Deformation and water-assisted diffusive mass transfer in rock salt

Abstract

Rock salt exhibits fully ductile crystal plastic flow as well as brittle-ductile damage and water-assisted diffusive mass transfer (dissolution-precipitation transfer) at shallow crustal and even surface conditions. These processes lead to a wide range of coupled phenomena that influence compaction creep of salt backfill, deviatoric creep of intact rock salt, microcrack damage and healing, and the evolution of microstructure, porosity and permeability. While the purely mechanical behaviour of salt is relatively well understood, the effects of water-assisted mass transfer, occurring in the presence of brine or adsorbed moisture, have received less attention. This paper reviews the thermodynamic driving forces governing fluid-rock interactions in stressed rock salt and salt backfill, and the resulting effects on deformation and microstructural change.