共查询到20条相似文献，搜索用时 31 毫秒
1.
2.
3.
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。 相似文献
4.
堆积层滑坡的岩土体渗透系数具有一定的不确定性,且渗透系数是饱和-非饱和渗流分析的重要参数,开展考虑其空间变异性的库岸堆积层滑坡渗流变形分析具有重要意义。以三峡库区中的白水河滑坡为研究对象,基于地面核磁共振技术获取的岩土体渗透系数,分析滑坡体渗透系数的空间变异特征,采用半变异函数方法求得滑坡体渗透系数的竖直波动范围,在此基础上建立渗透系数的非平稳随机场模型。以非侵入式随机有限元的方式开展库水升降两种工况下不确定模型与确定模型的流固耦合模拟,分析两种模型的渗流场、位移变形特征及其差异。结果表明：相比于确定模型,不确定模型孔压改变的滞后性更为明显,且库水下降工况下整体的变形更大,若忽略滑体渗透系数的非平稳空间变异特征将会低估滑坡的实际变形。 相似文献
5.
以颗粒状和粉末状膨润土防水毯(GCLs)为对象,运用GDS (global digital systems)全自动渗透仪开展渗透试验,研究CaCl_2溶液作用下GCLs渗透性能的温度效应,初步探讨其机理。试验表明:当水化液为0.05mol/L的CaCl_2溶液时,两种GCLs渗透系数随温度升高呈现增大趋势;当水化液为去离子水时,颗粒状GCL渗透系数随温度升高而减小,粉末状GCL渗透系数随温度升高而增大。去离子水情况下,膨润土吸附结合水量随温度升高而减小;CaCl_2溶液作用下,吸附结合水量较去离子水情况大幅降低。当CaCl_2溶液浓度一定时,膨润土膨胀指数随温度升高而略有增大;当温度一定时,膨润土膨胀指数随CaCl_2溶液浓度升高而显著减小。以去离子水进行试验时:颗粒状和粉末状GCLs渗透系数随温度的变化主要影响因素为凝胶态蒙脱石数量,其次为流体黏滞系数和吸附结合水量;颗粒状GCLs膨润土孔隙结构越不均匀,凝胶态蒙脱石数量的影响就越显著,导致渗透系数随温度升高而减小、固有渗透率随温度升高显著降低。以CaCl_2溶液进行试验时,两种GCLs渗透系数随温度变化的主要受流体黏滞系数和吸附结合水量的影响,而受凝胶态蒙脱石数量的影响较小。孔隙溶液性质、温度和膨润土类型均对GCLs的防渗性能具有重要影响。 相似文献
6.
水力传导度是描述孔隙介质物理特性的重要参数,水力传导度的空间变异性直接影响到水分与溶质在介质中的运移状况。由于基于随机理论的方法难于描述具有多重变异尺度的水力传导度的空间变异性,使得基于分形理论的方法得到了较快发展和应用。详细介绍并评述了分形理论和方法的基本特征及研究进展,水力传导度的空间变异分形与弥散尺度效应的关系及其对溶质运移的影响。 相似文献
7.
北塘水库库底地层渗透系数的随机特性分析 总被引：4，自引：0，他引：4
为研究渗透系数的随机分布特征,以滨海平原水库也是南水北调调节及事故备用水库的北塘水库库底地层为研究对象,通过野外取样、室内达西渗透实验和颗粒分析实验等手段,获取了库底地层渗透系数的两组数据及其空间分布,借助于SPSS软件的P—P图以及单样本K-S检验,对渗透系数的空间随机分布进行了分析。结果表明,与正态分布相比较,北塘水库库底地层渗透系数更接近对数正态分布,这为库区渗漏量计算的可靠性分析、库底沉积物渗透系数的空间变异特征分析等奠定了基础。 相似文献
8.
潜水水流的动态随机模拟是一个复杂而难解决的问题.通过建立二维潜水非稳定流模拟的摄动随机有限元模型, 把控制方程的主要参数渗透系数和给水度随机变量、及源汇项和边界条件看作随机变量.在充分考虑4种随机因素的条件下, 推导出求解潜水二维非稳定流均值和方差的9个方程; 重点介绍了不同方程数值离散的特殊处理方法.通过设定理想例子对模拟结果进行了分析, 表明随机变量中边界条件值方差、渗透系数方差变化对水头方差变化的影响很小, 给水度方差的变化对水头方差的变化影响很大.本模型考虑因素全面, 对一般的潜水非稳定流随机模拟都可应用.本研究给出了边界、渗透系数、给水度的随机因素对潜水动态模拟的影响, 丰富和补充了地下水运动的随机理论. 相似文献
9.
10.
将大规模渗流有限元计算与随机响应面法相结合,对双江口心墙堆石坝进行渗透稳定可靠性分析。在基于随机响应面法的可靠度分析框架内,堆石坝稳定渗流有限元计算过程和可靠度分析过程分开独立进行,通过对心墙渗透坡降较大区域的节点建立统一的渗透稳定功能函数,采用渗流有限元分析方法和随机响应面法,计算出该区域每个节点处的渗透破坏失效概率,并将最大失效概率作为心墙的失效概率。最后,分析了心墙渗透系数、覆盖层渗透系数、上游水位与心墙具有最大失效概率节点处渗透坡降的相关关系,以及心墙渗透系数和上游水位的变异性对心墙渗透破坏失效概率的影响。计算结果表明,随机响应面法3阶Hermite展开就能够保证良好的计算精度,且计算耗时较小;双江口堆石坝心墙具有最大失效概率节点处的渗透坡降与上游水位密切相关,而与心墙本身的渗透系数呈弱负相关关系,与覆盖层渗透系数的相关性不显著;随着上游水位变异性的增大,心墙失效概率急剧增大,而这种效应对于心墙渗透系数并不明显。研究成果为随机响应面法在实际工程中的应用奠定了一定的基础。 相似文献
11.
Nilo Cesar Consoli Karla Salvagni Heineck J. Antonio H. Carraro 《Geotechnical and Geological Engineering》2010,28(4):361-371
The objective of this study was to evaluate the effect of water-cement ratio and cement content on the hydraulic behavior of soil–cement–bentonite (SCB) and soil–bentonite (SB) mixtures permeated with water and diesel oil, to assist with the design of vertical cutoff walls constructed with those mixtures. The experimental program included unconfined compression tests, hydraulic conductivity tests and X-ray diffraction analysis. The test results indicated changes in hydraulic conductivity take place due to the variation of the water-cement ratio and permeant fluid. The hydraulic conductivity of the SB mixtures permeated with diesel oil was higher than the hydraulic conductivity of the same samples permeated with water. X-ray diffraction analyses suggest that this might be due to the decrease in double layer thickness and increase of seepage pore space imparted by diesel oil permeation. Conversely, Portland cement addition increased the hydraulic conductivity of the SCB specimens permeated with water, whereas subsequent diesel oil permeation reduced the hydraulic conductivity of the SCB specimens; this might be due to the relatively lower impact imparted by diesel permeation on the double layer characteristics of the bentonite stabilized with Portland cement. 相似文献
12.
以回灌过程中渗透系数衰减模型为基础,推导了不同回扬次数的渗透系数解析表达式;将其应用于Theis公式,获得了考虑渗透系数衰减以及暂时性堵塞率条件下回灌与回扬物理过程中含水层压强的解析表达式,更准确地刻画了回灌与回扬的物理机制。计算结果表明：在连续回灌不回扬过程中,井内灌压增长符合指数曲线特征,而采取回扬措施后,由指数连续上升转变为间断式阶梯上升;回扬次数越多,灌压下降越明显,但灌压变化幅度随回扬次数的递增而减小。根据解析解定义的两种堵塞率的结果,可以实现利用实验判断不同成分回灌水源对含水层堵塞机理的分析,从而达到科学制定回灌水源标准的目的。 相似文献
13.
Deformation effects of porosity variation on soil consolidation caused by groundwater table decline 总被引：1，自引：0，他引：1
Soil consolidation has been widely analyzed using the poroelastic theory. As soil consolidation proceeds, porosity variation leads to the changes in hydraulic conductivity, Young’s modulus, and body force. However, the combined deformation effect of porosity variation on soil consolidation is rarely examined. In this study, a poroelastic consolidation model used to simultaneously consider the changes in hydraulic conductivity, Young’s modulus, and body force was developed to investigate the combined deformation effect of porosity variation on soil consolidation caused by groundwater table decline. The results indicate that the deformation effect of porosity variation on soil consolidation is negligible when the body force number is <0.01. For body force numbers >0.01, soil displacement could be overestimated or underestimated if the combined deformation effect of porosity variation is not completely considered. The misestimation of soil displacement increases as the body force number increases. In addition, the combined deformation effect of porosity variation also affects the transmission of pore water pressure. Therefore, it could be concluded that a reliable analysis of soil consolidation must simultaneously account for the variations in hydraulic conductivity, Young’s modulus, and body force. 相似文献
14.
地下热水回灌过程中渗透系数研究 总被引：7，自引：2，他引：7
地下热水回灌是处理地热开发利用中所引发的热储层压力降低和弃水污染环境等问题的有效方法。第三系热储层的回灌过程中，由于物理阻塞和化学阻塞，导致热储层的渗透性下降。回扬可在短时间内消除或缓解堵塞问题，提高回灌效率。将利用回灌试验数据求得的渗透系数进行回归，得到渗透系数衰减方程。用数值方法模拟渗透系数对回灌的影响，对比渗透系数为常数与渗透系数变化两种情况，结果表明渗透系数衰减是第三系回灌能力下降的主要原因，渗透系数是影响回灌的重要因素。 相似文献
15.
Determination of hydraulic conductivity of sand-bentonite mixtures for engineering purposes 总被引：1，自引：0，他引：1
Pollution of the environment due to leakage from waste repositories is a well-known and wide spread problem. Emphasis has therefore been put on design of liners for such repositories, focusing on hydraulic conductivity and its variation with time, liner composition, water content, compaction etc. The paper addresses the hydraulic conductivity of sand/bentonite mixtures, especially the variation of the hydraulic conductivity as a function of bentonite content, compaction and degree of saturation. In order to better understand the variation of the hydraulic conductivity of a sand–bentonite mixture a new parameter k
1 has been proposed. The parameter reflects the amount of bentonite per pore volume and can easily be calculated based on the amount of bentonite and the dry density of the soil mixture. Thereby, the hydraulic conductivity can be predicted as a function of different degres of compaction. This method can be used for engineering purposes to predict the hydraulic conductivity at an early stage of a design to get an idea of the required design and hence, cost. 相似文献
16.
Modeling water-table fluctuations in a sloping aquifer with random hydraulic conductivity 总被引：1，自引：0，他引：1
To prevent environmental problems like water logging and increase in soil salinity which are responsible for the degradation of the top productive soils, an optimum ditch drainage design is required. For this purpose a knowledge of the spatio-temporal variation of the water table is essential. In this study the spatio-temporal variation of the water table in a sloping ditch drainage system has been modeled from a stochastic point of view, incorporating randomness in hydraulic conductivity to get the expression for the mean and the standard deviation of the water-table height. The hydraulic conductivity has been considered to be a realization of a log-normal distribution. Application of these expressions in the prediction of mean water-table variation with the associated error bounds has been demonstrated with the help of a ditch drainage problem of a sloping aquifer. The sensitivity analysis has also been carried out to see the effect of variability in the hydraulic conductivity on the water-table fluctuations. The error bounds quantified on the water-table height will thus help in the decision-making process for proper drainage design. 相似文献
17.
Philip T. Harte 《Environmental Earth Sciences》2017,76(6):251
A common assumption with groundwater sampling is that low (<0.5 L/min) pumping rates during well purging and sampling captures primarily lateral flow from the formation through the well-screened interval at a depth coincident with the pump intake. However, if the intake is adjacent to a low hydraulic conductivity part of the screened formation, this scenario will induce vertical groundwater flow to the pump intake from parts of the screened interval with high hydraulic conductivity. Because less formation water will initially be captured during pumping, a substantial volume of water already in the well (preexisting screen water or screen storage) will be captured during this initial time until inflow from the high hydraulic conductivity part of the screened formation can travel vertically in the well to the pump intake. Therefore, the length of the time needed for adequate purging prior to sample collection (called optimal purge duration) is controlled by the in-well, vertical travel times. A preliminary, simple analytical model was used to provide information on the relation between purge duration and capture of formation water for different gross levels of heterogeneity (contrast between low and high hydraulic conductivity layers). The model was then used to compare these time–volume relations to purge data (pumping rates and drawdown) collected at several representative monitoring wells from multiple sites. Results showed that computation of time-dependent capture of formation water (as opposed to capture of preexisting screen water), which were based on vertical travel times in the well, compares favorably with the time required to achieve field parameter stabilization. If field parameter stabilization is an indicator of arrival time of formation water, which has been postulated, then in-well, vertical flow may be an important factor at wells where low-flow sampling is the sample method of choice. 相似文献
18.
Modeling of subsidence and stress-dependent hydraulic conductivity for intact and fractured porous media 总被引：4，自引：0，他引：4
Summary This study investigates the changes in deformation and stress dependent hydraulic conductivities that occur as a result of underground mining in intact and fractured porous media. The intact porous medium is assumed to be comprised of regularly packed spherical grains of uniform size. The variation in grain size or pore space due to the effect of changing intergranular stresses results in a change in rock hydraulic conductivity. A model is developed to describe the sensitivity of hydraulic conductivity to effective stresses through Hertzian contact of spherical grains. The fractured porous medium is approximated as an equivalent fracture network in which a single fracture is idealized as a planar opening having a constant equivalent thickness or aperture. Changes in fracture aperture as a result of changes in elastic deformation control the variation of hydraulic conductivity. A model is presented to illustrate the coupling between strain and hydraulic conductivity. Subsidence induced deformations that result from mining induced changes in hydraulic conductivity in both intact and fractured media. These changes are examined and compared with results from a mining case study. 相似文献
19.
求解库岸边坡岩土体的渗透系数是研究滑坡渗流场及多场演化的基础,一般通过原位试验和室内试验求得,但试验成本较高且试验位置具有一定的随机性。本文以三峡库区马家沟滑坡为例,提出一种利用地下水位动态观测资料反演滑坡岩土层渗透系数的方法。具体步骤为:（1）依据滑坡的勘察资料和水位观测数据,构建滑坡数值模型;（2）利用SPSS生成不同渗透系数正交试验组合,并将渗透系数代入数值模型中计算监测井的水位,得到不同渗透系数及其对应的模拟水位数据;（3）应用遗传算法优化的支持向量机构建坡体模拟水位与渗透系数的非线性映射关系,再通过代入实际动态监测水位值求得滑坡岩土层的渗透系数;（4）将求得的渗透系数代入数值模型,用计算的模拟水位与实际观测水位进行对比验证。研究结果表明:遗传算法优化的支持向量机具有良好的学习预测效果,能准确预测渗透系数与水位的关系。该反演方法具有高效、准确的优点,反演结果的精度满足实际应用需要。 相似文献
20.
针对比利时HADES地下实验室PRACLAY现场加热试验,应用温度-渗流-应力耦合弹塑性模型,模拟现场加热过程中泥岩核废料处置库的水力学响应特征。采用单因素分析法,就泥岩热、水、力学参数对核废料处置库围岩孔压、温度、有效应力的影响进行了三维有限元分析。并基于参数敏感性分析结果,就温度、渗流、应力三场两两耦合作用对处置库围岩水力学响应的影响程度进行了系统分析。研究结果表明：泥岩热、水、力学参数中,渗透系数、弹性模量以及导热系数对加温所导致的超孔压的值影响较大;凝聚力、内摩擦角以及热膨胀系数对孔压的影响较小,但会显著影响围岩的有效应力;导热系数对围岩温度场的分布有决定性影响,温度传递的差异会显著影响围岩的孔压和有效应力;不同的热、水、力学参数对孔压、温度以及有效应力的影响机制是不同的,温度、渗流、应力三场两两耦合作用对围岩水力学响应的影响程度也存在显著的差异性。温度场对应力场、温度场对渗流场的耦合效应十分显著,加热后,围岩超孔压的产生以及热膨胀导致的有效应力变化会显著影响处置库的稳定。该研究结果在一定程度上可以为核废料处置库泥岩的热、水、力学参数的确定及耦合机制分析提供科学依据。 相似文献