Evalution Of Slope Stability For Dam Abutment Of Ru Mei Hydropower Station

Slope engineering is an ancient and ever new problem in the process of engineering construction. The main failure mode of slope includes plane slide, wedge slide and toppling failure. According to statistics, landslide hazards and slope disaster are important geological hazards. Every year the direct and indirect economic losses caused by landslide is amounted to20billion RMB in the whole country. So landslide stability and evaluation control has been a study field which the country paid attention. Especially in recent years, with the rapid development of the national economy, the large water conservancy and hydropower engineering and transportation construction, such as Three gorges Project and projects built in the upper reaches of the Yellow River, have been gotten a large development. The geological condition is complex in the project area. Therefore, in the construction of these projects, slope engineering research has been attracted attention.In this paper, the abutment slope of Rumei Hydropower Station in Tibet is used as the case study. Based on field research and data collection, the analysis of engineering geological conditions of dam site was performed. According to in-situ test, laboratory tests, and a variety of survey and design specifications, the physical and mechanical properties of the rock block, discontinuity and rock mass are researched, respectively. The failure mode of the slope is determined by using the kinematic and engineering geological analysis. Finally, combining the methods of the kinematic analysis, limit equilibrium and numerical analysis (FLAC3D), the abutment stability of natural slopes and artificial slope in three different operating conditions are examined.According to the research, the following results had been obtained:(1) Based on the field research and data collection, engineering geological conditions of the dam site area included topography, lithology, geological structure and hydrogeological condition was investigated.(2) The test data of laboratory rock block, in-situ joint and rock mass had been analyzed in detail. The joint strength parameter of different types in dam area had been researched. On the basis of rock mass in-situ deformation test, sonic test and point load test in different adit position, the relationship between geological strength index (GSI) and wave velocity was built. According to the Generalized Hoek-Brown Criterion, in-situ test data and long-term experience, the rock mass compressive strength, tensile strength, deformation modulus, cohesion and internal friction angle of the weathering degree, have been suggested.(3) Based on analysis of engineering geological conditions and determination of dominant joints, the failure mode of abutment slope was divided into4types which were rock slope damage, cataclastic rock mass slide, slide along strong weathered bottom and slide along different dominant joint sets. Out of them, the first type could be determined by kinematical analysis method and the rest could be determined by engineering geological analysis.(4) The B2-B2’profile is selected as a typical calculation cross-section. Respectively, the method of kinematic analysis, limit equilibrium method and FLAC3D method are used to analyze the stabiliy of the natural slope in three different conditions, such as nature, heavy rains and the design earthquake. The results show that:natural slopes in natural conditions, heavy rain conditions and the design earthquake conditions are in a stable or basic stable state, but do not exclude the occurrence of local sliding, collapse and possible toppling.(5) Respectively, the method of kinematic analysis, limit equilibrium method and FLAC3D method are used to analyze the stability of the natural slope in three different conditions, such as nature, heavy rains and the design earthquake. The result shows that:①in the natural condition, the stability factor of Ⅱ class2nd landslide in right bank is less than1.25. The landslide has a big possibility of sliding. All other slope stability factor is greater than the factor of safety and in a stable state.②in the heavy rain condition, the stability factor of Ⅰ class2nd landslide in right bank is between1.20and1.25, and the slope is in a basic steady state. The stability factor of Ⅳ class2nd landslide in right bank is less than1.20. The landslide has a big possibility of sliding. The rest of landslide stability factors are greater than the safety factors, the slopes are stable.③in the design earthquake condition, the stability factor of Ⅱ class2nd landslide in right bank is less than1. The landslide has a very big possibility of sliding along this sliding surface. The stability factor of Ⅳ class2nd landslide in right bank is between1.15and1.10. The slope is in the basic stable state and the rest of landslide stability factors are greater than the safety factors, the slopes are stable.