| There exists a gentle slope platform, whose form is convex, on the lower part of left bank accumulation body (front margin) of Xiluodu Hydropower Station. Because platform is just at the top of the water intake of diversion tunnel and spillway, A comprehensive excavation of the platform is needed. Due to the potential slipping signs, the obvious dislocation characteristics of sliding surface and the increasing deformation over time, the Excavation of slope has a greater influence on the safety of the cableway platformand and the water intake, what's more , it is closely related to the normal operation of power stations, therefore, it seems to be very necessary to understand the deformation mechanism of the slope, to make reasonable stability assessment and to forecast its hazards scientifically.To sum up, regarding the accumulation body as a study object, by virtue of integrated use of geological analysis, monitoring analysis, numerical simulation and the limit equilibrium and so on, this paper firstly analyzes the geographical and geological background of the study area, in addition, studies the deformation mechanism and the basic characteristics of the accumulation body, furthermore, initially determines the potential slip surface, the instability characteristics and the scope of instability after the excavation of the slope , finally estimates the development trend and stability of the slope. The research and the results as follows:(1) The left bank accumulation body at the top of the intake mainly consists of flood deposit, glacier deposits, the residue of ancient landslide. In addition, at the bottom of the accumulation body, there is a weak ancient sliding zone, which plays a vital role on the deformation adjustment of the excavation slope. The water table of the accumulation body is lower. (2)Analyzing the monitoring results and the results of three-dimensional numerical simulation, we know that the deformation of the excavated slope in the II~V District mainly have two modes: the superficial slope of IV District is shear deformation and II~IV District is deep slide deformation through the ancient sliding zone. Furthermore, the deep deformation can be divided into two types: one regards the ancient sliding surface as shear opening, tracking the ancient sliding zone around a length of about 50 m, and then breaking away from the ancient sliding surface, extending into the internal slope at the degree of 30 ~ 40. The current extension has been into the front slope platform, but has not developed into transfixion slippery surface. This kind of deep deformation is caused by the excavation activities, deformation adjustment and so on. The other one happens in the ancient sliding zone, 100m below the excavation, with the smaller deformation rate, slower development. This kind of deep deformation is caused by creep phenomenon due to the built-in stress adjustment before the slope excavation.Finally, we can arrive at the conclusion that the development trend of various deformations will be continued through a long-time creep deformation, but it won't have a greater impact on the stability of the slope.(3) Aimed at the all working conditions, which are before and after the excavation, under the condition of natural state, earthquakes, different Proportion saturated, by virtue of the transfer coefficient method and the Bishop of the limit equilibrium method, the corresponding safety factor can be calculated. Based on the above analysis, we know that several working districts are all stable under all the conditions, but there are differences in their safety reserves. In general, the safety reserves of II and V are higher, by contrary, the District III, IV have lower safety reserves relatively.In this paper, through the analysis of deformation mechanism aimed at the slope-excavation of the left bank accumulation body, the author wishes to provide some useful information on the slope treatment of Xiluodu hydropower station. |
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