Resistance of Caisson Tip with Internal Bevels for Suction Caissons Penetrating into Clay

Abstract

Suction caissons with internal bevels at the caisson tip can effectively reduce resistance to make them to penetrate into the seabed easily. This paper describes the failure mechanisms of the soil at the caisson tip with internal bevels during suction-assisted penetration. The theoretical solutions to the bearing capacity factors Nc and Nγ are deduced in terms of the caisson tip geometry ratio of the flat section of the caisson tip to the caisson wall thickness (m/t), the inclination angle (δ) of the internal bevel from the horizontal, adhesion factors (αi) along the inside and (αb) at the base of the caisson tip. The influences of the caisson tip geometry ratio, the inclination angle, and the adhesion factor on the bearing capacity factor Nc are investigated under two limit conditions with smooth and rough bases of caisson tip. Theoretical results indicate that the factor Nc increases with increasing caisson tip geometry ratio, adhesion factor, and decreasing inclination angle. In particular, factors Nc of the caisson tip with rough base are greater by 0.57 than those with a smooth base. Furthermore, factors Nc of the flat caisson tip (m = t) are greater by 2δ than those with full internal bevel (m = 0). Finally, the required suction to install the caissons was obtained through the force equilibrium in the vertical direction. The numerical simulation and experimental results are used to verify the rationality of the presented failure mechanisms and theoretical results.