| PCCP is widely used in municipal,power and water conservancy because it can withstand pressure inside and outside,water leakage prevention,anti-corrosion,fast water delivery,easy to install,affordable economy,And other engineering fields.However,at present,there are few studies on the laws of force and deformation caused by different construction disturbances of large-diameter PCCP pipelines at home and abroad.Based on the partial relocation of a PCCP water pipeline,this paper carefully studies the geometric parameters of the embedded prestressed steel cylinder concrete pipe(PCCP-E)selected in the project.A simulation model that can consider the connection between large-diameter PCCP pipes and the components of the original pipeline foundation was established by using MIDAS GTS/NX and ABAQUS finite element software.Based on the model,the displacement of the large-diameter PCCP pipeline and the displacement of the supporting structure under different working conditions such as the new pipe trench excavation depth,the new and old pipe trench distance,the overburden soil excavation,the pipe joint separation and the single pipe relocation are analyzed.And the change law of the drawing force of the pipeline weld after relocation,provides a reference for the actual project.The main research contents and conclusions of this paper are as follows:(1)Through the preliminary study of the domestic and foreign pccp pipeline relocation data,the development status of large-diameter pccp pipe and pipeline relocation at home and abroad and the application status of pccp pipeline are summarized.This paper discusses the excavation support of new steel pipe foundation pit during the pipeline relocation process.The theory analyzes the influence of the two relocation sections on the vertical displacement of the existing normal working pccp water pipeline during the excavation of the new steel pipe trough.(2)Without considering the influence of groundwater,through the finite element simulation of two different relocation sections,the excavation depth of the new pipe trough and the spacing of the new and old pipe troughs are studied for the displacement of the existing normal working pccp water pipeline.Influence,the analysis results show that the excavation of the new pipe trough has an impact on the existing pccp water pipe trough foundation,mainly causing the existing pipe trough to produce bulges;and it is affected by the excavation depth of the new pipe trough and the spacing of the new and old pipe troughs.According to the analysis results,the deeper the excavation of the new pipe trough foundation and the closer the spacing between the new and old pipe troughs,the excavation of the new pipe trough foundation pit makes the displacement of the existing pccp pipe trough larger.(3)For one of the relocation sections studied,the depth of new steel pipe excavation and the spacing between new and old pipe troughs shall be fixed,and the displacement of the groundwater level in the excavation condition of the new steel pipe trough will be considered for the displacement of the existing pccp pipe.Through the midas gts/nx simulation analysis,the depth of the groundwater table has an important influence on the displacement of the new steel pipe trough support structure,the ground subsidence and the displacement of the existing pccp water pipe,and the displacement of the new pipe trough support structure will also be on the existing pccp.The pipe groove has the influence of vertical displacement.For example,in the actual construction process,the groundwater level can be effectively controlled and the appropriate supporting structure can be adopted,which can effectively reduce the influence of the new steel pipe trench excavation on the original pccp water pipe.(4)Using the MIDAS GTS/NX finite element software to establish the finite element models of the two relocation sections,and study the existing trenches under the conditions of considering the excavation of new trenches and the effects of excavation of new trenches.Digging over the soil,cutting and separating the common pipe seat,single pipe water stop and single pipe relocation construction process affect the force-deformation of the adjacent work pipe.It is concluded from the simulation analysis that during the actual construction process,the excavation of the new steel pipe trough has an influence on the adjacent normal working water pipe,and the displacement of the near pipe is greater than the far pipe displacement;the adjacent working pipe is used when excavating the overburden There is a displacement effect that causes the working pipe to be lifted on the foundation;and the following original shared base pipe cutting separation and single pipe relocation also have an upward displacement effect on the adjacent normal working PCCP pipe.(5)Using the finite element analysis software abaqus to build a model of large-diameter pccp pipeline,through the simulation analysis of 2,3 and 5 pccp pipeline steel cylinders,core concrete and prestressed steel wire,the single pipe pull-out is adjacent The stress-deformation of the pipe section will affect the law of influence.At the same time,after the pipeline has been relocated,the weld stress of the welded joint between the new steel pipe and the original pccp pipe section will be studied accordingly.The new and old pipelines of different materials will be tested through simulation analysis and actual monitoring data.Whether the weld is subjected to force-deformation after normal operation meets the requirements for safe use.(6)Since the material of the new steel pipe is different from the material of the original PCCP pipeline,different settlement differences may occur due to creep in the future work.The influence of the settlement difference on the force-deformation of the PCCP pipeline is studied by simulation analysis.When the PCCP pipeline and the new steel pipe pipeline produce a settlement difference of not more than 8.1 mm,the drawing force generated by the welding of the two pipes does not exceed the drawing force of the two pipes when welding,but in the actual construction,timely monitoring is required to improve the welding quality.Meet construction requirements. |
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