The Deformation And Failure Modes Of The Fluctuation Belt Of Reservoir Bank Slopes And Stability Analysis And Evaluation Of Reserved Bedding Rock Slopes

Three Gorges project has great significance to promote the economic development of western China.Unfortunately,this project has brought great achievements to China’s economic development,it has also become one of the frequent geological disasters in China due to its complex hydro-geological environment,many disasters happened such as earthquakes,landslips,debris flows and so on.In the effect of the seasonal fluctuation of the water level,a fluctuation belt of Three Goreges Reservoir Region with an elevation difference of 30 m,was formed.Under the effects of the reservoir water level fluctuation,wave erosion and other forces,the fluctuation belt of reservoir bank slopes keep rebuilding,which has become a key area of the stability of bank slopes,the deterioration characteristics and overall stability of rock and soil mass of bank slopes have not been studied systematically.Relying on the National Natural Science Foundation of studying on the mechanism and stability control of the slope’s static(dynamic)force instability under the rock mass deterioration condition in the fluctuation belt of the reservoir bank slopes(41972266),based on the survey and analysis of the topographic and geological characteristics of Wushan section in Three Gorges Reservoir area,through wetting-drying test,direct shear test and Universal Distinct Element Code(UDEC for shaort)to simulate the deformation and stability of the reserved bedding rock slopes of reservoir bank,the main research contents and results of this study are as follows:(1)Based on the field survey data of Wushan section of Three Gorges Reservoir area,five categories weak rock formations which are easy to induce deformation and failure of reservoir bank slopes were summarized,and explained their disaster effect.In addition,the changes of rock mass morphology of rock bank slopes caused by the interaction of water and rock were classified into three categories: fragmentation,block fragmentation and plate fragmentation.(2)Based on the survey of the reservoir area,this paper found that the reservoir bank reconstruction models were not single,on the basis of the analysis of 15 typical cases of bank slopes reconstruction,five types of bank slopes reconstruction in Wushan section were proposed,which are: erosion damage,collapse damage,erosion and hollow damage of bedrock,corrosion and hollow damage of bedrock,and sliding damage,the main reconstruction model of soil bank and rock soil mixed bank slopes are sliding damage and collapse damage,the main reconstruction model of rock bank slopes are erosion damage,corrosion and hollow damage of bedrock and erosion and hollow damage of bedrock.(3)The shear strength index of the dolomitic limestone structure surface after the dry-wet cycles is as follows: within the dry-wet cycles range of the experiment,the cohesive force of dolomitic limestone tends to increase gradually,and the friction angle tends to decrease significantly.Using UDEC to analyze the stability and make an evaluation of the reserved rock bank slopes with a concave rock cavity in the fluctuation belt area,basing on the degradation process,numerical simulation results show that the failure process of slope model can be summarized as: with the increasing reduction factor of J region of the fluctuation of the reservoir bank slopes,firstly,blocks sliding around the J region,sliding blocks number gradually increased and the upper blocks of the concave rock cavity slightly open with the further increasing of the reduction factor,and than the open joints and fissures cut-through,and several rock formations broken and sliding failure appeared.