Numerical study on the suction force of jack-up mat foundation on marine clay seabed

Abstract

A deep layer of soft clay is widely present on the seabed in the offshore area of China. The traditional jack-up spudcan faces the problem of difficult insertion and extraction in clay seabed. Jack-up mat foundation is more suitable in soft clay than spudcan for its lower requirements on bearing capacity. Due to the poor permeability of clay, the uplifting process of the mat foundation needs to overcome a large soil suction force. In this study, three-dimensional numerical model is established to investigate the suction force of jack-up mat foundation on marine clay seabed. The elastoplastic constitutive model, which can describe the structural and over-consolidation of soft marine clay seabed, was embedded in commercial software ABAQUS through UMAT subroutine. The cohesive contact model was adopted to stimulate the interaction between mat foundation and the seabed soil. Field test was conducted to verify the accuracy of the numerical model. Then, the effects of degree of over-consolidation, degree of structural, depth of clay, interface stiffness and eccentric uplift loading on suction force are studied in detail. Numerical results show that the effects of degree of over-consolidation and structural of soil have significant influence on the suction force. The suction force first increases rapidly and then decrease gradually as the thickness of the upper dimensionless clay layer increases. With the increase of the uplift eccentricity, the suction force reduces continuously.