Pipe–soil interaction model for current-induced pipeline instability on a sloping sandy seabed

Abstract

As offshore exploitation moves to deeper waters, ocean currents become the prevailing hydrodynamic loads on pipelines, and at the same time a sloping seabed is always encountered. The prediction of lateral soil resistance is vital in evaluating pipeline on-bottom stability. Unlike previous pipe–soil interaction models used mainly for horizontal seabed conditions, a pipe–soil interaction model for current-induced downslope and upslope instabilities is proposed by using the limit equilibrium approach. The Coulomb’s theory of passive earth pressure for the sloping seabed is incorporated in the derivation. The model verification with existing full-scale tests shows good agreement between the experimental results and predicted ones. Parametric study indicates that the effect of slope angle on pipeline lateral soil resistance is significant in the examined range of slope angle from –15° to 15°. The critical pipeline embedment and corresponding passive pressure decrease approximately linearly with increasing slope angle.