Abstract: The buried polyethylene gas pipeline with scratches is prone to stress concentration under vehicle-mounted action, which speed up the damage of the pipeline, resulting in pipeline failure and ignition and explosion accidents. Based on the force transfer analysis, a nonlinear mechanical coupling model was established to explain the action path of vehicle-mounted, soil-scratched polyethylene pipe. The effects of load, internal pressure, buried depth, soil elastic modulus, and scratch depth on the pipe were analyzed. The results show that stress concentration occurs in the defect area of the scratched pipeline. The Mises stress is directly proportional to the changes of load, internal pressure, buried depth, and defect depth, and inversely proportional to the elastic modulus of soil under the condition of soil dead weight. When the Mises stress was 5.75 MPa or the internal pressure was 0.24 MPa, the maximum Mises stress reached the allowable stress. At an internal pressure of 0.52 MPa, the pipeline reached the yield strength and failed. When the scratch depth is shallow, the pipe failure starts from the middle part of the scratch front. When the ratio of the defect depth to the pipe wall thickness is a/t≥0.4, the stress concentration occurs at the end of the scratch, and the failure starts from both ends of the scratch.

Key words: scratch defect, polyethylene gas pipeline, force transfer, coupling, buried pipelines