Modeling of fluid flow and solid deformation for fractured rocks with discontinuous deformation analysis (DDA) method

This paper presents a numerical model for coupled hydro-mechanical processes in fractured hard rocks using the discontinuous deformation analysis (DDA) method. Detailed descriptions were given to the governing equations, basic assumptions, algorithms and their computer implementations, and verification results. The emphasis was on the physical behaviour of the coupled stress/deformation and fluid flow interaction in rock fractures. The strain-block geometry incompatibility in some DDA formulations was overcome by propel internal discretization of deformable blocks using triangle or quadrilateral elements. For the first time, explicit expressions for contributions from fluid pressure to the global stiffness matrix and load vectors of the discrete block systems were derived systematically for rigid blocks, triangle elements and quadrilateral elements, respectively, by closed form integration. The flow algorithm used a residual flow method for locating the free surfaces in unconfined flow problems, which was then coupled to the mechanical equations of motion for the coupled hydro-mechanical analysis, also for the first time. A laboratory experiment of fluid flow in a 2-D rectangular network was simulated to verify the residual flow algorithm in the new DDA code, with an acceptable agreement between the measured and calculated results. (C) 2001 Elsevier Science Ltd. All rights reserved.