Consolidation around offshore pipe embedment Using coupled analysis

Predicting the initial embedment of an as laid offshore pipeline is one of the most important design considerations for on-bottom stability analysis. An undrained approach, as similar to a strip footing analogy, is in practice for the estimation of immediate pipe embedment soon after lay. Although the undrained approach provides an initial estimation of the pipe embedment, the subsequent soil consolidation around the pipe wall and the corresponding increase in pipe settlements are overlooked in this method and should be accounted for a detail estimation. In this paper, these inadequacies of the undrained pipe embedment behavior are investigated using a coupled numerical analysis. ABAQUS FEM analyses were conducted for pipe embedment on soil assigned with Modified Cam Clay constitutive model (MCC). Both immediate embedment and the subsequent soil consolidation were investigated in correspondence to the excessive pore pressure generation and the subsequent dissipation below an embedding pipe. Based on these results, settlement of pipe on cohesive soil is quantified against a non-dimensional time delay, which would benefit designers in the estimation of ultimate embedment depth.