Characteristics Of Underground Pipeline Deformation And Damage Under The Influence Of Urban Tunnel Construction And The Mechanism Of Leakage

With the sustained and rapid development of China's economy and society,with the accelerated process of urbanization in China,the major cities have already opened operations underground rail transit system,many medium-sized cities have also included the construction of rail transportation in the development plan.However,while the urban rail transit system is making contributions to the economic development,and improving the quality of life at the same time,the frequent occurrence of subway tunnel construction accidents caused social and economic losses again and again,which not only seriously threat public safety but also shake the public expection and confidence on the underground rail transit system.There are many pipelines buried in the urban strata,and subway tunnel construction will inevitably cause disturbance of the surrounding strata,resulting in deformation or even damage to the pipeline.For underground pipelines,how to accurately predict the deformation law and deformation value of these pipelines before and during the construction of the tunnel,how to accurately determine the pipeline status is critical to the construction safety.For the tunnel construction,how to accurately determine the impact of underground water leakage on the formation,how to predict the scope of the impact caused by the pipeline leakage on the formation is also very important.In view of these problems,this paper has made the following research results:1.By means of the numerical simulation software Midas-NX and the finite difference software FLAC3D,in terms of three spatial positions between pipeline and tunnel(pipe-tunnel vertical,pipe-tunnel parallel,pipe-tunnel oblique),the influence of tunnel construction on underground pipelines under different spatial position relations is studied,concluded that the tunnel passes through the underground pipeline at the angle of 0° is the most favorable crossing angle.2.By means of the numerical simulation software Midas-NX and the finite difference software FLAC3D,the factors related to the settlement and deformation of underground pipeline are studied,such as pipeline material,pipeline strength,lining strength,pipe-tunnel spacing,pipe-tunnel angle,cutter thrust and other factors.3.By means of the seepage analysis software Geo-Studio,the influence of the pressure in the pipeline,the relative position of the pipe-tunnel and the degree of fracture of the pipeline on the seepage in unsaturated soil were studied.4.To Jing Guangqiao subway tunnel construction accident as a real case,the whole process of numerical simulation is carried out.The simulation results show that the evolution of the accident is that the sewage pipeline had initial leakage,the water weakened the ground,then the tunnel construction disturbance caused the deformation and damage of sewage pipeline,and eventually lead to formation subsidence and tunnel gushing.