Rock salt — the mechanical properties of the host rock material for a radioactive waste repository

For the long-term prediction of deformation, stress and permeability of a repository in a salt formation, one needs a reliable extrapolation of the mechanical behaviour of rock salt. This is only possible by means of material laws with a physical basis. A detailed description of the so-called composite model for transient and steady state creep is given, which is based on micromechanisms. This model is not only able to model deformation in a wide range of stresses and temperatures, but also after stress decrease, as well as the large differences in creep caused by variations in the distribution of impurities. As a result of this sound physical and experimental basis, the modelling results can be reliably extrapolated. ncy, healing, damage, failure, and deformation of rock salt is described by an elasto–viscoplastic constitutive equation. An important feature is the stress dependent dilatancy boundary which separates the dilatant domain from the compressible one and forms a kind of safety boundary. Finally, the relation between deformation, dilatancy, and permeability is addressed. This publication shows that far advanced tools exist for the prediction of the long-term as well as the short-term mechanical behaviour of a repository in a salt formation.