| Summary: | Previous studies of high-density polyethylene pipes have been based on the premise that residual stresses have no effects and have almost no role to play in the failure and performance of theses pipes. It is thought that previous studies have underestimated the effects of the residual stresses in pipes at the design stage particularly when assessing pipe-soil interaction and ground loading effects. This project tried to assess the effect of residual stresses in soil-pipe interaction of HDPE (PEIOO) pipes, and opened two main areas of research: (a) to investigate the actual residual stress profile in the pipes as a result of the manufacturing process; and, (b) to take these residual stress profiles, which have been previously ignored, in consideration to assess the performance of the pipe and the surrounding soil. A review of the existing techniques available for the determination of residual stresses was carried out and a literature review was done on how these techniques were used by various authors. On the whole, most of these techniques involved destructive tests that are believed, here, to alter the residual stress profile and magnitude in the pipe wall. The current study has tried to develop an innovative stress-optical technique for the determination of residual stresses with minimal alteration to the residual stress profile and its magnitude. After determining the residual stress profile and magnitudes by the new method, the interaction of the residual stress with internal pressure effects and ground loading effects on pipes is studied. The studies included the numerical modelling of the pipe when the residual stress in the pipe wall incorporated and the pipe subjected to internal pressure loading as well as external loadings from the weight of the surrounding soil. A number of earlier researchers have investigated the soil structure interaction parameters which affect the structural behaviour of buried flexible pipes. However, to date none of the studies have incorporated residual stresses in pipe-soil interaction modelling and the current study has raised awareness of the consequent absence in current design procedure [BS EN 1295-3; 1998].
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