Existing Pipelines Effected By Subway Station Construction With PBA Method

With the increasing of urban population and the improvement of motorization,the problem of urban traffic is getting more and more severe.Therefore,it is urgent to develop underground space engineering vigorously.Subway construction often have to travel through a large number of buildings above ground and underground pipelines,and the formation of cavity makes the stratum loss,leading to a certain degree of subsidence of stratum,which will necessarily affect the normal use of the underground pipeline above.If the protection measures of the underground pipeline was not appropriate,it would affect the normal use of the pipeline,even cause serious safety accidents.In the construction of various subway tunnels,the PBA construction(Pile-Beam Arch)method has the advantages of small excavation section,timely support and small influence on the ground and surrounding environment.Compared with other large span digs(such as the middle hole method,CRD method,etc.),The PBA construction method has a relatively small amount of disused engineering and good structure,so it is relatively economical.In order to avoid the occurrence of major safety accidents and reasonably control the project cost,the stress and strain analysis of pipeline in the construction process needs to be carried out.This paper is based on the PBA construction process in the amount water sandy foundation,using the finite element software ABAQUS in a subway station in actual construction process the PBA construction step sequence for numerical simulation analysis and calculation of each construction stage to the surface and the impact of both the underground pipeline.On this basis,adopt the reasonable reinforcement engineering personnel on pipeline protection measures,and by using the scene of the actual monitoring data proves the numerical analysis results of scientific.To provide reference for reasonable construction of the auxiliary measures,avoid safety accident.The research contents and related conclusions are as follows:(1)Calculate the structural internal force of straight wall arch structure caused by the elastic resistance with the beam theory of elastic foundation.When the top arch is subjected to the maximum internal force,the corresponding angular degree of the arch is calculated.The calculation results show that the corresponding arch angle is 66°.When the top arch is subjected to the maximum internal force,it provides reference for the engineering.(2)Record drawings based on the subway station and the settlement deformation monitoring data during construction,as the analysis platform of ABAQUS,reproduce the construction stress system transformation process and on the basis of summarizing the PBA method impact on surface subsidence.The analysis results show that the maximum impact of PBA construction method on land subsidence is in the residual soil phase of excavation arch.(3)Based on the elastic foundation beam theory and ABAQUS analysis results,analyse the types of pipelines and their corresponding safety control standards.In the view of the tunnel vertical under the pipeline through the working conditions,Analyse pipeline depth and pipeline material and other factors on the pipeline settlement.Compared the numerical simulation of pipeline with the actual monitoring value.The analysis results show that it is necessary to reinforce the surrounding rock of subway tunnel by grouting.On this basis,comparing the displacement and internal force variation of the pipeline before and after reinforcement,the scientific rationality of reinforcement measures was determined.