Simulation of the multiple-fracture model. Phase 1, benchmark test 2 of the DECOVALEX project

摘要

DECOVALEX is an international co-operative project for the development of coupled models and their validation against experiments in nuclear waste isolation. The emphasis of this project is on the coupled thermo-hydro-mechanical effects in jointed hard rock. In the first phase of DECOVALEX, two benchmark tests and one test case have been selected for modelling. This report describes the results of the second benchmark test, the Multiple-Fracture Model, as obtained by the AECL Research team. This problem relates to groundwater flow and coupled thermo-hydro-mechanical deformation in a simple system comprising several blocks of porous medium and several intersecting fractures. The simulation domain is defined to be a rectangular box that is made up of an assemblage of nine blocks separated by two sets of discontinuities (planar fractures). The rock mass is subjected to in situ stress and thermal loading as well as a hydraulic gradient. Both no-flow and adiabatic heat flux acting along a section of one of the lateral boundaries will induce expansion of the rock and cause shearing in the model. The MOTIF finite-element code, developed at AECL, has been employed to simulate this problem. The simulation results show that thermal expansion of the solid blocks reduced the aperture and, consequently, the permeability of the fractures. As a result, the fluid velocity along the horizontal fractures decreased with time, except in the vicinity close to the heat source, where the velocity initially increased and then decreased as a result of the decrease in permeability. (author). 9 refs., 7 tabs., 23 figs. (Atomindex citation 27:000694)