Evaluating the reliability of hydro-mechanical simulation: A benchmark of numerical techniques carried out by research group of MoMaS

The rock, and more precisely argilite, is a very impermeable material with a brittle mechanical behaviour. But a simple behaviour as perfect plasticity does not allow to simulate the fracturing of the rock. It is necessary to take into account a softening behaviour. Moreover consolidation phenomena linked to water flows induces significant changes in the mechanical state of the rock. Then, an essential question is to know if the numerical simulation for underground excavations using these models are reliable. For the present benchmark, we were interested only in the numerical aspects and not in the relevance of the behaviours laws themselves. These elements lead us to propose a benchmark in which hydraulic and mechanical conservation laws are imposed. The suggested tests, with increasing difficulties, represent (in 1d or 2d) hydro-mechanical simulations of excavation. It acts of an infinite cylindrical cavity with an initial state of stress, isotropic in the Id case and anisotropic in the 2d case, and for which the environment is completely saturated. The teams which take part in the study of this benchmark are the following: CEA with the software CASTEM; University of Lille with the software THM Passa; L3S (Liege) with the software LAGAMINE; LCPC with the software BIL; LAEGO with a private development of the free software CODE -ASTER; EDF with the software CODE ASTER. In the presentation we will discuss, in a detailed way, the results of the teams. We will emphasize the main differences and the main points of agreement. (authors)