Research On Characteristic And Precaution Measure Of Dangerous Rock Mass On The Slope Of Hongshiyan Barrier Lake Caused In Ludian “8.3” Earthquake

With the rapid development of economy in our country, the country’s demand for energy, especially clean energy, is increasing day by day, so, the development and utilization of water resources is very important to ensure the supply of energy. The hydropower resources in the southwest area are very abundant. In recent years, many large scale hydropower projects started to build or put into operation. Because of the weak geological environment conditions in the southwest region, the geological disasters happen frequently, the construction stage and operation stage of hydropower project are often threatened by geological disasters, and even lead to serious casualties, therefore, hydropower engineering geological disasters must be paid enough attention. Dangerous Rock Mass is one of the main types of geological disasters threaten hydropower project. In recent years, in the construction stage of hydropower station, rock has been dedicated to the research and treatment. In this paper, dangerous rock mass on the slope of Hongshiyan Lake Hydropower project Hydro-Junction was studied. the distribution, formation mechanism and instability mode of the research development of dangerous rock mass was studied, the stability of dangerous rock mass was evaluated, at the end of this paper, the author puts forward the suggestion of prevention and control measures. The main research results are as follows:(1)The geological environment data of the study area was collected, the field check and supplement was carried on. The general geological survey was used as the main means, UVA photography and 3D laser scanning technology were used as auxiliary means to carry on the investigation of rock mass to get the dangerous rock mass’ s position, geometric parameters and geological characteristics, distribution map of the dangerous rock mass was drawn.(2)The distribution of rock mass was studied. The type of dangerous rock mass was divided into four categories: falling, sliding, toppling, rolling(sliding) down type. The development and distribution law of dangerous rock mass on the left bank, right bank. and Zhenzhuyan slope was analysed, Analysis results shows that the type and quantity of the dangerous rock mass are related to the geological environment condition.(3)The influence of landform, lithology combination, geological structure, earthquake, water and other factors on the development of dangerous rock mass was analyzed, and the formation mechanism and instability mode of the dangerous rock mass in the study area affected by interior and exterior factors was studied.(4)Qualitative evaluation standard of Stability evaluation was established according to three aspects: characteristic of structural plane, weathering and rock mass structure, The stability calculation method suitable for the dangerous rock mass on the study area was summarized. The qualitative evaluation method for main evaluation method and quantitative evaluation for auxiliary method was adopted to evaluate the stability of rock mass in the study area.(5)Discontinuous deformation analysis(DDA) method numerical simulation software was used to analyze the typical Dangerous rock mass to evaluate its stability, instability modes and motion characteristics under natural state and seismic conditions. The "10.18" spillway tunnel side slope collapse was selected to be an example, its formation mechanism and instability mode was analyzed, and DDA was use to numerical simulation to verify the mechanism and instability mode. No. 1 Dangerous rock mass(ZZWY1) was numerically simulated, the simulation result shows that the instability will occur in the earthquake condition, then the surge damage may occur after the slope instability is calculated, the result shows that the surge harmfulness is low.(6)According to the degree of unloading characteristics and seismic damage on the slope, the distribution characteristic and stability classification of dangerous rock mass, different measures are used to control dangerous rock mass. For B1-1 area of the right bank, due to the serious earthquake damage, the method of slope excavation + bolting and shotcrete support method was consided;for the other areas of right bank, the method of small perturbation method clear danger rock+ shotcrete +active and passive blocking measure was proposed. For the top of The left bank slope, the method of excavation and + bolting and shotcrete support measure is effective, for the dangerous rock masses on the middle and lower parts of the slope, Considering the harmfulness to rural road and the weir dam, the author suggest that a tunnel should be excavate to make the rural road go extend through this area, and rock groove and retaining wall should be set on gentle slope of landslide accumulation body to intercept dangerous rock masses which threat the weir dam.