Research on the Influencing Factors of Pile Pulling Resistance for Jack-Up Rigs

During pile pulling operations of jack-up rigs, excessive pile pulling resistance and prolonged cycles frequently pose significant challenges, adversely affecting oilfield production efficiency. The magnitude and variation patterns of pile pulling resistance under complex marine conditions are critical determinants of operational safety. Consequently, achieving precise predictions of pile pulling resistance across various scenarios holds substantial significance. This study presents a small-scale numerical simulation of pile pulling resistance prediction for the spudcan of the jack-up rig, with a scale ratio of 30:1. First, a small-scale numerical calculation model was established using the Lagrangian method to simulate the pile pulling resistance of the spudcan, using the displacement control method to simulate the pile pulling process, obtained the relationship curves of pile pulling resistance and displacement. Next, the effects of varying backfill soil ratios (0%, 20%, 40%, 60%, 80%, 100%) and jetting efficiencies (0%, 20%, 40%, 60%, 80%, 100%) on pile pulling resistance were explored. Pile jetting efficiency means the percentage reduction in the adsorption force at the bottom of the spudcan. Subsequently, the differences in pile pulling resistance were simulated for spudcans initially positioned in dense sand, clay, and loose sand layers. Experimental validation corresponding to the small-scale numerical model will be presented in subsequent work, including comparisons with experimental results. The simulation results indicate that the initial pulling resistance sharply increases due to the negative excess pore water pressure in the soil beneath the spudcan. As the spudcan extraction distance increases, the suction forces within the underlying soil gradually dissipate, resulting in a significant decrease in pile pulling resistance, which subsequently stabilizes. The effect of jetting efficiency on pile pulling resistance is the most pronounced, with higher jetting efficiency significantly reducing the resistance. Furthermore, increases in both the backfill soil ratio and the initial spudcan depth result in higher pile pulling resistance.