裂隙岩体渗透系数确定方法综述

总结了近年来裂隙岩体渗透系数的确定方法,主要有现场水力试验法、裂隙测量法和离散裂隙网络渗流数值试验法。每种方法都有自己的适用性和测量尺度。裂隙岩体渗透系数存在尺度效应,针对不同尺度的研究对象,应尽量选取与渗流模型网格剖分尺度匹配的测量方法。裂隙的延伸具有方向性,测试点的布设应合理科学,不同测量方法需要结合起来才能得到裂隙岩体真实的渗透系数。     

五彩湾矿区一号矿井地下水水文地质参数获取的试验研究

水文地质参数是研究地下水运动的重要参数,抽水试验是获取水文地质有关参数的一种重要方法。本文以五彩湾矿区一号矿井地下水为研究对象,在分析区域水文地质条件资料的基础上,进行了7组单孔稳定流抽水试验。研究结果表明:对具有供水意义的第四系松散岩类孔隙含水层渗透系数为0.13~2.85 m/d,新近系碎屑岩类裂隙孔隙含水层渗透系数为0.07~0.316 m/d,白垩系碎屑岩类裂隙孔隙含水层渗透系数为0.02 m/d,侏罗系碎屑岩类裂隙孔隙含水层渗透系数为0.009~0.034 m/d。本次实验结果与对比收集资料结果完全一致。     

四川自一里水电站气垫式调压室围岩渗透性评价

结合自一里水电工程气垫式调压室设计厂房区岩体渗透性研究,提出了从定性分析到定量计算与评价,系统刻画岩体渗透性与分区评价,以满足气垫式调压室设计要求的实用方法.该方法以基础地质与水文地质研究为背景,从系统全面的裂隙测量与统计分析中,获取岩体裂隙空间发育规律和裂隙方向、隙宽、迹长、间距和裂隙率等统计特征值,运用裂隙岩体渗透张量理论,得出分布式岩体渗透主值和综合渗透系数;在此基础上,进行岩体渗透性分区与评价.评价得出:花岗岩夹变质砂岩透镜体的厂区岩体渗透性总体随深度变化,受接触带影响局部渗透性呈强弱交替变化;区内裂隙岩体的渗透性分3级,近地表浅层岩体渗透性较强,综合渗透系数为n×100m/d～n×10-1m/d,调压室区为中等～弱渗透性岩体,渗透系数为n×10-2m/d～n×10-4m/d.     

江汉平原典型含水层水文地质参数反演

含水层参数对于定性分析区域地下水资源评价、数值模拟及预报、开发利用与保护及科学管理具有重要意义,而江汉平原水文地质参数求解的研究却相对较少.2015年江汉平原1:50 000水文地质调查项目完成杨林尾图幅与陆溪口图幅,选择杨林尾图幅和陆溪口图幅中的4个代表性钻孔,分别做了3组抽水试验和一组压水试验.对抽水数据使用Dupuit公式法结合抽水稳定阶段数据求解含水层参数,同时利用Aquifer Test软件中Theis标准曲线法、直线图解法对抽水试验中非稳定条件下抽水数据对含水层参数求解,得到孔隙水含水层渗透系数及弹性给水度;利用压水试验工程规范求解基岩裂隙含水层的渗透系数.探讨了利用非稳定抽水试验条件下求解含水层参数方法的可行性及该方法的优势.计算结果表明:杨林尾镇浅层(20.2~64.55 m)含水层渗透系数为0.075 m/d,弹性给水度为5.8×10-2;深层(138~160 m)含水层渗透系数为9.89 m/d,弹性给水度为2.3×10-5;陆溪口镇浅层(19.4~36.4 m)含水层渗透系数1.26 m/d,弹性给水度为1.1×10-1;基岩渗透系数为0.012 m/d.通过结果对比分析发现对于单孔非稳定抽水试验,对前期水位降深数据筛选分析,同样可以利用非稳定井流理论反演含水层参数,结果比较可靠.      

随机单裂隙饱和/非饱和渗透系数研究

裂隙易在降雨作用下诱发滑坡等灾害,裂隙的饱和/非饱和渗透特性是研究此类问题的关键。利用精密数控机床制作随机粗糙裂隙面,并研制了一套仪器进行此随机粗糙裂隙的渗流试验,得到了裂隙的饱和渗透系数,然后通过间接方法预测此裂隙的非饱和渗透系数。研究发现,当裂隙平均开度为0.4 mm时,其饱和渗透系数为0.1 m/s。通过立方定律得到的水力等效隙宽为0.35 mm,小于其平均隙宽。同时裂隙的渗透系数与平均隙宽的平方成正比,这与立方定律的趋势相一致。研究得到了不同隙宽裂隙的非饱和渗透系数函数,当基质吸力小于进气值时,渗透系数为一常数,即为饱和渗透系数;当基质吸力大于进气值时,裂隙板的渗透系数急剧减小。当裂隙板的基质吸力达到其残余含水率对应的吸力值时,裂隙板的渗透系数基本稳定。在此情况下,基质吸力的继续增加对渗透系数的影响非常小,很难使渗透系数减小。     

水-岩作用下单裂隙灰岩渗流特性演化规律研究

针对某水电站地下洞室裂隙灰岩的渗漏问题,现场采集岩样和库水,设计进行了两种方案的水-岩作用试验,历时360 d,其中,方案1在浸泡过程中定期更换浸泡溶液,模拟地下水的长期浸泡和流动更新现象,方案2主要模拟长期浸泡过程。综合水-岩作用下裂隙面微观形貌特征以及浸泡溶液中离子浓度变化,分析水-岩作用下裂隙灰岩的渗流特性变化特征及机制。研究结果表明：在浸泡过程中,单裂隙灰岩的渗透系数呈“先快后慢”的增大趋势,浸泡360 d后,2.5、3.0、3.5、4.0 MPa等4种侧向应力在两种方案下单裂隙灰岩的渗透系数分别增大了729.90%～384.17%、549.04%～297.45%,侧向应力越小,裂隙岩样的渗透系数增大趋势越明显,增长趋势分别在120 d和90 d后趋于稳定。比较而言,方案1裂隙灰岩的渗透系数增长速率和幅度明显较大,为方案2的1.34～2.07倍。方案1定期更换浸泡库水,保持了浸泡溶液的不平衡状态,使得岩样与浸泡溶液间形成了较大的浓度梯度,增加了反应化学势,加快了裂隙表面矿物溶解、溶蚀速率,而方案2中,长期浸泡使得溶液中离子浓度逐渐接近平衡状态,导致裂隙面矿物溶解、溶蚀速率明显低于方案1。长期水-岩作用使得裂隙面粗糙度和波动性明显减小,局部坡度和起伏度逐渐减小,整体溶蚀深度逐渐增加,据此,建立了水-岩作用下单裂隙灰岩渗流通道演化模型,在长期水-岩作用下裂隙岩样的渗流通道逐渐向吻合度低、开度大的方向演化,从而导致了裂隙岩样等效水力开度及渗透系数的大幅度增长。相关研究思路和成果为裂隙岩体的水-岩作用模拟提供了较好的参考。     

空气扰动技术修复氯苯污染地下水的影响因素研究

通过实验室一维砂柱模拟研究了不同影响因素下空气扰动技术(air sparging,AS)修复氯苯污染地下水的效果,包括介质渗透性、曝气方式、共存污染物、残余饱和态氯苯。结果表明:介质渗透性极大地影响着AS的效果,渗透系数越大,去除效果越好。对渗透系数为10-5m/s数量级及其以下的介质应用AS较为困难;在曝气时间相同的情况下,对于渗透系数为5.1×10-4m/s的中砂,脉冲曝气较连续曝气效果好,对于渗透系数为6.2×10-3m/s的粗砂,2种曝气方式效果相仿;苯和氯苯共存时各污染物的去除存在协同作用;AS对残余饱和态氯苯的去除存在着明显的拖尾效应。     

基于野外Guelph入渗法与室内变水头达西法的土壤饱和渗透系数变化规律

为揭示土壤饱和渗透系数的变化规律,在江汉平原杨林尾-陆溪口地区分别采用Guelph入渗仪和改进的TST-55型土壤渗透仪开展了土壤饱和渗透系数实验。结果表明:采用Guelph入渗法在粉砂质黏壤土中测得冲积物饱和渗透系数相对较大,数量级在10~(-2)～10~(-1)之间,最高达到7.50×10~(-1) m/d,最小为1.40×10~(-2) m/d;湖积物饱和渗透系数在1.86×10~(-3)～4.99×10~(-2) m/d之间;而残积物的为6.05×10~(-3) m/d,相对较小;同为粉砂壤土,相同水位埋深条件下甘蔗地和小麦地(同为耕地)的土壤饱和渗透系数明显比林地的大,这与土壤翻耕及根系、虫孔发育等有关;在相同水位埋深条件下,粉砂壤土的土壤饱和渗透系数普遍比粉砂质黏壤土的大,主要是因为粉砂质黏壤土比粉砂壤土的黏粒比重大、孔隙比相对较小的缘故。室内变水头达西法和Guelph入渗法测得的土壤饱和渗透系数分别介于5.43×10~(-5)～2.10×10~(-3) m/d和1.57×10~(-3)～7.50×10~(-1) m/d之间。室内变水头达西法所测结果明显偏小,主要原因包括:①Guelph入渗法进行现场原位测试时,土壤有效直径相对于室内变水头达西法使用的环刀直径要大得多;②室内变水头达西法所用土样为单一岩性,而Guelph入渗法为原位土层,常常具有双层或多层结构;③Guelph入渗试验期间恰逢雨季,地下水位埋深小,当支持毛细水带接近地表时,Guelph入渗试验将受支持毛细水的影响,从而使Guelph入渗法所测得的结果产生误差。     

不同侧压力系数下裂隙网络岩体非线性渗流特性

基于人工裂隙网络模型,展开一系列不同边界荷载作用下含不同交叉点个数的裂隙网络渗流试验。针对所有试验工况,模型进水口水压力范围均为0～0.6 MPa,侧压力系数均由1.0增加至5.0。试验结果表明：裂隙网络体积流速和水力梯度之间的相关性可以通过Forchheimer函数进行拟合,拟合方程中线性和非线性项系数均随着侧压力系数的增加逐渐增大,而随着裂隙网络交叉点个数的增加逐渐减小;渗流试验过程中,非线性效应系数E和水力梯度J之间的相关性可采用一个幂指数函数进行描述,随着水力梯度的增加,非线性效应系数逐渐增大;随着侧压力系数的增加,裂隙网络临界水力梯度呈现逐渐增大的趋势,对于所有裂隙网络交叉点个数（1～12）,当侧压力系数由1.0增加至5.0,临界水力梯度由0.63～12.13增加至6.01～81.55;提出数学模型 对归一化导水系数 随水力梯度的增大而减小的特征进行分析,随着侧压力系数的增加,两者之间的拟合曲线逐渐上移,拟合系数 整体呈现逐渐增大的趋势。裂隙网络的等效渗透系数随侧压力系数的增加逐渐降低。     

三峡库区泄滩滑坡非饱和渗流分析及渗透系数反演

泄滩滑坡的水文地质结构比较复杂,滑体、滑带及滑动影响带为多孔连续介质,透水层基岩为裂隙介质。采用等效连续介质模型模拟裂隙岩体,建立了泄滩滑坡饱和－非饱和渗流的有限元计算模型。然后采用BP网络对非饱和有限元渗流计算进行了模拟,并根据蓄水期水库水位及滑坡体地下水位监测资料,采用遗传算法对泄滩滑坡各地层渗透系数进行了反演。反演的滑体饱和渗透系数为4.89?10?2 cm/s,与现场原位试验值1.78?10?2 3.2?10?2 cm/s相当;反演的滑带饱和渗透系数为4.66?10?5 cm/s,远比室内试验值2.74?10?7 5.73?10?7 cm/s大。这种差异在一定程度上反映了土体参数的尺度效应。     

Regional fracture network permeability using outcrop scale measurements

Estimating the hydraulic properties of fractured aquifers is challenging due to the complexity of structural discontinuities that can generally be measured at a small scale, either in core or in outcrop, but influence groundwater flow over a range of scales. This modeling study uses fracture scanline data obtained from surface bedrock exposures to derive estimates of permeability that can be used to represent the fractured rock matrix within regional scale flow models. The model is developed using PETREL, which traditionally benefits from high resolution data sets obtained during oil and gas exploration, including for example seismic data, and borehole logging data (both lithological and geophysical). The technique consists of interpreting scanline fracture data, and using these data to generate representative Discrete Fracture Network (DFN) models for each field set. The DFN models are then upscaled to provide an effective hydraulic conductivity tensor that represents the fractured rock matrix. For each field site, the upscaled hydraulic conductivities are compared with estimates derived from pumping tests to validate the model. A hydraulic conductivity field is generated for the study region that captures the spatial variability of fracture networks in pseudo-three dimensions from scanline data. Hydraulic conductivities estimated using this approach compare well with those estimated from pumping test data. The study results suggest that such an approach may be feasible for taking small scale fracture data and upscaling these to represent the aquifer matrix hydraulic properties needed for regional groundwater modeling.     

高水压力作用下裂隙岩体渗透性的变化研究

渗透系数是表征裂隙岩体透水性能的一个重要参数,当水压力较小时,岩体的渗透系数变化不明显,但在高水压力条件下,岩体的渗透系数会发生明显变化,这给我们在进行渗流分析时带来了一定的困难,因为多数情况下是将渗透系数当作定值来计算的。在高压水条件下,基于非达西流方程,推导了裂隙岩体的渗透系数与水压力之间的表达式,并给出了常规压水或低水压力、高压压水时水力劈裂前后渗透系数的计算公式。现场压水试验结果表明,当岩体发生水力劈裂后,渗透系数增加明显,此时可以通过压水量和水压力的变化量来计算裂隙岩体的渗透系数。通过几个抽水蓄能电站的高压压水试验结果验证了裂隙岩体水力劈裂前后渗透系数的变化规律,并与实际裂隙岩体的渗透系数进行了比较,其误差在10%左右,表明本文给出的渗透系数表达式的合理性和准确性,为水利水电工程的渗流分析及渗漏量的计算提供了渗透系数选择的依据。     

Estimating regional-scale permeability–depth relations in a fractured-rock terrain using groundwater-flow model calibration

The trend of decreasing permeability with depth was estimated in the fractured-rock terrain of the upper Potomac River basin in the eastern USA using model calibration on 200 water-level observations in wells and 12 base-flow observations in subwatersheds. Results indicate that permeability at the 1–10 km scale (for groundwater flowpaths) decreases by several orders of magnitude within the top 100 m of land surface. This depth range represents the transition from the weathered, fractured regolith into unweathered bedrock. This rate of decline is substantially greater than has been observed by previous investigators that have plotted in situ wellbore measurements versus depth. The difference is that regional water levels give information on kilometer-scale connectivity of the regolith and adjacent fracture networks, whereas in situ measurements give information on near-hole fractures and fracture networks. The approach taken was to calibrate model layer-to-layer ratios of hydraulic conductivity (LLKs) for each major rock type. Most rock types gave optimal LLK values of 40–60, where each layer was twice a thick as the one overlying it. Previous estimates of permeability with depth from deeper data showed less of a decline at <300 m than the regional modeling results. There was less certainty in the modeling results deeper than 200 m and for certain rock types where fewer water-level observations were available. The results have implications for improved understanding of watershed-scale groundwater flow and transport, such as for the timing of the migration of pollutants from the water table to streams.     

Research of in-situ hydraulic test method by using double packer equipment

Double packer equipment for hydraulic test can be used to measure pressure of test zone directly, and it is frequently used to perform many kinds of hydraulic tests and take groundwater sample from borehole. The test method of this equipment mainly includes the test design, implementation, interpretation and synthetic analysis. By adopting the double packer equipment for hydraulic test, the parameter distribution of rock permeability along borehole can be acquired, as well as the connectivity, water conductivity and water bearing capacity of the disclosed structure and the chemical characteristics of the deep groundwater. It is a necessary method for the research and evaluation of the complex hypotonicity terrace site selection under geological conditions. This method is not only suitable for the geological disposal of high level radioactive waste, but also can be used in the site selection of underground facilities such as storage of petroleum and carbon dioxide. Meanwhile, it has a good application prospect in other hydrogeological investigation fields.     

What can be learned from sequential multi-well pumping tests in fracture-karst media? A case study in Zhangji, China

A fracture-karst aquifer is a karst aquifer with a fractured rock matrix, and its parameters are difficult to determine. Two sequential pumping tests in a fracture-karst aquifer system at the Zhangji well field of China are considered, one carried out before (in 2000) and one after (in 2005) the operation of a pumping station in the well field (2003–2005). The sequential tests serve multiple purposes. First, they provide a cross check of the parameters obtained. Second, they can be used to assess the effect of long-term groundwater exploitation of the aquifer. A three-dimensional finite-element transient flow model has been developed to simulate groundwater flow at the site. Generally good agreement has been found between the simulated and observed hydraulic heads for both tests. The hydraulic parameters obtained from the 2005 test are generally consistent with their counterparts from the 2000 test. However, a small but steady increase of hydraulic conductivities from 2000 to 2005 at the site has been observed. A 10-year prediction of groundwater resources has been made and indicates that the well field can accommodate the proposed 8.0?×?10⁴ m³/day exploitation rate under relative drought conditions without causing a steady decline of groundwater levels.     

裂隙岩体渗透性理论研究进展

裂隙岩体的渗透性是地质灾害、水电工程、矿山工程等研究中需要考虑的重要因素之一。岩体裂隙本身的渗透性取决于它的空间几何参数,因此,可以通过直接测量裂隙的几何要素计算出岩体的渗透系数。岩体的结构及其透水性直接关系到建筑物围岩的稳定及安全.通过水力劈裂试验,可以真实地反映高水压作用下岩体的结构和渗透性的变化规律.以某水电站工...     

The hydraulic conductivity of the fractures intersecting Cambrian sandstone rock masses, central Jordan

This paper outlines the hydraulic characteristics of fractured rock masses and their implication in engineering works. The hydraulic behavior of subsurface fracture systems has been evaluated by means of hydraulic testing using packer tests and by fracture analysis. A comparison of the borehole results with those of surface fracture mapping provides a reasonable correlation between the two methods of measuring fractured rock hydraulic conductivity. The mean hydraulic conductivity value obtained from the boreholes is 36.5 LU (9.26᎒^-5 m/s), while the mean value of hydraulic conductivity obtained from field mapping of fracture data is in the order of 1᎒^-5 m/s. Based on the hydraulic conductivity values the sandstone rock mass can be considered medium to highly conductive; nevertheless, it seems to be almost impervious at greater depth. The empirical relationships which have been derived between hydraulic conductivity and both rock quality designation (RQD) and rock mass rating (RMR) indices indicated that the mean value of hydraulic conductivity of the rock mass could be estimated to be in the order of 10^-5 m/s, which is confirmed by the packer tests.     

Alternative water resources in granitic rock: a case study from Kinmen Island,Taiwan

Kinmen Island is a small, tectonically stable, granitic island that has been suffering from a scarcity of fresh water resources due to excessive annual evapotranspiration over annual precipitation. Recent studies further indicate that shallow (0–70 m) sedimentary aquifers, the major sources of groundwater supply, have already been over-exploited. Therefore, this preliminary study is to investigate the existence of exploitable water resources that can balance the shortage of fresh water on this island. Site characterization data are obtained from island-wide geophysical surveys as well as small-scale tests performed in a study area formed by three deep (maximum depth to 560 m) vertical boreholes installed in mid-east Kinmen northeast to Taiwu Mountain. Vertical fracture frequency data indicate that the rock body is fractured with a spatially correlated pattern, from which three major fracture zones (depths 0–70, 330–360, and below 450 m) can be identified. Geologic investigations indicate that the deepest fracture zone is caused by the large-scale, steeply dipping Taiwushan fault. This fault may have caused a laterally extensive low-resistivity zone, a potential fractured aquifer, near Taiwu Mountain. The middle fracture zone is induced by the Taiwushan fault and intersects the fault approximately 21 m southeast of the study area below a depth of 350 m. Slug testing results yield fracture transmissivity varying from 4.8 × 10⁻⁷ to 2.2 × 10⁻⁴ m²/s. Cross-hole tests have confirmed that hydraulic connectivity of the deeper rock body is controlled by the Taiwushan fault and the middle fracture zone. This connectivity may extend vertically to the sedimentary aquifers through high-angle joint sets. Despite the presence of a flow barrier formed by doleritic dike at about 300 m depth, the existence of fresh as well as meteoric water in the deeper rock body manifests that certain flow paths must exist through which the deeper fractured aquifers can be connected to the upper rock body. Therefore, groundwater stored within the Taiwushan fault and the associated low-resistivity zone can be considered as additional fresh water resources for future exploitation.     

Developing conceptual hydrogeological model for Potsdam sandstones in southwestern Quebec,Canada

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.