Research On Development And Failure Mechanism Of Surface Subsidence In Urban Area

In recent years,the scale of cities in my country has continued to expand,and the construction of urban municipal engineering has led to more and more frequent road collapse accidents in major cities,causing significant loss of life and property,and arousing widespread concern in the society.Urban surface subsidence refers to the continuous disturbance of the stratum caused by construction projects during the urban development process,resulting in the formation of soil caves in the soil layer and gradually develop until the stratum soil reaches the limit state of bearing capacity and finally the surface instability occurs.In this paper,indoor model tests and numerical calculation methods are used to study the collapse mechanism of soil caverns.First,collect written reports about surface collapse accidents in urban areas in my country in recent years,classify and analyze the characteristics of existing surface collapse accidents,summarize and analyze the forms of collapse,and take the development and collapse process of the collapsed soil cave as the research object.Secondly,through the establishment of a three-dimensional model test to study the development and failure process of the soil cave,the image processing system is used to analyze the surface deformation data and the final failure shape of the soil cave during the test,and the measurement points in the development process of the soil cave are analyzed through the earth pressure measurement test.The changing process of the overburden stress.The test results show that:when the soil cave is destroyed,the settlement velocity of the cave top changes suddenly;the law between the height of the collapse inside the soil cave and the diameter of the soil cave is in good agreement with the geometric law proposed by Platts theory;the failure mode of the soil cave and its buried It is directly related.As the buried depth becomes larger,the earth hole changes from the altar-shaped damage to the straight-cylinder damage.Then,on the basis of the indoor model test,a finite element analysis calculation method was established to study the collapse of soil cave development.The process of soil cave failure was simulated from both the buried depth of the soil cave and its development model.The numerical simulation results showed that When a collapse accident occurs in a shallow soil cave,the settlement of the ground is less noticeable and the risk is relatively high.When the buried depth of the soil cave is further increased,the soil cave will collapse in a funnel.Furthermore,based on the finite element calculation method,a quadratic regression orthogonal test was designed to discuss the critical effects of the fill cohesion,Poisson's ratio,elastic modulus,and internal friction angle parameters on the collapse of the shallow soil cave.For the influence of radius,a fitting formula for the limit radius of the soil cave under the influence of multiple factors is obtained.The fitting result shows that the cohesion parameters of the fill have the greatest influence on the limit radius of the soil cave.Finally,a collapse accident case is selected for finite element calculation and analysis,and the calculation results are consistent with the experimental rules and the field collapse results.