Study On Surface Settlement And Deformation Law Of Adjacent Pipelines In Double-line Shield Tunnel Construction

With the development of the city and the increase of population,the contradiction between the shortage of urban rail transit facilities and people ’s traffic demand is becoming more and more prominent.The most common damage in the subway shield construction process is the excessive settlement deformation of the surface and underground pipelines.This thesis takes the shield section from Dongli Sanjing Road Station to Dongli Liujing Road Station of Tianjin Metro Line 11 as the research object.The methods of indoor soil test,numerical simulation and field monitoring are used to study the surface settlement and deformation law of adjacent pipelines in double-line shield tunnel construction.The main research contents and conclusions are as follows :(1)Through the conventional geotechnical test of soft soil in Tianjin subway,the relevant physical and mechanical parameters of the stratum are obtained.Based on the test results,the engineering characteristics of high water content,low permeability and large fluidity of soft soil layer in Tianjin subway are summarized.Combined with the important engineering conditions such as the engineering characteristics of soft soil layer,tunnel design and surrounding environment of Tianjin Metro,the shield machine is selected for the shield crossing the soft soil layer from the aspects of selection principle and selection basis,and finally the composite earth pressure balance shield machine is adopted.(2)The theoretical calculation of surface settlement and underground pipeline deformation in shield construction is expounded in detail.Combined with the actual situation of oblique crossing pipeline in field engineering,the allowable maximum vertical displacement of pipeline is obtained by using the appropriate empirical formula of vertical displacement of pipeline.By consulting a large number of relevant engineering standards and specific engineering control standards,the surface settlement control standards applicable to Tianjin metro shield tunnel are summarized.(3)The finite element simulation software Midas GTS NX is used to simulate the three-dimensional simulation calculation of the shield tunneling process.The distribution law of surface settlement caused by double-line shield tunnel construction under different construction procedures,different double-line spacing and tunnel burial depth is analyzed.According to the settlement distribution law,the reasonable construction procedure and double-line spacing are obtained.(4)By analyzing the variation law of the settlement deformation and longitudinal stress state of the pipeline after the double-track tunnel passes through the pipeline under different pipe tunnel spacing,different pipeline materials and different pipe tunnel relative positions,it is finally obtained that the smaller the pipe tunnel spacing,the greater the maximum settlement of the pipeline and the greater the longitudinal stress.In the construction,special attention should be paid to the construction of the shield tunnel under the pipeline when the pipe tunnel spacing is small;the maximum settlement of the pipeline is negatively correlated with the elastic modulus of the material.When the pipe tunnel is in the oblique space position,the maximum settlement of the pipeline is the largest and the influence range is the widest,which is the situation that needs to be paid attention to during shield tunnel construction.(5)According to the influence law of pipeline deformation caused by double-line shield tunnel undercrossing pipeline construction under different conditions,combined with the actual project of Tianjin Metro double-line tunnel obliquely crossing sewage pipeline,the optimal design of soil chamber pressure and grouting pressure of shield machine is carried out.(6)The safety control measures taken in the early stage of shield construction and during the construction process are introduced.Based on the surface settlement monitoring data of the Sanliu section of Tianjin Metro Line 11,the proposed construction technology and optimized shield tunneling parameters can effectively control the surface and pipeline settlement deformation caused by shield tunnel construction,which verifies the feasibility of the optimized parameters of shield tunnel construction.