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1.
Developing conceptual hydrogeological model for Potsdam sandstones in southwestern Quebec,Canada 总被引：1，自引：1，他引：0
A hydrogeological study was conducted in Potsdam sandstones on the international border between Canada (Quebec) and the USA (New York). Two sandstone formations, arkose and conglomerate (base) and well-cemented quartz arenite (upper), underlie the study area and form the major regional aquifer unit. Glacial till, littoral sand and gravel, and marine silt and clay discontinuously overlie the aquifer. In both sandstone formations, sub-horizontal bedding planes are ubiquitous and display significant hydraulic conductivities that are orders of magnitude more permeable than the intact rock matrix. Aquifer tests demonstrate that the two formations have similar bulk hydrologic properties, with average hydraulic conductivities ranging from 2?×?10?5 to 4?×?10?5 m/s. However, due to their different lithologic and structural characteristics, these two sandstones impose rather different controls on groundwater flow patterns in the study area. Flow is sustained through two types of fracture networks: sub-horizontal, laterally extensive fractures in the basal sandstone, where hydraulic connectivity is very good horizontally but very poor vertically and each of the water-bearing bedding planes can be considered as a separate planar two-dimensional aquifer unit; and the more fractured and vertically jointed system found in the upper sandstone that promotes a more dispersed, three-dimensional movement of groundwater. 相似文献
2.
Pump tests and geophysical logs acquired in a fluvial sandstone aquifer within the resource-rich Moncton Subbasin of New Brunswick, Canada, have been used to characterize fracture patterns and flow directions for purposes of developing a water-wellfield protection plan. Fracture patterns consist of three high-angle sets, and a low-angle set parallel to bedding. NW-trending high-angle fractures, predominantly in fluvial sandstone units, appear to be most important in controlling groundwater flow directions. This contrasts with an earlier regional hydrogeological study that attributed most flow to sub-horizontal bedding-plane fractures. Water levels monitored during a 72-h pump test revealed drawdown extension parallel to the NW-trending fracture set. Drawdown curves indicate that the aquifer is laterally constrained—likely reflecting differences in fracturing observed between the channelized sandstone and surrounding shale units. As a result, groundwater flow induced by pumping is influenced by both fracture anisotropy and by the heterogeneity of the fluvial depositional environment. Relationships observed between fracture patterns, regional geological structure and lithology provide a basis for extrapolating the conceptual model to other nearby areas in the region, where potential impacts of geological resource development on groundwater are attracting public concern. 相似文献
3.
我国北方煤田上覆地下水系统含水层以砂岩为主,是矿井主要充水水源。除浅部、露头区外,上覆砂岩地下水系统总体上构成非径流型蓄水构造,弹性贮存是其地下水主要赋存状态,压力传导、局部渗流为地下水动力学模式,矿井涌水主要为承压含水层弹性释放。非充填开采,煤层上覆地层周期性冒裂形成冒裂二元结构体,其自身释水(弹性、重力)与其外侧含水层断面弹性释水叠加形成矿井涌水。冒裂二元结构体释水随冒裂周期发生,时间短暂。外侧含水层断面释水可用非稳定流定降深沟(渠)流方程描述,进而获得外侧含水层断面释水单宽流量。外侧含水层释水断面随冒裂周期性延展累积,迭代更新,矿井涌水流量随之变化。在研究、刻画外侧含水层释水断面延展、迭代时空规律基础上,给出含水层断面释水流量预测方法、公式,与冒裂二元结构体自身周期性释水流量叠加,获新的矿井涌水量预测方法—非稳定释水-断面流法。 相似文献
4.
Borehole geophysical logging of four production wells completed in Precambrian metagranite in Fauquier County, Virginia (USA), was conducted to characterize stratigraphy, collect water-bearing fracture orientations and describe vertical hydraulic gradients in the vicinity of each borehole. Long-term (48–90 h) single-well pump test data were reevaluated for each well to better characterize this locally important aquifer system. Single-well aquifer test analyses indicate mid-to-late-time infinite acting radial flow conditions within the fractured rock aquifer, followed by increasing late-time contribution of stored groundwater from recharge boundaries. Later-time pump test results are believed to indicate that water-bearing fractures within the metagranite are ultimately recharged by groundwater stored within the regolith. Assumptions about the presence of a recharge boundary sourced by the regolith were tested with a simple groundwater flow model that was calibrated to observed drawdown data associated with one of the long-term pump tests. This study identifies fracturing associated with shear-related metamorphic fabrics in the wellbore and demonstrates the significance of these fractures as mechanisms for accessing groundwater. Results from this investigation indicate that shear-related metamorphic fabrics can be important structures for integrating transmissive fracture networks within the Marshall Metagranite and possibly within other Blue Ridge basement rocks possessing similar metamorphic history.
相似文献5.
《Applied Geochemistry》2002,17(8):1047-1060
Due to the scarcity of water resources in semiarid sedimentary basins, hill reservoirs are often constructed to recharge groundwater and limit runoff induced water loss. The impact of such reservoirs on groundwater chemistry is investigated in the aquifers of the El Gouazine watershed, Central Tunisia. Three groundwater types are recognised, Ca–HCO3, Na–Cl and Ca–SO4. The strong similarity between host rock and groundwater chemistries indicates significant rock–water interaction. A flowpath, along which the chemical composition of the groundwater evolves, can be identified using the contrast in stable isotope signature between upstream and downstream groundwater. Shallow upstream groundwater is recharged by the infiltration of rainwater with the rate of recharge strongly linked to the permeability of the host lithology. Calcium and HCO3 are supplied to an alluvial aquifer from a more rapidly recharged limestone aquifer with the concentration of Ca and HCO3 ions decreasing by dilution. The alluvial aquifer is also enriched in Ca and SO4 during the downstream flow of groundwater through gypsiferous materials. There is evidence of mixing between meteoric groundwater and evaporated reservoir water. Below the reservoir and partly responsible for reservoir leakage is a sandy aquifer, formed by weathering and erosion of a sandstone host which also supplies water to the alluvial aquifer. 相似文献
6.
7.
Deccan basalts of west-central India are hydrogeologically inhomogeneous rocks. A proper understanding of the physical framework of the basalts within which groundwater resides and moves is a key to the hydrogeology of these rocks. Two types of basalt, the vesicular amygdaloidal basalt and the compact basalt, occur as alternate layers in the volcanic pile. Although the rocks are generally inhomogeneous, structures in the basalt, such as sheet joints and vertical joints, serve as zones of groundwater flow. In the shallow subsurface, two groundwater systems are operative. Groundwater system A consists of a vesicular amygdaloidal basalt underlain by a compact basalt, whereas groundwater system B consists of a vesicular amygdaloidal basalt overlain by a compact basalt. Groundwater system A has a better developed network of openings and, as a consequence, this system has a higher transmissivity and storage coefficient than groundwater system B. Wells tapping groundwater system A have higher yields on average and irrigate more hectares of cropland than do wells tapping groundwater system B. This simple systems concept offers a practical methodology for understanding the geometry of the physical framework that contains groundwater in the Deccan basalts. The efficacy of the concept is in its widespread utility for the region. The concept may also be extrapolated to help understand the hydrogeology of deeper Deccan basalt groundwater systems. 相似文献
8.
根据露头、 岩心、 薄片、 古地磁、 成像测井、 岩石力学实验等资料;对东濮凹陷北部三叠系砂岩储层构造裂缝特征及形成期次进行分析。东濮凹陷三叠系砂岩储层主要发育北北东、 北东和近东西向3组高角度构造裂缝;裂缝走向近于平行或垂直主断层;倾向为北西和南东。二马营组裂缝较为发育;和尚沟组和刘家沟组裂缝相对不发育。储层裂缝为3期;分别为燕山早期的北西向扩张裂缝和北北西、 北西西向剪切裂缝;燕山晚期形成北东向拉张裂缝;喜马拉雅期形成北北东、 北东向拉张裂缝、 北北东向剪切裂缝和东西向扩张裂缝。古、 今构造应力场和岩石力学性质的各向异性分析表明;现今构造应力场最大水平主应力和岩石抗压强度的各向异性均影响燕山早期北西向裂缝的张开度及有效性。储层裂缝表现为两期;分别为燕山晚期的北东向拉张裂缝、 喜马拉雅期的北北东、 北东向拉张裂缝;北北东向剪切裂缝和东西向扩张裂缝。研究结果阐明了东濮凹陷北部三叠系砂岩储层构造裂缝特征及发育规律。 相似文献
9.
Relation of tectonic structure to groundwater flow in the Beypazari region, NW Anatolia, Turkey 总被引：1，自引：0，他引：1
Ahmet Apaydin 《Hydrogeology Journal》2010,18(6):1343-1356
The Beypazari region in NW Anatolia (Turkey) is characterized by high water demand and stress on available water resources. Tectonic structures control the groundwater flow, hydraulic head and well yield in the study area, which is located in the central part of the Beypazari Neogen basin. The impact of major tectonic structures on groundwater flow in the Cakiloba-Karadoruk aquifer is described. This aquifer is of sedimentary composition and underwent tectonic deformation, post-Miocene, forming northeast-striking asymmetric synclines, anticlines, monoclines, high-angle reverse faults and N–S striking tensional faults. Some of these structures affect groundwater flow by separating the aquifer system into sub-compartments, each having unique recharge, boundary and flow conditions. The groundwater system is compartmentalized into three sub-systems under the impacts of the Zaviye and Kanliceviz faults: (1) Arisekisi, (2) Elmabeli and (3) Southern sub-systems. The southern part of the Arisekisi sub-system and the Southern sub-system are characterized by a syncline and the aquifer is confined in the central part of the syncline. The Elmabeli sub-system has unconfined conditions. Consequently, the effects of tectonic structures are shown to be important for selecting well locations, evaluating groundwater use, groundwater management, and contaminant control in the study area, and also in other tectonic regions. 相似文献
10.
《Applied Geochemistry》1998,13(2):143-153
The Cretaceous Chalk [Ulster White Limestone Formation (UWLF)] in Northern Ireland has been diagenetically altered to a hard, low porosity, low matrix-permeability rock. It subcrops extensive beneath thick horizontal Tertiary Basalt lavas, but has a restricted strip of outcrop (approximately 80 km2) around the periphery of the overlying igneous rock. Despite its nature and location, numerous springs issue from the Chalk and are used for public and local supply, although little is known about the origin of the groundwater or the type of flow within the Chalk. We have addressed these unknowns using hydrogeochemical data from both rock types and surface stream waters, and fluorescent dye tracing. We have demonstrated that leakage recharge from the basalt to the Chalk accounts for less than 20% of the total water issuing from the Chalk springs using geochemical mass balance of conservative species and discharge data. The majority of the discharge derives from streams coming off the basalt and entering sink holes in the Chalk aquifer. Field and water tracing evidence shows that groundwater flow in the Chalk is dominated by conduit and fissure flow near to the outcrop areas. Karstification has been widespread near outcrop but has not ocurred in the sub-basalt region. Beneath the basalts, the Chalk exhibits different hydraulic properties due to the reduced recharge and dissolution potential that has prevented extensive development of fissure permeability in the UWLF. The Chalk aquifer thus appears to be strongly zoned in terms of the source of water, flow regime and recharge rate. 相似文献
11.
矿井防治水的理论和工程实践表明，水文地球化学方法是矿井水害预防和治理工作中较为有效的一种方法，以平顶山矿区、肥城矿区为例，阐述了水文地球化学方法在水害研究中的某些应用，在平顶山矿区、环境同位素（氢、氧）和统计分析（聚类分析）技术的研究结果，进一步证实和校正了以往对该区水流系统的概念模型，即局部水流系统和过渡水流系统（或西南部和东北部子系统）的划分仅适于寒武系灰岩含水系统；砂岩含水层在矿区中、北部低山区接受大气降水补给，并有可能补给薄层灰岩含水层。在肥城矿区，地下水示踪试验结果表明，该区的GF9，F7－1、F7－3断层在试验段内具有较强的导水性，奥灰水可通过上述断层并以不同特征的通道和速度继续径流并补给各井下出水点，因而是该区煤矿安全的主要威胁。 相似文献
12.
冯记沟煤矿地处西部干旱区,地表水及地下水极为贫乏。矿井井下的主要含水区段为侏罗系直罗砂岩含水层（Ⅱ）、一煤-六煤砂岩含水层（Ⅲ）和采空区积水。现生产二号井煤矿开采过程中,由于三煤层顶板的垮落,裂隙增加,Ⅲ含水层与Ⅱ含水层连为一体。目前二号井的正常涌水量为115m^3／h,最大涌水量280m^3／h。根据勘探资料及水质分析结果,对矿区地下水进行了评价,认为矿井地下水不宜作生活饮用水,处理后可做为锅炉用水、冷却用水、绿化灌溉用水及混凝土建筑用水。 相似文献
13.
鄂尔多斯盆地白垩系含水层系统分析 总被引：18，自引：2，他引：16
从地下水含水层系统的角度对鄂尔多斯盆地白垩系地下水系统进行了划分和分析。由于下白垩系统保安群为一套陆相碎屑岩建造,岩性复杂,由砂岩、粉砂岩和泥岩组成的频繁交替、重复叠置的多层层状结构,决定了鄂尔多斯白垩系自流水盆地是多层结构的地下水系统。这种重复叠置的多层层状地质结构,决定了地下水含水层系统的多层性、承压性及层与层之间的相对封闭性。根据沉积旋回和含水介质的性质,在全盆地范围内把白垩系地下水系统从上向下划分为：罗汉洞含水岩组、环河含水岩组和洛河含水岩组。通过对这3大含水岩组分别进行了分析认为,洛河含水岩组和环河含水岩组分布范围广、,含水层厚度大、天然资源丰富,是盆地区具供水意义的主要含水岩组。罗汉洞含水岩组因分布面积小,含水层厚度差异大、水质变化大,除陇东地区外,大部分地区供水价值较小。 相似文献
14.
Faults and fractures are a critical store and pathway for groundwater in Ireland’s limestone bedrock aquifers either directly as conductive structures or indirectly as the locus for the development of karst conduits. From the quantitative analysis of post-Devonian faults and fractures in a range of lithological sequences, this report describes the principal characteristics of Cenozoic strike-slip faults and joints, the youngest and the most intrinsically conductive fractures within Irish bedrock. Analysis of these structures in more than 120 outcrop, quarry, mine and cave locations in a range of bedrock types, provides a basis for: (1) definition of quantitative models for their depth dependency, lithological control, scaling systematics and links to preexisting structure, (2) conceptualisation of their impact on groundwater behaviour, and (3) estimation of groundwater flow parameters. The quantitative models provide constraints on fracture-controlled flow connectivity. Commonly observed decreases in sustainable flows and water strike interceptions with depth are attributed to increasing confinement and decreasing fracture connectivity and dissolution. Faults and joints have quite different end member geometries, with faults having strongly heterogeneous scale-independent properties and joints more often showing scale-dependent stratabound properties. The highest and most sustainable groundwater flows are usually associated with the complexity of structure of Cenozoic faults and of preexisting Carboniferous structures (on which conductive fracturing localises), enhanced by karstification and strongly jointed limestone bedrock particularly in the near-surface. Increased groundwater flow is promoted within bedded, rather than massive (i.e. unbedded), limestone sequences, characterised by bedding-parallel fractures and karst connecting otherwise subvertical fractures and subvertical wells.
相似文献15.
D. I. Cendón S. I. Hankin J. P. Williams M. Van der Ley M. Peterson C. E. Hughes 《Australian Journal of Earth Sciences》2014,61(3):475-499
Groundwater residence time in the Kulnura–Mangrove Mountain aquifer was assessed during a multi-year sampling programme using general hydrogeochemistry and isotopic tracers (H2O stable isotopes, δ13CDIC, 3H, 14C and 87Sr/86Sr). The study included whole-rock analysis from samples recovered during well construction at four sites to better characterise water–rock interactions. Based on hydrogeochemistry, isotopic tracers and mineral phase distribution from whole-rock XRD analysis, two main groundwater zones were differentiated (shallow and deep). The shallow zone contains oxidising Na–Cl-type waters, low pH, low SC and containing 3H and 14C activities consistent with modern groundwater and bomb pulse signatures (up to 116.9 pMC). In this shallow zone, the original Hawkesbury Sandstone has been deeply weathered, enhancing its storage capacity down to ～50 m below ground surface in most areas and ～90 m in the Peats Ridge area. The deeper groundwater zone was also relatively oxidised with a tendency towards Ca–HCO3-type waters, although with higher pH and SC, and no 3H and low 14C activities consistent with corrected residence times ranging from 11.8 to 0.9 ka BP. The original sandstone was found to be less weathered with depth, favouring the dissolution of dispersed carbonates and the transition from a semi-porous groundwater media flow in the shallow zone to fracture flow at depth, with both chemical and physical processes impacting on groundwater mean residence times.Detailed temporal and spatial sampling of groundwater revealed important inter-annual variations driven by groundwater extraction showing a progressive influx of modern groundwater found at >100 m in the Peats Ridge area. The progressive modernisation has exposed deeper parts of the aquifer to increased NO3? concentrations and evaporated irrigation waters. The change in chemistry of the groundwater, particularly the lowering of groundwater pH, has accelerated the dissolution of mineral phases that would generally be inactive within this sandstone aquifer triggering the mobilisation of elements such as aluminium in the aqueous phase. 相似文献
16.
The link between stress and hydrologic properties was examined at two sites that are distinguished by different rock types
and different stress states. This investigation is based upon the analysis and interpretation of geophysical logs obtained
in water wells at the two locations. At the northeast site (Newark Basin), the hydrologic characteristics of sedimentary rocks
are dependent upon the relationship to the current regional stress field of two primary types of orthogonal features that
serve as preferential pathways for fluid flow. Subhorizontal bedding-plane partings are highly transmissive near the surface
and delineate transversely isotropic fluid flow at shallow depths. With increasing depth, the subhorizontal planes become
less dominant and steeply dipping fractures become more influential hydrologically. These high-angle features define anisotropic
flow pathways that are preferentially oriented along strike. At the southwest site (west Texas), extrusive rocks are subjected
to topographically modified tectonic and gravitational stresses that vary spatially within a valley setting. The attendant
changes in stress invariants cause fracture connectivity within the rock mass to systematically increase with depth along
the valley flanks, but to remain relatively low in the central valley. The degree of fracture connectivity predicted within
this valley configuration is consistent with variations in transmissivity determined at several well locations. In each of
these cases, the idealized understanding of the hydrologic system is enhanced by considering the effects of regional and local
stresses that act upon the fractured-rock aquifer.
Electronic Publication 相似文献
17.
煤炭开采后峰峰矿区奥陶系岩溶水硫酸盐演化过程研究 总被引：5，自引：3，他引：2
文章运用水化学和同位素水文学等手段,寻求奥陶系岩溶水硫酸盐演化过程的“指纹”,通过不同含水层间水化学、稳定同位素差异的比对,分析其与上覆含水层间的水力联系和硫动力分馏过程,阐述采矿活动影响下峰峰矿区奥陶系岩溶水硫酸盐的演化过程。研究结果表明:煤矿开采后,峰峰矿区奥陶系岩溶水硫酸盐含量普遍增高,演化特征呈现多样性,存在多种硫动力分馏过程。分馏动力主要来自矿坑水和孔隙水通过导水裂隙的渗漏（越流）补给,以及脱白云石化过程中自身蒸发岩矿物（石膏）的溶解。 相似文献
18.
Groundwater processes and sedimentary uranium deposits 总被引：8，自引：0，他引：8
Hydrologic processes are fundamental in the emplacement of all three major categories of sedimentary uranium deposits: syngenetic,
syndiagenetic, and epigenetic. In each case, the basic sedimentary uranium-enrichment cycle involves: (1) leaching or erosion
of uranium from a low-grade provenance; (2) transport of uranium by surface or groundwater flow; and (3) concentration of
uranium by mechanical, geochemical, or physiochemical processes. Although surface flow was responsible for lower Precambrian
uranium deposits, groundwater was the primary agent in upper Precambrian and Phanerozoic sedimentary uranium emplacement.
Meteoric or more deeply derived groundwater flow transported uranium in solution through transmissive facies, generally sands
and gravels, until it was precipitated under reducing conditions. Syndiagenetic uranium deposits are typically concentrated
in reducing lacustrine and swamp environments, whereas epigenetic deposits accumulated along mineralization fronts or tabular
boundaries.
The role of groundwater is particularly well illustrated in the bedload fluvial systems of the South Texas uranium province.
Upward migration of deep, reducing brines conditioned the host rock before oxidizing meteoric flow concentrated uranium and
other secondary minerals. Interactions between uranium-transporting groundwater and the transmissive aquifer facies are also
reflected in the uranium mineralization fronts in the lower Tertiary basins of Wyoming. Similar relationships are observed
in the tabular uranium deposits of the Colorado Plateau.
Received, May 1998 · Revised, July 1998 · Accepted, September 1998 相似文献
19.
Coalfields in North China encompassing more than ten Provinces contain six to seven coal seams in the Permo-Carboniferous strata. The lower three seams, accounting for 37% of the total reserves, are threatened with karst water from the underlain Ordovician limestone. Hundreds of water inrush incidences have occurred in which a large amount of water suddenly flows into tunnels or working faces under high potentiometric pressure and over 30 mines have been flooded over the last 20 years. Large-scale dewatering or depressurizing of the karst aquifer was considered essential to avoid water inrushes and keep the mines safely operational. This practice has caused sinkholes, dry springs, water supply shortage, and groundwater contamination in the surrounding areas, which is environmentally not permitted. One of the alternative water control measures is to make full use of the rock layer between the coal seam and the karst aquifer as a geological barrier. Similar to the application in the nuclear industry where a geological barrier is used to contain radioactive wastes, the barrier of this application is considered a hydraulic barrier as well with the objective to prevent or constrain water flow from the underlying aquifer into mines. Its effectiveness to constrain water flow is described by a parameter referred to as hydrofracturing pressure (Phf). When the water pressure in the underlying aquifer exceeds Phf, a wedging effect takes place within the fractures of the geological barrier and, as a result, water inrush occurs. In-situ hydrofracturing tests were used to determine Phf in bauxite and silty sandstone at tunnels. The Phf in the silty sandstone is larger than that in the bauxite but they both vary with depth (distance from the bottom of the tunnel). Based on the test results, a new safety criterion for water inrush was derived for mines and it has been successfully applied to mining practices with the minimum effort of dewatering in the karst aquifer. The same criterion can also be applied to tunneling and quarrying in areas with similar geological conditions. 相似文献
20.
Lalibela is a medieval settlement in Northern Ethiopia famous for its 11 beautifully carved rock hewn churches, registered as World Heritage Site in 1978. The rock hewn churches are grouped into three based on their proximity: the Bete Medhane Alem (Church of the Holy Saviour), Bete Gabriel–Rufael (Church of St. Gabriel–Rafael) and Bete Giorgis (Church of St. George) groups. The churches are carved out of a single, massive scoriaceous basalt hill which was deposited along an East–West extending palaeovalley in the Oligo-Miocene Trap basalt of the northwestern Ethiopian plateau.The Rock Mass Rating (RMR) classification scheme was used to classify the rock mass (assuming each church as a separate rock mass) based on their uniaxial compressive strength and the spacing and conditions of discontinuities. Though most of the churches are hewn from medium to high strength rock mass, discontinuities make them vulnerable to other deteriorating agents mainly weathering, and water infiltration. Most of the rock hewn churches are affected by pre-carving cooling joints and bedding plane discontinuities, and by mostly but not necessarily post-carving tectonic and seismic induced cracks and fractures. Material loss due to deep weathering triggered by rain water infiltration and uncontrolled groundwater seepage affects most of the churches, particularly the Bete Merqorios (Church of St. Mark) and Bete Aba Libanos (Church of Father Libanos) churches. The scoriaceous basalt which is porous and permeable allows easy passage of water while the underlying basalt is impermeable, increasing the residence time of water in the porous material, causing deep weathering and subsequent loss of material in some of the churches and adjoining courtyards. 相似文献