Bucket foundation has broad application prospects in marine engineering as a competitive foundation. By providing internal cylindrical and cruciform skirts inside the bucket foundation,. the performance of the bucket foundation can be improved . But penetration resistance will also increase. However, few large deformation numerical analysis is carried out to simulate the penetration process of the bucket foundation with internal skirts.
In this paper, three-dimensional large deformation finite element (LDFE) models for bucket foundations with and without internal cylindrical and cruciform skirts considering strain softening effect of soft soil were established using the coupled Eulerian-Lagrangian (CEL) approach. It was found that the elevation of the soil surface inside the bucket is higher than that of initial soil surface when the penetration depth ratio is relatively small for the bucket foundation with internal cylindrical and cruciform skirts. However, with increase of the penetration depth ratio, the increased frictions on the cylindrical and cruciform skirts drive the soil inside the inner cylinder downward, and the elevation of the soil surface inside the inner cylinder is lower than that of initial soil surface. It is also lower than that of soil surface between outer and inner cylinders. The average lateral friction per unit area on each skirt decreases from outer to inner skirt. The soil flow can explain well for the evolution of the penetration resistance.