UBC Theses and Dissertations
A field investigation to study the response of buried polyethylene natural gas pipelines subjected to ground movement Groves, Jeremy F.
The performance of buried natural gas pipelines located in areas prone to ground movement is a major concern for utility owners since the failures of such pipeline systems during service is extremely serious due to the potential for loss of life, as well as the associated environmental and economical impacts. With plastic pipes now the industry standard for most utility distribution systems (e.g., medium density polyethylene (MDPE) pipes for natural gas distribution), understanding the response of these extensible pipes when subjected to ground movements is an important consideration and critical for their integrity. Through previous research work conducted at the University of British Columbia (UBC) on the subject of extensible natural gas pipelines subject to relative ground movements, a new analytical model was developed to account for the soil-pipe interaction mechanisms for buried MDPE pipes. The new approach can be used to estimate the relative ground surface movements needed for pipe failure, which is an important consideration for evaluating the field-performance of pipe systems in areas prone to landslide movements. In order to further validate the new analytical model, a large-scale field-testing program was implemented that consists of five MDPE pipeline alignments buried at a site which is part of a slow-moving landslide. The pipelines were instrumented with over 200 strain gauges that provide pipe strain data induced due to continuing ground movements at the research site. Along with the pipe strain data, close monitoring of the system for overall pipe and ground surface movements is ongoing, and the collected information is expected to provide a reliable database of ground movement and associated pipe strain to further validate the new analytical model. Laboratory element-level testing was conducted to investigate the effects of strain gauge stiffening on local strain readings on the MDPE pipes used in this study. The results indicate that the strain gauge installation procedures used throughout this research have minimal stiffening effects on the pipes. In addition to implementing the field experiment, a framework for using the field data to predict the axial pipe strain for the pipes in this study using the new UBC model is presented.
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