Centrifuge modelling of pipelines shallowly embedded in liquefied submarine slopes

Abstract

Marine pipelines are widely used for transporting hydrocarbon material. However, they can be damaged by marine geo-hazards such as seabed liquefaction, as they may sink, float or be dragged by the moving soil. One of the triggering mechanism of seabed liquefaction is the increase of seabed inclination as a result of the souring process or human construction activities. Experiments are carried out to simulate seabed liquefaction and to study the drag forces on a shallowly buried gas pipe at a centrifugal acceleration field of 50g. A tilting mechanism is applied to trigger sample liquefaction. A fluidization system equipped at the bottom of the strongbox is designed to prepare fully saturated, loose and uniform samples. Viscous fluid made of Hydroxypropyl Methylcellulose powder is used as the pore fluid. A hollow model pipe is embedded in the sand layer shallowly with a specific embedment ratio. The pipe fixities are made to be adjustable for adjusting pipe locations horizontally and vertically. Strain gauges attached on fixities are used to monitor the loads exerted on the pipe. The effect of the presence of pipes on the sand layer instability is presented. Furthermore, the drag forces acting on the pipe at a specific embedment ratio is discussed.