Study On The Stability Of ?~# Landslide In The Lower Reaches Of Cihaxia Of The Yellow River

Along with the advancement of the western development strategy in our country,a large number of hydropower stations have already been built or are built in upper reaches of the Yellow River.Among them,Qinghai province has become the first choice for hydropower station dam site because it has the unique geographical advantage with many gorges.However,due to its location in a ravine area with deep river valleys and steep slopes,there are a large number of slope stability problems around the hydropower station,which seriously affect the normal operation of the hydropower station.This paper takes Cihaxia Hydropower Station ?#landslide as the research object and introduces the geological environmental conditions in the study area in detail.The basic characteristics and formation mechanism of the landslide are analyzed by means of field investigation,exploration and testing of the landslide.The stability of the landslide under natural,heavy rain,and earthquake conditions is analyzed by adopting the limit equilibrium method,FLAC3D finite difference method and Monte-Carlo method.The sensitivity analysis of the shear strength parameters and seismic forces of the sliding zone soil was made,and targeted treatment measures were proposed.The main research results are as follows:(1)Through the collection of geological environment data of the study area,field investigation,exploration,and testing,the morphological characteristics of landslides,engineering geological characteristics,physical and mechanical parameters and formation mechanisms of landslide are analyzed and studied.(2)The stability of the landslide is calculated by using the limit equilibrium method.The results of the stability calculation show that on the whole,the landslide under natural conditions is in a stable state;the landslide under heavy rain conditions is in an under-stable state;the stability of the landslide under earthquake conditions is slightly lower than under heavy rain conditions,but the steady state has not changed.(3)The FLAC3D is used to conduct three-dimensional numerical simulation of the landslide,and the calculation results of the stability coefficient are basically consistent with the limit equilibrium method.Numerical simulation results show that the maximum displacement of the upstream sliding body under the three conditions appears at the trailing edge of the sliding body;the maximum displacement of the downstream sliding body under natural,heavy rain,and earthquake conditions gradually shifts from the trailing edge of the sliding body to the toe of the slope.The maximum shear strain increment indicates that the potential sliding surface of the landslide is basically the same as the original sliding surface.(4)Reliability analysis of landslide stability based on Monte Carlo method.The calculation results show that the overall instability probability of the landslide under natural conditions is basically 0%;the overall probability of landslide instability under heavy rain conditions is about 32%;the overall probability of instability of the landslide under earthquake conditions is about 40%.From natural to rainstorm and earthquake,landslide has changed from stable to under-stable.(5)Analysis of the sensitivity of landslide stability factors shows that landslide instability is the most sensitive to changes in the friction angle of the soil in the sliding zone,followed by the horizontal seismic force coefficient;the cohesion and vertical seismic force coefficient have little effect.Considering the risk of instability of the landslide under special conditions such as heavy rains and earthquakes,combined with the results of sensitivity analysis,a treatment plan of "anti-slide pile+interception drainage" is proposed for the landslide.