Sliding risk of jack-up platform re-installation close to existing footprint and its countermeasure

摘要

Analysis on the sliding risk of jack-up platform re-installation close to the existing footprint is conducted with finite element method. An effective countermeasure to reduce the sliding risk is suggested and an example analysis for an existed jack-up platform re-installation in a typical block with two layer soil within design driving depth in China sea area is carried out. Taking into consideration fluid seepage in pore structure, sliding contact friction, and the material and geometric nonlinear properties, a fluid-solid coupling finite element model for the spudcan-soil interaction is constructed. By comparing the numerical simulation result with the experimental result published in the literature, the reliability of the finite element model is verified. With the model, the failure process, the movement pattern of foundation and the spudcan-soil interaction under the impact of the footprint are analyzed. The study shows: in pitching pile the plastic failure zone appears at the low corner close to the spudcan first, then the area beneath the spudcan, and the plastic area becomes larger to form a connecting region finally as the loading increases continuously; the migration pattern of soil around the spudcan changes sharply with the distance between the spudcan and the footprint increasing; at the same time the peak value of the horizontal sliding force increases first then decreases gradually. In the final pitching pile position, ‘stomping’ in advance in appropriate distance and depth can reduce the sliding risk of a jack-up platform re-installation effectively.