Probabilistic undrained bearing capacity of shallow foundations under combined loading in three-dimensional spatially variable soils

Shallow foundations are widely employed in offshore engineering. However, there is a limited number of studies that investigate the probabilistic undrained bearing capacity of shallow foundations in three-dimensional space. This study utilize random finite element method to explore the probabilistic undrained bearing capacity of skirted circular foundations in three-dimensional spatially variable soils. Results show that the failure mechanism under vertical loads can vary dramatically in the presence of spatial variability, while its effect on the failure mechanism under horizontal loads or moments is minimal. The variation of stochastic uniaxial capacities becomes larger with increasing coefficient of variation of soil strength and scale of fluctuation or decreasing embedment ratio. The probabilistic failure envelopes are affected by embedment ratio and soil heterogeneity index in terms of the shape and size, while the probability level and random field parameters mainly have an impact on the size rather than the shape of the failure envelopes. The application of the expressions describing the failure envelopes in different normalised loading planes was demonstrated through an example.