Stress State Evolution of a Cemented Granular Material Subjected to Bond Dissolution by Discrete Element Modeling

Rock weathering is a common phenomenon to consider in various engineering applications that involve underground operations, such as underground storage or geothermal energy extraction. This weathering is induced by the circulation of a reacting fluid in the pores of the rock and can induce changes in materials properties and stress state. This work presents discrete elements simulations of the dissolution of sedimentary rocks to study their stress state evolution. The rock is modeled as a cohesive granular material subjected to debonding. Oedometric conditions are considered during the weathering and the evolution of the coefficient of lateral earth pressure k0, a proxy of the stress state, is tracked. In particular, the influence of the degree of cementation, the confining pressure, the initial value of k0 and the history of loading are investigated. It has been observed that cemented granular materials tend to reach an attractor configuration for the stress state with the increase of the degree of dissolution. k0 aims to reach the attractor value k0attr, between 0.3 and 0.4, when all the bounds are dissolved, independently of the initial state. Two main mechanisms have been observed to explain this evolution of the interparticles force configurations and thus of the stress state: the collapse of the unstable chain forces (stable only due to the cementation) and the softening of the grains.