On the constitutive relations of rock salt

A reliable prediction of the thermo-mechanical behavior of underground structures in rock salt is necessary for the design and the safety analysis of a repository in a formation of rock salt. This behavior can be determined by numerical tools such as the finite-element method if the constitutive relations of rock salt are known. In the past decades relations are derived from lab tests and from in situ tests. The paper summarizes the main results of these tests and of the benchmark activities performed in the COSA project. This project was carried out with the aim to verify and validate the numerical tools. Based on the results of this project it is included that at this moment there is no set of constitutive relations, derived from laboratory samples, which can be used to predict accurately observed in situ behaviour. It has been shown however that by changing some of the constitutive parameters it is possible to arrive at a fair description of the in situ experiments. (orig.)