Study On The Stability Of “Three Sections” Slope Considering Tension And Shear Progressive Failure

The“three sections”mechanism of sliding-tension cracking-shearing refers to the three-stage development of slope deformation and failure,i.e.,the lower part creeps along the horizontal structural plane,tension crack at the rear edge and shear at the middle locking section.The“three sections”landslide is a typical landslide geological hazard in Western China,which has caused huge losses to people's lives,property and engineering construction.Therefore,it is very important to study the stability of“three sections”slope.Slope failure is a progressive process with multiple failure modes.However,most slope stability studies only considered the shear failure modes of geotechnical materials,and rarely consider the progressiveness of slope failure.The main reason for the occurrence of“three sections”landslide is self-weight stress field.However,most previous studies on“three sections”landslide are based on static analysis,and little consideration is given to creep.In this paper,the above problems are systematically studied.The main work and conclusions are as follows:?1?A strain softening model considering aging characteristics Svisc is formed by connecting the tension-shear strain softening model in series with the Burgers model.This model can be used to describe the deterioration of local rock and soil strength parameters and the continuous effect of self-weight stress field on the slope during tension and shear progressive failure.?2?A general criterion for the failure of the slope is studied,which is that the failure zone runs through the foot of the slope to the top of the slope.Based on the initial stress method of elastoplastic calculation,an index I_cs for quantitatively displaying the tension and shear sliding surface of the slope is studied.From the aspects of failure criterion,reduction coefficient,sliding surface display and reduction range,a slope strength reduction method considering tensile and shear progressive failure is studied.This method further improves the theory of slope strength reduction method.The failure criterion and the sliding surface quantitative display index I_css program is written in FISH language embedded in FLAC3D.?3?The sliding trend and safety factor calculation formula of slope vector sum method considering tensile and shear progressive failure are derived in this paper.The standard genetic algorithm is improved,which is applied to search the most dangerous sliding surface of the slope.From the aspects of sliding trend,safety factor and sliding surface search,a slope vector sum method considering tension and shear progressive failure is studied.This method further improves the theory of slope vector sum method.?4?A Zhana numerical slope model considering historical causes and evolution processes is established based on the Svisc model and the slope strength reduction method and vector sum method considering tension and shear progressive failure.The formation mechanism of the Zhana landslide is analyzed.Gradual expansion of the failure zone shows the development characteristics of the“three sections”mechanism of sliding-tension cracking-shearing.The safety factor and the position and shape of the most dangerous sliding surface evolution law conforms to the three-stage theory of the development of high slopes in natural valleys.The sliding surface quantitative display index I_css has good applicability in practical engineering.