Investigation of pull-out behaviour of small diameter medium density polyethylene pipes

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Pipelines play an important role in modern society through transporting liquids and gases from the source to theusers. According to Natural Resources Canada, about 825,000 kilometers of oil and gas transmission, gatheringand distribution pipelines traverse Canada. Many of these pipelines pass through the areas prone to landslides.Soil movement due to landslides may cause longitudinal, transverse or combined loads on the pipelines,depending upon the orientation of the pipeline with respect to the moving ground. The existing designguidelines for structural integrity assessment of pipelines in landslide areas were developed based on theobservations for rigid pipes, which may not be applicable to flexible pipes, such as Medium DensityPolyethylene (MDPE) pipes. However, flexible polyethylene pipes including MDPE pipes have been widelyused over the last few decades due to their various advantages. The design method for the assessment of theperformance of MDPE pipelines subjected to landslide loading is not well-developed. Full-scale tests and finiteelement (FE) modelling of MDPE are also very limited. In the proposed research, a set of full-scale tests ofsmall diameter MDPE pipe will be conducted using the facility at Memorial University of Newfoundland(MUN) to develop a database and an improved understanding on the behaviour of pipes under the loads fromground movements. The test program will consists of following: i) axial pullout testing of plane pipes; ii) axialpullout testing of pipes with Tee-junctions (branched pipes); and iii) lateral pullout testing for pipes, buried inloose and dense sand. Laboratory element testing will be conducted to find geotechnical parameters anddevelopment of constitutive models for sand and the strain rate dependent behavior of MDPE pipe materials.FE modelling techniques will be developed using Abaqus FE software to simulate the observed response fromthe full-scale pipe tests. The findings from this research will be useful to the Canadian pipeline industry,enabling them to assess pipeline conditions in unstable ground and thus to make more effective managementdecisions to ensure structural integrity of the pipeline and minimize the risk of pipeline failure.