A three-dimensional model for transient fluid flow through deformable fractured porous media

A three-dimensional model for simulating transient fluid flow through deformable jointed rock masses has been developed. The model is based on a discrete fracture element approach to establish the fully-coupled relation between fluid flow and rock matrix deformation. Biot's general three-dimensional poroelasticity theory has been adopted as a basis to derive the coupled formulations of stress and single phase fluid flow in elastically deformable porous media. Fluid flow rate in a fracture is governed by the cubic law. The dominant flow parallel to the fracture planes is assumed to be laminar. Due to the special geometrical features of fractures, a relative displacement approach has been used to derive the governing equations for fracture deformations and fluid flow. Two sets of coupled partial differential equations, one for porous media and the other for fractures, have been solved numerically using the Galerkin-weighted finite element method for spatial discretization and the generally-weighted time-stepping finite difference scheme for temporal discretization.; Six different problems have been chosen for the model verification, and all comparisons in the model testing show that the results obtained from this model either give excellent agreements with analytical solutions or approximate some field data. A number of critical parameters have been investigated to examine their effects on the coupling phenomena. These parameters are: rock matrix deformability, rock matrix porosity and permeability, initial joint aperture, and rock matrix and joint permeability ratio and stiffness ratio. Several case studies have been conducted to demonstrate the use of the model for solving a variety of geotechnical engineering related problems. The case problems studied include some porous rock samples with one or two joints, an underground opening within a jointed rock mass and a dam on a jointed rock foundation. All of these problems are three-dimensional in nature and time-dependent.