Simplified design methods for pipelines subject to transverse and longitudinal soil movements: Discussion

Abstract

The simple method for analysing the behaviour of buried pipeline subjected to transverse and longitudinal soil displacement, and proposed by the original authors, was critiqued. It was argued that in the transverse movement case, the assumptions of elastic-perfectly plastic soil and elastic pipe may have oversimplified the actual behaviour of the soil and the pipe, and that the use of a single value of ks was insufficient to model the nonlinear load displacement relationship. While the solution proposed by the original authors was simple and easy to use , it may be usable only in preliminary design. For detailed design a more rigorous solution has to be used, such as for example a beam on elastic foundation program that takes into account the plastic behaviour of the pipe and non-linear load-displacement relationship of the soil. It was pointed out that in actual practice most pipelines are laid in an excavated trench and then backfilled with other material and the backfill is usually weaker than the natural ground. This fact of two different materials can affect the value of the resistance factor. The reviewer (1994) derived a number of design charts to determine correction factors which have been checked against the results of a full-scale pipe loading test, and found excellent agreement. 3 refs.