Study On Toppling Deformation Characteristics And Treatment Measures Of The Reservoir Slope Of A Hydropower Station On Yellow River

The hydropower station is located,in the territory of Guide County in Qinghai province.the design of the the normal water level is 2452m,the total storage capacity is 10.56×10⁸m³ and its installed capacity is 120×10⁴KW.The geological conditions of the dam site is complex,Affected by the strong toppling deformation of the Reservoir slope,currently,the right bank slop of the dam has obvious deformation after the reservoir impoundment..tension cracks occurred in the top rear platform extending continuously.the platform is abt 30m to top and the surface of the slop has obvious deformation phenomenon,they will seriously threaten peoples lives and the operation of the hydroelectric engineering.In this paper,taking the right bank slope of this hydropower station as a practical example.based on predecessors’research results,combining with the slope deformation monitoring data,adopting geological analysis method and numerical simulation analysis method to analyze the deformation characteristic,destruction mechanism and potential damage range,finally make a reasonable treatment program,the specific content and research results are as follows:（1）The stability of the reservoir slope which formed by the massive granite is mainly determined by four groups advantage structural surface.According to the available data from exploration adits and previous research results,building the toppling deformation degree classification system of the reservoir slope and corresponding geological model.（2）In the paper,the deformation boundary and scope of reservoir slope are studied in view of deformation area and deformation characteristics.At the same time,combining with the slope deformation monitoring data,analyzing the characteristic of each part of the reservoir slope and the results showed that:the main deformation area in the study area is from 2#beam to 5#beam,slightly upstream direction and toward the river bed;the level variation has influenced the deformation rate in each part of the deformation area obviously,and rainfall has influenced the deformation of slope surface,especially when heavy rains,this influence is greater;the monitoring data of landslide deep deformation obtained with inclinometer show that,the reservoir slope don’t has a fixed and adverse sliding surface within the scope of the monitoring.（3）Through analysising two terms observations taken by three-dimensional laser scanning machine between July 2014 and November 2014,we can find that:the main deformation of the top platform as a whole is vertical deformation,furthermore,this situation will still last for a quite long period in future;the horizontal and vertical deformation of the main deformation area（2#、3#、4#and 5#beam）are apparent,especially the deformation of terrain mutation part is bigger;on the slop surface oflow elevation,each beams deformation mainly toward to the offshore direction,and there are signs of sliding at lower part of 5#beam;Shuanghang beam the upstream boundary of deformation area and 1#beam have the same deformation law,their stability is good.（4）Combining the result from physical simulation experiment,analysis the interaction mechanism of every factor.At the same time,using the discrete element software of UDEC to analysis the deformation and destruction characteristics of the reservoir slope under different conditions,such as:natural situation、impounding conditions and impounding conditions&earthquake.In natural situation,the toppling bending deformation belt is mainly concentrated on the dividing line between A rock and B₁ rock mass;And under the working condition of impounding&earthquake,the toppling bending deformation belt extend to the dividing line between B₂rock and C rock mass.（5）On the basis of analyzing the deformation characteristics、rupture mechanism of the reservoir slope and the qualitative analysis of the harmfulness,3DEC is applied to simulate and analyze the deformation of the slope after it was excavated and retained,results show that:the original slope deformation mainly concentrated in A rock and a part of B rock.after excavation,the deformation of he reservoir slope get effectively control,but due to the upheaval caused by excavation unloading,in the top rear platform and the excavation face appeared the tensile deformation,the local stability of the reservoir slope is affected;And the supporting measures can effectively control deformation caused by excavation.（6）Using limit equilibrium method to carried out in different conditions of stability calculation after slope excavation with supporting conditions.result shows that:the stability coefficient of the slop basically meet the relevant specification requirements after excavation with supporting conditions,and possess more margins in safety.However,under the impounding and earthquake,the stability coefficient of the slop is about 1.2,the slope is at basically stable state.