Wave-Induced Liquefaction and Floatation of a Pipeline in a Drum Centrifuge

This paper discusses the floatation of a buried pipe in association with wave-induced liquefaction of sand beds. Centrifuge wave tests in a drum channel were performed with viscous scaling introduced such that the time-scaling laws for fluid wave propagation and consolidation of the soil were matched. The characteristics of liquefaction under irregular waves as well as regular waves were investigated. Under severe wave conditions, the loose sand beds underwent liquefaction, and the liquefied zone propagated downward in the course of wave loading. It was found that the floatation of the buried pipe was a consequence of progressive liquefaction. With the occurrence of liquefaction at a shallow soil depth, the buried pipe started moving upward and the motion of the pipe increased markedly in association with the downward progress of liquefaction during wave loading. Finally, the pipe reached the soil surface. The effects of a gravel layer replacement over a sand bed on wave-induced liquefaction and pipe floatation were also examined. A gravel cover over the sand bed with a range of 120° above the pipe prevented significant vibratory motion of the liquefied soil and floatation of the pipe.