Mechanical Analysis Of Roadbed Void Caused By Pipeline Damage And Its Detection Technology

In recent years,urban road and foundation collapse accidents have occurred frequently at home and abroad,which seriously threaten people's life safety and normal life.Systematically analyzing the causes and mechanical mechanisms of subsurface cavities,have great engineering significance for detecting hidden collapse dangers of road and preventing the occurrence of similar accidents.This paper relies on Tianjin Transportation Science and Technology Development Plan Program(2016A-02-01),uses FLAC3 D finite difference software to analyze the mechanics of soil with buried pipelines and underground voids according to the soil characteristics of Tianjin coastal area,and comprehensively analyses the influence of the space position and size of the underground voids,soil condition and it's mechanical parameters and other external factors on the stability of the voids and road structure,and summarizes the methods of judging the stability of the underground voids,which provide technical guidance for practical engineering application.The main research contents are as follows:(1)According to the existing accident analysis report,causes of collapse accidents of urban road and subgrade due to pipe defects are analyzed.According to limit equilibrium theory,the horizontal ultimate span formula of cavity to keep stable state is deduced.(2)By using FLAC3 D software,choose reasonable parameters to build the model,select appropriate constitutive model,boundary conditions,initial conditions and contact conditions,and make the mechanical analysis of the soil after the void has been carried out,and give the judging conditions of the void instability and the ground structure instability.(3)By using the method of controlling variables,quantitatively analyze the magnitude relation among the thickness of overburden soil layer,the height of cavity and the radius of ultimate span for stability of cavity.(4)Firstly analyze the sensitivity of the influence of gravity,modulus,Poisson's ratio,cohesive strength and internal friction angle on the stability of cavity since there are many mechanical parameters of soil.Secondly analyze the comprehensive influence of sensitivity factors on the safety of ground structures.(5)Analyze the influence of physical parameters of the buried pipeline,pavement structure and other external loads such as vehicular loads on ground structure safety.(6)Combined with the existing method of nonivasive testing technology and the engineering example,summed up the method to judge the stability of underground cavity and pavement structure safety.