共查询到17条相似文献,搜索用时 156 毫秒
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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。 相似文献
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等效水力隙宽和水力梯度对岩体裂隙网络非线性渗流特性的影响 总被引:1,自引:0,他引:1
等效水力隙宽和水力梯度是影响岩体裂隙网络渗流特性的重要因素。制作裂隙网络试验模型,建立高精度渗流试验系统;求解纳维-斯托克斯方程,模拟流体在裂隙网络内的流动状态,研究等效水力隙宽和水力梯度对非线性渗流特性的影响。结果表明,当水力梯度较小时,等效渗透系数保持恒定的常数,流体流动属于达西流动区域,流量与压力具有线性关系,可采用立方定律计算流体流动;当水力梯度较大时,等效渗透系数随着水力梯度的增加而急剧减少,流体流动进入强惯性效应流动区域,流量与压力具有强烈的非线性关系,可采用Forchheimer方程计算流体流动。随着等效水力隙宽的增加,区别线性和非线性流动区域的临界水力梯度呈幂函数关系递减。当水力梯度小于临界水力梯度时,控制方程可选立方定律;当水力梯度大于临界水力梯度时,控制方程可选Forchheimer方程,其参数A和B可根据经验公式计算得到。其研究结果可为临界水力梯度的确定及流体流动控制方程的选取提供借鉴意义。 相似文献
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碳酸盐岩单裂隙渗流-溶蚀耦合模型及其参数敏感性分析 总被引:1,自引:1,他引:0
岩溶地下水系统是由碳酸盐岩裂隙含水介质演化形成的,系统初始的裂隙网络介质特征及边界条件决定了其演化过程。为揭示岩溶系统演化过程中裂隙介质特征和边界条件的影响程度,建立了裂隙溶蚀扩展的渗流-溶蚀耦合模型,并对不同边界条件下不同隙宽的单裂隙溶蚀扩展特征进行了模拟分析。结果表明:裂隙溶蚀扩展受水的侵蚀性(CO2分压)、水动力条件(水力梯度)、裂隙介质特征(裂隙初始隙宽)等综合作用影响,Ca2+的平衡浓度、水力梯度以及裂隙初始隙宽等参数的增加均能促进裂隙的快速扩展。在这些参数中,初始隙宽B0对岩溶发育的影响最为敏感,水力梯度J和Ca2+平衡浓度Ceq对岩溶发育具有相同的敏感性;此外,随着各参数值的不断增大,参数变化对岩溶发育的敏感程度越来越低。 相似文献
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通过解析法和数值方法对层状裂隙的渗透等效性进行了研究,分析了两种方法对等效性计算结果的差异,得到不同分析方法的适用条件;分析了层状裂隙岩体中不同种类裂隙隙宽的变化对等效渗透性的影响,得到了层状裂隙岩体等效渗透性的一般规律. 相似文献
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通过相似单裂隙岩体冻结三轴试验,研究裂隙倾角、迹长、隙宽、围压和温度对单裂隙岩体力学特性的影响,试验结果表明:裂隙岩体力学参数与倾角呈二次函数分布,与迹长呈指数函数分布,通过拟合式(3)可近似计算岩体强度;岩体强度与围压呈线性分布,负温条件下泊松比和弹性模量受围压影响较小;隙宽小于0.1 mm或大于0.8 mm时,岩体强度随隙宽增大而减小,隙宽在0.1~0.8 mm之间时,岩体力学参数几乎不受隙宽影响;岩体强度随温度降低而增大的作用机制是岩体孔隙水和裂隙水冻结成冰,增大了颗粒间的凝聚力和摩擦角;裂隙倾角影响破裂面的起始位置,迹长影响破裂面的扩展规模,围压影响破裂面的延伸方向;倾角对岩体强度影响最大,迹长次之,温度影响最小。 相似文献
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借助变异函数的优点,即能够反映区域化变量张开度的空间变化相关性和随机性特征,利用Kriging方法对单裂隙中张开度进行估值,由交叉验证法的拟合结果认为估值结果较为合理,并且通过溶质运移试验验证了Kriging法对单裂隙张开度的估值是可行的。 相似文献
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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
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Groundwater flow in fractured rocks is modeled using a coupled model based on the domain decomposition method. In the model, the fractured porous medium is divided into two non-overlapping sub-domains. One is the rock matrix, in which the medium is described using a continuum model. The other consists of deep fractures and fissure zones, where the medium is described using a discrete fracture network (DFN) model. The two models are coupled through the continuity of the hydraulic heads and fluxes on the common boundaries. The coupled model is used to simulate groundwater flow in a hydropower station. The results show that the model simulates groundwater levels that are in agreement with the measured groundwater levels. Furthermore, the model’s parameters relating to deep fractures and fissure zones are verified by comparing three different models (the continuum model, coupled model, and DFN model). The results show that the coupled model can capture and duplicate the hydrogeological conditions in the study domain, whereas the continuum model overestimates and the DFN model underestimates the measured hydraulic heads. A sensitivity analysis shows that fracture aperture has a considerable effect on the groundwater level. So, when the fracture aperture is large, the coupled model or DFN model is more appropriate than the continuum model in the fracture domain. 相似文献
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A. Aydin 《Environmental Geology》2001,40(6):672-677
This review focuses on studies of flow, transport and deformation processes at a scale of a single discontinuity. The paper
provides an evaluation of: (1) various methods suggested for geometrical characterization of void structure; and (2) theoretical
and practical problems arising from significant differences between the actual geometry of fracture void structure and its
parallel plate representation. The use of an equivalent aperture concept is shown to be seriously misleading in: (a) evaluation
of flow regime, and hence selection of appropriate flow laws; (b) correlating tracer and hydraulic tests, and assessment of
solute transport properties; and (c) relating hydraulic and mechanical apertures, and predicting influence of stress perturbation
and deformability.
Received: 2 August 1999 · Accepted: 30 November 1999 相似文献
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Rock and flow parameters of three karstic-fissured-porous aquifers in the Krakow-Silesian Triassic formations were measured
using various methods and compared. Though cavern and fissure porosities are shown to be very low (cavern porosity below 0.5%
and fracture porosity below 0.2%), they contribute dominantly to the hydraulic conductivity (from about 1.3×10–6 to about 11×10–6 m/s). Matrix porosity (2–11%) is shown to be the main water reservoir for solute transport and the main or significant contributor
to the specific yield (<2%). Though the matrix porosity is shown to be much larger than the sum of the cavern and fissure
porosities, its contribution to the total hydraulic conductivity is practically negligible (hydraulic conductivity of the
matrix is from about 5×10–11 m/s to about 2×10–8 m/s). On the other hand, the matrix porosity (for neglected cavern and fissure porosities) when combined with tracer ages
(or mean travel times) is shown to yield proper values of the hydraulic conductivity (K) by applying the following formula:
K≅(matrix porosity×mean travel distance)/(mean hydraulic gradient×mean tracer age). Confirming earlier findings of the authors,
this equation is shown to be of great practical importance because matrix porosity is easily measured in the laboratory on
rock samples, whereas cavern and fracture porosities usually remain unmeasurable.
Received: 21 February 1997 · Accepted: 13 May 1997 相似文献
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Quantification of Aperture and Relations Between Aperture,Normal Stress and Fluid Flow for Natural Single Rock Fractures 总被引:1,自引:0,他引:1
Pinnaduwa H. S. W. Kulatilake Jinyong Park Pirahas Balasingam Robert Morgan 《Geotechnical and Geological Engineering》2008,26(3):269-281
Accurate quantification of rock fracture aperture is important in investigating hydro-mechanical properties of rock fractures.
Liquefied wood’s metal was used successfully to determine the spatial distribution of aperture with normal stress for natural
single rock fractures. A modified 3D box counting method is developed and applied to quantify the spatial variation of rock
fracture aperture with normal stress. New functional relations are developed for the following list: (a) Aperture fractal
dimension versus effective normal stress; (b) Aperture fractal dimension versus mean aperture; (c) Fluid flow rate per unit
hydraulic gradient per unit width versus mean aperture; (d) Fluid flow rate per unit hydraulic gradient per unit width versus
aperture fractal dimension. The aperture fractal dimension was found to be a better parameter than mean aperture to correlate
to fluid flow rate of natural single rock fractures. A highly refined variogram technique is used to investigate possible
existence of aperture anisotropy. It was observed that the scale dependent fractal parameter, K
v, plays a more prominent role than the fractal dimension, D
a1d, on determining the anisotropy pattern of aperture data. A combined factor that represents both D
a1d and K
v, D
a1d × K
v, is suggested to capture the aperture anisotropy. 相似文献
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An integrated linear/non-linear flow model for the conduit-fissure-pore media in the karst triple void aquifer system 总被引:2,自引:0,他引:2
Most karstic aquifer media may be characterized as the triple-void media with highly-varied hydraulic properties, including matrix pore, fissure and conduit, in which liner flow may co-exist with non-linear flow. In this paper, an attempt is made to couple linear flow with non-linear flow in a single unified flow governing equations by introducing the concept of equivalent hydraulic conductivity (EHC) and deriving a general Darcys law for various flow. The expression of EHC in the karst conduit and fissure are also derived. The procedures of numerical implementation are demonstrated via an ideal model and a case study of karst aquifer system in the Beishan Ore Formation area, Guangxi Autonomous Region, China. 相似文献