Study On Deformation And Stability Of Right Bank Slope In Nabang Hydropower Station

Nabang hydropower station is a diversion type power station, which is located at a nearly 20km long river section between the downstream of No.3 hydropower station plant in Mengnai river and the convergence of Mulei river in Yingjiang county in Dehong Dai autonomous region. And Nabang hydropower station is 49m high, with its dam site away from Yingjiang county about 67km, power plant away from Yingjiang county about 90km and from Kunming city about 800km.Based on the field engineering geological survey and deformation monitor data of righ bank slope, there are following several major researches on deformation and stability of slope under the condition of natural self-weight stress and rainfall.(1)Deep analysis into deformation and monitoring data of the five monitor points, concerning about the influence on the commence and convergence time of the deformation of the slope by rainfall, some major results are concluded:Obviously, the commence and convergence time of the deformation of the slope laps with the time section of heavy and intensive rainfall about 20 days. Furthermore, rainfall not only triggers the soar in displacement of slope, but also makes the movement of the slope have the same direction, namely towards the river and upstream.(2)Using FLAC3D to run 2D and 3D modeling analysis under the condition of natural self-weight stress and rainfall, this paper obtains some regulations on the displacement field and stress field of slope, helpful for the judgment on the stability of slope. Some important results are as follow:right bank slope is basically stable under the condition of natural self-weight stress without large deformation. While under the condition of rainfall, slope is unstable, and the primary failure mechanism of right bank slope is "compress-shear" with a coming penetrating trend in plastic zone.(3)In LEM, we adopt imbalance thrust force method to determine the FOS under the condition of natural self-weight stress and rainfall and the state of every blocks, then dig out several conclusions:FOS is 1.609 under natural self-weight stress condition, while considering rainfall, a 30% discount in physical and mechanical parameters of rock strength, FOS is 1.0652 and the slope is unstable. In addition, Block 5 and Block 9 are resistance sections of slope. The rock strength of slope is weaken by rainfall, with a highly probability in resulting in tension fracture surface in trailing edge of slope in the range of elevation 1104-1250m, especially in elevation 1250m around, and shear opening of slope in the range of elevation 960-1060m, especially in elevation 950m or 980m around.