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1.
Permeability and stress in crystalline rocks 总被引：2，自引：0，他引：2
Groundwater from crystalline rocks is a significant resource in many areas of the world. It is also an important medium for contaminant transport from, for example, deep nuclear waste repositories. Stress distributions in fractured rocks are important in controlling groundwater flow in several ways: (i) palaeostress fields are responsible for the evolution of fracture systems which transmit groundwater; (ii) current in situ stress fields will influence the shape and aperture of fractures; (iii) humans can influence the natural stress field in a rock mass to enhance fracture flows. The significance of stresses for groundwater flow can be investigated by field techniques (hydraulic fracturing), laboratory techniques (stress cells) or by numerical modelling. 相似文献
2.
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
3.
W. Zhou 《Environmental Geology》2001,40(7):797-808
Two-phase flow in fractured rock is an important phenomenon related to a range of practical problems, including non-aqueous phase liquid contamination of groundwater. Although fractured rocks consist of fracture networks, the study of two-phase flow in a single fracture is a pre-requisite. This paper presents a conceptual and numerical model of two-phase flow in a variable fracture. The void space of the fracture is conceptualized as a system of independent channels with position-dependent apertures. Fundamental equations, governing two-phase displacement in each channel, are derived to represent the interface positions and fractional flows in the fracture. For lognormal aperture distributions, simple approximations to fractional flows are obtained in analytical form by assuming void occupancy based on a local capillary allowability criterion. The model is verified by analytical solutions including two-phase flow in a parallel-plate fracture, and used to study the impacts of aperture variation, mobility ratio and fracture orientation on properties of two-phase flow. Illustrative examples indicate that aperture variation may control the distribution of wetting and non-wetting fluids within the fracture plane and hence the ability of the fracture to transmit these fluids. The presence of wetting fluid does little to hinder non-wetting fluid flow in fractures with large aperture variations, whereas a small volume of non-wetting fluid present in the fracture can significantly reduce wetting fluid flow. Large mobility ratios and high fracture slope angles facilitates the migration of non-wetting fluid through fractures. 相似文献
4.
Wang Mingyu The University of Arizona Tucson Arizona USA Department of Water Resources Environmental Engineering China University of Geosciences Beijing Chen Jinsong Wan Li Department of Water Resources Environmental Engineering 《中国地质大学学报(英文版)》2001,12(3)
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5.
Tian Kaiming Wan Li Department of Water Resources Environmental Science China University of Geosciences Beijing 《中国地质大学学报(英文版)》2000,11(4)
ＩＮＴＲＯＤＵＣＴＩＯＮＴｈｅｔｈｅｏｒｅｔｉｃａｌｃａｌｃｕｌａｔｉｏｎｓｏｆｗａｔｅｒｍｉｇｒａｔｉｏｎ ,ｗｈｅｔｈｅｒｉｎａｎｉｎｄｉｖｉｄｕａｌｆｒａｃｔｕｒｅｏｒｉｎａｆｉｓｓｕｒｅｎｅｔｗｏｒｋ ,ｈａｖｅａｌｌｂｅｅｎｂａｓｅｄｏｎｔｈｅｅｑｕａｔｉｏｎｆｏｒｖｉｓｃｏｕｓｆｌｏｗｂｅｔｗｅｅｎｐａｒａｌｌｅｌｐｌａｔｅｓ.ＷｉｌｓｏｎａｎｄＷｉｔｈｅｒ ｓｐｏｏｎ (1976 )ｆｉｒｓｔａｃｃｏｍｐｌｉｓｈｅｄａｈｙｄｒａｕｌｉｃｓｉｍｕｌａｔｉｏｎｏｆｆｒａｃｔｕｒｅｗａｔｅｒｃｒｏｓｓ… 相似文献
6.
基于人工交叉裂隙模型,通过室内透水试验,得到了不同进口与出口组合时的流量和压力变化的关系曲线。同时结合串联裂隙水力学开度的计算公式,利用最小二乘法求解超静定方程组,计算交叉裂隙中每个裂隙单元的水力学开度。通过拓扑得到裂隙交叉点的几何尺寸,并求解Navier-Stokes方程,研究裂隙交叉对其水力特性的影响。结果表明,通过室内试验和串联裂隙水力学开度计算公式相结合的方法,可以准确计算每个裂隙单元的水力学开度。当雷诺数Re较小时,交叉点内部的流体成稳态层流流动;当雷诺数较大（比如Re≥100）时,可以观测到明显的漩涡,说明流体的惯性力远大于黏性力,经典的立方定律不再适用。对于1个进口2个出口的情况,出口的流量分配比率与雷诺数成二次函数关系,随着雷诺数的增大,流量分配比率的非线性越来越明显,其最大分配比率变化超过15%。出口的水力学开度e与初始水力学开度（即力学开度E0）的比值e/E0和雷诺数Re也具有二次函数关系。当Re10时,e/E0呈现出较强的非线性;利用该关系式可以得到修正的立方定律,从而进一步求解交叉裂隙的水力特性问题。 相似文献
7.
The fluid flow in rock fractures during shear processes has been an important issue in rock mechanics and is investigated in this paper using finite element method (FEM), considering evolutions of aperture and transmissivity with shear displacement histories under different normal stress and normal stiffness conditions as measured during laboratory coupled shear-flow tests. The distributions of fracture aperture and its evolution during shearing were calculated from the initial aperture, based on the laser-scanned sample surface roughness results, and shear dilations measured in the laboratory tests. Three normal loading conditions were adopted in the tests: simple normal stress and mixed normal stress and normal stiffness to reflect more realistic in situ conditions. A special algorithm for treatment of the contact areas as zero-aperture elements was used to produce more accurate flow field simulations, which is important for continued simulations of particle transport but often not properly treated in literature. The simulation results agree well with the measured hydraulic apertures and flow rate data obtained from the laboratory tests, showing that complex histories of fracture aperture and tortuous flow fields with changing normal loading conditions and increasing shear displacements. With the new algorithm for contact areas, the tortuous flow fields and channeling effects under normal stress/stiffness conditions during shearing were more realistically captured, which is not possible if traditional techniques by assuming very small aperture values for the contact areas were used. These findings have an important impact on the interpretation of the results of coupled hydro-mechanical experiments of rock fractures, and on more realistic simulations of particle transport processes in fractured rocks. 相似文献
8.
离散裂隙渗流方法与裂隙化渗透介质建模 总被引：4，自引：1，他引：4
流体渗流模拟的连续介质方法通常适用于多孔地质体，并不一定适用于裂隙岩体，由于裂隙分布及其特征与孔隙差异较大。若流体渗流主要受裂隙的控制，对于一定尺寸的裂隙岩体，多孔介质假设则较难刻划裂隙岩体的渗流特征。离散裂隙渗流方法不但可直接用于模拟裂隙岩体非均质性和各向异性等渗流特征，而且可用其确定所研究的裂隙岩体典型单元体及其水力传导（渗透）张量大小。主要讨论了以下问题：（1）饱和裂隙介质中一般的离散流体渗流模拟；（2）裂隙岩体中的REV（典型单元体）及其水力传导（渗透）张量的确定；（3）利用离散裂隙网络流体渗流模型研究裂隙方向几何参数对水力传导系数和REV的影响；（4）在二维和三维离散裂隙流体渗流模型中对区域大裂隙和局部小裂隙的处理方法。调查结果显示离散裂隙流体渗流数学模型可用来评价不同尺度上的裂隙岩体的水力特征，以及裂隙方向对裂隙化岩体的水力特征有着不可忽视的影响。同时，局部小裂隙、区域大裂隙应当区别对待，以便据其所起的作用及水力特征，建立裂隙化岩体相应的流体渗流模型。 相似文献
9.
Cubic law with aperture-length correlation: implications for network scale fluid flow 总被引：2，自引：2，他引：0
Christian Klimczak Richard A. Schultz Rishi Parashar Donald M. Reeves 《Hydrogeology Journal》2010,18(4):851-862
Previous studies have computed and modeled fluid flow through fractured rock with the parallel plate approach where the volumetric flow per unit width normal to the direction of flow is proportional to the cubed aperture between the plates, referred to as the traditional cubic law. When combined with the square root relationship of displacement to length scaling of opening-mode fractures, total flow rates through natural opening-mode fractures are found to be proportional to apertures to the fifth power. This new relationship was explored by examining a suite of flow simulations through fracture networks using the discrete fracture network model (DFN). Flow was modeled through fracture networks with the same spatial distribution of fractures for both correlated and uncorrelated fracture length-to-aperture relationships. Results indicate that flow rates are significantly higher for correlated DFNs. Furthermore, the length-to-aperture relations lead to power-law distributions of network hydraulic conductivity which greatly influence equivalent permeability tensor values. These results confirm the importance of the correlated square root relationship of displacement to length scaling for total flow through natural opening-mode fractures and, hence, emphasize the role of these correlations for flow modeling. 相似文献
10.
对交叉裂隙渗流传质特性的定量描述是研究整个裂隙网络渗透传质特性的基础。为真实模拟水流及溶质在三维交叉裂隙中的运移过程,首先通过三维轮廓仪获取天然岩石裂隙表面的形貌数据,再应用三维重构技术生成相应的三维交叉裂隙模型,随后求解Navier-Stokes方程,假定溶质运移满足Fick定律,模拟水流和溶质在三维交叉裂隙中的运移过程。通过对比粗糙裂隙模型与平行平板模型的模拟结果发现：粗糙度对流体的分布及流动状态存在显著的影响;不同进、出口工况下的流体流动及溶质运移状态亦表明：裂隙交叉的几何形貌会显著地影响溶质混合行为。这些结果表明,目前被广泛采用的平行平板模型在评估岩体内特别是交叉口的物质运移特性时将导致较大的偏差,在将来的研究中有必要针对裂隙交叉口的几何特征建立修正的模型以提高评估的准确性。 相似文献
11.
裂隙的剪胀特性及扩展演化规律对岩体的渗流特性具有重要影响。为揭示裂隙剪胀及扩展演化对岩体渗流的影响,基于残余强度提出了一种能较好描述岩石硬化-软化特性的全剪切本构关系;结合剪切变形与裂隙开度的关系,利用最小势能原理和立方定律,建立了压剪作用下考虑裂隙剪胀特性的渗流应力耦合模型;假定压剪作用下裂隙发生Ⅰ型扩展,提出了伴有翼型裂纹的渗流模型,该模型不仅考虑了岩石的剪胀特性,更反映了裂隙扩展过程渗流的演化规律。对不同裂隙粗糙度的剪切应力-位移曲线进行分析,全剪切本构模型表现出较高的拟合精度。在剪切应力-位移关系基础上,通过剪切渗流试验数据对压剪作用下渗流模型进行验证,结果表明,该模型能较好地描述岩体剪胀阶段渗透性演化规律。利用等效裂隙简化裂隙网络,并通过试验数据进行验证,证实了裂隙扩展过程渗流-应力耦合模型的准确性与适用性。 相似文献
12.
Middle and lower Ordovician carbonate rock in the Tabei Uplift of the Tarim Basin forms important fractured reservoir beds. Core and log data indicate that tectonic fractures, as the main fractures in the Tabei Uplift, could be mainly classified into two types: oblique fractures and approximately vertical fractures. The fractures are mainly NNW‐trending and NNE‐trending, coincident with the large faults nearby. Fracture abundance was also controlled by lithology, and faults nearby played a significant role. Cores, thin sections and tests show that these carbonate rocks have as much as 2.5% fracture porosity and as much as 150 md fracture permeability. Based on the intersection of fractures in cores, together with fluid inclusion temperature data, and the timing of faulting from seismic profiles, tectonic fractures were considered to be mainly formed in three periods: the late Silurian when the first‐stage oblique fractures were formed, the late Permian when approximately vertical fractures were formed, and the late Tertiary when the second‐stage oblique fractures were formed. Lower Cambrian source rocks started to enter the stage of generous hydrocarbon generation and expulsion in the Silurian. Ordovician source rocks started to enter the stage of generous hydrocarbon generation and expulsion in the Permian and enter the over‐mature stage in the late Tertiary when light oil was generated. Timing of tectonic fractures formation and burial history analysis suggest that fractures formation might coincide with oil accumulation when fractures provided the pathway and storage space for the low permeability and low porosity reservoir beds caused by previous compaction and cementation. Considering the presence of a large amount of fracture‐developed dolomite in the deeper Ordovician Penglaiba Formation, the undrilled Penglaiba Formation should be paid more attention. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
13.
认识深部裂隙岩体中的地下水渗流特征(流速、渗流路径等),是深部地质工程开发建设的重要前提。近年来,分布式光纤测温技术作为识别深部裂隙岩体地下水渗流特征的有效方法,在国外开展了大量的研究,但在国内鲜少见在实际场地开展的相关工作。本研究以我国首个地下实验室场址甘肃北山新场花岗岩岩体中的两个钻孔(BSQ02及BSQ03)为试验对象,开展基于分布式光纤测温(Fiber-Optic Distributed Temperature Sensing,FO-DTS)的现场温度-水力试验,实现了对钻孔地下水温度的高精度、连续性观测。通过分析现场试验获取的钻孔温度-深度剖面随时间的变化,推断BSQ02在试验过程中存在外源地下水的流入,然后结合钻孔柱状图对钻孔中的入流导水裂隙进行了定位;基于现场观测数据建立了钻孔的渗流-传热耦合数值模型,反演估算出钻孔中地下水平均流速为0.01 m·s-1,通过裂隙流入地下水温度小于钻孔中原地下水温度,两者之间的温度差为0.7 ℃,通过裂隙流入的地下水流速为1×10-5 m·s-1,获取了地下水的渗流特征。该项工作可为基于分布式光纤测温技术的裂隙介质地下水渗流规律研究提供借鉴与指导。 相似文献
14.
Sung-Hoon Ji Kyung Woo Park Doo-Hyun Lim Chunsoo Kim Kyung Su Kim William Dershowitz 《Hydrogeology Journal》2012,20(7):1341-1353
The development and implementation of a hybrid discrete fracture network/equivalent porous medium (DFN/EPM) approach to groundwater flow at the Gyeong-Ju low- and intermediate-level radioactive waste (LILW) disposal site in the Republic of Korea is reported. The geometrical and hydrogeological properties of fractured zones, background fractures and rock matrix were derived from site characterization data and implemented as a DFN. Several DFN realizations, including the deterministic fractured zones and the stochastic background fractures, whose statistical properties were verified by comparison with in-situ fracture and hydraulic test data, were suggested, and they were then upscaled to continuums using a fracture tensor approach for site-scale flow simulations. The upscaled models were evaluated by comparison to in-situ pressure monitoring data, and then used to simulate post-closure hydrogeology for the LILW facility. Simulation results demonstrate the importance of careful characterization and implementation of fractured zones. The study highlighted the importance of reducing uncertainty regarding the properties and variability of natural background fractures, particularly in the immediate vicinity of repository emplacement. 相似文献
15.
交叉裂隙作为裂隙网络的基本结构是控制场地尺度非饱和渗流特性的关键。随着流量的减小,交叉裂隙非饱和渗流将从连续、稳定的线状流转变为非连续、非稳定的滴状流,但目前对后者的研究还很少。在滴状流条件下,开展了交叉裂隙非饱和流动特性的理论和试验研究,发现了交叉裂隙滴状流存在毛细力驱动以及重力与毛细力联合驱动两种分流驱动模式。基于瞬态静力平衡方法,提出了一套液滴分流理论及计算模型,实现了动态分流过程的定量化描述与预测。结合模型预测与可视化试验,详细探究了两种模式下液滴的分流过程,阐明了动态分流行为受重力、毛细力、黏滞力共同控制的细观机制,并揭示了液滴长度、裂隙倾角、通道中液体的累积等因素对界面流速、分流体积比例的影响。研究成果为低流量、低饱和度条件下非饱和裂隙岩体渗流的预测与控制提供了理论及试验支撑。 相似文献
16.
Analysis of contaminant transport through fractured crystalline rocks has received considerable attention, particularly with regard to subsurface nuclear waste repositories. Most of the studies have employed the dual continuum approach, with the fractures and the rock matrix as the two continuums, assuming that fractures control the overall conductivity of the rock and the porous matrix just provides storage. However, field observations of rock fractures have shown that the real situation can be very complex. Based on some recent investigations, it has been reported that the portion of the rock matrix adjacent to many open fractures is physically and chemically altered. These alterations, referred to as the fracture skin, can have different sorption and diffusion properties compared to those of the undisturbed rock matrix and this may influence the transport of solutes through such formations. In the present study, a numerical model is developed to simulate conservative solute transport in a fractured crystalline rock formation using the triple continuum approach ?? with the fracture, fracture skin and the rock matrix as the three continuums. The model is solved using a fully implicit finite difference scheme. Contaminant migration in the fractured formation with and without skin has been simulated. It is observed that contaminant penetration along the fracture is enhanced at large flow velocities. The effect of flow velocity on conservative solute transport is investigated for different fracture apertures and fracture skin thicknesses. The influence of flow velocity on contaminant transport is demonstrated to be more with change in fracture aperture than with change in skin thickness. 相似文献
17.
This paper proposes a three-dimensional coupled hydrothermal model for fractured rock based on the finite-discrete element method to simulate fluid flow and heat transport. The 3D coupled hydrothermal model is composed of three main parts: a heat conduction model for the rock matrix, a heat transfer model for the fluid in the fractures (including heat conduction and heat convection), and a heat exchange model between the rock matrix and the fluid in the fractures. Four examples with analytical solutions are provided to verify the model. A heat exchange experiment of circulating water in a cylindrical granite sample with one fracture is simulated. The simulation results agree well with the experimental results. The effects of the fracture aperture, fluid viscosity, and pressure difference on the heat exchange between the fluid and rock are studied. Finally, an application concerned with heat transport and fluid flow in fractured rock is presented. The simulation results indicate that the 3D fully coupled hydrothermal model can capture the fluid flow and temperature evolution of rocks and fluids. 相似文献
18.
A field study (Massachusetts, USA) of the factors controlling the depth of groundwater flow systems in crystalline fractured-rock terrain 总被引：4，自引：3，他引：1
Groundwater movement and availability in crystalline and metamorphosed rocks is dominated by the secondary porosity generated through fracturing. The distributions of fractures and fracture zones determine permeable pathways and the productivity of these rocks. Controls on how these distributions vary with depth in the shallow subsurface (<300 m) and their resulting influence on groundwater flow is not well understood. The results of a subsurface study in the Nashoba and Avalon terranes of eastern Massachusetts (USA), which is a region experiencing expanded use of the fractured bedrock as a potable-supply aquifer, are presented. The study logged the distribution of fractures in 17 boreholes, identified flowing fractures, and hydraulically characterized the rock mass intersecting the boreholes. Of all fractures encountered, 2.5% are hydraulically active. Boreholes show decreasing fracture frequency up to 300 m depth, with hydraulically active fractures showing a similar trend; this restricts topographically driven flow. Borehole temperature profiles corroborate this, with minimal hydrologically altered flow observed in the profiles below 100 m. Results from this study suggest that active flow systems in these geologic settings are shallow and that fracture permeability outside of the influence of large-scale structures will follow a decreasing trend with depth. 相似文献
19.
Stress-Dependent Fluid Flow and Permeability in Fractured Media: from Lab Experiments to Engineering Applications 总被引：5，自引：3，他引：5
J. Zhang W. B. Standifird J.-C. Roegiers Y. Zhang 《Rock Mechanics and Rock Engineering》2007,40(1):3-21
Summary. Permeability is a physical property in rocks of extreme importance in energy engineering, civil and environmental engineering,
and various areas of geology. Early on, fractures in fluid flow models were assumed to be rigid. However, experimental research
and field data confirmed that stress-deformation behavior in fractures is a key factor governing their permeability tensor.
Although extensive research was conducted in the past, the three-dimensional stress-permeability relationships, particularly
in the inelastic deformation stage, still remain unclear. In this paper, laboratory experiments conducted on large concrete
blocks with randomly distributed fractures and rock core samples are reported to investigate fluid flow and permeability variations
under uniaxial, biaxial and triaxial complete stress-strain process. Experimental relationships among flowrate, permeability
and fracture aperture in the fractured media are investigated. Results show that the flowrate and stress/aperture exhibit
“cubic law” relationship for the randomly distributed fractures.
A permeability-aperture relationship is proposed according to the experimental results. Based on this relationship, stress-dependent
permeability in a set of fractures is derived in a three-dimensional domain by using a coupled stress and matrix-fracture
interactive model. A double porosity finite element model is extended by incorporating such stress-dependent permeability
effects. The proposed model is applied to examine permeability variations induced by stress redistributions for an inclined
borehole excavated in a naturally fractured formation. The results indicate that permeability around underground openings
depends strongly on stress changes and orientations of the natural fractures. 相似文献
20.
Qinghua Lei Xiaoguang Wang Jiansheng Xiang John-Paul Latham 《Hydrogeology Journal》2017,25(8):2251-2262
A study about the influence of polyaxial (true-triaxial) stresses on the permeability of a three-dimensional (3D) fractured rock layer is presented. The 3D fracture system is constructed by extruding a two-dimensional (2D) outcrop pattern of a limestone bed that exhibits a ladder structure consisting of a “through-going” joint set abutted by later-stage short fractures. Geomechanical behaviour of the 3D fractured rock in response to in-situ stresses is modelled by the finite-discrete element method, which can capture the deformation of matrix blocks, variation of stress fields, reactivation of pre-existing rough fractures and propagation of new cracks. A series of numerical simulations is designed to load the fractured rock using various polyaxial in-situ stresses and the stress-dependent flow properties are further calculated. The fractured layer tends to exhibit stronger flow localisation and higher equivalent permeability as the far-field stress ratio is increased and the stress field is rotated such that fractures are preferentially oriented for shearing. The shear dilation of pre-existing fractures has dominant effects on flow localisation in the system, while the propagation of new fractures has minor impacts. The role of the overburden stress suggests that the conventional 2D analysis that neglects the effect of the out-of-plane stress (perpendicular to the bedding interface) may provide indicative approximations but not fully capture the polyaxial stress-dependent fracture network behaviour. The results of this study have important implications for understanding the heterogeneous flow of geological fluids (e.g. groundwater, petroleum) in subsurface and upscaling permeability for large-scale assessments. 相似文献