Research On Deformation Monitoring And Control Technology For The Tunneling Across The Existing Underground Pipelines

Subway construction plays an important role in promoting the rapid development of cities,Urban underground pipeline is the infrastructure to ensure the normal operation of the city,The deformation and failure of the pipeline will affect the construction and normal operation of the urban subway tunnel.Therefore,it is importance to ensure the safety of existing pipelines during the construction of Metro Tunnels,This paper is based on the underground pipeline project of Xi’an Metro Line 4 through underground excavation.By means of theoretical analysis,field monitoring and numerical simulation,the deformation mechanism,control measures of surface and pipeline of underground during the pipeline through underground excavation are studied.The main contents and conclusions are as follows.（1）Systematically expounded the relevant knowledge of underground pipelines,Combined with the construction principle of mining method,the deformation law of adjacent pipelines induced by underground excavation is studied from the theoretical point of view.（2）FLAC^3D software was used to study the factors affecting the deformation of the pipeline in the Loess Area,According to the simulation results,the function of the width of the settlement trough,the maximum settlement,the width of the settlement trough and the settlement of the pipeline are obtained,The curves of pipeline settlement,maximum rotation angle,additional bending moment and shear force under different working conditions are calculated,Conclusions are as follows:（1）The main soil layer influencing the site difference is the new loess in Xi’an;（2）Because of the different construction methods,the pipeline settlement from large to small is Step method,bench reservation core soil,short step +temporary invert method,CD method,CRD method;（3）the influence of the pipeline and lie under the soil pipe soil separation would happen between the pipeline pressure of soil above the line to have the opposite effect,increasing the probability of shear failure line oninterfaces;（4）The larger the pipe diameter,the smaller the pipe settlement,but the greater the additional stress;（5）The maximum settlement value of the pipeline is not very different from that of the tunnel,but the vertical operating line is more and more vulnerable to the additional bending moment and shear force;（6）through calculation,the buried depth of 2 m or less line,its Angle,controlled by the bending moment and shear force are less than standard,in actual engineering,if the embedded depth of 2 m or less and the condition of no special pipe can not be considered;（7）All landowners and tunnel parallel pipeline,when the distance pipeline tunnel directly above horizontal distance acuity 1.5 B,pipeline settlement is small,if no special circumstances,you do not need to take protective measures.（3）Combined with FLAC simulation and theoretical calculation results,using short steps and temporary invert method,the results show that the development of pipeline settlement appears in the process of underground excavation,the settlement mainly concentrated in the process between-1.5 and 1.5D.The measured results are similar to the simulation and calculation results.After adopting the appropriate construction methods and measures,the deformation of the pipeline caused by construction can meet the requirements of the specification,and the relevant conclusions and reinforcement techniques can provide reference for similar projects.