AXIAL PIPE-SOIL INTERACTION BEHAVIOUR OF PARTIALLY EMBEDDED OFFSHORE PIPELINES

Abstract

This thesis presents results of centrifuge model tests and three-dimensional large deformation finite element (LDFE) analysis on axial pipe-soil sliding behaviour of partially embedded subsea pipelines. 3D re-meshing and interpolation technique with small strain (RITSS) approach was adopted using ABAQUS’s mesh-to-mesh solution mapping feature with Cam-Clay model. The parameters studied include soil properties, interface friction coefficient, embedment depth and post-lay reduction in vertical load. Embedment depth and post-lay load reduction were found to exercise the strongest influence on the post-consolidation and sliding behaviour. Empirical relationships correlating centrifuge experiments and numerical modelling are proposed to quantify the axial pipe-soil friction for the complete range of consolidation history. These relationships provide a basis for the evaluation of axial pipe-soil friction corresponding to arbitrary sliding velocity, which can be used in routine analysis and design of as-laid underwater pipelines in soft clayey soils. Finally, the feasibility using effective stress 3D RITSS approach to model global pipe-soil response is also demonstrated on a significant length of pipeline.