WEIMOS: Simulations of two geomechanical scenarios in rock salt resembling structures at WIPP

Abstract

Joint Project WEIMOS (2016-2022) aims to improve geomechanical rock salt models used to analyze high-level radioactive waste disposal in rock salt formations. The project focuses on four research topics: 1) deformation behavior at low deviatoric stresses, 2) damage reduction and healing of rock salt, 3) deformation behavior resulting from tensile stresses, and 4) influence of inhomogeneities (layer boundaries, interfaces) on deformation. The impacts of progress in the first three research areas are demonstrated with simulations of two typical underground scenarios resembling structures at the Waste Isolation Pilot Plant (WIPP): a long open drift with a dam introduced after 30 years (Virtual Demonstrator I), and a vertical slice through part of an underground repository comprising two main drifts and seven emplacement chambers (Virtual Demonstrator II). Each project partner simulated both scenarios with her/his material model, after calibrating it against numerous laboratory tests on WIPP and Asse rock salt. The results show that (1) the higher creep rates at low deviatoric stresses in rock salt, as reliably measured during the WEIMOS project, must be considered in a constitutive model in order to get realistic results for predictions of displacements, convergences, stresses, as well as damage and dilatancy; (2) the constitutive models are able to evaluate damage reduction and healing in the DRZ around a dam now based on an improved experimental basis; (3) tensile stresses have considerable influence on the evolution of damage and dilatancy in the DRZ.