Numerical investigation of bearing capacity due to spudcan penetration in sand overlying clay

Numerical studies were carried out to investigate the bearing capacity of spudcan foundations of offshore jack-up rigs in sand overlying normally consolidated clay by using the coupled Eulerian–Lagrangian (CEL) method. The hypoplastic model was used to describe the sand, whereas the viscohypoplastic model was used to describe the clay. The illustration of the development of the shear bands due to penetration revealed the failure mechanisms of a spudcan penetrating in loose – medium-dense – dense sand overlying clay. The influence of the density of the upper sand on the bearing capacity and “punch-through” failure mechanism as well as the effect of spudcan diameter were investigated. The bearing capacity profile has been distinguished with four phases: (I) mobilization of the peak shear value of the sand layer: the first peak value may be observed in this phase; (II) mobilization of the residual shear value of the sand layer: the second peak value may be observed at the end of this phase; (III) reduction of the shear resistance of the sand layer because of the disappearance of the Prandtl zone; (IV) punch in the clay layer: the resistance from the upper sand layer may be neglected.