Abstract: The geological structures of the left bank slope at Baihetan hydropower station are extremely complicated. Many steep faults and interlayer staggered zones are the most significant risks which influence the stability of the left bank slope. Based on the analysis of the survey and field monitoring data, a numerical software UDEC was then adopted to build the numerical model for deformation analysis of the left bank slope. Under the condition of unsupported excavation, the stress and displacement changes of the key points of F17, LS331 and LS3319 at hanging wall and footwall rock masses were analysed to identify the potential instability failure areas. Meanwhile, the behaviours of potentially unstable block reinforced using pre-stressed anchorage cables were simulated at different construction procedures. The deformation characteristics, failure mechanisms and overall stability of the left bank slope were comparatively analysed using different models. Numerical modelling and field observation both show that the slope stability is strongly related to rock mass structural planes. Moreover, the deformation and damage of the left bank slope are mainly induced by the shear failure of interlayer staggered zones and tensile fracture of faults under unloading conditions. Pre-stressed anchorage cables can efficiently improve the stability and reduce the deformation of the rock slope. To efficiently control the shear deformation of rock slope, the excavation and support should be carried out simultaneously. The obtained results have particular significance to the design of reinforcement and construction process.

Key words: Baihetan hydropower station, rock slope, numerical simulation, deformation and failure mechanism, pre-stressed anchorage cables, reinforcement scheme