A Slip-Line Field Solution for the Ultimate Bearing Capacity of a Pipeline Under Oblique Loading on a Clayey Seabed

Predicting the ultimate bearing capacity of a deep-sea pipeline on the soft clayey seabed is crucial to on-bottom stability and global buckling analyses. Based on the slip-line field theory, an analytical solution is derived for the undrained bearing capacity of an obliquely loaded pipeline on a clayey seabed obeying the Tresca criterion. For a wished-in-place pipeline, the failure mechanisms and the corresponding pipe-soil interface conditions are proposed for the vertical and the lateral instability mode separately. Based on the derived slip-line field solution, a series of failure envelopes are established for various pipe-soil interface conditions. The analytical solutions match well with the previous numerical and theoretical results. The parametric study indicates that the embedment-to-diameter ratio and the loading angle are the key parameters for the bearing capacity of an obliquely loaded pipeline.