The tailings of potash mining are piled up in huge heaps with heights of up to more than 200 m and a ground area of often more than a square km. The material behaviour of the salt is strongly visco-plastic, so that the slopes of the heaps are moving constantly at slow rates. As the strength of the salt is rate-dependent, structural analysis of the slope stability has to consider the deformations and deformation rates and the interaction of subsoil and slope. Due to the complex material behaviour the structural analysis is accompanied by an extensive measuring programme within the Observational Method. The paper focuses on two slopes of tailing heaps, where huge deformations partly at accelerating deformation rates occurred, due to natural respectively man-made slip-surfaces in the subsoil. The deformation rates were critically high and deformations induced serviceability problems to infrastructure at the base of the slope. It is shown, how the restoration of the endangered slopes and infrastructure was established. The concept of restoration is based on both intensive measuring and numerical simulations
