Ultimate Limit States of Foundation on Random Unsaturated Soils

This paper investigates stochastically the case of a shallow foundation resting on unsaturated heterogeneous soil under rainfall infiltration. Porosity is assumed to vary spatially while other soil parameters are constant. The study employs Monte-Carlo analysis to estimate numerically probabilistic bearing capacity and rotation (represented by off-centred rotating moment) in ultimate limit states. Bearing capacity failure is induced by constant rate strain loading until a sufficient number of elements fail to form continuous shear bands. While off-centred rotating moment is the result from the same loading process due to the simultaneous effects of partial saturated condition and spatial variability of porosity. The study shows that the average of the bearing capacity varies marginally in ultimate limit states as the soil becomes more variable (i.e. increasing coefficient of variation). As the soil becomes more correlated with correlation length between 50 and 200% of the foundation width, there are no apparent changes in the mean and standard deviation of the ultimate bearing capacity. The off-centred rotating moment is maximum when the correlation length is equal to the foundation width.