Abstract: The on-bottom stability of deepwater seabed pipelines is affected by the vertical penetration depth and resistance. In this study, the coupled Eulerian-Lagrangian approach (CEL) was used to simulate the vertical penetration of pipelines in cohesive soil, and the effects of strain rate behavior and strain softening on bearing capacity of pipelines were studied by subprogram VUSDFLD. The resistance provided by the heaved-soil on both sides of the pipeline during the penetration process was analyzed and the sensitivity analysis of the resistance was implemented, then a surface heave capacity factor was proposed. Results indicated that bearing capacity factor of the pipeline increases significantly with the increase of strain rate parameter. A high sensitivity of soil leads to a fast softening rate of soil and a low bearing capacity factor of pipeline. The surface heave capacity factor mainly depends on the submerged weight of the soil. Moreover, the greater the penetration depth, the more obvious the effect of the submerged weight of soil on the bearing capacity of surface heave. An expression describring the surface heave capacity is developed by fitting the numerical results.

Key words: surface heave, pipeline, penetration resistance, Coupled Eulerian-Lagrangian(CEL), strain rate, strain softening