Influence Of Underground Pipeline Failure On Adjacent Pipeline Deformation

With the continuous advancement of urbanization in China,the urban scale is becoming larger and larger,and the urban underground pipe network system in China is becoming more and more perfect.Underground pipeline,as a means of transportation of natural gas,oil,tap water and other resources,has the advantages of fast,convenient transportation and does not occupy ground space.It is the basic component of urban water supply,gas supply,thermal supply,sewage and other underground lifeline system.In the process of progressive failure of rigid underground pipelines,local pipe strength will inevitably decrease,which will inevitably lead to the displacement of soil around the pipelines,destroy the initial stress balance in the soil,and then lead to stress concentration and excessive deformation of adjacent pipelines.However,at present,there is no in-depth study and Study on the problems that the existing underground pipelines destroy the disturbed soil balance,resulting in the stress and deformation of the adjacent pipelines subjected to uneven forces.On the basis of the pipeline control standard and the research on pipe-soil interaction by domestic and foreign scholars,this paper studies the influence of existing underground pipelines on adjacent pipelines by means of theoretical analysis,numerical simulation and laboratory test.The main contents and conclusions are as follows:(1)Based on the principle of tunnel shield and karst cave subsidence,the deformation law of adjacent pipelines induced by the failure of existing underground pipelines is studied from the basic theory of predecessors;the stress mechanism and failure mode of adjacent pipelines are analyzed;and the factors affecting the deformation of adjacent pipelines and their degree of influence are analyzed.(2)ABAQUS finite element software is used to simulate various factors affecting pipeline deformation in sandy soil area,and the deformation laws of adjacent existing pipelines under different conditions are compared and analyzed.Among them,the relative position,diameter,buried depth,pipe material and joint type of the existing underground pipeline and adjacent pipeline are the influencing factors of the simulation study.(3)According to the requirements of the test,the test equipment and system are developed independently to study the influence of the failure of existing underground pipelines on the deformation of adjacent existing pipelines.(1)The pipe soil synergistic deformation and the deformation around the pipe in the process of underground pipeline failure.(2)Distribution characteristics of earth pressure and additional stress around adjacent pipelines during the failure process of existing underground pipelines.(3)Using Match ID technology to monitor soil displacement,and provide reference for the soil displacement around the pipe line.The results of ABAQUS simulation are in good agreement with those of laboratory tests,which leads to the conclusion that:(1)According to sensitivity analysis,the order of influence degree of each factor from strong to weak is: buried depth > diameter > relative position.(2)The direct factor of the deformation of underground pipeline is the pressure of the soil around the pipeline on its side and the friction with the pipeline.The modified Gauss curve formula is used to fit the gravity displacement data of adjacent pipelines obtained from numerical simulation and model test,and the modified parameters of the Gauss curve are obtained.According to the modified Gauss curve,the settlement of pipeline can be estimated.(3)According to the above rules,we can get some measures to protect underground pipelines:(1)It is advisable to bury underground pipelines half a metre deep,which is easily damaged by live ground loads when they are too shallow;(2)When the diameter of underground pipelines is less than 80 mm,the rigidity of pipelines decreases and the settlement is very large;(3)Special measures should be taken to protect underground pipelines when the diameter of underground pipelines is less than 80 mm;When the lower existing pipeline and the adjacent pipeline are in the same vertical plane and the adjacent pipeline is above,if the collapse of the pipeline body causes the settlement of the soil around the pipeline,under the influence of gravity,the part of the adjacent pipeline corresponding to the subsidence area will subside,so in the process of pipeline distribution,try to keep the two adjacent pipelines not in the same vertical plane.