A new semi-analytical method for estimation of anisotropic hydraulic conductivity of three-dimensional fractured rock masses

The hydraulic characteristics of rock masses usually show strong anisotropy due to the existence of oriented structure planes. A new semi-analytical method is proposed for estimation of the anisotropic hydraulic con-ductivity of fractured rock masses based on the discrete fracture network (DFN) description and the Snow's model (Snow, 1969). In this method, the number of intersections on a fracture is a key parameter to construct correction coefficient, which are used to adjust the contribution of each individual fracture to the macro hy-draulic conductivity tensor. In this way, the initial Snow's model is extended from infinite connectivity condi-tions to finite connectivity conditions. The correction coefficient is determined by using a mathematical optimization method in the condition of networks following isotropic orientation distribution and polydisperse size distribution. Then, the new method is applied to estimate the directional hydraulic conductivity of engi-neering rock masses with complex anisotropic oriented fracture networks. The results show that the directional hydraulic conductivities predicted by the proposed semi-analytical method are in good agreement with the referential numerical results. The proposed semi-analytical model can be used to predict the anisotropic hy-draulic conductivity of complex fractured rock masses with less processing time and lower memory requirements than numerical models.

Automated summary

This study proposes a semi-analytical method for estimating the anisotropic hydraulic conductivity of fractured rock masses based on the discrete fracture network (DFN) description and Snow's model. It extends the initial Snow's model from infinite connectivity conditions to finite connectivity conditions by constructing correction coefficients to adjust the contribution of each individual fracture to the macro hydraulic conductivity tensor. The correction coefficients are determined using a mathematical optimization method under isotropic orientation and polydisperse size distribution conditions. The method is applied successfully to predict the directional hydraulic conductivity of engineering rock masses with complex anisotropic oriented fracture networks.