岩体裂隙粗糙度表征及其对裂隙渗流特性的影响

Roughness characterization of rock fracture and its influence on fracture seepage characteristics

岩体裂隙粗糙程度对裂隙渗流特性的影响显著。利用三维光学扫描系统获取岩体裂隙面点云数据,结合SURFER和GEOMAGIC STUDIO等软件计算裂隙面节理粗糙度系数JRC和表面粗糙比率Rs,建立JRC与Rs的定量关系,开展应力、渗流和化学耦合作用下石灰岩裂隙渗流试验,研究JRC和Rs对粗糙裂隙渗流特性的影响。结果表明:JRC与Rs呈对数函数关系,其平方根R2为0.9128,该表征公式与裂隙渗流试验结果最大相对误差MRE、平均绝对误差MAE和均方根误差RMSE分别为6.93%、0.34和0.27。JRC与渗流量、稳定期渗透率分别呈二次函数和对数函数关系,Rs和各参数的拟合关系与JRC相同。JRC值越大,渗流量和渗透率越小,且三场耦合作用下裂隙面JRC和Rs值均有所增大。该表征方法可用于岩体裂隙面粗糙度估算,由裂隙面JRC值可预测该裂隙渗流量和稳定时刻渗透率。

Roughness of rock fracture has a significant influence on the seepage characteristics of fracture.The point cloud data of rock fracture surface was collected by three-dimensional(3D)optical scanning system.The joint roughness coefficient(JRC)and surface roughness ratio(Rs)were calculated by SURFER and GEOMAGIC STUDIO,and the quantitative relationship between JRC and Rs was established.The effects of JRC and Rs on the fracture seepage characteristics in limestone were investigated by conducting seepage tests under the coupling effect of stress,seepage and chemical interaction.The results show that JRC is a logarithmic function of Rs,with the R-squared(R^(2))of 0.9128.The maximum relative error(MRE),mean absolute error(MAE)and root mean square error(RMSE)between the proposed characterization formula and seepage test results are 6.93%,0.34 and 0.27,respectively.JRC shows quadratic function and logarithmic function with the seepage flow and permeability at stable period,respectively.The fitted relationships of Rs and each parameter are consistent with that of JRC.The larger JRC is,the smaller the seepage flow and permeability are.The values of JRC and Rs of the fracture surface increase under the coupling effect of HMC(hydrological-mechanical-chemical)three fields.The characterization method proposed in this study can be used to estimate the surface roughness of rock fracture.Meanwhile,the value of JRC can be applied to predict the seepage flow and the permeability at stable seepage period.