Response of submarine pipelines to impacts from dropped objects: Bed flexibility effects

Effects of soil-pipe interaction on the response of continuously supported offshore pipelines subjected to transverse impacts caused by dropped objects are studied. For this, the impact on an internally pressurized pipeline resting on a flexible bed has been numerically simulated. The numerical model has first been validated against different sets of experimental data from the authors and a number of researches. A relatively extensive parametric study has then been carried out to examine effects from variations in the pipe geometry, internal pressure, boundary conditions, indentor shape and orientation, embedment depth of the pipe into the soil bed and subsoil mechanical properties on the pipeline response. It has been noticed that the presence of internal pressure results in substantial increase in the impact force. It, however, reduces the denting length, causing the deformation to become spatially more localized. It has also been shown that the flexibility of pipe bed plays an important role in the impact energy dissipation. This effect becomes more pronounced when the internal pressure is relatively low.