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 the**users. According to Natural Resources Canada, about 825,000 kilometers of oil and gas transmission, gathering**and 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 design**guidelines for structural integrity assessment of pipelines in landslide areas were developed based on the**observations for rigid pipes, which may not be applicable to flexible pipes, such as Medium Density**Polyethylene (MDPE) pipes. However, flexible polyethylene pipes including MDPE pipes have been widely**used over the last few decades due to their various advantages. The design method for the assessment of the**performance of MDPE pipelines subjected to landslide loading is not well-developed. Full-scale tests and finite**element (FE) modelling of MDPE are also very limited. In the proposed research, a set of full-scale tests of**small 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 from**ground movements. The test program will consists of following: i) axial pullout testing of plane pipes; ii) axial**pullout testing of pipes with Tee-junctions (branched pipes); and iii) lateral pullout testing for pipes, buried in**loose and dense sand. Laboratory element testing will be conducted to find geotechnical parameters and**development 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 from**the 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 management**decisions to ensure structural integrity of the pipeline and minimize the risk of pipeline failure.