Multiphysics coupling mechanical behavior and high-fidelity prediction modeling for large-diameter submarine pipeline during directional drilling pullback process

Shore-to-shore directional drilling is essential for efficient and safe pipeline installation. During long-distance pullback of large-diameter pipes, mechanical behavior exhibits strong nonlinearity, spatiotemporal variation, and multiphysics coupling. Conventional prediction models, based on static assumptions and uniform geology, often ignore rate effects, time-varying mud properties, and soil heterogeneity, reducing accuracy and increasing risk in complex projects. This study systematically examines multiphysics coupling impacts on pullback mechanics. A 3D numerical model integrates large-deformation pipe dynamics, unsteady mud flow, and nonlinear soil plasticity, incorporating rate-dependent friction, time-varying mud rheology, and random geological variability. A resulting high-fidelity pullback force model combines dynamic, geological, and time-dependent mud effects. Results show that compared with traditional methods, the proposed model reduces average prediction error from 18.3% to 4.8%. Geological heterogeneity is the main cause of pullback force fluctuations, reaching 20–40%, with soil cohesion as the most sensitive parameter. These findings provide a reliable tool and guide for precise prediction, proactive control, and risk mitigation in subsea pipeline construction.