Year

2014

Degree Name

Doctor of Philosophy

Department

School of Civil, Mining, and Environmental Engineering

Abstract

Underground rock strata are often fractured and their permeability is mainly governed by interconnected fracture networks. Flow through fractures must be studied in order to design and operate underground activities such as tunnelling and mine operations, as well as groundwater and petroleum extraction. Flow through a fracture is primarily influenced by its aperture, and because fracture apertures can be distributed widely within a rockmass, they have closures as well as wide openings depending on the location and in-situ stress conditions. Past research studies have been carried out on defining the equivalent aperture to predict fracture flows from uni-directional flow models. However, in most civil engineering applications, plane strain conditions can be assumed (e.g. tunnels, rock slopes), and in such situations two-dimensional fracture models have been suggested for stationary fracture walls. Modelling flow through deformable fractures in plane stain, two-dimensional domain would provide profound insight into rock fracture hydraulics, and these models available now have been simulated using common numerical flow solvers. In this regard, a customised numerical solver to simulate fracture hydraulics would be an important addition to this research area.

In contrast to available literature, in this PhD study, an equivalent twodimensional flow model was derived from the three-dimensional Navier-Stokes theory for deformable rock fractures. The proposed model contains pressure-velocity coupled equations, and a numerical solution is subsequently introduced by modifying the SIMPLE (Semi Implicit Method for Pressure Linked Equations) algorithm. The Writer’s own computer programme (Rock Fracture Flow Solver or RFFS) was developed to solve the proposed model using MATLAB computer language. Laboratory experiments were carried out for mated and dislocated fracture specimens using the high pressure triaxial apparatus (HPTPTA) designed and built in University of Wollongong. The fracture apertures were measured by replicating them and scanning the surfaces using a 3D laser scanner. Flows through the rock fractures were simulated using the Rock Fracture Flow Solver (RFFS), and the validity of the proposed model was verified for general underground fracture flow situations.

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