The Hyperbolic Progressive Shear-failure Mode Of Soil And Its Application In Stability Analysis Of Landslide

The poor geological conditions of our country mountainside area provide favourable conditions to geological disasters.In recent years,with the rapid development of economic construction,human engineering activities and natural factors,a trend of landslide disasters increases year by year.The landslide caused massive casualties and economic losses.Based on this,the characteristics of shear strength,failure mechanism,shear deformation of soil-structure contact surfaces,strength mechanics model of geotechnical materials and landslide stability are studied systematically and in-depth.The main research contents and results are as follows:A new kind of stress-displacement sensor was developed,which can monitor the stress and displacement of local points on the contact surface.A large indoor direct shear test of contact surface between red clay in Chongqing and structure is carried out by using this sensor.Furthermore,stress and deformation response evolution characteristics of contact surface under shear loads and different soil compactness,normal stress is discussed.The shear failure of contact surface between soil and structure is characterized by progressive failure;the normal stress of the contact surface and the compaction degree of the soil have a significant influence on the progressive failure;the test results indicate that the peak stress along the shear direction of the contact surfaces show obvious inhomogeneity features.The shear stress obtained from direct shear apparatus is average shear stress.i.e.the value of shear stress measured at any time is the integral of the shear stress distribution function on the shear surface.The stress and deformation response characteristics of the contact surface under different compaction degrees and normal stresses are researched by numerical simulations.The gradual fracture characteristics of the contact surface of soil and structure between compaction degrees and normal stresses are obtained.The numerical results and experimental results are mutual verification and mutual complement.While,a certain deviation is also existed.The reason for the deviation is analyzed in this paper.The shear strength and strength parameters of soil and structure contact surface are studied according to the results of large direct shear test.The results show that the shear strength cannot meet the linear strength criterion of M-C.The relationship between shear stress and strain,which shows the softening of stress after peak shear stress,can not satisfy the ideal elastic-plastic model.In order to describe this stress softening effect,the resistance force of contact surface is divided into generalized adhesion force and frictional force.Based on this,a hyperbolic model is proposed in this paper.Author present method to determine model parameters and the strength criterion.The hyperbolic model can preferably describe ideal elastic-plastic model and the mechanical characteristics of elastoplastic softening materials.The destruction of the landslide is a gradual process,points on the slide surface are in different stress states at any time.In traditional landslide stability analysis,strength of each point on the slide surface is calculated based on M-c linear strength criterion.That is to say,all points on the sliding surface are in peak shear stress state,it is not existed.In order to describe the different stress state of the sliding surface more accurately,the concept of the key block of landslide is put forward and proposed to the analyses on the stability of progressive landslide through the hyperbolic progress-ive shear-failure mode of soil-hyperbolic model.In this paper,new displacement-force slice method is obtained based on the unbalanced thrust method,stability formulas are presented,and two cases are analysed.The stability coefficients procured through the new model is smaller than those gotten from the conventional model(the total cross-section peak stress state),because the conventional method of stability calculation doesn't consider the stress softening phenomenon of rock and soil materials,which is contradictory to the reality and dangerous.