ABSTRACT
Thermoplastics pipes are used widely for the transport of gas, water and wastewater. The pipes are generally embedded at shallow depth prior to the application of any internal pressure and progressively loaded by backfill and traffic such that they deform in an approximately elliptical shape, resulting in the mobilisation of passive resistance in the surrounding ground. The soil-pipe interaction in such a system is complex and is largely determined by the properties of the pipe material and constitutive behaviour of the soil. Determination of the deformation state of any pipe is governed by a number of factors such as geometry of the soil-pipe system, traffic loading, soil behaviour and installation procedure. In this paper, current practices for design of flexible pipes subject to combined loading by gravity and internal pressure are critically examined, especially in light of the recent experience in Europe. The basis of a programme of research with the objective of identifying an improved methodology is then outlined.
