Stability Analysis And Control Measures Research Of Danbo Colluvial Slope In Yangfanggou Hydropower Station

Yangfanggou hydropower station locates on the middle reaches of the river in Yalong River in Sichuan province,with 512.48 million m~3 total reservoir capacity,53.85 million m~3reservoir regulation capacity,and 1500MW power plant capacity,which is a first-class and large first-type project.Danbo colluvial clay locates on the dam site upstream of Yangfanggou hydropower station on right bank of Yalong River,about 0.5 km away from the dam site.The colluvial clay distributes in elevation between 2050 to 2465 m,north-south direction along the river,about 560 m long east-west,about 330 m width north-south.The middle-upper part of the colluvial clay is the mixed soil gravel layer with argillaceous weak cementation.The bottom is the gravel soil layer with medium dense feature.The colluvial clay is close to the dam site.If the slip occurs after water storage,it will affect safe operation of power station.Thus,it is necessary to evaluate its stability.The qualitative and quantitative stability analysis of the colluvial clay are conducted in this paper.Results show that it’s necessary to take measures for the colluvial clay to meet the engineering safety control standard.Then,a variety of reinforcement scheme is analyzed and the suitable scheme is selected out.Quantitative analysis uses the SLOPE module in the GeoStudio system software.SLOPE/W is a widely used slope stability analysis program in the world,using the limit equilibrium theory(including force balance and moment balance)to calculate soil slope and rock slope safety factor.The main content of this research is as follows:(1)Through investigation and data collection at the site of the project,the regional geology and basic geological conditions of the colluvial clay is found out,and the body composition,unloading situation,the deformation and failure forms of the colluvial clay is obtained.(2)At the site and indoor,soil physical and mechanical tests have been carried out respectively,which obtain the physical mechanical indexes and determine the parameters of slope stability analysis,providing reliable design parameters for the stability analysis and treatment design of the colluvial clay.(3)Slope stability sensitivity analysis is conducted by the material degradation.(4)Three main landslide profiles are selected for stability analysis with limit equilibrium method.Different conditions that are by the combination of three basic conditions including natural condition,rainstorm and earthquake are calculated respectively.The calculation results show that overall stability of the three profiles is good.Except the individual working safety coefficient is slightly lower than control standard,the rest conditions can satisfy the specification requirements.However,local stability of the three profiles did not meet the specification requirements under a few conditions.(5)On the basis of above analysis,in combination with the present domestic slope reinforcement processing experience,a variety of reinforcement scheme is put forward,and the corresponding calculation model is set up in order to calculate the stability of the slope reinforcement scheme under various load combination.Strengthening plan adjustment and refinement is implemented,the feasibility and effectiveness of reinforcement scheme is evaluated,and three key scheme is selected out.Then further comparison of the three key scheme is conducted,and most suitable scheme is determined finally.Calculation analysis results of this paper show that,although there is a wealth of practical experience in slope management,it is still necessary to carry out quantitative analysis of multiple schemes the large excavation and unloading treatment scheme for the colluvial clay can more economically bring larger stability and security,which has a certain reference significance for similar projects.