Some Experience with 30 Years Old Buried (uPVC) Pipes from the Viewpoint of Stress and Strain

Abstract

This contribution reports on the experience with (uPVC) pipes used for gas distribution in the Netherlands. An extensive research program has been carried out in order to determine the behaviour of buried PVC pipes, some of which have been in service for over 30 years. This research program covers both theoretical and experimental studies, the latter being the subject of this contribution. Over the last three years a lot of pipe deformation measurements were carried out on pipes buried under different circumstances concerning soil type, burial depth and loading conditions. The results clearly show that buried PVC pipes behave quite well from the viewpoint of stress and strain. The results of measurements on old pipes when compared with results from measurements on newly installed pipes and from different stress calculation methods, also indicate that the buried pipes are not in a situation of constant stress, but in a constant strain situation. This supports the idea of using the short-term modulus of elasticity for calculation of the pipe deflection instead of the long-term value.