Stress-strain behavior of rock salt of flat and steep storage

In order to intensify the understanding of the stress-strain behavior of 'clean halite' and 'argillaceous halite' from the WIPP, the Institute of Soil Mechanics and Foundation Engineering of the Technische Universitat Braunschweig were left 20 core samples. The experimental data obtained is used for deriving parameters for high-quality material models to describe the stress- and time-deformation behavior of the two salt facies. Rock salt shows a brittle fracture behavior at the used strain rate. With a low confining pressure the specimens reach the ultimate strength followed by the typical post failure behavior of rock salt. Already below the ultimate stress state there is a volume expansion observable, i.e. to a loosening of the specimen by dilatancy due to micro-cracking. The volumetric strain rate will be greatest when the fracture stress is reached. The visual differences between the two facies suggest varying composition of impurities and accompanying minerals. Such inhomogeneities affect the mechanical behavior depending on the volume ratio. It seems that in each case different fracture mechanisms dominate. This impression cannot be confirmed by the experiments.