The effects of strain rate and soil remolding on uplift response of buried submarine pipelines

Abstract

Buried submarine pipelines are key components of offshore hydrocarbon extraction facilities. These pipes carry oil and gas maintained at high internal temperature and pressure. The thermal stresses developed because of temperature differences between laying and operational phases of these pipes may subject them to buckling. Several researchers have studied the soil response when the pipe undergoes upheaval buckling. However, the existing design methodologies do not consider the effects of strain rate and soil remolding on undrained shear strength of soil and its consequential effect on uplift capacity. In the present study, the effects of strain rate and remolding on uplift response of buried pipes are studied. The large deformation finite element approach has been used to model pipe-soil interactions for different values of strain rate parameter, pipe velocity, soil sensitivity, pipe embedment and soil unit weight. It is seen that the effects of strain rate on uplift capacity may be significant and a model is proposed that can quantify these effects. On the other hand, soil remolding is found not to affect the peak uplift resistance significantly as peak resistance is mobilized at relatively small pipe displacements.