Studies on pullout capacity of anchors in marine clays for mooring systems

In marine applications, single point or spread mooring systems are used for providing temporary berthing of vessels. In this investigation, it is suggested that pile anchors and suction anchors can be used depending on the water depth. By testing a model, the influence of parameters like mooring chain inclination, consistency of the clayey soil in the seabed and anchor embedment ratios on pullout capacity has been brought out. Tests were carried out on single pile, 2-pile, 4-pile anchors made out of pipe piles of 25.4 mm dia with length to diameter ratios, L/DL/D of 10, 14 and 18 and model suction anchors (closed-top caisson) of 113 mm dia with L/D=2L/D=2, 3 and 4. These were installed in a model test bed made out of soft marine clay. The results indicate that in respect of pile anchors as of the chain inclination changes from horizontal to vertical direction, the pullout resistance shifts from passive earth pressure to skin friction. The results in respect of suction anchors can be interpreted in terms of various components proposed.