Study On Deterioration Mechanism And Deformation Instability Model Of Red Layer Slope In Central Yunnan Under Multi-Field Coupling

Yunnan Province,especially central Yunnan,is one of the areas widely distributed in red-layered soft rock.In recent years,with the rapid development of yunnan expressway construction,due to the special lithological characteristics of red layer soft rock,under the earthquake,rainfall and human engineering activities,the problem of slope landslide collapse in central Yunnan has occurred frequently,which has brought great threats to the safety of people’s lives and property and the construction of the project.In view of this,based on the Yuchu Expressway in central Yunnan,this paper conducts an in-depth study on the problem of easy disintegration and softening of red-layer soft rock in central Yunnan region when exposed to water,especially the prominent problems of slope instability and catastrophe of red-layer soft rock under the combined action of gravity,earthquake and rainfall after engineering excavation disturbance,and reveals the deterioration mechanism and deformation instability mode of red-layer soft rock slope under multi-field coupling.The results of this paper are as follows:(1)Two representative rock samples were selected as research objects,and XRD,XRF,electron microscopy scanning and other technical means were used to understand the composition of the material composition and microstructure of the rock before and after encountering water,and the results showed that the red layer soft rock contained a large number of hydrophilic minerals,and the dissolution of these minerals was significant after immersion,resulting in the increase of rock pores and the destruction of the structure.At the same time,it lays a research foundation for the study of the degradation characteristics of soft rock under the action of water rock.(2)Study the changes in physical and mechanical properties and failure patterns of red layer soft rock under the action of water rock.Through the basic geotechnical test,the basic properties of the two rocks such as moisture content,density,water absorption and permeability were understood;through the uniaxial compression test of the three aqueous states and the static triaxial test under different aqueous states and different confining pressures,the compressive strength and shear strength indicators were obtained,and the strength deterioration law and failure form of the red layer soft rock under the action of water rock were analyzed;through the dynamic triaxial test under cyclic load,the cumulative strain and dynamic stress-dynamic strain relationship of the rock mass under dynamic action were analyzed.The law of dynamic elastic modulus change was obtained,and the results showed that water and confining pressure were also important factors affecting the deterioration of the dynamic properties of rock masses.(3)The deterioration properties of red layer soft rock under the action of water rock were studied.Through experimental research,it is found that soft rock shows different degrees of softening,disintegration and expansion under the action of water,and according to the experimental phenomena and results,the three hydrological properties of soft rock are characterized and graded on the basis of previous research,and finally the deterioration mechanism of soft rock is summarized.(4)Based on FLAC 3D numerical simulation software,a numerical model is established,and the deformation and instability mode of the red slope under the coupling effect are calculated under the action of gravity,gravity + earthquake and fluid-structure interaction.The stress displacement response and deformation failure mode of the high slope of the road graben only under gravity are studied,and the influence of the interlayer structure of the red layer slope on the deformation instability mode of the slope is demonstrated;in the coupling between gravity and earthquake,the dynamic response mode of the red layer slope under the coupling of strong earthquake and gravity is studied by analyzing the parameter changes of slope displacement and acceleration caused by the application of seismic waves,and the change law of the rock mass saturation,displacement field change and potential sliding surface of the interlayer slope with different rainfall time in the fluid-structure coupling is studied.The instability characteristics and failure patterns of the lower slope of rainfall over time are obtained.