| Plastic pipe reinforced by cross helically wound steel wires(PSP)is a new type of the composite pipe with the excellent performance.It uses the high-strength steel wires to form the mesh skeleton as reinforcement.The high-density polyethylene is used as the matrix basis.The reinforcement and the two mats are tightly bonded together with an adhesive resin.This unique structure makes the PSP to have the high strength and the characteristics of corrosion resistance.It is lighter than the composite pipe with metal plate of the reinforcement material.In recent years,PSP has been widely used the various municipal engineering and industrial transportation due to its high production efficiency and superior comprehensive performance.At present,the research on PSP still focused on the properties and optimization of the pipes themselves.The research on the mechanical behavior of buried PSP under complex loads is still in its infancy and almost studies have only one load.The existing research results on steel pipes and PE pipes cannot be directly applied.In order to improve the safety of the buried PSP pipes.The National Natural Science Foundation of China provides the financial support for the project,"Study on the Progressive Damage Failure Behavior and Mechanism of Bonding Interface of Steel Wire Reinforced Plastic Composite Pipe Based on Nonlinear Viscoelastic Cohesion Theory"(Project No.51805378).Using the finite element method and the failure behavior of PSP pipes under tie-up and settlement load is discussed.The effects of various factors on PSP failure behavior is discussed.The method for evaluating the strength of buried PSP pipes is proposed.The main research contents are as follows::(1)The Drucker-Prager model is selected as the constitutive model of the soil.The finite element model is established.The finite element software is used for analysis and calculation.The strength limit of the steel wire is used as the failure judgment criterion to determine the limit load conditions.(2)Under the tie-up loads,the compression effect of the soil on the cross section of PSP is the main cause of failure.But the location of the maximum stress remains unchanged,which appears at the arch line of the inner wire of the pipeline below the center of the tie-up zone.When it fails,the tie-up load have the inverse proportion to the length,width and internal pressure is direct proportion with to the buried depth of the pipeline.(3)Under the settlement load,the buried PSP undergoes the severe tensile deformation.The deformation in the transition zone is "S".As the settlement displacement increases,the stress on the pipeline gradually increases.But the position of the dangerous point remains unchanged,which appears at the inner layer of steel wire at the junction of the settlement zone and the transition zone,the inner layer of steel wire on the upper surface at the junction of the transition zone and the non-settling zone.When the buried PSP pipe fails,the settlement load is proportional to the length of the transition zone and inversely proportional to the internal pressure of the pipe.The buried depth of the pipeline has little effect on the settlement load.(4)Two methods for evaluating the strength of buried PSP under typical complex loads are proposed.Under the tie-up load,the safety for the buried PSP pipe is determined by using fitting to failure equation of tie-up loading,length and width of tie-up area.In settlement cases,the safety for the buried PSP is determined with the relation curve between the settlement load and the length of the transition section.The failure load equation is obtained.If the judgment equation is correct,it can be determined that the load is within the load range of the PSP pipe,and the pipeline can continue to be used safely.Otherwise,the PSP pipe has potential safety hazards and needs to be checked in time... |
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