Abstract: The left bank of Baihetan hydropower station is a high slope, which is a three-dimensional (3D) complex block system with strongly unloaded rock mass. The 3D geomechanical model test was adapted to investigate the slope deformation characteristic, failure process and mode, destruction mechanism, slope stability, and reinforcement effect. The model test shows that the slope failure exhibits the mode of the block sliding failure, which demonstrates the shear slipping among the bottom surfaces, the tensile crack along the trailing edge surface, and the block sliding along the bottom surface and side surface. The failure process basically experienced three stages, including the initially crack of discontinuities, crack expansion throughout the block boundaries, and the instability of the slope. The general safety factor of the left bank slope was obtained through the comprehensive geo-mechanical model test. The safety factors of given blocks were compared with the calculation results of both 3D-LEM and BEM, which shows good agreements. Simultaneously, the relative displacements at the interface of LS337 were monitored. From the results, we can see that by the reinforcement of the deep concrete replacement caverns, the sliding deformation among the bottom surfaces is effectively controlled, and the safety factors of the combination blocks of related discontinuities are improved, and the effect of slope reinforcement is more obvious. This paper provides significant guidance for the stability and reinforcement of the left bank slope of the 3D complex block system with the strongly unloaded area in Baihetan or other similar engineering slopes.

Key words: rock slope, 3D block system of discontinuities combination, geo-mechanical model test, safety factor, Baihetan hydropower station