Large-scale experimental investigation of the installation of suction caissons in silt sand

Offshore wind power is a rapidly growing area of electricity in China. In the present paper, interaction mechanisms between the caisson for wind turbines and saturated silt sand are investigated with laboratory tests based on two different installation methods, jacking installation and suction installation. For the jacking installation process, the results indicate that the soil pressures inner and outer the skirt of the caisson vary with a similar feature and the magnitudes of the two are nearly balanced. The tip resistance plays a key role in the total jacking installation resistance. This paper examines the predictive performance of qc method and API approach for jacking installation resistance. It is demonstrated that the qc method provides better predictions. The resistance coefficients are recommended. For the case of suction installation, however, the changes of soil pressures inner and outer the skirt are contrasting. Specifically, the inner pressure and tip resistance fall dramatically, but the outer pressure increases when suction is applied. Seepage effect is found to be an important mechanism for the installation of suction caisson. The reduction ratios of the inner friction and tip resistance follow a power-function with the normalized suction. Based on the test results, a prediction method for the required suction has been developed and evaluated.