Thermo-Hydro-Mechanical Response of a Buried Subsea Pipeline to Internal Blast Loading with Imperfect Pipe–Soil Thermal Contact

A buried subsea pipeline subjected to an internal explosion experiences a rapid pressure pulse and sustained wall heating, while imperfect thermal contact at the pipe–soil interface governs heat transfer into the surrounding saturated seabed soil. This study develops an axisymmetric semi-analytical model with axial variation (2.5D) that couples a thermoelastic steel pipe wall to thermoporoelastic seabed soil. The model incorporates mechanical interface compliance, an impermeable hydraulic boundary, and four thermal contact laws defined by contact resistance and a temperature partition coefficient. Fourier and Laplace transforms reduce the governing equations to modified Bessel solutions, and a comparison with a published pressure-only lined tunnel solution verifies the mechanical formulation. The transient temperature, heat flux, displacement, stress, pore pressure, and Darcy discharge are examined for the four laws. The results show that the pressure pulse and heat conduction act on different time scales. Contact resistance delays heat transfer through a heat flux-dependent temperature jump, whereas temperature partition governs the relation between the pipe-side and soil-side temperatures. For the reference parameters, combining resistance and partition produces the greatest reduction in heat transfer and the weakest soil-side thermal and hydraulic responses. The thermal contact law markedly affects the interface temperature, heat flux, wall stress redistribution, and pore pressure but has only a small effect on the radial displacement. Imperfect thermal contact should therefore be included when evaluating the coupled response of buried subsea pipelines under internal blast loading.