Uniaxial Capacities of Sand-Filled Large Cylindrical Structures in Soft Foundation

Large diameter cylindrical structures are a kind of large-diameter thin-walled structures which are suitable for a verity of coastal projects such as embankments, breakwaters, wharfs and sea cofferdams. The amount of cylinder material per meter is independent of the cylinder diameter, and the bearing capacities of the structure, especially the horizontal and moment bearing capacities, increase with the increase of its diameter. This kind of structure is economic, reliable and easy to construct. In construction, multiple vibration hammers are installed at the upper part of the cylinder, and as the hammers vibrate synchronously, the soil adjacent to the cylinder wall is disturbed, allowing the large cylinder to sink under its dead weight. The prospect for applying this kind of structure in soft foundation is bright. However, due to the complexity of the interaction mechanism between the large cylinder, internal sand and saturated soft soil foundation, the bearing characteristics of sand-filled large cylindrical structures in soft foundation, especially the effect of the internal sand on the bearing capacities, are not clear. In this paper, the effects of internal sand filling height, foundation depth and soil undrained shear strength on the uniaxial capacities and the failure mechanism of sand-filled large cylindrical structures are studied via finite element numerical analysis. Meanwhile, uniaxial capacities of sand-filled large cylindrical structures are compared with those of suction bucket foundations and non-sand-filled large cylindrical structures in identical conditions. In addition, approximating expressions for calculating the bearing capacities of sand-filled large cylindrical structures are proposed to provide reference for the design of such structures.