Research On Uplift Capacity Of Spud Foundation For Jack-up Self-elevating Drilling Platform

Soft soil condition, especially in Bohai, may cause spud foundation punch-through failure which may be a major cause of foundation failure of jack-up self-elevating drilling platform. The safe usage of jack-up depends on the smooth penetration, effective working and easy uplift. The latest part would be the subject in the dissertation. The chief aim of this study is to investigate the uplift behavior with the different soil condition and spud foundation shape by theory analysis and numerical simulation.A review of the existing domestic and oversea studies relating to the uplift of spud foundation has been presented. Then various parameters controlling the resistance force has been analyzed and discussed during spud foundation uplifting as well as the classic formulation and experience formulation on uplift resistance are given in the paper. The pulling up process of jack-up spud foundation is simulated by commercial FEM software ABAQUS. Considering spud foundation-soil interaction, initial earth stress and soil boundary effect .etc, ABAQUS is used to calculate the maximum of pulling-up force by Mohr-Coulomb elastic-plastic soil modeling. Many parameters including the soil parameters such as Young's modulus E and cohesive shear c, and spud foundation parameters such as diameter D and upper slope angle, as well as penetration depth d, which effect the uplift resistance of spud foundation, have been discussed and relative curves about relationship between theses parameters have been plotted in the paper.Meanwhile, soil is considered as saturated porous cohesive media so that the liquid-solid coupling is used to simulating the pulling up process of spud foundation by ABAQUS. Comparing the former result, the uplift force is greater because the mud suction force, which is developed by different change of pore pressure beneath spud foundation. The suction force, compared the total uplift resistance, is given as well as the relationship between suction force and cohesive shear c.At last, the spud foundation of Bohai No.5 jack-up unit is analyzed by the comparison between theory analysis and numerical simulation. As a result, the numerical model is practical and effective, which is a useful tool to calculate the uplift force of spud foundation for jack-up self-elevating drilling platform.