Sample records for aquicludes

  1. Research on downward crack closing of clay aquiclude in shallow coal seam safety mining

    Institute of Scientific and Technical Information of China (English)

    HUANG Qing-xiang; ZHANG Wen-zhong


    The water resisting property ofaquiclude is the key factor of water conservation and safety mining,and the mining induced cracks in aquiclude is major factor of water resisting property.The aquiclude is composed by loess layer and red clay layer in Yushuwan Coal Mine,and the water reaction property of clay and loess of aquiclude was tested by soil mechanics method.The permeability coefficient of the loess is 0.856 m/d and the clay is 0.434 rn/d.The dilatability coefficient of the loess is 16.1% and the clay is 14.6%.Through physical solid-liquid simulation with whole stress-stain similarity,the distribution of "downward crack zone" and "upward crack zone" was found to be the major factor of aquiclude stability.The downward crack closing length is about 30% of the downward crack length.The expanding of clay and loess with water are principal factors of downward crack closing.At last,the mechanical model of downward crack closing was constructed,and the criterion of crack closing was put forward at all.This work will provides the theoretical base for aquiclude stability research and safety mining in shallow seam.

  2. Study on water resisting property of subsurface aquiclude in shallow coal seam mining

    Institute of Scientific and Technical Information of China (English)

    HUANG Oing-xiang


    According to the characteristic of clay aquiclude of overburden, the propersimulation materials and proportions of mixture for simulating the plastic clay aquicludelayers were developed, and the plastic similarity conditions were setup. Thus, the simili-tude and simulation method in whole stress-strain was progressed. Furthermore, thesimulation condition and material proportions in water reaction property and crack closingproperty were also put forward. Based on systematical tests, the development and distri-bution of mined cracks in roof and subsurface aquiclude was found and the stability ofaquiclude was analyzed at all. At last, the key section and key index of aquclude stabilitywas advanced. It is found that the movement of clay aquiclude follows the movement ofthe underlying bedrock layers. The basic caving mechanism of the overburden roof stratawas also presented.


    Institute of Scientific and Technical Information of China (English)

    王经明; 葛家德; 吴玉华; 邓西清; 贺兆礼


    This article proposes a water inrush mechanism of progressive intrusion of pressurewater up into the coal floor aquiclude according to injection tests and observations. A numericalmodel and a criterion of water inrush are established based on the mechanism. The theory is suc-cessfully used in predictions of water inrush.

  4. Experimental research of overburden movement and subsurface water seeping in shallow seam mining

    Institute of Scientific and Technical Information of China (English)


    Shallow seam coal field has the largest coal reserve in China. Mining in shallow depth causes serious problems, and subsurface dewatering is a major issue. In this paper, the physical simulating models were prepared to study overburden movement and aquiclude stability in the shallow seam mining of Yushuwan Coalfield, China. According to the characteristic of clay aquiclude and bedrock in the overburden, the proper simulation materials for simulating the plastic clay aquiclude layers and brittle bedrock layers were determined by the stress-strain tests and hydrophilic tests. The physical simulating models of solid medium and two phases of solid-liquid medium were carried out to simulate the failure and caving process of the roof and overburden, as well as the subsurface water seeping. Based on the simulation, it was found that the movement of clay aquiclude follows the movement of the underlying bedrock layers. The stability of aquiclude is mainly affected by cracks in fracture zone. The tests also showed that the best way to control the stability of aquiclude is to reduce the subsiding gradient, and there is a possibility of ground water conservation under longwall mining in Yushuwan Mine. This research provides a foundation for further study on mining dewatering and water conservation.

  5. Partitions, Compartments and Portals: Cave Development in internally impounded karst masses.


    Osborne R. Armstrong L.


    Dykes and other vertical bodies can act as aquicludes within bodies of karst rock. These partitions separate isolated bodies of solublerock called compartments. Speleogenetically each compartment will behave as a small impounded-karst until the partition becomesbreached. Breaches through partitions, portals, allow water, air and biota including humans to pass between sections of caves thatwere originally isolated.

  6. The hydrogeochemistry of methane : evidence from English groundwaters


    Darling, W. G.; Gooddy, D.C.


    The presence of methane (CH4) in groundwater is usually only noticed when it rises to high concentrations; to date rather little is known about its production or natural ‘baseline’ conditions. Evidence from a range of non-polluted groundwater environments in England, including water supply aquifers, aquicludes and thermal waters, reveals that CH4 is almost always detectable, even in aerobic conditions. Measurements of potable waters from Cretaceous, Jurassic and Triassic carbonate and sandsto...

  7. Caves and Karsts of Northeast Africa.


    Halliday William R.


    At least potentially karstifiable rocks cover much of the surface of Egypt and northern Libya. Study of caves and other karstic features of this region has been hampered by lack of roads, rapid disintegration of the surface of friable, poorly consolidated limestone, wind-blown sand and other factors. Interbedding with marly aquicludes hampers speleogenesis locally. Calcareous and evaporite karsts are present, however, and their waters are important albeit generally limited resources. Large qu...

  8. Research on the water-inrush risk of coal floors based on Fisher-evaluation and AHP (United States)

    Xu, D. J.; Wei, W. X.; Xiang, S. Y.


    There are many factors that influence floor water-inrush. Based on the widely collected data of floor water-inrush in China, the evaluation factors in this paper consist of water pressure, aquifer type, aquiclude thickness, floor failure depth and fault throw. These are used to build a single Fisher evaluation model and a Fisher evaluation with weighting model of an analytic hierarchy process (AHP). By comparision, through AHP weighting value, the interclass distribution of the data in the Fisher model is relatively more concentrated than the single Fisher evaluation method. It would produce higher reliability and more extensive application value.

  9. Investigation of a shallow aquifer near the Fenton Hill hot dry rock site using DC resistivity

    Energy Technology Data Exchange (ETDEWEB)

    Pearson, C.F.


    A shallow aquifer in the base of the Tertiary volcanic sequence was investigated using a series of 9 DC Schlumberger soundings taken within 10 km of the Fenton Hill hot dry rock geothermal site. The aquifer dips to the southwest following the top of the Abo formation, which acts as an aquiclude. Depth increases from 130 m in the eastern part of the study area to 260 m at 1.5 km west of the Fenton Hill site. Aquifer resistivities varied from 13..cap omega..-m to 126..cap omega..-m, which could be caused by variable permeability in the aquifer. Using results from empirical studies permeabilities ranging from 40 darcies to less than 0.3 darcies were estimated with the highest values occurring nearest to the Fenton Hill site.

  10. Site qualification studies of the UCG-SDB at North Knobs, Wyoming

    Energy Technology Data Exchange (ETDEWEB)

    Davis, B.E.; Krajewski, S.A.; Ahner, P.F.; Avasthi, J.M.; Dolde, M.E.; Greenman, C.A.; Miranda, J.E.


    The site qualification program for the North Knobs UCG site near Rawlins, Wyoming has been completed. This site will be the location for the field tests of Underground Coal Gasification of Steeply Dipping Beds undertaken by Gulf Research and Development Company for DOE in a cost shared contract. Site characterization included a comprehensive geotechnical analysis along with vegetation, historical, and archeological studies. The G coal seam chosen for these tests is a subbituminous B coal with a true seam thickness of 22 feet and has thin coal benches above and below the main seam. The water table is at 90 feet below the surface. Hydrologic studies have defined the seam as an aquiclude (non-aquifer). The site is deemed restorable to regulatory requirements. Evaluation of this site indicates total acceptability for the three-test program planned by GR and DC.

  11. Nonlinear coupling analysis of coal seam floor during mining based on FLAC3D

    Institute of Scientific and Technical Information of China (English)

    YAO Duo-xi; XU Ji-ying; LU Hai-feng


    Based on the hydro-geological conditions of 1028 mining face in Suntuan Coal Mine, mining seepage strain mechanism of seam floor was simulated by a nonlinear coupling method, which applied fluid-solid coupling analysis module of FLAC3D. The results indicate that the permeability coefficient of adjoining rock changes a lot due to mining. The maximum value reaches 1 379.9 times to the original value, where it is at immediate roof of the mined-out area. According to the analysis on the seepage field, mining does not destroy water resistance of the floor aquiclude. The mining fissure does not conduct lime-stone aquifer, and it is less likely to form damage. The plastic zone does not exactly correspond to the seepage area, and the scope of the altered seepage area is much larger than the plastic zone.

  12. 小庄矿井采煤对地下水的影响及保水采煤措施%The influence of underground coal mining on groundwater and measures for water conservation while mining in Xiaozhuang mine

    Institute of Scientific and Technical Information of China (English)

    徐海红; 乔皎; 王铮


    针对煤炭开采易造成地表塌陷及含水层破坏等问题,采用类比法计算了彬长矿区规划新建的矿井——小庄矿井开采导水裂缝带高度,在此基础上分析了采煤对地下水的影响,并提出保水采煤的措施。经计算,采用分层开采时产生的导水裂隙带最大高度为147.84 m,在三盘区将导通安定组隔水层,造成宜君组、洛河组承压含水层破坏,导通区域面积为0.7736 km2。因此,在可能导通的区域应进行保水采煤以保证安定组隔水层的稳定,从而达到保护具有供水意义的含水层和保障矿井生产安全的双重目的。%Aiming at the problems such as collapse of ground surface and damage of aquifer induced by coal mining this paper calculates height of water flowing fractured zone in XiaoZhuang mine by using the analogy method. In addition, based on this, we analyzed the influence of mining and put forward water conservation while mining.Calculated from experimental data, height of water flowing fractured zones has an absolute maximum of 147.84 m by slice mining. Breakover of aquiclude of Anding Formation results in the destruction of confined aquifer of Luohe Formation in the third panel, the breakover area reached 0.7736 km2. Mining with water conservation should be applied in the area where the breakover may occur to ensure the stability of the aquiclude of Anding formation so as to achieve the double goals of protecting the water supplying aquifer and ensuring the safety of mine production.

  13. Developing a geological 3D model for the Tanour and Rasoun spring catchment area using ArcGIS and GOCAD (United States)

    Hamdan, Ibraheem; Benhsinat, Mohamed; Wagner, Bianca; Sauter, Martin


    Key words: Karst, 3D model, GOCAD, ArcGIS, Jordan. Tanour and Rasoun karst springs (around 75 km northwest of the capital city of Amman in Jordan) are used as main local water supply for the surrounding villages. Carbonate rocks are the predominant rock type in the study area (Upper Cretaceous age). The karstification degree is moderate to high, with the availability of different karst features like dolines, caves, dry valleys, and highly fractured rocks. During the last years, the water supply from these springs had to be disconnected for several times due to microbial contamination and waste water pollution from local olive oil mills. For better understanding of the geological and the hydrogeological setting of the study area, in addition to the delineation of the groundwater catchment area for Tanour and Rasoun springs, a geological 3D model of the main geological formations within the study area was established using ArcGIS and GOCAD. The model is based on geological maps and well data; it was established for seven geological layers that act as prominent aquifers and aquicludes. ArcGIS software was used for data preparation, processing and interpolation of varying thickness, while GOCAD used for geometrical modeling steps. After the completion of the first modeling steps, major faults are included. Then the subsurface catchments will be delineated and compared with the superficial watersheds. The model still under development and open for further development.

  14. High=porosity Cenozoic carbonate rocks of South Florida: progressive loss of porosity with depth (United States)

    Halley, Robert B.; Schmoker, James W.


    Porosity measurements by borehole gravity meter in subsurface Cenozoic carbonates of South Florida reveal an extremely porous mass of limestone and dolomite which is transitional in total pore volume between typical porosity values for modern carbonate sediments and ancient carbonate rocks. A persistent decrease of porosity with depth, similar to that of chalks of the Gulf Coast, occurs in these rocks. Carbonate strata with less than 20% porosity are absent from the rocks studied here. Aquifers and aquicludes cannot be distinguished on the basis of porosity. Aquifers are not exceptionally porous when compared to other Tertiary carbonate rocks in South Florida. Permeability in these strata is governed more by the spacial distribution of pore space and matrix than by total volume of porosity present. Dolomite is as porous as, or slightly less porous than, limestones in these rocks. This observation places limits on any model proposed for dolomitization and suggests that dolomitization does not take place by a simple ion-for-ion replacement of magnesium for calcium. Dolomitization may be selective for less porous limestone, or it may involve the incorporation of significant amounts of carbonate as well as magnesium into the rock. The great volume of pore space in these rocks serves to highlight the inefficiency of early diagenesis in reducing carbonate porosity and to emphasize the importance of later porosity reduction which occurs during the burial or late near-surface history of limestones and dolomites.

  15. Proceedings of GeoEdmonton 2008 : the 61. Canadian geotechnical conference and 9. joint CGS/IAH-CNC groundwater conference : a heritage of innovation

    Energy Technology Data Exchange (ETDEWEB)

    Martin, D. [Alberta Univ., Edmonton, AB (Canada); Skirrow, R. [Alberta Transportation, Edmonton, AB (Canada); Froese, C. [Alberta Geological Survey, Edmonton, AB (Canada)] (comps.) (and others)


    This conference provided a forum for more than 500 delegates from industry, government universities and research centres to share their professional knowledge on research and development that affects all sectors of geotechnical engineering, applied geology and hydrogeology. Accomplishments in the geoenvironmental field were also highlighted. The geotechnical sessions were entitled: pile foundations and load testing; excavations and special foundation issues; reinforced soil and soil-structure interactions; advances in modelling, constitutive issues; advances in modelling, consolidation and other applications; advances in modelling, discrete elements and slope stability; embankments and dams; landfills and barriers; fundamental soil mechanics; soil mechanics and ground movement; GIS and remote sensing; landslides and slopes; cone penetration tests and liquefaction assessment; rock mechanics; engineering geology; geoenvironmental sustainability; oilsand and petroleum geomechanics; and, oilsand tailings. The hydrogeology sessions were entitled: paste tailings and cemented paste backfill; acid mine drainage and containment issues; contaminated sites; cold regions; instrumentation, insitu testing and field applications; transportation geotechniques; urban geohazards; staff retention and motivation; geotechnical education for modern practice; regional issues and studies; policy, regulation and conservation; groundwater and development; groundwater and surface water interactions; groundwater and terrain interactions; aquicludes and aquitards; general hydrogeology; and, geochemistry and contaminant hydrogeology. The conference featured more than 250 presentations, of which 42 have been catalogued separately for inclusion in this database. refs., tabs., figs.

  16. Integrierter Einsatz von Scherwellenseismik und Direct-Push-Verfahren zur Erkundung eines urbanen Grundwasserleiters (United States)

    Hoffmann, S.; Beilecke, T.; Polom, U.; Werban, U.; Leven, C.; Engeser, B.


    In a highly permeable urban aquifer with a lower cretaceous mudstone aquiclude in the district “Südstadt” of Hannover/Lower Saxony, a stationary plume of chlorinated hydrocarbons was investigated within a research framework on the use of monitored natural attenuation. In the vicinity of the isolated contaminant source a glacial channel was detected as a possible secondary source supplying the plume. Due to dense housing the channel morphology and possible pathways could not be mapped accurately by classical geological methods. Therefore, the structure of the aquifer was mapped with shear wave seismics on seven profiles covering a range of more than 3.5 km, utilizing a newly developed mobile land streamer unit. The seismic profiles were adjusted with 16 electric conductivity (EC) and penetration logs measured with direct push, delivering a high resolution image of the near surface bedrock. Due to its mobility and the characteristics of shear wave seismics this combination of methods is ideally suitable for work on sealed surfaces.

  17. Caves and Karsts of Northeast Africa.

    Directory of Open Access Journals (Sweden)

    Halliday William R.


    Full Text Available At least potentially karstifiable rocks cover much of the surface of Egypt and northern Libya. Study of caves and other karstic features of this region has been hampered by lack of roads, rapid disintegration of the surface of friable, poorly consolidated limestone, wind-blown sand and other factors. Interbedding with marly aquicludes hampers speleogenesis locally. Calcareous and evaporite karsts are present, however, and their waters are important albeit generally limited resources. Large quantities of fresh water are lost through submarine springs downslope from Libya’s Gebel al Akhdar range; the caves and karst of that range may be among the world’s greatest. A recent attempted compendium of caves and karsts of Egypt and Libya contains several important errors; the supposed 5+ km Ain Zayanah Cave does not exist and the Zayanah System includes several smaller caves. The Bir al Ghanam gypsum karst of northwest Libya, however, has caves up to 3.5 km long. In Egypt, the Mokattam, South Galala, Ma’aza, Siwa and Western Desert karsts and the “White Desert” chalk karst of Farafra Depression are especially important. Qattara and nearby depressions may be karstic rather than structural in origin. Unique Wadi Sannur Cave is the world’s largest gour and a potential World Heritage site. Little knownsandstone karsts or pseudokarsts in southwestern Egypt may contain analogues of features recently identified on Mars. The well-publicised Uweinat caves of northwestern Sudan are talus caves.

  18. 煤层底板承压水导升带影响因素正交模拟试验%Orthogonal test of the influential factors of confined water-conducting zone in coal floor

    Institute of Scientific and Technical Information of China (English)

    边凯; 杨志斌


    Confined water-conducting zone is an important factor for mining safety assessment in mining under water pressure, in order to study the role of the influential factors, based on the fluid-solid coupling theory, the hydrogeological conceptual model and numerical model of coal floor water inrush was established, then orthogonal simulation test of five factors and five levels was carried out by using numerical simulation software FLAC3D. The results show that confined water-conducting height is closely related to water pressure of aquifer and permeability coefficient of aquiclude, the greater the confined water pressure and permeability coefficient, the higher the initial water-conducting height. The influential order of the factors for the experimental results isE>C>D>B>A,E (permeability coefficient of aquiclude) andC (confined water pressure) significantly affect the result of the experiment. Different initial head pressure cause different head pressure attenuation rate during the process of confined water conduction. The greater the initial head pressure, the greater the head decay rate, this will increase with the conducting height. The fact that the change of the influencial factors leads to the changes of confined water pressure reveals the law of coal floor confined water conductivity in coal mining process, provides the theoretical basis for the safe mining of coal under pressure.%承压水导升带是煤层带压开采安全评价的重要因素。为了综合研究其影响因素的作用,基于流–固耦合理论,建立了煤层底板突水的水文地质物理概念模型和数值模型,采用FLAC3D数值模拟软件开展了工作面宽度(A)、隔水层厚度(B)、承压水压力(C)、煤层埋深(D)、隔水层渗透系数(E)5个因素5水平的有空列正交模拟试验。结果表明:煤层底板承压水导升高度与底板含水层水压和隔水层渗透性关系密切;各因素对试验结果的影响程度强弱顺序是 E

  19. Development of isotopically heterogeneous infiltration waters in an artificial catchment in Chuzhou, China

    International Nuclear Information System (INIS)

    The existence of spatial and temporal isotopic variability of infiltration waters during storm events can pose substantial difficulties in the use of stable isotopes for tracing sources and flow paths of water contributing to storm flow. The 490 m2 Hydrohill experimental catchment near Nanjing, China, was used to investigate the development of isotopic heterogeneity in subsurface waters. This catchment contains a network of lysimeters, troughs and wells installed within a 1 m thick layer of silty loam emplaced above a concrete aquiclude. During a storm on 1989-07-05, a complete suite of samples (precipitation, surface runoff, unsaturated zone flow from four lysimeters, saturated zone flow and groundwater from 16 sites) was collected and analysed for δ18O. The contributions of rain water to subsurface flow ranged from 5 to 95%, depending on the time, location and depth of sampling. During peak flows, many subsurface waters are apparently composed of mixtures of rapidly moving rain water travelling through macropores, with smaller amounts of pre-storm water flowing downwards by matrix flow; as the soils drain between rain pulses, the subsurface samples approach their pre-storm isotopic compositions. Surface and shallow subsurface processes appear to have a significant effect on the development of isotopic variability in soil waters and shallow groundwaters. Thus, if such shallow hill slope waters are a significant source of water to streams during storm events, then an understanding of the processes and flow paths on the hill slope is critical to the development of accurate models of storm flow generation. (author). 7 refs, 5 figs

  20. The Application of Stress-Strain Test in Floor Damage Depth Testing%应力应变法在底板破坏深度测试中的应用

    Institute of Scientific and Technical Information of China (English)

    周江东; 吕育强


    The floor aquiclude of Liu Jialiang coal mine in XuanGang area are faced with water inrush due to Ordovician high pressure water with mining. Controlling and preventing water inrush from coal floor had been the main task ,which need evaluate the floor damage depth under mining. Stress-strain test is used to detect the floor damage depth during mining as a new way, taking the ultimate strain of concrete when it is broken as the standard to evaluate the floor damage depth, good results was achieved that the floor damage depth was 13m Under full-mechanized caving mining.It provided reliable da-ta for rational evaluation of water inrush from floor under mining with pressure in working face 8416.%文中针对轩岗矿区刘家梁煤矿受底板下伏奥陶系灰岩岩溶裂隙水威胁的情况,指出当前底板突水防治成为矿井防治水的主要工作任务,需要探查回采工作对底板的破坏程度。通过采用应力应变法进行底板破坏深度测试,利用混凝土的破坏时产生的极限应变作为判断底板岩层破坏深度的依据,得到综放开采条件下采场底板破坏深度为13 m,为合理评价带压开采条件下8416工作面底板突水提供了可靠的数据支撑。

  1. Research about the Control of Geological Structure on Karst Groundwater system in Zhangfang, Beijing,China. (United States)

    Qiao, X.


    Carbonate formations are intensively distributed throughout Zhangfang, fangshan, in West Mountain area in Beijing. Karst groundwater exits among the geological fracture network which is characterized by the different arrangements and levels in different types of fracture networks and structures. The influence of the tectonic environment on the dynamic change rule and the enrichment regulation of karst system is significant for the exploitation and protection of karst groundwater resources. From the control function of fault and fracture point of view, based on the developmental and distribution pattern of multi-episodic tectonism, this study analyzed fractures in the three-fold structural units characterized by NE-NW and NS trends and discussed the influence of multi-episodic tectonism on the groundwater flow system and rich water zones. The results showed that the geological fracture underwent two episodes of tectonism, thrusting nappe in the Jurassic and extension in the Cretaceous. The overprint of two episodes resulted in a number of faults with high hydraulic conductivity, which serve as conduits. The superiority joints groups are in the NE and NW directions, with conjugated characteristics. The high-angle or vertical dips directly benefit infiltration. The fractures in the intersection areas have formed groundwater runoff channels and strong space, controlling water-rich zones such as Baidai, Ganchi-Changgou and Gaozhuang-Shiwo. Magmatic rock and the aquiclude also contribute to the rich water zones and the location of springs, all of which have important significance for water supply. Keywords: system of Karst groundwater, geological structure, fracture network, hydrogeological flow field, Zhangfang karst area

  2. The impermeability of limestone aquifuge in bottom coal seam floor and its application in Xinji Second Coal Mine%新集二矿下组煤底板石灰岩层隔水性及应用研究

    Institute of Scientific and Technical Information of China (English)

    白海波; 戎虎仁; 杨城; 韦晓琪; 王延蒙; 陈耀杰


    Limestone layer is often regarded as the main cause of coal mine water damage and water inrush events, which actually happened more than once in old mining area in Huainan. A conception has been put forward that reconstruction or direct utility of relative impermeability of floor limestone layer can solve the problem of high water pressure and thin aquiclude and ensure safety during mining under pressure. Xinji Second coal mine has been selected as the research field which is located in the southern edge of the midwest coalfields and comprehensive methods have been used to research including the index test of rock composition, chemical action of compositions of groundwater, and rock mechanic, micro-pore structure, the laboratory experiment about permeability and the field test about hydrogeolog-ic drilling, geophysical prospecting. The research results show that:1) Xinji Second Coal Mine is cut by faults all around, with the top covered by quaternary system and metamorphic nappe. The in-situ stress changes from tensile in the shallow part to compressive at a depth under 500 m. The crack of deep rock layer is not easy to open up. 2) The hydrochemical type is Cl-Na. Salinity is greater than 1.5 g/L and rock voids is filled by the precipitation. 3) The permeability and water rich property of limestone floor is poor, so it can be regarded as aquiclude. It is confirmed that inrush boreholes mostly close to the large faults and water yield is small and disappear quickly through boreholes in the coal mine. Safe mining of the first coal mining face and safety tunneling of the second working face testify the result that the floor limestone layer is aquiclude and the water-resisting key strata after reconstruct is correct.%石灰岩层往往成为煤矿开采防水害的主要对象,且淮南老矿区也发生了多次底板灰岩层突水,为解决新区水压高、传统隔水层薄的问题,提出改造或直接利用底板石灰岩层相对隔水性实现带压安

  3. Uma classificação físico-hídrica dos solos A physico-hydrical soil classification

    Directory of Open Access Journals (Sweden)

    T. B. Ottoni Filho


    minus field capacity values and steady state infiltration rate. On this basis, 10 soil orders and 28 soil classes are defined. Input variables are: density of solids, bulk density, porosity, field capacity, wilting point, and steady state infiltration rate. The classification is based on strictly numerical criteria, and there are no components of subjective evaluation. The nine principal orders, containing three classes each, are: aerated-aquiferous soils (I; aerated-mesaquiferous soils (II; mesaerated-aquiferous soils (III; mesaerated-mesaquiferous soils (IV; aerated-aquicludeous soils (V; mesaerated-aquicludeous soils (VI; unaerated-aquiferous soils (VII; unaerated-mesaquiferous soils (VIII; unaerated-aquicludeous soils (IX. One last order is possible (order X: the flooded soil order, with only one class. The methodology is applied by selecting soils from literature with varying textural classes, from sands to very fine clayey soils. It is demonstrated that there is no direct relation between the textural class and the soil system class or order. It is suggested that the methodology could also be utilized as a tool for soil management or for the evaluation of agricultural capability of lands where other information (meteorological, phythological, topographic, and management level is included. Furthermore, the methodology contains useful information for irrigation system projects.

  4. The Pliocene Yafo Formation in Israel: Hydrogeologically inert or active? (United States)

    Avisar, D.; Rosenthal, E.; Shulman, H.; Zilberbrand, M.; Flexer, A.; Kronfeld, J.; Ben Avraham, Z.; Fleischer, L.

    For several decades the ``Saqiye beds'' (later renamed Yafo Formation) underlying the Coastal Plain aquifer (Kurkar Group) aquifer of Israel, were regarded as an extremely thick, tectonically undisturbed, and absolutely impervious aquiclude. Following intensive groundwater exploitation from the overlying Kurkar Group aquifer, brackish and saline waters were locally encountered in the lower parts of this aquifer and always at the contact with the underlying Yafo Formation aquiclude. The present study revealed that this aquiclude is not a uniform and impervious rock unit, but rather an alternation of pervious and impervious strata within the Yafo Formation containing highly pressured fluids of different - mostly high - salinities. The permeable beds are at an angular unconformity and in direct contact with the overlying Kurkar Group aquifer. The Yafo Formation and the underlying and overlying rock units are dislocated by numerous fault systems, which facilitate accessibility of brines into the Kurkar Group aquifer. The mobilization of the saline fluids and their injection into the Kurkar Group aquifer could be due either to diffusion of saline fluids occurring in the permeable horizons of the Petah Tiqva Member through the clays of the Yafo Formation or to their upconing following intensive pumping in the Coastal Plain aquifer. It could have also been caused by up-dip movement of saline water as the result of overpressure generated by major accumulation of gas in the permeable horizons. Another possible mechanism could be hydraulic contact with pressurized brines up-flowing along fault zones from deep-seated Jurassic or Cretaceous reservoirs. The squeezing of saline interstitial water from the clays of the Yafo Formation into the overlying Kurkar Group aquifer, is of secondary importance for groundwater salinization (its input is comparable with salt input from rain). Depuis longtemps, les «couches de Saqiye», nommées maintenant formation de Yafo, constituant le

  5. Spatiotemporal relationships among Late Pennsylvanian plant assemblages: Palynological evidence from the Markley Formation, West Texas, U.S.A (United States)

    Looy, Cindy V.; Hotton, Carol L.


    organic beds appear to have formed as a single genetic unit, with the kaolinite forming an impermeable aquiclude upon which a poorly drained wetland subsequently formed. Within a single inferred glacial/interglacial cycle, lithological data indicate significant fluctuations in water availability tracked by changes in palynofloral and megafloral taxa. Palynology reveals that elements of the dryland floras appear at low abundance even within wetland deposits. The combined data indicate a complex pattern of succession and suggest a mosaic of dryland and wetland plant communities in the Late Pennsylvanian. Our data alone cannot show whether dryland and wetland assemblages succeed one another temporally, or coexisted on the landscape. However, the combined evidence suggests relatively close spatial proximity within a fragmenting and increasingly arid environment. PMID:26028779

  6. Evidence of spring formation and subrosion-induced sinkhole development at Ghor Al-Haditha, Jordan, from repeated close-range photogrammetry (United States)

    Al-Halbouni, Djamil; Eoghan, P. Holohan; Leila, Saberi; Hussam, Alrshdan; Thomas, Walter; Ali, Sawarieh; Torsten, Dahm


    The widespread development of sinkholes and land subsidence poses a major geological hazard to infrastructure, local population, agriculture and industry in the Dead Sea area. For assessment of the key physical factors in this development, repeated photogrammetric and field surveys at Ghor Al-Haditha in Jordan have been undertaken. Recent results provide evidence for subrosion based on strong periodic water flows, as the basic underlying physical process of such land subsidence phenomena. From combined Helikite- and Quatrocopter-based photogrammetric surveys, high resolution Digital Surface Models from October 2014 and October 2015 are compared. Change detection reveals: (1) active subsidence in a hundred metre-scale depression zone, (2) a highly-dynamic spring and canyon system connected with recent sinkhole collapses and (3) the rapid formation of new sinkholes both in alluvium and mud cover sediments. The formation of new sinkholes has been documented locally by means of aerial and field observations during a storm with strong rainfall. A new artesian spring formed in the former Dead Sea bed (mud-flat) at this event. The alluvial sediment load of the stream, a periodic location change of the spring and a connected uphill sinkhole cluster formation provide strong evidence for subrosion of weak material with subsequent underground void collapse. Additionally a documented lake and its' subsequent drainage forming a new canyon reveals the local penetration of the aquiclude behavior of the mud-flat in the major depression area, which can be explained by an under-saturated groundwater flow at a strong hydrostatic gradient. Furthermore an enlargement of the investigated area in the 2015 survey indicates a continuation of subsidence and sinkhole activity towards the North. It reveals several points of emanation of water streams in the mud-flat beneath the alluvial cover and vegetation as an indicator of relatively fresh groundwater inflow. This repeated photogrammetry

  7. Fluid transport processes in the passive margins of the Eastern Mediterranean (United States)

    Bertoni, Claudia; Foschi, Martino; Cartwright, Joe; Levell, Bruce


    We analyse and produce a synoptic model of the different styles of fluid transport occurring in the various passive margin settings in the Eastern Mediterranean. The common tectonic-stratigraphic setting is dominated, from the Mesozoic, by the interaction of the Tethyan platforms with Cenozoic to recent, mainly clastic, deposits interacting with the ubiquitous thick late Miocene (Messinian) evaporitic sediments. This created different specific modes of fluid-lithology coupling behaviours, and generated an extraordinary suite of seismically resolvable fluid flow phenomena, including mud volcanoes, pockmarks, dissolution/collapse structures, chimneys and pipes. We integrate this evidence with the analysis of the regional pressure/temperature gradient, and with published hydrocarbon generation models, to propose a regional synthesis of all fluid transport processes in a specific basinal context. We place the fluid flow evidence observed in the Eastern Mediterranean in the framework of the three main fluid flow settings, which are typically defined in sedimentary basins, in terms of depth: 1) A thermobaric fluid regime, where fluid transport is limited and convection can be the dominant transport mechanism, 2) A thermogenic regime, where fluids supplied by hydrocarbon generation can migrate by hydraulic fracturing and advection (along open faults/conduits), by matrix flow and in the longer term, by diffusion processes, 3) A shallow compactional regime, where the fluids are generated by sediment dewatering and shallow diagenesis, and the main transport mechanism is characterised by vertical fluid flow, either through advection and hydrofracturing along faults, or matrix flow. In the Eastern Mediterranean passive margins, this depth-related subdivision needs to be modified in order to accommodate the influence of the laterally and vertically extensive evaporitic series, which acts as a regional aquitard/aquiclude to water or a seal to hydrocarbon flow. The presence of

  8. An ecological mechanism to create regular patterns of surface dissolution in a low-relief carbonate landscape (United States)

    Cohen, M. J.; Martin, J. B.; Mclaughlin, D. L.; Osborne, T.; Murray, A.; Watts, A. C.; Watts, D.; Heffernan, J. B.


    Development of karst landscapes is controlled by focused delivery of water undersaturated with respect to the soluble rock minerals. As that water comes to equilibrium with the rock, secondary porosity is incrementally reinforced creating a positive feedback that acts to augment the drainage network and subsequent water delivery. In most self-organizing systems, spatial positive feedbacks create features (in landscapes: patches; in karst aquifers: conduits) whose size-frequency relationship follows a power function, indicating a higher probability of large features than would occur with a random or Gaussian genesis process. Power functions describe several aspects of secondary porosity in the Upper Floridan Aquifer in north Florida. In contrast, a different pattern arises in the karst landscape in southwest Florida (Big Cypress National Preserve; BICY), where low-relief and a shallow aquiclude govern regional hydrology. There, the landscape pattern is highly regular (Fig. 1), with circular cypress-dominated wetlands occupying depressions that are hydrologically isolated and distributed evenly in a matrix of pine uplands. Regular landscape patterning results from spatially coupled feedbacks, one positive operating locally that expands patches coupled to another negative that operates at distance, eventually inhibiting patch expansion. The positive feedback in BICY is thought to derive from the presence of surface depressions, which sustain prolonged inundation in this low-relief setting, and facilitate wetland development that greatly augments dissolution potential of infiltrating water in response to ecosystem metabolic processes. In short, wetlands "drill" into the carbonate leading to both vertical and lateral basin expansion. Wetland expansion occurs at the expense of surrounding upland area, which is the local catchment that subsidizes water availability. A distal inhibitory feedback on basin expansion thus occurs as the water necessary to sustain prolonged

  9. Land subsidence, structures and processes at the Dead Sea shoreline as revealed by a near-field photogrammetry survey at Ghor Haditha, Jordan (United States)

    Al-Halbouni, Djamil; Holohan, Eoghan P.; Walter, Thomas; Alrshdan, Hussam; Sawarieh, Ali; Dahm, Torsten


    Rapid recession of the Dead Sea in the last few decades has led to an increasing rate of sinkhole formation around the lake shore. The development of these sinkholes and other land subsidence phenomena poses a major geological hazard to the local population, agriculture and industry. For a better understanding of the underlying physical processes and for determining current and future areas of sinkhole hazard, we conducted field investigations and a first low altitude ("near-field") aerial photogrammetric survey with a Helikite Balloon at Ghor Haditha, Jordan, in October 2014. From the near-field photogrammetry, we generated a high resolution Digital Elevation Model of the surveyed area. This enables a detailed quantification of sinkhole sizes and distribution as well of morphological parameters such as the sinkhole depth/diameter ratio (D). Values of the latter are generally greater in the mechanically stronger alluvial fan sediments (D = 3.0 - 0.4) than in the weaker muds of the former Dead Sea lakebed (D = 0.3 - 0.1). Importantly, the point of emanation of a very recent and sediment-laden stream at c. 10m below the former floor of the Dead Sea can be structurally and morphologically connected to the main sinkhole area. This provides evidence for channelised subterranean groundwater flows beneath this area. From our observations, two processes were identified as key factors for the development of large land subsidence structures and local sinkhole clusters: (1) Subrosion of weak material due to groundwater following preferred flow paths of ancient and current wadi riverbeds and (2) rapid dissolution of soluble material (salt) in this aragonite-rich mud. The heterogeneous geology and alternation of aquifers (alluvial fan sediments) and aquicludes (mud-flats) lead to the formation of complex subsurface flow channels that represent the secondary porosity of the internal structure of karst aquifers. As a consequence of these subterranean channels, local bending and

  10. Hydrogeological characteristics of the Paraíba do Sul river flood plains: a case study of a mining area in the Tremembé municipality, SP, Brazil

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    Marcelo dos Santos Targa


    Full Text Available The sand mining activity in the São Paulo part of the Paraíba do Sul River Valley started in the 1950s, in the area of Jacareí municipality, located in the Southwestern part of the basin. From there, it advanced by the neighboring municipalities, fostered by urbanization and industrialization processes, especially of São Paulo Metropolitan Region. The lack of detailed hydrogeological studies in this area motivated this study that had the objective of verifying the hypothesis that sand mining pits interfere on the quality and storage of the water in the quaternary sedimentary aquifer. This study focused specifically in the eastern part of the Tremembé Municipality, São Paulo State, in a mining place called “Mineração Paraíso”. The investigation involved infiltration and flow tests, laboratory analyses of soil physical parameters and estimation, water quality indices and infrastructure construction for equipment installation including piezometers, dynamic penetration tests – (SPT - Standard Penetration Test, wells opening and office analyses. The soil physical parameters analyses revealed high porosity (66% in the friable soils. This in addition to the high levels of transmissivity (15.5 m2/h measured in Well 1 and 33 m2/h in Well 3, obtained from the flow test, increases the speed of the transportation of solutes including bacteria, to the underground water. Results of the granulometric analyses showed that the sand mining technique is not only predatory, but also inefficient, since the sand at the bottom of the pit is left unexploited, as well as the bentonite clay found in the deeper layers. According to the penetration tests (SPT, the aquifer has an average thickness of 5.5 m and an upper layer of impermeable organic clays that confine the sand deposits. Furthermore, an aquiclude composed of green bentonitic clays was identified just below the confined layer. However, it is necessary to point out that the confinement condition

  11. Ice marginal dynamics during surge activity, Kuannersuit Glacier, Disko Island, West Greenland (United States)

    Roberts, David H.; Yde, Jacob C.; Knudsen, N. Tvis; Long, Antony J.; Lloyd, Jerry M.


    The Kuannersuit Glacier surged 11 km between 1995 and 1998. The surge resulted in the formation of an ice cored thrust moraine complex constructed by subglacial and proglacial glaciotectonic processes. Four main thrust zones are evident in the glacier snout area with phases of compressional folding and thrusting followed by hydrofracture in response to the build-up of compressional stresses and the aquicludal nature of submarginal permafrost and naled. Various types of stratified debris-rich ice facies occur within the marginal zone: The first (Facies I) comprises laterally continuous strata of ice with sorted sediment accumulations, and is reworked and thrust naled ice. The second is laterally discontinuous stratified debris-rich ice with distinct tectonic structures, and is derived through subglacial extensional deformation and localised regelation (Facies II), whilst the third type is characterised by reworked and brecciated ice associated with the reworking and entrainment of meteoric ice (Facies III). Hydrofracture dykes and sills (Facies IV) cross-cut the marginal ice cored thrust moraines, with their sub-vertically frozen internal contact boundaries and sedimentary structures, suggesting supercooling operated as high-pressure evacuation of water occurred during thrusting, but this is not related to the formation of basal stratified debris-rich ice. Linear distributions of sorted fines transverse to ice flow, and small stratified sediment ridges that vertically cross-cut the ice surface up-ice of the thrust zone relate to sediment migration along crevasse traces and fluvial infilling of crevasses. From a palaeoglaciological viewpoint, marginal glacier tectonics, ice sediment content and sediment delivery mechanisms combine to control the development of this polythermal surge valley landsystem. The bulldozing of proglacial sediments and the folding and thrusting of naled leads to the initial development of the outer zone of the moraine complex. This becomes

  12. 3D coexisting modes of thermal convection in the faulted Lower Yarmouk Gorge (United States)

    Magri, Fabien; Inbar, Nimrod; Möller, Peter; Raggad, Marwan; Rödiger, Tino; Rosenthal, Eliyahu; Siebert, Christian


    Numerical investigations of 3D modes of large-scale convection in faulted aquifers are presented with the aim to infer possible transport mechanisms supporting the formation of thermal springs in the Lower Yarmouk Gorge (LYG), at the border between Israel and Jordan. The transient finite elements models are based on a geological model of the LYG that introduces more realistic structural features of the basin, compared to previous existing models of the area (Magri et al., submitted). The sensitivity analysis of the fault permeability showed that faults cross-cutting the main regional flow direction allow groundwater to be driven laterally by convective forces within the fault planes. Therein thermal waters can either discharge along the fault traces or exit the fault through adjacent permeable aquifers. The location of springs can migrate with time, is not strictly constrained to the damage zones and reflects the interplay between the wavelength of the multicellular regime in the fault zone and the regional flow toward discharge areas in the lowlands. The results presented here suggest that in the LYG case, crossing flow paths result from the coexistence of fault convection, that can develop for example along NE-SW oriented faults within the Gorge, and additional flow fields that can be induced either by topography N-S gradients, e.g. perpendicular to the major axe of the Gorge, or by local thermal convection in permeable aquifers below Eocene aquiclude. The sensitivity analysis is consistent with the analytical solutions based on viscous-dependent Rayleigh theory. It indicates that in the LYG coexisting transport processes likely occur at fault hydraulic conductivity ranging between 2.3e-7 m/s and 9.3e- 7 m/s (i.e. 7 m/yr and 30 m/yr). The LYG numerical example and the associated Rayleigh analysis can be applied to study the onset of thermal convection and resulting flow patterns of any fractured hydrothermal basin. References Magri F, Möller S, Inbar N, M

  13. A Study on Saltwater Intrusion Around Kolleru Lake, Andhra Pradesh, India

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    Full Text Available Kolleru Lake, the largest natural fresh water lake in Andhra Pradesh in India, located between Krishna and Godavari deltas is acting as a natural flood balancing reservoir and is fed directly by water from the seasonal rivers Budameru, Ramileru and Tammileru, and is also connected to the Krishna and Godavari drainage system consists of over 68 inflowing drains and channels. Over-exploitation of groundwater and land use conversions to aqua-culture are becoming the sources for salt-water intrusion to this lake and coastal aquifers, in specific, are highly vulnerable to seawater intrusion. Hydrogeomorphological study indicates that the potential aquifers around the Kolleru lake are paleo beach ridges and buried river courses. All other geomorphic features either aquiclude or aquitards are may not be considered as prospective zones for groundwater. Though there are number of open wells present in the villages used for potable water earlier, people switched over to imported water as their drinking water source may be due to significant contaminationof groundwater resources. Present land use activities like aqua-culture, agriculture, large-scale industries and allied industries in and around the Kolleru lake region has large contribution for the change of water quality. The paleo beach ridge areas, where the permeability of the sandy soil is very high, are also converted into aqua ponds. Integrated study using remote sensing, hydrogeology, hydrochemistry and geophysical investigations revealed the extent of salt-water intrusion up to the northern part of the lake which is about 40 km from the coast line. The electrical resistivity of aquifers is less than 1.0 (ohm-m having salinity of more than 1.2 ppt and the resistivity is around 20 (ohm-m where the salinity is less than 0.5 ppt, has also served as an excellent criteria for delineating the fresh-water and salt-water interface. Lenses of fresh water/ brackish water are noticed only in the beach

  14. Eight years of groundwater monitoring at the building site of the MOSE system for the safeguard of Venice (United States)

    Casasso, Alessandro; Sethi, Rajandrea; Di Molfetta, Antonio


    The survival of Venice is threatened by the continuous increase of frequency and intensity of tidal floods. To prevent these events, a safeguarding system known as MOSE is under construction at the inlets of the Lagoon of Venice. Four arrays of mobile barriers will be lifted in the case of exceptionally high tides (>1.10 m) to insulate the Lagoon. The prefabrication of the mobile barriers required a large construction area close to the final installation sites. Given the lack of space in the inlets of Lido and Chioggia, two basins of the future navigation locks were used for this purpose, and a system of water pumps and wells was therefore installed in each site to ensure the accessibility and safety of the construction areas. The impact of dewatering on the aquifers on the mainland in Punta Sabbioni (inlet of Lido) was monitored by means of continuous hydraulic head measurements in a network 25 piezometers, 11 screened in the phreatic aquifer and 14 in the shallowest confined aquifer. These aquifers are separated by a 5 m thick clayey aquiclude, and a 30 m thick impervious layer isolates them from the underlying confined aquifers, which were therefore not monitored. Each monitoring well was equipped with an automatic water pressure transducer and the hourly recorded hydraulic heads were compensated with the barometric pressure. The time series were compared with the natural driving forces (tides, rainfall, evapotranspiration) and the anthropogenic impact sources (dewatering pumping, slurry walls, land reclamation channels). The dynamics of seawater intrusion were also studied through monthly measurements of the vertical profiles of the electrical conductivity (EC) of groundwater. The monitoring activity was successful in assessing the impacts of the construction works. A drawdown was observed in the confined aquifer due to the dewatering pumping, with a maximum displacement of some 5 m on the mainland and an extension of some 1000 m from the dewatered basin. By

  15. Kinematics of the 1991 Randa rockslides (Valais, Switzerland

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    M. Sartori


    mineralogical alteration of the fault gouge accumulated along the sliding surface, reducing its angle of internal friction, and sealing the surface against water circulation. Once this basal fracture began to act as an aquiclude, the seasonal increase of the hydraulic head in the fissures promoted hydraulic fracturing on the highly stressed edges of the key block. Acceleration of this mechanical degradation occurred during the 20-year period before the 1991 rockslides, giving rise to an increasing rockfall activity, that constituted a forewarning sign. The final triggering event corresponded to a snow-melt period with high water table, leading to fracturation around the key block. On 18 April 1991, the key block finally failed, allowing subsidiary orthogneiss blocks to slide. They fell in turn over a period of several hours. The 9 May 1991, rockslide was the first of a series of expected future retrogressive reequilibrium stages of the very fractured and decompressed paragneisses, which lie on the orthogneiss base cut by the 18 April event.

  16. A refined genetic model for the Laisvall and Vassbo Mississippi Valley-type sandstone-hosted deposits, Sweden: constraints from paragenetic studies, organic geochemistry, and S, C, N, and Sr isotope data (United States)

    Saintilan, Nicolas J.; Spangenberg, Jorge E.; Samankassou, Elias; Kouzmanov, Kalin; Chiaradia, Massimo; Stephens, Michael B.; Fontboté, Lluís


    hydrocarbons in sandstone. Other minor H2S sources are identified. Upward migration and fluctuation of the hydrocarbon-water interface in sandstone below shale aquicludes and the formation of H2S along this interface explain the shape of the orebodies that splay out like smoke from a chimney and the conspicuous alternating layers of galena and sphalerite. Intimate intergrowth of bitumen with sphalerite suggests that subordinate amounts of H2S might have been produced by TSR during Pb-Zn mineralization. Gas chromatograms of the saturated hydrocarbon fraction from organic-rich shale and from both mineralized and barren sandstone samples indicate that hydrocarbons migrated from source rocks in the overlying Alum Shale Formation buried in the foredeep into sandstone, where they accumulated in favorable traps in the forebulge setting.

  17. Impacts of convection on high-temperature aquifer thermal energy storage (United States)

    Beyer, Christof; Hintze, Meike; Bauer, Sebastian


    Seasonal subsurface heat storage is increasingly used in order to overcome the temporal disparities between heat production from renewable sources like solar thermal installations or from industrial surplus heat and the heat demand for building climatisation or hot water supply. In this context, high-temperature aquifer thermal energy storage (ATES) is a technology to efficiently store and retrieve large amounts of heat using groundwater wells in an aquifer to inject or withdraw hot or cold water. Depending on the local hydrogeology and temperature amplitudes during high-temperature ATES, density differences between the injected hot water and the ambient groundwater may induce significant convective flow components in the groundwater flow field. As a consequence, stored heat may accumulate at the top of the storage aquifer which reduces the heat recovery efficiency of the ATES system. Also, an accumulation of heat at the aquifer top will induce increased emissions of heat to overlying formations with potential impacts on groundwater quality outside of the storage. This work investigates the impacts of convective heat transport on the storage efficiency of a hypothetical high-temperature ATES system for seasonal heat storage as well as heat emissions to neighboring formations by numerical scenario simulations. The coupled groundwater flow and heat transport code OpenGeoSys is used to simulate a medium scale ATES system operating in a sandy aquifer of 20 m thickness with an average groundwater temperature of 10°C and confining aquicludes at top and bottom. Seasonal heat storage by a well doublet (i.e. one fully screened "hot" and "cold" well, respectively) is simulated over a period of 10 years with biannual injection / withdrawal cycles at pumping rates of 15 m³/h and for different scenarios of the temperature of the injected water (20, 35, 60 and 90 °C). Simulation results show, that for the simulated system significant convective heat transport sets in when

  18. Calculation of infiltration coefficient of precipitation based on long-term observation data of spring water:a case study of ore deposit bearing karst water in Dazhuyuan bauxite mining area in Wuchuan%利用泉水长观资料计算降水入渗系数--以务川自治县大竹园铝土矿区岩溶充水矿床为例

    Institute of Scientific and Technical Information of China (English)



    Dazhuyuan bauxite mining area in Wuchuan Autonomous County is a positive landform of mountain platform syncline.The deposits are ore deposits filled with karst water with deep depth of water level.At-mospheric precipitation is the only recharge source of the ground water.In the north,east and west there are escarpments or steep slopes.Metallogenic series and aquiclude occur on the foot of escarpments.A surface watershed is distributed along the upper edge of escarpments with an opening to the west,and forms a com-plete hydrogeological unit.The ground water in the syncline runs from east to west and collects at Meigudong for discharge.The bauxite layer directly touches the thin and discontinuous roof of shale of Liangshan For-mation (P2 l ),and the strong aquifer above of limestone of Maokouqixia Formation (P2m +q )is in direct contact with ore bed,while the karst pipelines are well developed.Therefore,it is more appropriate to apply the water balance method in terms of calculating the water inflow in the mine.The observational data of spring water is used to calculate infiltration coefficient,so as to predict the water inflow in the mine and to evaluate the water yield property of the aquifer.%务川自治县大竹园铝土矿区为高山台地向斜正地形,岩溶充水矿床,水位埋藏较深,大气降水是地下水的唯一补给源,北、东、西为陡崖或陡坡,崖脚为矿系和隔水层,沿陡崖上部边缘分布一条开口向西的地表分水岭,形成完整的水文地质单元,地下水在向斜内由东向西汇集于梅古洞排泄。铝土矿层直接顶板梁山组(P2 l )页岩,厚度小,不连续,其上部茅口栖霞组(P2 m +q )灰岩强含水层与矿层直接接触,并且岩溶管道发育。因此,计算矿坑涌水量的方法用水均衡法较为恰当,即利用泉水观测资料计算入渗系数,从而达到预测矿坑涌水量、评价含水层富水性的目的。

  19. 浅埋煤层高强度开采覆岩(土)破坏演化及溃沙控制技术%Failure characteristics of overburden rock (soil) and sand control technology in high strength mining of shallow coal seam

    Institute of Scientific and Technical Information of China (English)

    张玉军; 李凤明


    随着我国煤炭资源的大规模和高效开采,薄基岩浅埋深的矿区常发生切冒、抽冒、台阶下沉,造成水资源和环境破坏严重.但是,赋存于萨拉乌苏组含水层下伏的连续黏土层的存在,使得基岩及其黏土隔水层组合结构下采动破坏规律不同于传统的基岩岩层,这将为防治矿井突水和实现保水采煤提供了条件.论文采用数值模拟和理论分析的方法,模拟了“黏土隔水层-基岩风化带-基岩”结构特征下不同黏土层与基岩厚度条件下覆岩(土)裂隙发育、顶板破断运动的基本特征,获得了浅埋深条件下采动覆岩(土)的破坏变异规律与发育高度,分析了渍沙的致灾因素和预测判据,并据此提出防治突水溃砂的技术手段.研究结果表明:浅埋煤层“沙土基型”覆岩(土)结构条件下,由于不同基岩与土层厚度的控制作用,使得覆岩(土)破坏发育高度和特征产生变异;水砂源、通道、动力源和空间是近松散含水层溃砂的主要致灾因素,并提出了预测溃沙发生的判据;可通过防止顶板切冒、含水砂层水头压力疏降、局部注浆固沙和合理留设防砂(塌)煤岩柱等技术控制浅埋煤层渍砂灾害发生.%With the large-scale and efficient mining of coal resources in China,local caving and bench convergence accidents frequently occur in the mining area with thin bedrock and shallow depth,which cause serious water resources and environmental damage.However,the mining failure rules of bedrock and clay aquiclude combination structure are different to traditional rock strata because of continuous clay layer,which will provide conditions for the prevention and treatment of mine water inrush and water preserved mining.In this paper,the methods of numerical simulation and theoretical analysis were conducted to simulate the basic characteristics of overlying rock (soil) fracturing and roof breaking movement under the "clay aquifuge