The mechanism of steady friction between seabed pipelines and clay soils

Abstract

The large-amplitude lateral soil resistance between an on-bottom pipeline and the seabed is an important design parameter in assessing pipeline behaviour during lateral thermal buckling or under the impact of a submarine slide. This paper describes a series of centrifuge model tests that shed light on the underlying behaviour during large-amplitude lateral pipe movement. It is shown that at large displacements the lateral response is governed predominantly by the passive resistance of the growing berm of soil ahead of the pipe. Using a new analysis of this growing soil berm, based on conservation of volume, the ‘local' embedment of the pipe relative to the top of the idealised soil berm is defined. In this way, the normalised lateral pipe–soil resistance, H/s u D, from tests encompassing a range of pipe weights and initial embedments follows a single trend line. This idealisation of the response is more consistent than the usual terminology of a pipe–soil friction factor.