Modeling of the Visco‐Plastic Compaction Behavior of Crushed Salt Based on Micromechanical Deformation Mechanisms

ABSTRACT Using crushed salt as a backfilling material for sealing radioactive waste repositories within rock salt formations has many advantages, particularly its compositional similarity to the host rock and the fact that it is derived from the mining process. As a backfill, it serves multiple purposes, including mechanical stabilization, heat transfer, and sealing. Numerical simulations are essential for evaluating the long‐term effectiveness of these safety functions and enhancing our understanding of repository systems. These simulations not only play a crucial role in the safety analysis of repositories but also aid in identifying suitable locations for them. High‐quality constitutive models are indispensable for these simulations to ensure accurate and reliable results. The visco‐plastic behavior of crushed salt deformation can be decomposed into compaction creep, dislocation creep, fracture and grain rearrangement creep, and pressure solution creep. This contribution presents the BGR‐CS constitutive model, which accounts for the aforementioned deformation mechanisms. The underlying creep mechanisms are derived from examining microscale processes within a representative volume element (RVE). Initially, compaction and dislocation creep occur in the grain contact zone, where applied stress is localized. A high initial void ratio leads to an increased creep rate during the creep process. Pressure solution creep is modeled as a diffusion‐controlled process in the contact zone, with the creep rate derived from the mass balance of salt ions. The material model has been implemented in the in‐house Finite Element software JIFE MP and validated through laboratory experiments.