Study On Engineering Characteristics And Slope Stability Of Carbonaceous Shale In He Bai Expressway

Carbonaceous shale is widely distributed in the southwest of China.It has engineering characteristics such as fast weathering speed,low strength and obvious softening in water.It is easy to cause roadbed diseases and brings great difficulties to expressway construction.Combining Hechi-Baise Expressway,this paper studies the field geological survey,laboratory test,roadbed filling test,slope treatment and stability analysis of carbonaceous shale along the highway.The main results are as follows:(1)Chemical compositions of rock samples with different weathering degrees were identified and physical and mechanical properties and disintegration properties were tested.The results show that the chemical composition and physical and mechanical properties of carbonaceous shales with different weathering degrees are quite different.Weathering cracks reduce the strength of rock mass,rock disintegration in water,and roadbed filling needs to be considered.(2)The mechanism of dynamic consolidation of carbonaceous shale roadbed is studied,and the measures and evaluation methods of dynamic consolidation for filling carbonaceous shale roadbed are put forward.Dynamic consolidation can improve the compaction effect and reduce the impact of subsequent collapse.(3)Carbonaceous shale excavation slopes are classified,failure modes of different types of slopes are studied,and corresponding treatment measures are put forward,which are applied to engineering practice.The right side slope of K14+960 is selected for stability analysis by BISHOP method,ABAQUS finite element software and polar plane projection method.The slope stability coefficients under different calculation methods are studied.The analysis results show that the in-situ stress release caused by excavation has great influence on the slope stability,and timely closure has obvious effect on the slope stability.