Influence of spatial variability of soil elastic modulus on elastic settlement of rectangular footing under fuzzy uncertainty

摘要

It is quite unlike having a uniform soil stratum in-situ because of various methods of formation of the soil over depth. Different depositional processes make the soil nonhomogeneous and more commonly a material (soil) with inherent variability, which necessitates considering inherent soil variability in line with the reliability assessment of geotechnical structures. Therefore, in this paper, an attempt is made to assess the reliability of elastic settlement of rectangular footing resting on both homogeneous and layered cohesionless soil strata using the fuzzy set theory coupled with the finite element method. The elastic modulus of the soil is assumed as a fuzzy variable following the triangular membership function. Moreover, spatial variability of soil elastic modulus is considered for both isotropic and anisotropic scales of fluctuation. Analyses are carried out for both homogeneous and layered (stronger layer underlain by a weaker layer) soil medium. A parameter indicating the required limiting settlement to achieve zero probability of failure is proposed, and a number of design charts are presented for different aspect ratios of footing and scales of fluctuation of soil elastic modulus. Results reveal that the increment in the failure probability is observed as the aspect ratio of footing increases. It is also noticed that the anisotropic scale of fluctuation always predicts conservative results in terms of foundation safety.