不同JRC粗糙单裂隙水力开度3D数值模拟研究

3D Numerical Simulation Study on Seepage Characteristics of Different JRC Rough Single Fractures

岩石的过水能力主要决定于其中的裂隙,其表面粗糙度的影响不可忽视,单裂隙是一个简单的理论验证装置。为了探究不同结构面粗糙度系数JRC的水力开度e h变化,提出在不同雷诺数条件下e h和JRC的定量关系。研究开展了不同JRC粗糙单裂隙渗流特性3D数值模拟。首先,数值化5条Barton提出的标准轮廓曲线并导入COMSOLMultiphysics软件;然后进行扫掠操作,构建了不同JRC的3D单裂隙模型;进一步,设置不同的边界条件和初始条件,求解3D单裂隙中不可压缩粘性流体Navier-Stokes方程和连续方程;最后,基于立方定律和求解得到的流场参数,定量不同JRC的3D单裂隙e h。研究结果表明,Forchheimer方程线性系数A和非线性系数B对JRC有着明显的依赖关系,也受到平均开度E的影响;E对于粗糙裂隙中的流体流动影响明显,然而在一定范围内的JRC对流体流动的非线性行为起促进作用;在E相近时,JRC值越大的裂隙模型中,低流速的区域越多;粗糙裂隙中的e_(h)和Re是负指数关系,考虑Re的e_(h)与JRC的定量关系为e_(h)=E_(2)JRC^(-2.5)Re^(-0.21)。研究得到不同Re条件下Re和JRC值的定量关系,促进了区域地质相关的工程设计优化,也可以为工程地质灾害提供理论依据。

The conductive of rock is mainly determined by its fractures,and the impact of its surface roughness can not be ignored.Single fracture is a simple theoretical verification device.In order to investigate the variation of hydraulic aperture e h under different roughness coefficient JRC values of structural plane,the quantitative relationship between e h and JRC under different Reynolds numbers was proposed.In this study,3D numerical simulation of rough single fracture seepage characteristics with different JRC values was carried out.Firstly,5 standard contour curves proposed by Barton were numerically analyzed and then imported into COMSOL Multiphysics software.Then,the 3D single crack model with different JRC values is constructed by scanning operation.Furthermore,the Navier-Stokes equations and continuous equations of incompressible viscous fluid in 3D single crack are solved by setting different boundary conditions and initial conditions.Finally,3D single crack eh with different JRC values is quantified based on the cubic law and the flow field parameters obtained.The results show that the linear coefficient A and the nonlinear coefficient B of Forchheimer equation are obviously dependent on the JRC value,and are also affected by the average aperture E.E has an obvious effect on fluid flow in rough cracks,but JRC values within a certain range promote the nonlinear behavior of fluid flow.When E is similar,the fracture model with larger JRC value has more regions with low flow velocity.The relationship between eh and Re in rough cracks is negative exponential,and the quantitative relationship between e_(h),Re and JRC value is considered as follows e_(h)=E_(2)JRC^(-2.5) Re^(-0.21).The quantitative relationship between Re and JRC values under different Re conditions is studied,which promotes the optimization of regional geologically related engineering design.It can also provide a theoretical basis for engineering geological disasters.