Study On The Criterion Of Ground Subsidence Of Pregnant Soil Cave In Urban Area Based On Cusp Catastrophe Theory

In recent years,road collapses in major cities in China have become more and more frequent,causing huge economic and property losses,accompanied by the death of life,causing widespread concern in society and the media.Ground collapse refers to the progressive subsidence or sudden collapse of the surface caused by the movement of material in the soil.Its manifestation is dominated by field depression,and the shape of the collapse pit is mostly conical,cylindrical and spherical.Ground collapse is usually closely related to underground holes.This thesis uses the theory of catastrophe,numerical simulation and model test to study the related aspects of such subsidence.The main work and achievements are as follows:First,find relevant literature and data,analyze a large amount of literature data,understand the research status of the depression,summarize the existing research results,and propose the key issues to be solved in the research of the depression.Secondly,according to the sudden characteristics of the depression,the evolution process of urban pavement collapse is analyzed,and the criterion of surface instability above the soil cave is established by using the catastrophe theory.Then,FLAC^3D is used to simulate the development process of three-dimensional soil caves.The results of the calculations show that the instability criterion of the surface instability during the development of underground caverns established by discrete and continuous methods is derived from plasticity.The consistency and simultaneity of the soil displacement trend in the area and the hole cover layer are verified.The quantitative calculation criterion is consistent with the numerical simulation results.The thickness of the critical cover layer is not sensitive to the change of Poisson's ratio and elastic modulus.The greater the elastic modulus The soil layer is more prone to sudden collapse.The safe settling value is sensitive to changes in elastic modulus.The critical cover soil thickness is more sensitive to changes in cohesion than the friction angle.Based on the regression orthogonal experiment,the regression formula of silt safety allowable settlement is obtained.Finally,the ground collapse test was designed.The dynamic displacement of the surface during the development of the soil cavity was obtained by using the visual measurement tool,and the ground deformation evolution process during the formation and development of the soil cavity was obtained.According to the calculation is accurate.