| With the continuous acceleration of China’s urbanization process,infrastructure construction has entered a stage of rapid development.As one of the five modern transportation modes,pipes have been widely used in municipal,power,communication,gas,water supply,and drainage.Highdensity polyethylene(HDPE)double-wall corrugated pipe is a standard plastic buried pipe,which is widely used in the municipal drainage field due to its advantages of corrosion resistance,small friction resistance,economy,and easy installation.As a typical flexible buried pipe,the deformation of HDPE corrugated pipe is greatly affected by the compaction of backfill around the pipe.However,the compaction of backfill is often challenging to meet the specification requirements in actual projects,resulting in local loosening of backfill.At the same time,the particular cross-sectional structure with a smooth corrugated exterior wall and smooth interior wall makes the mechanical deformation mechanism more complicated.In the existing research,the strain distribution of HDPE corrugated pipe under external load has not been clearly defined.Therefore,this paper carried out the mechanical deformation research of HDPE double-wall corrugated pipe buried in partially loose backfill under operation load,aiming to provide a theoretical basis for deformation and failure of existing operation pipes.The main research contents and conclusions are as follows:(1)Through ABAQUS,a “real” finite element model of pipe-soil interaction of double-wall corrugated pipe is established,and the soil model is finely meshed in Hypermesh,which reduces the number of elements and dramatically improves the calculation efficiency of the model.The accuracy of the model is verified by comparing the field test data with the simulation data,which provides a basis for the research on the stress and deformation of real corrugated pipe.The analysis shows that the strain distribution of the liner and valley are basically the same,and the liner strain is always smaller than the valley strain.The distribution of crest strain is more complex and is more susceptible to loose backfill.Under the condition of good compaction backfill,the circumferential strain distribution of pipe with different diameters are similar,and the strain values at the crests and valleys of pipes are proportional to the diameter.The deformation of the pipe is constrained by the radial displacement of the valley.The liner strain of the small diameter pipe is tensile,while the strain of the large-diameter pipe is compressive.(2)The lower the compaction degree of the backfill,the higher chance of the circumferential strain of the pipe.When the backfill is partially loose,the pipe often has strain concentration near the interface between the good compaction backfill and the loose backfill.The response of pipe to the loose backfill is determined by the position and size of the loose area,and is more susceptible to the influence of position.Under poor backfill conditions,the failure form of the pipe is affected by the diameter of the pipe.Small diameter pipes may be damaged due to strain concentration,while large diameter pipes are more likely to be damaged by local bending.(3)Based on the above verified three-dimensional pipe-soil model,the sewage-air flow field in the pipe is established in FLUENT,and the pipe-soil-fluid is coupled by Mp CCI.The reliability of the coupled model is verified by experiments.Based on the model,the stress and deformation of the pipe under real operation load are studied,and it is found that the sewage reduces the liner strain in the contact area with the sewage.The higher the depth of sewage or the lower the flow rate,the smaller the liner strain,and even the area near the pipe bottom changes from compressive strain to tensile.Under the action of sewage,the decrease of liner strain increases the difference between valley and liner strain,which leads to local bending of the interior wall more easily. |
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