Stability Impact Of Reservoir Bank Between Yunyang And Fengdu Owing To Operation Water Level Adjustment Of The Three Gorges Project

In recent years,the shortage of water resources has become a serious restriction factor for the further development of society and economy.Relevant departments and some scholars put forward "the implementation of the new development concept,the practice of new flood resources utilization thought,to utilize the achievement of flood forecasting technology,according to the practice of the Yangtze river flood control joint scheduling,basic guarantee in downstream flood control level is not lower,under the condition of the reservoir flood control impact acceptable,research potential capacity of the mining area of the three gorges reservoir flood,flood season running water level of three gorges project To fully develop and utilize the water resources of the Yangtze River,especially the flood resources".The preliminary adjustment of operating water levels in flood season were 148 m,150 m,152 m and 155 m.In view of the stability problem of reservoir bank caused by the adjustment of operating water level in flood season of the Three Gorges Project,some typical treatment projects in Yunyang-Fengdu section of the reservoir area were selected to conduct a comparative study on the stability of reservoir bank under different flood season water levels by combining the transfer coefficient method and the reliability method.The preliminary results were as follows:(1)According to the comparative calculation results of the stability of six typical reservoir bank management projects in Yunyang-Fengdu section,it can be seen that the stability coefficients of the reservoir bank all increase after the adjustment of operating water level in flood season,but the total added value was not large.At 148 m and 150 m water level,the stability coefficient increased slightly,while at 152 m and 155 m,the stability coefficient increased slightly.In general,After the operation water level adjustment of the Three Gorges Project,the various water level adjustment schemes generally showed a favorable trend for the stability of the reservoir bank in the Yun-Fengdu section of the Three Gorges reservoir area.(2)After adjusting the operating water level,the sensitivity analysis of the physical and mechanical parameters affecting the stability of the bank slope was carried out in combination with Yunyang and Fengdu reservoir bank projects under different operating water levels.It was found that the internal friction Angle of the sliding surface has the greatest influence on the stability of the bank slope,followed by the cohesion of the sliding surface and the sliding weight degree.(3)According to the statistical analysis of the survey data of two typical reservoir banks in Yunyang and Fengdu,the internal friction Angle of the sliding surface,the cohesion of the sliding surface and the sliding weight degree do not reject normal distribution or lognormal distribution.In reliability analysis and calculation,it was suggested that the internal friction Angle of the sliding surface should adopt normal distribution,the cohesion force of the sliding surface should adopt logarithmic normal distribution,and the weight degree of the sliding surface should adopt normal distribution.(4)Two typical sliding reservoir banks,Yunyang and Fengdu,were selected to compare the stability of bank slope by using the reliability theory and the traditional safety factor method.The results showed that the failure probability of bank slope decreased with the increase of operating water level,and the change of failure probability was more obvious than the change of stability coefficient.When the coefficient of variation of friction Angle and cohesion of sliding surface was greater than 0.10,the stability of reservoir bank was greatly affected.Therefore,full attention should be paid to the change of the friction Angle and the cohesion of the sliding surface of the reservoir bank when the operating water level was increased.