Analysis And Improvement On Stability Of Cutting Slope In K1460-800 Longbai Expressway,Guangxi

Geotechnical engineering characteristics,climate,and hydrological regional differences contribute to the regional characteristics of geotechnical hazards.In different areas of Guangxi,there is a great difference in the property of rock slope.Therefore,the sliding mechanism,stability analysis and control measures are often different.Mudstone and shale slope is widely distributed in the north,northeast,south and southeast of Guangxi Province.There are often loose layers on the surface of slopes due to strong weathering,which is prone to cause geological disasters such as landslide and collapse with the joint effect of continuous rain or heavy rain.Therefore,it is necessary to study the mudstone slope in this area.This paper takes the case of mudstone slope collapse accident in K1460+800,Longbai expressway,Guangxi as the research object to calculate the stability of landslide and to predict its development trend by on-site investigation,identifying landslide basic properties,morphological characteristics and its formation mechanism,with the application of the limit equilibrium method and finite element analysis method.On the basis of the above work,reasonable measures of landslide are put forward.The results of this paper are as follows:(1)With the on-site investigation of the engineering geological environment of the study area,the reference of relevant geological data,and the deformation monitoring of the landslide,the slope belongs to the middle conversion type of middle landslide.Due to the continuous rain,the slope soil becomes weak,which mechanically means the destruction of the balance of the slope.The soil’s absorbing water increases the weight of the rocksoil layer on the mountain slope behind the left side of the road.Meanwhile,surface water infiltrates and accumulates into medium weathered rock layer with relatively poor permeability,softening the interface between rock and soft interlayer,and reducing the shear strength of the rock mass,which eventually leads to the occurrence of landslide.(2)With the laboratory engineering test and parameter inversion analysis,the shear strength parameters of slip soil are obtained.According to the results of limit equilibrium stability analysis,it is known that although the slope has slided once,it is still possible that the sliding may occur again under the adverse factors such as continuous rainfall or rainstorm.(3)It can be seen in the calculation results by finite element analysis that the displacement of slope occurs mainly in highway cutting slope and the lower part of the embankment slope consists mainly of loose deposit accumulated in the critical angle of repose,so the stability is poor.It can also be seen according to the nephogram of the maximum shear strain that the data is the largest in the bottom of the slope,so the slope is still in a critical stable state and landslide is very likely to happen again.This result is in accordance with the one obtained by limit equilibrium method.(4)According to the calculation results of the landslide thrust,the thrust of the landslide is so large that the sliding force can not be counteracted by using the common strengthening methods such as anti slide pile or anchor.Therefore,the solution should be based on the types and the causes of landslide,taking the measure of unloading the mid-posterior part,assisted with back edge slope anchorage.Meanwhile,based on the principle that treating water comes before treating slopes,improving the slope drainage system would be an effective measure.