Behavior of eccentrically loaded shallow foundations resting on composite soils

Abstract

Composite soils are a mixture of fine- and coarse-grained soil with a proportion that improves the density, permeability and strength properties of the mix. When the underlying soil does not provide adequate settlement and load carrying properties, composite soil as a cushion layer beneath the shallow foundation can be used. Thus, this paper investigates the influence of using gravel-clay and sand-clay mixture under the shallow foundation subjected to eccentric vertical load. Field investigations and experimental testing were first conducted to evaluate the in-situ soil properties and available fine- and coarse-grained material in Babol, Iran. Then, three-dimensional finite element method was employed to predict the behavior of the eccentrically loaded shallow foundation resting on the composite soil in terms of bearing capacity improvement BCI and normalized average settlement, Ravg of the foundation, based on the data collected in previous stage. According to the results, foundation over sand-clay mixture (SCM) showed a comparatively better performance in comparison with gravel-clay mixture (GCM). Ultimately, nonlinear regression technique was utilized to incorporate the effect of cushion layer in the relationship to calculate the bearing capacity reduction factor.