Effect of Spatial Variability of Soil Properties on Bearing Capacity of Strip Footing under Fuzzy Uncertainty

Abstract

The present study investigates the effect of spatial variability of soil parameters on the probability of failure of strip footings against bearing pressure resting on a homogeneous and two-layered soil system. The uncertain parameters (soil properties) are considered as fuzzy variables described by a triangular membership function. To incorporate spatial variability in reliability analysis, both isotropic and anisotropic scales of fluctuation are considered in the numerical simulation. Several design charts (in terms of failure probability) are presented for soil deposits having different friction angles under both isotropic and anisotropic field conditions. Variation of the probability of failure with different coefficients of variation (COVs) of soil internal friction angle is also examined. Scales of fluctuation or spatial correlation lengths are also varied within a wide range to identify the effect on the probability of failure. For a homogeneous soil stratum, results reveal that the difference in the failure probability can increase up to 53% for the variation of COV of soil friction angle and scale of fluctuation. It was also found that the effect of spatial correlation length is significant up to a certain distance which is a function of width of the footing, but beyond that, the effect is negligible.