Mechanical response of buried polyethylene pipelines under excavation load during pavement construction

Polyethylene (PE) pipelines are the most popular kinds of urban gas pipelines used in industry. With rapid development of urban pavement construction and increasing demand of natural gas in China. Urban gas pipe accidents caused by pavement mechanical construction have taken place more frequently in recent years, which becomes one main reason for accidents caused by third party damage. Thus, it is of great importance to investigate the failure mechanism of urban pipeline under mechanical excavation for safe operation of urban gas pipelines. A rigorous 3D finite element model was established for mechanical response of PE pipe under mechanical excavation in this study. Soil, tooth of the mechanical excavator and pipe were all modelled by continuum solid elements. Surface to surface contact algorithm was utilized simulating the actual interaction between excavation tooth, pipe and soil. Failure procedure of PE pipeline under excavation load was investigated in detail in a baseline analysis based on two commonly adopted criteria, the stress based failure criterion and the strain based criterion. Parametric analysis was also conducted to discuss the effects of excavation position, pipe diameter, pipe wall thickness and internal pressure on PE pipe's mechanical response. Results show that, large stress and strain will occur at longitudinal ends of the dent in the pipe induced by excavation load. And large ovality will occur in the whole contact area of the pipe. The strain based criteria is more suitable for safety assessment of PE pipe, as the outstanding plastic performance of PE material. The excavation position and internal pressure have little influence on pipe's response, while increasing the pipe diameter and wall thickness can decrease the pipe stress and ovality to a certain extent.