ABSTRACT
The behavior of underground structures related to salt strata usually concerns different time scales, both short-term and long-term, during their life cycle. The main factors influencing this behavior include transient boundary conditions and different physics involved (deformation, groundwater flow, thermal effects) as well as nonlinear rock constitutive responses. Finite Element (FE) analysis is a standard and useful tool for considering the aforementioned factors in a unified framework, including time-dependency and multi-physics coupling. In this paper, a fully coupled FE formulation, implemented in the PLAXIS FE package, is presented. Rock time-dependent behavior is modeled by a double power viscoplastic law whereas plastic failure is modeled by Mohr-Coulomb and Hoek-Brown constitutive laws. An implicit integration scheme combined with an automatic adaptive sub-stepping strategy allows reducing computation time while ensuring numerical stability and accuracy. Some numerical examples are performed to demonstrate the efficiency and accuracy of the numerical implementation by analyzing obtained simulation results and comparing them against analytical solution, as well as available measurements and numerical data.
