Stability Evaluation Of Multi-slip Landslides Based On Progressive Yield Theory

Landslide is a frequent geological hazard,which will cause serious economic losses.The main cause of landslide is the weakening of shear strength of rock and soil in slope body.When the sliding force on the sliding surface is greater than the anti-sliding force,the rock and soil will slide along the sliding surface towards the free surface.Strength reduction method is an effective method for landslide stability analysis.Many scholars at home and abroad have expanded and deepened it up to now.For example,dynamic strength reduction method takes yield proximity YAI as an index to judge the yield of rock and soil.By reducing shear strength parameters c and ?.Until the displacement of the characteristic part of the slope changes abruptly or the plastic zone penetrates,studying the process from local failure to overall failure of the slope.Multi-slip landslides are different from single-slip landslides.There are two or more slip surfaces in rock and soil,and they are related to each other.If the sliding body slides first along the main sliding surface,a new free surface will be formed,and the back rock and soil will slide along the main sliding surface under traction.Affected by the sliding deformation of the back rock and soil mass,secondary sliding surfaces are developed in the soil mass.The soil mass will slide along the main sliding surface and the secondary sliding surface.At present,no scholar has applied the dynamic strength method to study the deformation mechanism of Multi-Slip landslides.This paper takes Jinshan Avenue No.1 Multi-Slip landslide as an example,applies the dynamic reduction method to study the deformation mechanism of Multi-Slip landslides,and calculates the stability coefficient and residual sliding force of Multi-Slip landslides by combining the transfer coefficient method.It can be used to guide the treatment of Multi-Slip landslides.The main contents and methods of this paper are as follows.(1)The particularity of Multi-Slip landslides.Multi-slip surface landslide is different from single-slip surface landslide.There are two or more slip surfaces in rock and soil,and they are related to each other.If the sliding body slides first along the main sliding surface,a new free surface will be formed,and the back rock and soil will slide along the main sliding surface under traction.Due to the sliding deformation of the rear rock and soil,secondary sliding surface is developed in the soil.The soil will slide along the main slip surface and secondary slip surface.If multi-level creep occurs directly in rock and soil,with the continuous expansion of multiple plastic zones,forming a coherent whole sliding surface.Rock and soil will slide along the multiple surfaces.(2)The concept and application of yield proximity YAI.Yield proximity,which is used to judge the yield of surrounding rock at first,describes the comparison between the parameters of the present state described by a point and the relative safest state.The shear strength parameters of rock and soil are reduced by strength reduction method,which will change the stress state of soil unit,applying yield approach index to judge the condition of rock and soil.When 0 ?YAI<0.2.the rock and soil yield;when 0.2?YAI?1.0,the rock and soil do not yield.Therefore,combining the strength reduction method with yield proximity,a method is proposed for analyzing soil yield,which is called progressive yield theory.The theoretical analysis method is applied to study the progressive yielding process of soil mass.(3)The progressive yield theory is applied to study the deformation mechanism of Multi-Slip landslides.The deformation and failure of multi-sliding surface landslide is a process of progressive failure,just like single sliding surface.Soil yields and the plastic zone expands continuously in the soil,forming main slip surface and secondary slip surface.The rationality of the theoretical analysis method is verified by the example of multi-stage sliding surface landslide,and attempt to study the deformation and failure of multi-sliding Surface Landslide No.1 Jinshan Avenue.In this paper,the deformation mechanism of No.1 Multi-Slip landslide is analyzed,and the sliding deformation process of No.1 Multi-Slip landslide of Jinshan Avenue and other three landslides is inverted.(4)Factors cause Multi-Slip landslide of No.1 Jinshan Avenue.Water is the main factor that induces landslide of Jinshan Avenue.Soil in the survey area is easy to soften when it meets water.The shear strength parameters c and ? decrease,and the shear strength weakens.Rock and soil yield and produce plastic zone.Secondly,the soil in the site is loosely structured,with large voids,which is easy to infiltrate into the water body and enhances the contact with water.Finally,in the site,the topographic fluctuation height difference is large,and the occurrence of rock strata obliquely intersects with the sliding direction of landslide,which is conducive to soil accumulation and precipitation infiltration in the site.(5)Control scheme design.The deformation mechanism and stability calculation results of No.1 Landslide of Jinshan Avenue are used to guide the scheme design.The Multi-Slip Surface Landslide of No.1 Jinshan Avenue has a circular chair shape in the plane.The sliding deformation mainly concentrates in the middle of the whole landslide,being approximately elliptical in the plane.The main slip surface and a secondary slip surface are developed in the interior of the slope,and the whole slope is in an unstable state under rainstorm conditions.According to the sliding deformation of the landslide,combined with the stability coefficients of the secondary sliding surface and the main sliding surface and the final residual sliding force,putting forward an effective control scheme.