of the scope of the founda-tion treatment is an important part of the composite foundation reinforcement.
Institute of Scientific and Technical Information of China (English)
郑宇; 王天勇; 杨铮; 金灿国; 王建华; 张相勇; 董素芹
2013-01-01
The design and construction method of dynamic compaction plus cement fly-ash grave ( CFG) pile were introduced to enhance the bearing capacity of foundation and control foundation settlement in thick backfill by an engineering example. The standard penetration test and static loading test were carried out to topsoil compacted by dynamic compaction, and the bearing capacity of the composite foundation processed by dynamic compaction and CFG was detected by static loading test of single pile composite foundation and vertical compression static loading test of single pile. The results show that the bearing capacity and deformation of composite foundation are acceptable and can meet the requirement of related codes. Moreover, the engineering example shows this method can shorten the construction period and is economic, convenient and safe.%通过工程实例,介绍了在较厚回填土中采用强夯+ CFG桩复合地基进行地基处理以提高地基承载力及控制沉降的设计及施工方法.强夯后对表层土进行标准贯入试验及静力载荷试验,打入CFG桩后对复合地基承载力进行单桩复合地基静载荷试验与单桩竖向抗压静载荷试验检测,结果表明地基承载力与变形均满足规范要求.工程实例表明采用此方法可节约造价、缩短工期且安全可靠.
锚杆静压桩群桩效应分析%Analysis of effect for anchored silent group pile
Institute of Scientific and Technical Information of China (English)
韩红娟; 郑七振
2012-01-01
In order to improve comprehension for the rule of interaction between pile, soil and pile caps, the software ABAQUS was applied to stimulate the different working properties of anchored silent group piles'foundation under different pile length, side length, pile spacing, number of pile and thickness of piles cap. The effect coefficient of group pile and undertaking ratio of pile cap will decreased with the increase of pile length and number of piles, but not the pile spacing. The results will be useful to the guidance of pile foundation design and make the design of pile to accord with real working conditions.%为促进对桩-土-承台相互作用规律的认识,本文主要运用ABAQUS模拟了锚杆静压桩(方桩)的不同桩长、桩边长、桩间距、桩数以及承台厚度情况下,锚杆静压桩群桩基础的工作性状.桩长的增长和桩数的增加,都会导致群桩效应系数和承台荷载分担比的降低；而随着桩间距增大群桩效应系数和承台荷载分担比增大.这些结论都有助于指导桩基设计,使得桩基设计更符合其实际工作状况.
Aerospace applications of magnetic bearings
Downer, James; Goldie, James; Gondhalekar, Vijay; Hockney, Richard
1994-01-01
Magnetic bearings have traditionally been considered for use in aerospace applications only where performance advantages have been the primary, if not only, consideration. Conventional wisdom has been that magnetic bearings have certain performance advantages which must be traded off against increased weight, volume, electric power consumption, and system complexity. These perceptions have hampered the use of magnetic bearings in many aerospace applications because weight, volume, and power are almost always primary considerations. This paper will review progress on several active aerospace magnetic bearings programs at SatCon Technology Corporation. The magnetic bearing programs at SatCon cover a broad spectrum of applications including: a magnetically-suspended spacecraft integrated power and attitude control system (IPACS), a magnetically-suspended momentum wheel, magnetic bearings for the gas generator rotor of a turboshaft engine, a vibration-attenuating magnetic bearing system for an airborne telescope, and magnetic bearings for the compressor of a space-rated heat pump system. The emphasis of these programs is to develop magnetic bearing technologies to the point where magnetic bearings can be truly useful, reliable, and well tested components for the aerospace community.
Nanoprecipitation in bearing steels
Energy Technology Data Exchange (ETDEWEB)
Barrow, A.T.W. [SKF University Technology Centre, Department of Materials Science and Metallurgy, University of Cambridge, Cambridge CB2 3QZ (United Kingdom); Rivera-Diaz-del-Castillo, P.E.J., E-mail: pejr2@cam.ac.uk [SKF University Technology Centre, Department of Materials Science and Metallurgy, University of Cambridge, Cambridge CB2 3QZ (United Kingdom)
2011-11-15
{theta}-phase is the main hardening species in bearing steels and appears in both martensitically and bainitically hardened microstructures. This work presents a survey of the microstrucural features accompanying nanoprecipitation in bearing steels. Nanoprecipitate structures formed in 1C-1.5Cr wt.% with additions of Cr, Mn, Mo, Si and Ni are studied. The work is combined with thermodynamic calculations and neural networks to predict the expected matrix composition, and whether this will transform martensitically or bainitically. Martensite tetragonality, composition and the amount of retained austenite are related to hardness and the type of nanoprecipitate structures in martensitic grades. The {theta}-phase volume fraction, the duration of the bainite to austenite transformation and the amount of retained austenite are related to hardness and a detailed quantitative description of the precipitate nanostructures. Such description includes compositional studies using energy-dispersive spectroscopy, which shows that nanoprecipitate formation takes place under paraequilibrium. Special attention is devoted to a novel two-step bainite tempering process which shows maximum hardness; we prove that this is the most effective process for incorporating solute into the precipitates, which are finer than those resulting from one-step banitic transformation processes.