A hydromechanical approach for anisotropic elasto-viscoplastic geomaterials: Application to underground excavations in sedimentary rocks

Abstract

To better describe excavation operations in deep geological formations, several aspects should be considered, especially the material anisotropy, time-dependent behavior, and hydromechanical coupling. In the present paper, a hydromechanical model based on the framework of continuous porous media was proposed. The mechanical elasto-viscoplastic constitutive model accounted for the material elastic and non-elastic anisotropies, using a transformation between the real transversely isotropic material and a fictitious isotropic material. Considering the hydraulic behavior, the permeability was expressed as a function of the volumetric viscoplastic strain. The model was applied to a case study of two tunnel excavations in an anisotropic rock under an initial anisotropic stress state. The results of the numerical simulations using a finite element code were in good agreement with the field convergence and permeability data. Keywords: Hydromechanical behavior, Transverse isotropy, Tunnel excavation, Viscoplasticity, Permeability