Influence Analysis Of Perpendicular Crossing Pipe Jacking Constructed Above Existing Shield Tunnel

With the development of our country’s urban rail transportation network, more and moresubway is been building. Pipe Jacking is a kind of trenchless construction method which hadwidely used in the city municipal pipeline construction. Under this trend, the pipe jackingconstruction in the city will be built crossing above a existing subway tunnel. The surroundingsoil disturbance caused by pipe jacking will induce displacement and deformation. It isharmful for subway tunnel. This paper based on the construction of a sewer pipeline builtperpendicularly crossing above a existing shield tunnel in Hangzhou. The deformationregularity and influence law of the existing subway tunnel was researched in the process ofpipe jacking construction. The main research contents and results are as follows:(1) From the construction characteristics of pipe jacking, soil and underground pipeline’scharacteristics disturbed by pipe jacking construction was systematically discussed. Analysisshows that the deformation of subway tunnel is mainly affected by the loss of soil.(2) Because the pipe jacking construction would affect the subway tunnel’s normal use,so it was necessary to carry out monitoring and measurement based on the project of a certainsewage pipeline built crossing above a subway in Hangzhou. The law of the subway tunnel’svertical displacements, horizontal displacements and ground settlement was analyzed in theprocess of pipe jacking construction. Studies showed that the subway tunnel’s disturbancezone under pipe jacking’s excavation are10meters before and after the subway tunnel. Thelargest subway tunnel’s deformation was under the pipe jacking axis, and its sharp was likecurve groove. The location of the relationship of subway tunnel affected the tunnel’sdeformation.(3) Based on the engineering background, using the software FLAC3D, the process ofpipe jacking construction built crossing above subway tunnel was analyzed. The simulationresults and engineering field monitoring results was compared, and the reliability of the modelwas also be verified. By changing the vertical distance of subway tunnel and pipe jacking line,the pipe diameter, pipe material and surrounding soil’s characteristic of the shield tunnel, itsdisplacement rule of existing shield tunnel was analyzed. The study showed that the results ofnumerical simulation and the measured were in conformity with the overall trend curve,simulation results are satisfactory. The deformation of subway tunnel was greatly influencedby the different pipe jacking construction conditions. In actual engineering, choose suitableconstruction parameters is helpful to control deformation of subway tunnel. (4) According to the research results and practical situation, construction controlmeasures were summarized, it included the construction of risk control and advice, thedisturbed zone soil consolidation and monitoring control. After analyzed the results ofmonitoring, this measures were proved effectively to control the deformation of metro tunnel,and this experiences were accumulated, it can provide reference for other similar projects.