Numerical investigation of spudcan penetration under partially drained conditions

Abstract

Estimation of spudcan penetration resistance during jack-up rig installation is critical to determine its final resting depth under full pre-load. The penetration resistance profile is conventionally calculated by assuming undrained conditions for clay and fully drained conditions for sand in current practice, but partial drainage in intermediate soils, such as in silts and sandy silts, leads to the resistance in between. This paper reports the results from a series of numerical investigations conducted to explore spudcan penetration response, which spans from fully undrained to fully drained conditions. The investigation is carried out using a large deformation finite-element approach within the framework of effective stress analysis. The numerical approach is validated by simulating existing centrifuge tests. Parametric studies are then performed using a wide range of normalized penetration velocity. The transition point where partially drainage occurs is identified, and is compared with those obtained from centrifuge tests. The variation of normalized penetration resistance with normalized velocity is compared with the published experimental data on UWA kaolin and silt. The backbone and consolidation index curves for Malaysian kaolin are subsequently provided to quantify the influence of different drainage conditions. Finally, the partial drainage effects for spudcan and penetrometers is compared and discussed.