In order to deepen the comprehension of the stress-strain behavior of 'clean halite' and 'argillaceous halite' from the WIPP, 20 core samples were left to the Institute of Soil Mechanics and Foundation Engineering of the Technische Universität Braunschweig. The experimental data is obtained to derive material parameters for high-quality material models which describe the stress- and time-deformation behavior of the two salt facies. Rock salt shows a brittle fracture behavior at the used strain rate of 1.0 10-5 s-1. With a low confining pressure the specimens reach the ultimate strength followed by the typical post failure behavior of rock salt. A volume expansion is already observable below the ultimate stress state, i.e. to a loosening of the specimen by dilatancy and micro-cracking. The volumetric strain rate will be at its maximum when the fracture stress is reached. The visual impression shows a clear difference between the two types of salt. Therefore, the salt facies are likely to show a different stressstrain behavior, because in each case different fracture mechanisms should dominate. But this impression cannot be confirmed by the conducted experiments.

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