Model tests on penetration and seepage behaviors of a scaled suction caisson in sand

This study presents a new type of the offshore mooring foundation named as a scaled suction caisson (SSC), of which concept is inspired from the kinetic function of the scaled skin of snakes. When the SSC penetrates into the soil, the penetration resistance effectively decreases due to decreasing the friction force between the soil and sidewall. However, the bearing capacity increases due to increasing the friction force between the soil and sidewall when the SSC is subjected to pull load. A series of the suction-assisted installation model tests are carried out to investigate the penetration and seepage behaviors of the scaled suction caisson in sand. The result indicates that penetration resistance of the SSC increases with decreasing the aspect ratio H1/D1 of the scale structure. For example, when the aspect ratio H1/D1 equals 10, the penetration resistance decreases by 3.1% compared with the traditional suction caisson. And as the aspect ratio H1/D1 decreases from 10 to 5, the penetration resistance increases by 9.9%. In spite of these cases, it shows that reasonable selection of H1/D1 is helpful or not an obstacle to penetration. Furthermore, it is found that the height of the soil plug effectively decreases by the intermittent suction-assisted installation. The formula of calculating the penetration resistance of the SSC during suction-assisted installation is presented in terms of the excess pore water pressure distribution inside and outside the sidewall. The calculation results agree well with the model test results, indicating that the proposed formula of calculating the penetration resistance is reliable.