STUDY ON STABILITY EVALUATION AND SUPPORTING WORK DESIGN FOR HIGH AND STEEP ROCK SLOPE IN MATERIAL DEPOTS

 Slope in material depots for hydropower station construction is generally characterized by great height and great slope angle. Considering its usage,this type of slope is usually designed as temporary slope with,therefore,temporary supporting scheme. Due to the rapid unloading caused by rock exploration,large deformation and failure happen frequently within such slope. Two slopes in material depots for the construction of Pubugou hydropower station in Sichuan Province,China,were taken as examples in this study. The supporting scheme were of dynamic design,that is,the design of supporting work was kept updated according to the monitoring of deformation in the progress of rock exploration. This paper concludes the dynamic design method and flowchart employed for these two slopes and puts forward a practical methodology for stability evaluation and supporting work design for such slopes. Firstly,three engineering geological problems about the selected slopes are summarized: （1)overall instability controlled by particular combination of weak discontinuities； （2)block instability； and（3)instability of cataclastic rock masses. Secondly,the overall slope stability is evaluated followed by local stability evaluation on the basis of dynamic investigation of rock mass during excavation. Dynamic design for slope supporting works during rock exploration obeys a general rule,ensuring overall stability,controlling local distortion and paying attention to potential instable zone. The instable zones,which could be determined and delineated by qualitative analysis were designed and constructed prior to others. Rules for the design of supporting works and standard for construction are stipulated for the blocks and cataclastic rock masses susceptible to deforming during rock exploration. To ensure security of construction and reduce the cost for slope supporting,the excavation scheme was adjusted from time to time for potential distortion zone. The practice in slopes at Pubugou hydropower station shows that the proposed method can fasten excavation of high slope and reduce the cost for slope stabilization.