Axial pipe-soil interaction behaviour of offshore pipelines

Pipe-soil interaction behaviour in the axial direction is an important design parameter for offshore pipe design. Governed primarily by the axial interaction behaviour, the undue thermal expansion of the pipe wall could cause the pipe to either freely expand, or buckle on the foundation seabed. Therefore, it is emphasized that by controlling the axial interaction behaviour, the overall pipe on-bottom stability can be effectively managed. This paper presents laboratory experiments performed at Monash University to understand the pipe-soil interaction behaviour in the axial direction. A special 2-D actuator test setup was developed to study axial walking of pipe on clay seabed under drained and undrained loading conditions. The effect of pipe loading rate, pipe embedment, and shutdown cycles on axial friction force were explored. Based on the experimental results, the pre-peak, peak and residual components of the axial force-displacement curve were identified and explained using a simplified theoretical framework.