Dynamic response of pipelines in liquefiable seabed under nature loadings: Waves and currents.

In this paper, an elastoplastic modeling method is presented for dynamic consolidation of liquefiable seabed around a pipeline subjected to ocean environmental loadings (i.e. wave and current). Special attention is given to the cyclic plasticity modeling of liquefiable marine sediments and the evolving soil-pipeline interactions, in association with the Biot's dynamic consolidation theory. Motivated by the experimental findings, this paper extends a Masing-type model to the liquefaction-induced deformation regime of marine sediments within the cyclic plasticity framework. A novel plastic flow rule is developed to capture the cyclic-shearing-induced volumetric strain and hence exercise direct control over the response pattern of excessive pore water pressure (EPWP). Then, a model calibration procedure is outlined, with respect to cyclic laboratory sample tests under various loading paths. Finally, the combined actions of current on the wave-induced dynamics of liquefiable seabed around a buried pipeline are studied by numerical examples. The results demonstrate that the propagation of ocean current has major consequences for the wave-induced soil-structure interactions such as EPWP response, liquefaction pattern of seabed over the contact areas and uplift of pipeline. The liquefaction triggering of seabed and the consequence for the dynamic response of pipeline in the wave and current environment are also investigated. • The cyclic plasticity of liquefiable seabed around pipeline under wave and current is modeled. • A newly-observed cyclic shear-volume coupling model is incorporated into the plastic flow rule. • Model calibrations are carried out by element simulation of liquefaction against laboratory tests. • Influences of current on the wave-induced liquefaction and uplift of pipeline are investigated. [ABSTRACT FROM AUTHOR]