Stress effects on permeability in a fractured rock mass with correlated fracture length and aperture
Stress effects on permeability in a fractured rock mass with correlated fracture length and aperture
复制标题
DOI：
10.1016/j.ijrmms.2008.01.015
复制
发表时间：
2008-12
影响因子：
7.2
通讯作者：
A. Baghbanan;L. Jing
中科院分区：
文献类型：
--
作者：
A. Baghbanan;L. Jing
采用离散元法研究了裂隙开度与裂隙迹线长度相关时应力对裂隙岩体渗透率和渗流模式的影响。基本假设是岩石基质是不可渗透的和线性弹性的，并且流体仅在裂缝中流动。基于Bandis模型和裂缝开度与长度的相关性，提出了一种新的预测裂缝正应力-正位移行为的非线性算法。结果表明，当在模型边界处施加小的应力比（K=水平/垂直应力）时，裂缝网络的总渗透率通常会降低。然而，从几个较大的裂缝较高的水力传导系数的贡献，防止急剧减少的整体渗透性，与模型相比，假设均匀的裂缝孔径。随着应力比的大值，整体渗透率和流动模式都由高传导性的较大裂缝和具有剪切滑移和扩张的裂缝的组合控制，具有大大增加的整体渗透率和剪切诱导的流动通道。随着应力比的增加，建立裂隙岩体的等效渗透率张量和代表性单元体积（REV）变得越来越困难。这些结果表明，相关和非相关的孔径和裂隙长度分布之间存在显著差异，并突出了当岩石裂隙几何参数相关时，裂隙岩石流体力学行为的尺度和应力相关性。
The effect of stress on permeability and fluid flow patterns in fractured rock masses is studied when distributed fracture aperture is correlated with fracture trace length, using a discrete element method (DEM). The basic assumptions are that the rock matrix is impermeable and linearly elastic, and that the fluid flows only in fractures. A new nonlinear algorithm is developed for prediction of normal stress–normal displacement behavior of fractures based on the Bandis model and the correlation between aperture and length. The results show that when small stress ratios (K=horizontal/vertical stress) are applied at the model boundaries, the overall permeability of the fracture network is generally decreased. However, contribution from a few large fractures of higher hydraulic conductivity prevents drastic reduction of the overall permeability, compared with models that assume uniform fracture apertures. With large values of the stress ratio, both the overall permeability and flow patterns are controlled by a combination of highly conductive larger fractures and fractures with shear slipping and dilation, with much increased overall permeability and shear-induced flow channeling. With increasing stress ratios, it becomes more and more difficult to establish an equivalent permeability tensor and representative elementary volume (REV) of a fractured rock, compared with the unstressed model. These results show significant difference between correlated and non-correlated aperture and fracture length distributions, and highlight more significant scale and stress dependence of hydro-mechanical behavior of fractures rocks when geometric parameters of rock fractures are correlated.