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 processe s in fractured hard rocks using the discontinuous deformation analysis (DDA ) method. Detailed descriptions were given to the governing equations, basi c assumptions, algorithms and their computer implementations, and verificat ion results. The emphasis was on the physical behaviour of the coupled stre ss/deformation and fluid flow interaction in rock fractures. The strain-blo ck geometry incompatibility in some DDA formulations was overcome by propel internal discretization of deformable blocks using triangle or quadrilater al elements. For the first time, explicit expressions for contributions fro m fluid pressure to the global stiffness matrix and load vectors of the dis crete block systems were derived systematically for rigid blocks, triangle elements and quadrilateral elements, respectively, by closed form integrati on. The flow algorithm used a residual flow method for locating the free su rfaces in unconfined flow problems, which was then coupled to the mechanica l equations of motion for the coupled hydro-mechanical analysis, also for t he first time. A laboratory experiment of fluid flow in a 2-D rectangular n etwork was simulated to verify the residual flow algorithm in the new DDA c ode, with an acceptable agreement between the measured and calculated resul ts. (C) 2001 Elsevier Science Ltd. All rights reserved.