ANALYTICAL MODELING OF BENTONITE EXTRUSION OF CRACK IN ROCK FRACTURE

Abstract

The bentonite extrusion of crack in rock fracture must be predicted to evaluate the performance of the natural barrier system for high-level radioactive waste disposal. This paper presents a simple analytical model for predicting the bentonite extrusion of closed-end crack by considering the swelling behavior of bentonite. The swelling behavior of bentonite is assumed to be caused by volume expansion due to the absorption and diffusion of trapped fluid in closed-end crack into bentonite. A governing equation is derived based on the balance of forces exerting on bentonite, and numerical solutions are derived by solving ordinary differential equations simultaneously. The analytical results obtained suggest that bentonite extrusion depends on the external swelling pressure and viscous resistance force in the initial stage of the extrusion process, and that bentonite fills the crack over a long period owing to the absorption and diffusion of trapped fluid.