Abstract: The stability of unloading block on the left bank slope has been a critical issue for Baihetan hydropower station. Study on the geologic condition, failure characteristics and deformation mechanism indicates that the sliding failure of three dimensional rock blocks along discontinuities is the main potential failure mode of the left slope. General limit equilibrium method and continuum mechanics method both have some limitations in analyzing the stability of complex block system. In this paper, the method of automatically identifying block is employed to establish the block system model of the left slope. Three-dimensional elasto-viscoplastic block element method(BEM) is adopted to calculate the strength reserve safety factor of sliding blocks. And the controlling discontinuities and the key blocks are revealed. Research results are consistent with both the general limit equilibrium analysis and geomechanical model test, which supports the reinforcement measures for the left slope. The study in this paper could be a guide for the stability analysis of complicated rock block system.

Key words: rock slope, block system, block element method, safety factor, Baihetan Hydropower station