Reliability assessment of shallow foundations on undrained soils considering soil spatial variability

Structural design using partial safety factors aims at achieving an homogeneous safety level in geotechnical design without the use of more complex reliability analysis. In this work, the different Design Approaches proposed by Eurocode 7 for shallow foundations resting on the surface of undrained soils are compared in terms of the resulting reliability indices. The influence of both centered and eccentric loads, as well as homogeneous and heterogeneous isotropic and anisotropic distributions for the variability of soil properties were investigated in the reliability analysis. A finite element implementation of the upper bound theorem of limit analysis is combined with Latin Hypercube sampling to compute the probabilistic response of shallow foundations. Considering realistic probabilistic distributions for both permanent and live loads, First Order Reliability Method is used to calculate the reliability index of such structures designed according to the different Design Approaches present in Eurocode 7. The results obtained show that the Eurocode 7 leads to satisfactory reliability indices, but that significant differences between Design Approaches exist.