The bearing capacity of foundations under combined loads is usually evaluated by using failure loci instead of the traditional limit bearing capacity formulae. In this paper, based on the assumption that foundations are simplified as footings on the surface of undrained twolayered clay soil with full adhesion between footing and subsoil, a series of numerical analyses for bearing capacity of strip foundations under V-H loading is performed by using general-purpose finite element analysis software ABAQUS. The effects of soil strength profile and loading combination on the failure envelopes and failure mechanism are investigated. Failure loci in V-H load space are presented and can be used to develop and improve the design of offshore foundations.
Offshore and harbor structures with large size are being built with unprecedented speed in coastal area with the increasing exploration and utilization of marine source and space, In contrast to onshore structures, offshore structures and harbor structures often encounter complicated geologic conditions and combined loading conditions. Besides the permanent vertical load (V) due to self-weight of structures, offshore foundations are also subjected to environmental forces, such as lateral force (H) and overturning moment (M), brought about by waves, currents and winds, and the effect of environmental forces is instantaneous or cyclic. As far as the calculation for bearing capacity of foundation under combined loading is concerned, Meyerhof (1953), Hansen (1970), Vesic (1975) and Bolton (1979) have done lots of researches and suggested semiempirical solutions. In these formulae, the decreases of vertical capacity resulted by eccentricity or inclination of loads are estimated by introducing eccentric distance or inclination factors, respectively. However these solutions do not satisfy the case in which foundation is subjected to forces composed of loads with a large scope of varying magnitude, and neither do the inhomogeneous foundations.
