Dump slope in the open-cast mining pit is always a safety issue, as it can experience catastrophic destruction due to the slope failure caused by various factors, such as atmospheric conditions (especially precipitation), vegetation and so on. The precipitation has direct influence on the water content change with the infiltration water into the unsaturated slope especially during the heavy rainfall event. The significant effects of vegetation on the slope stability can be essentially contribute to two major aspects, water movement via the soil-plant-atmosphere continuum and soil reinforcement by the root system. The aim of this study is to investigate the hydrological regime in the dump slopes and the influence of the saturation degree on the stability of dump slopes under the consideration of precipitation and vegetation with the program PCSiWaPro~R (by Technical University of Dresden).Physical model tests of a sand slope at TU Dresden showed that it was the partial saturated condition that had already caused mechanical instabilities. Using the simulation program PCSiWaPro~R, the distribution of the water saturation in the partial saturated slope area under transient boundary conditions can be simulated. It is based on solving the Richard's Equation in two spatial dimensions using the finite element method. The integration of a weather generator into PCSiWaPro~R allows a transient flow calculation with respect to atmospheric conditions (precipitation, evaporation, daily mean temperature and sunshine duration) and removal of water by plant roots and leaves. With PCSiWaPro~R a case study in an open-cast mining pit in Saxony (Germany) has been carried out to simulate the hydrological process in the dump slope especially for the unsaturated zone; then with the simulation results, the stability analysis models could be applied to verify how detailed water content and vegetation influence the stability of the dump slope.
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