Capacity of modified suction caissons in marine sand under static horizontal loading

Experimental and finite element analyses were conducted on the bearing capacities of modified suction caissons (MSCs) in saturated marine fine sand under static horizontal loading. Results show that the MSC can provide higher horizontal and moment bearing capacity and limit lateral deflection in comparison to a regular suction caisson. The bearing capacity of the MSC increases with increasing external skirt dimensions and the internal compartment aspect ratio, however, decreases with increasing the loading eccentricity. Several equations are proposed to calculate the maximum moment bearing capacities, which take the external skirt width, the internal compartment aspect ratio and the loading eccentricity into account. The deflection and the net earth pressure distribution methods are used to determine the rotation center position and these two methods are proved to be satisfactory. It is found that the rotation center moves downwards and forwards with increasing horizontal loading, then tends to be a stable position when the maximum load is approaching. The distance between the rotation center and the caisson lid at failure decreases with increasing external skirt dimensions, the internal compartment aspect ratio and the loading eccentricity. Based on the simulation results, an expression to estimate the combined capacity of the MSC was proposed.