Stress-dependent permeability of fractured rock masses: a numerical study

被引:447
作者
Min, KB
Rutqvist, J
Tsang, CF
Jing, LR
机构
[1] Royal Inst Technol, KTH, Dept Land & Water Resources Engn, Engn Geol & Geophys Res Grp, S-10044 Stockholm, Sweden
[2] Univ Calif Berkeley, Lawrence Berkeley Lab, Div Earth Sci, Berkeley, CA 94720 USA
基金
美国能源部;
关键词
stress-dependent permeability; fractured rock; distinct element method; discrete fracture network; channeling;
D O I
10.1016/j.ijrmms.2004.05.005
中图分类号
P5 [地质学];
学科分类号
0709 ; 081803 ;
摘要
We investigate the stress-dependent permeability issue in fractured rock masses considering the effects of nonlinear normal deformation and shear dilation of fractures using a two-dimensional distinct element method program, UDEC, based on a realistic discrete fracture network realization. A series of "numerical" experiments were conducted to calculate changes in the permeability of simulated fractured rock masses under various loading conditions. Numerical experiments were conducted in two ways: (1) increasing the overall stresses with a fixed ratio of horizontal to vertical stresses components; and (2) increasing the differential stresses (i.e., the difference between the horizontal and vertical stresses) while keeping the magnitude of vertical stress constant. These numerical experiments show that the permeability of fractured rocks decreases with increased stress magnitudes when the stress ratio is not large enough to cause shear dilation of fractures, whereas permeability increases with increased stress when the stress ratio is large enough. Permeability changes at low stress levels are more sensitive than at high stress levels due to the nonlinear fracture normal stress-displacement relation. Significant stress-induced channeling is observed as the shear dilation causes the concentration of fluid flow along connected shear fractures. Anisotropy of permeability emerges with the increase of differential stresses, and this anisotropy can become more prominent with the influence of shear dilation and localized flow paths. A set of empirical equations in closed-form, accounting for both normal closure and shear dilation of the fractures, is proposed to model the stress-dependent permeability. These equations prove to be in good agreement with the results obtained from our numerical experiments. (C) 2004 Elsevier Ltd. All rights reserved.
引用
收藏
页码:1191 / 1210
页数:20
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