The Study On Deformation And Failure Mechanism Of The Gently Inclined Bedding Rock Slope With Weak Interlayer

The landform of guizhou province belongs to plateau mountain in southwest China.It is inevitable to excavate the slope in the foundation construction.In the early stage,gently inclined bedding slope is considered to be stable because of slow dip.However,gently inclined bedding slope with weak intercalation instability damage has great impact on the construction.In this paper,based on tutor's scientific research project "Geological disaster monitoring and early warning and decision support platform for research in guizhou province",Yunpantou landslide as the research object,clarifies the regional geological conditions and the engineering geological conditions in the region,summarizes the instability characteristics and the failure mechanism of landslide,analyzes the instability mechanism of Yunpantou landslide by using floor-friction simulation and UDEC numerical simulation method,considers the influence of two factors,the dip and moisture content of weak intercalation,on gently inclined bedding slope failure,and summarizes the failure mechanism of gently inclined bedding slope with weak intercalation.The main results are as follows:(1)The structure of Yunpantou landsilde is mainly composed of triassic limestone composition group limestone and argillaceous limestone with mudstone.The slope is generally hard and soft interbedding.The rock mass structure is relatively broken with a lot of crack.There are four groups of weak interlayer in slope with low mechanical parameters and lead to the structure of slope the same as “sandwich biscuit”.It provides material foundation and structure condition for the formation of landslide.(2)The deformation and failure mode of Yunpantou landslide is sliding-tension type.When the slope is manually excavated,the weak interlayer 2 and 3 are exposed on the surface,providing the ground conditions for the creep deformation of rock mass along the weak interlayer.The early creep causes the fissure of the slope to expand and expand continuously,cutting the rock mass with the weak interlayer.Under the influence of external rain and other factors,the strength of the weak interlayer is further reduced,and the shallow sliding block is more broken,and the final sliding body slides downward along the weak interlayer.(3)The indoor mechanical tests were conducted on the weak interlayer soil samples obtained at the site.The results are as follows:(1)The moisture content of the laminated soil is 50.16%,and the plastic limit is 25.47%.The determination of boundary moisture content indicates that the soil in the weak interlayer is clay in a plastic state.(2)The content of clay was 67.74%.The grain size distribution curve reflects the difference of particle size in soil,the soil particles are not uniform and belong to a good cohesive soil.(3)The mineral composition in the soil was mainly montmorillonite,with a content of 61.2%.It shows that the weak interlayer soil has strong water absorption and expansibility.(4)The shear strength index of soil in the interlayer decreased significantly with the increase of moisture content,the internal friction Angle ? is more sensitive than the cohesive force C and the water reaction.The shear strength index C and? are linearly dependent and correlated well with the water content ?.(4)The failure process of landslide is studied by the bottom friction test in the physical simulation experiment.The evolution of slope in the experiment can be divided into micro-crack development stage,crack development stage,slip mass deformation stage and total failure stage.After the main deformation characteristics of slope excavation slope surface crack is obvious and gradually development will be divided into shallow sliding body small slider,slope foot are the key block,instability of a key block,the sliding body assumes the disintegration of "domino effect" type cracking and deforming toward the direction along the bottom of the weak layers 2 and 3.The deformation mechanism of the slope is caused by the slippage of the excavation.(5)Containing weak interlayer of bedding rock slope with special lithology and slope structure,after artificial excavation,slope of internal cracks expanding,cutting rock mass,together with the weak intercalations under rainfall and gravity,occur along weak interlayer sliding of rock mass.The dip and moisture content of weak interlayer are important factors which influence the stability of slope,meet with the increase of moisture content of weak intercalations,front key block in the stage of the landslide destroyed on the support of the rock at the back of the time gradually become shorter and interlayer inclination,the greater the degree of slope rock mass deformation and destruction,the greater the slope toe block accumulation phenomenon more serious,displacement of the slope rock mass will be increased with the increase of interlining dip increase,and causes the key block less time support for the back of the block.This is the reason for the instability of the soft interlayer rock slope and the innovation point of this paper.