Undrained pullout capacity of modified suction caisson in clay by finite element limit analysis

The modified suction caisson (MSC) adds a short-skirted structure around the regular suction caisson to increase the bearing capacity and limit deflection. In this study, the undrained pullout capacity of MSC in nonhomogeneous clay with shear strength increasing linearly with depth was investigated using the finite element limit analysis. An implicit dimensionless pullout bearing capacity factor was proposed by considering the effects of adhesion factor alpha of the soil-suction caisson interface, embedment ratio d/l, diameter ratio D/d, and embedded length ratio L/l. Results indicate that the MSC can effectively provide a higher undrained pullout capacity. The tends to increase with increasing the embedment ratio d/l, diameter ratio D/d, and embedded length ratio L/l, and to decrease with increasing the adhesion factor alpha of the soil-MSC interface. A theoretical method of calculating the pullout capacity of the MSC was also proposed in terms of the vertical static force equilibrium.