Numerical study on the effect of SLWR buoyancy configuration on pipe-soil interaction based on co-rotational method

The buoyancy module installed on the steel lazy-wave riser makes the riser locally S-shaped, which weakens the motion transmission from the top to the bottom but makes the pipe-soil interaction more susceptible to the buoyancy configuration. In this study, a two-dimensional planar static numerical model considering the riser global motion coupled with the nonlinear seabed interaction is developed. The planar co-rotating beam element is established based on the co-rotating coordinate method, the vertical soil resistance is simulated by the semi-empirical pipe-soil interaction model. And the global displacement of the riser and the soil resistance of the seabed are coupled in the co-rotational framework by the principle of minimum potential energy. Finally, the parametric effects of buoyancy configurations and riser structural characteristics are analysed. The results show that the established numerical model is suitable for solving the vertical pipe-soil interaction between riser and nonlinear seabed. Compared with SCR, the maximum embedment depth of SLWR in the TDZ is reduced by 23.5%, and the maximum vertical soil resistance is reduced by 8.26%. In the two buoyancy configuration adjustment methods, increasing the buoyancy section length obviously changes the shape of SLWR, resulting in significant changes in the embedment depth and vertical soil resistance.