Influence of Shallow Gas on the Bearing Capacity of Jacket Platform Pile Foundation

In response to the phenomenon of shallow gas overflow under the in-service jacket platform, this study evaluates the impact of shallow gas on the bearing capacity of pile foundations and the overall safety of offshore jacket platforms.The stratigraphic working conditions were categorized. Based on unsaturated soil strength theory, a theoretical formula for the shear strength of unsaturated soil was established. The pile-soil shear strength and the t-z, q-z, and p-y curves related to pile foundation bearing capacity under different working conditions were calculated. An analysis and calculation model of the jacket platform affected by shallow gas was established using SACS software, and the bearing capacity of the platform pile foundation was analyzed under various working conditions. The calculation and analysis show that changes in the characteristic parameters of sand or silt layers caused by shallow gas seepage significantly affect the safety of the pile foundation of the jacket platform. This results in the safety factor for the bearing capacity of some piles failing to meet code requirements. The research results help clarify the mechanism by which shallow gas seepage weakens pile foundation bearing capacity, provide guidance for developing prevention and mitigation strategies against shallow gas hazards, and offer recommendations for ensuring the safe operation of offshore platforms.