Research On Collapse Mechanism Of Municipal Buried Pipeline

The municipal buried pipeline is the "underground lifeline" of the city operation,but due to the particularity of laying and running of the buried pipeline,it is easy to have functional or structural defects.Among these defects,collapse is a kind of defect that occurs frequently and has a serious impact on the function of the pipeline.The paper analyzes the stress conditions and collapse laws of pipelines.The research results can provide the results of the previous pipeline layout,and offer guidance for the follow-up pipeline trenchless repair.The main work completed is as follows:(1)collecting and analyzing the mechanism of pipeline collapse,obtaining the influencing factors of pipeline collapse and measures to prevent pipeline collapse.(2)based on the results of the pipeline operation in Tianhe District and Liwan District of Guangzhou,the collapse probability of different pipes,pipe diameters and pipeline positions is obtained by extracting and analyzing the collapse results.(3)ABAQUS finite element analysis software was used to analyze the stress of the collapsed pipelines,and the collapse displacements of different pipe materials,different pipe diameters,and different positions of the pipelines were further studied.We have obtained the collapse degree and probability response rule of the pipes under different conditions;(4)comparison of actual pipeline operation results and ABAQUS finite element analysis results.The results are as follows: the value of the collapse displacement of the same diameter and different materials pipeline : cast iron pipe < concrete pipe <steel pipe<PE pipe,the vertical stress on the pipeline increases with the relative stiffness of the pipeline.The larger the diameter of the pipeline with the same diameter and different materials pipeline are,the easier the pipeline collapses and the larger the collapse displacement is;the vertical stress on the pipeline also increases with the increase of the pipe diameter.The maximum collapse displacement of the other pipes occurs at about 1/3 of the length of the pipeline except the cast iron pipe which occurs at the 1/5 of the length of the pipeline.In addition to the 800 mm PE pipe and the 400 mm PE pipe,the maximum vertical stress respectively occurs at the 1/3 of the length of the pipeline and the 1/5 the length of the pipeline,and the maximum vertical stress of the other pipes all occur at the 1/2 of the length of the pipeline.