Abstract
This article is the summary for the thesis (Huang, 2018) receiving the best doctoral thesis award from the Japanese Society for Rock Mechanics (JSRM) in the year of 2018. Firstly, the effects of fracture surface roughness, normal stress, shear displacement and shear directivity on permeability of 3D self-affine rough fractures are studied, and a predictive model is proposed to estimate the permeability of rough fractures during shear. Secondly, a numerical analysis of the shear effect on the hydraulic response of 3D fracture intersection model is presented. Simulation results reveal the development and variation of preferential flow paths through the model during the shear. Finally, a numerical procedure is originally developed to address flow problem through 3D rock discrete fracture networks (DFNs). In this method, fractures are modeled as circular discs with arbitrary size, orientation and location. Fracture networks are established with fractures following statistical distributions, after which the model is triangulated and fluid flow is calculated by solving the Reynolds equation using Galerkin method. The results show that the permeability of 2D DFN models underestimates the permeability of 3D DFNs by approximately 10.45~80.92%. A multi-variable regression function is proposed for predicting 3D fracture network permeability. The proposed model provides a simple method to approximate permeability of 3D fracture networks using parameters that can be easily obtained from analysis on outcrop trace maps of fractured rock masses.
