Experimental and numerical study of the geometrical and hydraulic characteristics of a single rock fracture during shear
Experimental and numerical study of the geometrical and hydraulic characteristics of a single rock fracture during shear
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DOI：
10.1016/j.ijrmms.2011.09.009
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发表时间：
2011-12
影响因子：
7.2
通讯作者：
X. Xiong;Bo Li;Yujing Jiang;T. Koyama;Chuhan Zhang
中科院分区：
文献类型：
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作者：
X. Xiong;Bo Li;Yujing Jiang;T. Koyama;Chuhan Zhang
在恒法向载荷边界条件下，对两个具有天然岩石断裂特征的人工岩石裂隙进行了剪切-流动耦合试验。利用剪切-流动耦合试验得到的孔洞空间几何模型，利用考虑流体惯性效应的三维N-S方程进行了数值模拟。试验和数值模拟结果表明，岩石裂隙几何特征和水力特征的演化呈现出三个阶段的特征。由于流体的惯性效应，裂隙内某一空隙空间几何形状的透射率与流体流动的雷诺数有关，这可以用Navier-Stokes方程来表示，但不能用一些简化的方程来表示，如立方定律、雷诺方程或Stokes方程。机械孔径通常大于由实测流量反算出的水力孔径，两者之间的差异与裂缝的几何特征密切相关。提出了用局部机械孔径的标准差与其平均值之比、裂隙表面局部斜率的标准差和雷诺数来描述水力孔径与机械孔径之间的关系的数学方程。
Coupled shear-flow tests were conducted on two artificial rock fractures with natural rock fracture characteristics under constant normal loading boundary conditions. Numerical simulations using the 3-D Navier–Stokes equations taking account of the inertial effects of fluid were conducted using the void space geometry models obtained from the coupled shear-flow tests. The test and numerical simulation results show that the evolutions of geometrical and hydraulic characteristics of rock fracture exhibit a three-stage behavior. Transmissivity of a certain void space geometry within a fracture is related to the Reynolds number of fluid flow due to the inertial effects of fluid, which can be represented by the Navier–Stokes equations, but cannot be represented by some simplified equations, such as the cubic law, the Reynolds equation or the Stokes equations. The mechanical aperture is usually larger than the hydraulic aperture back-calculated from measured flow rate, and the difference between them is found strongly related to the geometrical characteristics of the fractures. A mathematical equation is proposed to describe the relation between hydraulic aperture and mechanical aperture by means of the ratio of the standard deviation of local mechanical aperture to its mean value, the standard deviation of local slope of fracture surface and Reynolds number.