| Yan'an is a narrow city formed by three mountains and two rivers.Urban construction inevitably faces a large number of side slope problems.However,Yan'an is located in the hinterland of the Loess Plateau and is an area with a high incidence of geological disasters.In recent years,there have been many landslides and collapses that caused casualties.Therefore,studying the characteristics,causes and prevention measures of loess landslides has important theories and reality.significance.This paper selects the Xiaonangou landslide in Yan'an City as the research object,analyzes the basic characteristics of the landslide,explores the causes of formation,calculates the stability,and optimizes the treatment plan.The specific content is as follows:(1)Through the landslide survey,the geological environmental conditions,landslide body structure,landslide scope,scale,and physical and mechanical parameters of the rock and soil of the Xiaonangou landslide were obtained.The landslide is 100m long,40-60m wide,and has an area of about 4100m~2.The thickness of the landslide body is 5.0?23.8m,the average thickness is 13.0m,and the volume is about 52,000 m~3.Except for the rear edge part is located in the limestone loess,most of the other sliding surfaces are located in the clay layer;the overall water content of the landslide body is Between 10%?22%,with the deepening of the depth,the increase rate is about 0.137%/m?0.194%/m.(2)The effect of rainfall on the moisture content of the slope body is simulated,the effect of rainfall on the stability of the slope body is analyzed,and the causes of landslide are discussed.The volumetric moisture content of the local loess of the slope body reaches more than 0.4 after heavy rainfall,and heavy rainfall is the main reason for the change of moisture content of the slope;the stability coefficient of the slope body under natural conditions is 1.103,and the stability of the slope body under heavy rainfall conditions decreases to 1.012;the rainfall scours the slope body in the rainy season,and the large amount of surface water infiltration along the slope surface fissures forms a water fall hole,and the relative water insulation of the underlying powder clay makes the local loess body in a high moisture content for a long time.state,the shear resistance of the slope body loess is weakened.(3)The concentrated rainfall in July,August and September every year in Yan'an City is the main factor of landslide formation.A large amount of rainwater washes the slope body,and surface water forms a water fall hole after a large amount of infiltration along the fissure of the slope surface,and the water fall hole forms a water flow channel and stress concentration area in the slope body.Under the influence of heavy rainfall,the slope eventually evolves into a landslide.(4)The stability and thrust calculation of the 1-1' section of the Xiaonangou landslide was carried out using the unbalanced thrust method.Under the natural working condition,the stability coefficient is 1.057,which is in the basic stability state.Under the saturation condition,it is 0.945,which is in the unstable state.The remaining thrust was calculated,and the remaining thrust was 217.40k N/m when the safety coefficient was 1.15,and 541.74k N/m when the safety coefficient was 1.30.Accordingly,two sets of solutions were designed,mainly pre-stressed anchor cable anti-slip pile and double pile,and the safety,economy,construction difficulty,construction period and environment of the management solution were evaluated by using multi-objective entropy power decision method.The multi-objective entropy decision method was used to evaluate the safety,economy,construction difficulty,construction period,and environment of the management plan,and finally the comprehensive management plan based on pre-stressed anchor piles was selected. |
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