Abstract: Pipelines are widely used in the petroleum industry for oil and gas transportation, and the interaction between pipelines and seabed is crucial for assessing pipeline behavior during lateral thermal buckling. This paper presents a numerical investigation on the pipe-soil interaction behaviour using a recently developed sequential limit analysis approach for deep-water pipelines on soft clay. This approach, primarily based on upper-bound limit analysis, is capable of handling the extremely large deformation problems and implementing the strain softening and strain rate effects. During the analysis, the pipe was laterally driven forward with the elevation of its invert fixed, differing from existing work in which the pipe can dive or rebound during the lateral displacement. The evolution of vertical (V) and horizontal (H) soil resistance was examined, and the validity of the present model is demonstrated using comparisons with centrifuge data. V-H yield envelopes were derived during the analysis to investigate the influence of load path on pipe response. The equivalent friction ratio, H/V, was found to increase linearly with lateral displacement. This study aims to provide guidance for the controlled buckling design for deep-water pipelines, and show the potential of SLA in solving large displacement soil-structure problems in undrained clay.

Key words: clay, deep-water pipelines, pipe-soil interaction, limit analysis, yield envelope