Study On The External Pressure Bearing Capacity Of The Composite Structure Of PE Pipe And CIPP Lining

Polyethylene(PE)pipeline is a kind of flexible pipeline with good corrosion resistance,good toughness,light weight and low cost,which is widely used in various municipal underground pipeline networks in China.However,due to insufficient consideration in design,improper construction or changes in external load conditions,some buried PE pipelines have produced or are about to produce deformation defects,which will not only change the flow area of the pipeline and reduce the fluid transport capacity,but also cause local stress concentration,greatly increase the risk of pipeline damage and failure,and even cause the settlement of overlying soil,resulting in ground subsidence and other disasters.How to improve the external pressure bearing capacity of the existing buried PE pipe and improve the overall stability of the pipe structure when the environmental load changes is the key technology to build a high toughness,high quality,green low carbon and low disaster city.The Cured-in-place-pipe(CIPP)trenchless repair technology can directly make a closely bonded glass fiber reinforced resin lining inside the pipeline without excavating the ground,forming a CIPP liningoriginal pipeline composite structure to improve the bearing capacity of the existing pipeline.At present,most of the research at home and abroad focuses on repairing rigid pipes such as reinforced concrete pipes,and there are few reports on the improvement of bearing capacity of flexible pipes such as PE pipes by CIPP lining.Based on this,this thesis uses the combination of theoretical calculation,indoor model test and numerical simulation to explore the influence of natural curing CIPP lining on the bearing performance of PE pipes in different deformation stages.The research results of this thesis can provide theoretical and data support for the design of municipal PE pipes based on CIPP technology.The main work and achievements of this thesis are as follows :In this thesis,theoretical calculation,indoor model test and numerical simulation are used to explore and analyze the bearing capacity of the natural curing CIPP lining-PE pipe composite structure.The research results of this thesis can provide data support for the design and operation and maintenance of CIPP engineering of municipal pipelines.The main work and achievements are as follows :(1)Under laboratory conditions,CIPP lining was designed and installed by natural curing process to form a bonded PE pipe-CIPP lining composite structure sample.Aiming at the natural curing process,the calculation model of ring stiffness of PE pipe-CIPP liner composite structure was constructed by plate load test.(2)A series of indoor tests on the bearing capacity of single pipe and CIPP liningPE pipe composite structure were carried out.The effect of CIPP lining repair on the bearing capacity of existing pipelines was proved.CIPP technology can greatly improve the bearing capacity of PE pipe joints.The load increase level varies from 200 % to 500 %,and the failure modes of PE pipe joints and composite structure pipe joints under plate load are revealed.The influence of various factors on the repair effect of CIPP was studied and analyzed.(3)A series of model tests were carried out on the size of existing pipelines,the bonding effect between existing PE pipelines and CIPP lining interfaces,the elliptical defects of existing pipelines and different external load forms by the control variable method.The results show that the smaller the DR value of the composite structure,the smaller the increase of CIPP lining reinforcement load.Interface bonding can improve the bearing capacity of CIPP lining reinforced composite structure,but the overall coordination stability of the structure is poor.The initial ovality will reduce the bearing performance of the composite structure,and the original pipe section is more likely to be damaged during loading.(4)A series of model tests were carried out on the size of existing pipelines,the bonding effect between existing PE pipelines and CIPP lining interfaces,the elliptical defects of existing pipelines and different external load forms by the control variable method.The results show that the smaller the DR value of the composite structure,the smaller the increase of CIPP lining reinforcement load.Interface bonding can improve the bearing capacity of CIPP lining reinforced composite structure,but the overall coordination stability of the structure is poor.The initial ovality will reduce the bearing performance of the composite structure,and the original pipe section is more likely to be damaged during loading.