Effect of inner skirts on soil plug formation and penetration behavior during bucket foundation installation

The installation processes of bucket foundations with linear skirt, cruciform skirts, and the inner bucket and cruciform skirts are simulated by establishing a large deformation analysis method. The soil flow mechanism and penetration resistance of foundations considering the strain softening and the strain rate effect are investigated. The calculation formulas for the equivalent height of the soil plug and the penetration resistance are given. The results show that the soil flow will result in gaps between the soil and the foundation skirt. The soil plug effect becomes more obvious as the number of compartments increases, and the plug volume ratio (PVR) serves as a useful indicator for predicting the equivalent height of soil plugs. The end bearing capacity factor remains nearly constant regardless of penetration depth, whereas the friction coefficients between the skirts and the soil vary due to soil flow.