Precise simulation of deepwater J-laying pipeline in the TDZ by refined VFIFE method

The deepwater J-lay pipeline exhibits pronounced dynamic responses in the touchdown zone (TDZ) compared to the S-lay pipeline. This paper demonstrates a refined numerical model built upon the vector form intrinsic finite element (VFIFE) method for the J-laying pipeline, employing the equivalent beam particle technique to discretize the pipeline into beam elements and particles. The model precisely captures stress-strain behaviors at the pipeline cross-section in the TDZ and enables a comprehensive analysis of static and dynamic responses. The simulation for a 12-inch diameter pipeline at a 1000 m laying depth is implemented and compared to the calculation from OrcaFlex with the consistent results. The stress and strain in the lower section are higher than those in the upper section, where peak stress and strain reach 177.95 MPa and 0.080%. Moreover, the internal force distribution in the TDZ is systematically analyzed under varying pipe diameters, submerged weights, and laying angles. Increasing the pipe diameter amplifies internal forces, while submerged weight primarily affects tension and bending moment. And raising the laying angle from 70 degrees to 85 degrees sharply increases peak stress and strain. The proposed model provides a precise tool for analyzing deepwater J-laying pipeline behaviors in the TDZ.