Deep Penetration of Spudcan Foundation Into NC Clay

The excessive penetration of spudcan foundation in jackup rigs can be costly in offshore operation. Thus, the accurate prediction of load-penetration response becomes increasingly important in offshore design. The performance of spudcan foundation during installation, subjected to vertical loading on normally consolidated (NC) clay, is investigated physically and numerically. Experiments are carried out on kaolin clay in a drum centrifuge and FE analyses are performed using AFENA. During initial penetration, soil flows towards the ground surface and therefore heave occurs close to the spudcan edges. It flows back on top of the spudcan right after the heave passes the spudcan shoulder and shortly a substantial back flow causes the spudcan to be fully embedded. When penetration ratio (d/D) reaches 0.75, a deep failure mechanism achieves. Soil failure mechanisms play a key role for evaluating bearing response at various penetration depths. By comparing FE results with centrifuge test results, an identical bearing capacity factor of N_c = 10.5 is obtained for deeply embedded spudcan. The roughness of the soil-spudcan interface has shown 10% difference in bearing capacity when d/D is larger than 1.5.