Multi-level fracture network model and FE solution for ground water flow in rock mass

Abstract

It is one of the issues of subsurface water resource research to investigate the models for ground water flow in rock mass. The models currently used in the literatures can be summarized as the three types of the (equivalent) continuum model, the fracture network model and the double porous media model. In this paper, the new multi-level fracture network model is proposed for ground water flow in rock mass. According to the scale and permeability, the ruptures, faults, fractures, joints and pores in rock mass are divided into four levels, i.e., the level-1 real fracture network, the level-2 random fracture network, the level-3 equivalent continuum system and the level-4 continuum system. The level-1 real fracture network is composed of larger ruptures and faults, whose distribution and hydro-mechanical parameters can be determined from the real geological data. Based on the fractures measurement and statistics, the level-2 random fracture network is simulated by means of Monte-Carlo technique. The level-3 equivalent continuum system is established to reflect the overall behavior of small joints by means of the theory of hydraulic conductivity tensor. The level-4 continuum system is composed of pores in rock, whose behavior can be represented by the homogeneous and isotropic parameters. These fracture networks of four levels are related to each other by water balance to form the multi-level fracture network model for ground water flow in rock mass. The iterative steps for finite element numerical solution for the proposed model is discussed, and an engineering example is also given to show the applicability of the model and the solution method.