Undrained bearing capacity of spatially random soil for rectangular footings

In this study, a new approach for the evaluation of the 3-D random bearing capacity in rectangular footings is described. The soil strength spatial variability is modelled by random fields. Those fields are discretized via Vanmarcke’s spatial averaging approach to single random variables, which correspond to particular slip surfaces or volumes (energy dissipation regions). A series of numerical analyses is performed for a variety of foundation shapes and isotropic and anisotropic correlation structures for soil strength parameters. The results show that the consideration of three-dimensional cases for relatively long foundations offers significantly lower bearing capacity coefficients of variation. Thus, its impact on reliability assessments is crucial. The worst case correlation length for the bearing capacity mean values is observed and discussed.