Peridynamic modelling of coupled hydro-chemical processes in clay erosion

Hydro-chemical interactions at the interface between host rock and clay buffer in geological disposal facility for nuclear waste can lead to buffer erosion. The erosion of clay buffer can induce loss of a critical component of the engineered barrier system and migration of highly hazardous radionuclides into the environment. Classical local continuum formulations based on partial differential equations that have been used for modelling the hydro-mechanical behavior of soils are not suitable for analysis of this discontinuous physical phenomenon, whereas non-local formulations offered by peridynamics (PD) provide clear advantages. In this study, a bond-based PD formulation of coupled clay extrusion and sol transport in a fracture is presented. Pyramid, the PD model used in this study, accounts for the effect of van der Waals forces, repulsive electrostatic double layer forces, and friction forces between the particles on clay extrusion. A 2D case study of clay extrusion and erosion under water flow in a fracture is presented. The case study is compared with experimental results of erosion of compacted MX-80 bentonite reported in the literature to demonstrate the accuracy of formulations and the Pyramid model. This validation shows the potential applications and prediction capability of the Pyramid model for evaluating the erosion of clay buffer under geological disposal conditions .