The Study Of The Critical Thickness Of Overlying Layer Of Cylindrical Collapse Based On Cusp Catastrophe Model

In recent years,many cities in our country have experienced ground collapse,causing casualties and huge economic losses,which aroused widespread concern in society.Ground collapse refers to the gradual subsidence or sudden collapse of the ground caused by the movement of underground materials under the influence of natural factors or human engineering.Most of the collapsed pits formed by the collapse are cylindrical and funnel-shaped.This paper uses catastrophe model,numerical software simulation and model test to study the cylindrical collapse.The main achievements are as follows:Firstly,a large number of collapse accidents are counted.According to the shape of the collapsed pit formed,the collapse is divided into cylindrical collapse and funnel collapse,and the research object of this article is proposed as the cylindrical collapse.Secondly,the parameter range and collapse mechanism of the cylindrical collapse are speculated.In view of the sudden occurrence of collapse,the cusp catastrophe model is introduced to derive the criterion of the displacement instability of the surface during the development of the cylindrical collapse cavity,and then the critical thickness of the overburden is determined.Then,FLAC^3D is used to simulate the development process of the cylindrical collapse hole,the influence of various parameters of the soil on the surface displacement is studied,and the parameter combination of the most unfavorable combination of clay is obtained.In the case of the most unfavorable combination of parameters,the influence of the initial depth and radius of the hole on the critical thickness of the overlying layer is studied separately.It is found that the initial buried depth has no effect on the critical thickness of the overlying layer,and there is a certain functional relationship between the critical thickness and the pore size,and the relationship is fitted.A quadratic regression orthogonal test is designed,considering the influence of clay cohesion,elastic modulus,friction angle and Poisson's ratio,a calculation formula for the critical thickness of the cladding layer on the hole is obtained considering multiple factors.Finally,an indoor model test of cylindrical collapse is designed,using digital and image-related techniques to obtain the displacement value of the ground surface during the development of the hole,and using the ground displacement instability criterion to judge the ground stability of the hole during the development.Compared with the test result,the control is consistent.