Drained Lateral Breakout Resistance of Subsea Pipelines

Abstract

The lateral resistance between a subsea pipeline and the surrounding seabed is important for assessing stability and susceptibility to lateral buckling. The breakout, or peak, lateral resistance can exhibit undrained or drained behaviour depending on the rate of pipeline displacement relative to the permeability of the seabed. A drained response is common in coarse-grained soil but also can occur in transitional soil such as silty sands. While undrained breakout resistance is well understood, robust solutions for drained lateral breakout resistance of exposed subsea pipelines are lacking. The models currently used in practice exclude links to relevant soil properties such as the soil or interface friction angles despite their influence on the drained lateral breakout resistance. The lack of an industry-wide accepted approach for assessing drained lateral breakout resistance leads to an increase in the level of uncertainty being applied in routine design. To address this gap in pipe–soil interaction assessment, a parametric study using limit and finite element analyses is presented to illustrate the sensitivity of various input parameters on the lateral breakout resistance. The numerical results are compared to established drained lateral resistance models and model test data.