Bearing capacity of circular footing on sand: A critical state approach

Abstract

There has been extensive research into the bearing capacity of circular footing under vertical centric load. Although the scatter values for the bearing capacity factor Nγ that have been suggested by different methods, the classical solution is still being widely used in the design codes. Sand particle morphology, footing diameter D, mean effective stress level pˊ, and sand relative density Dr, are some of the variables influencing the surface footing bearing capacity in sandy soil. Different sands may have various mobilization friction angles and, thus, various stress-strain responses, although they may have the same relative densities Dr and mean effective stresses pˊ. Therefore, it is possible that estimating bearing capacity factors based on peak friction angle may not accurately reflect the actual bearing capacity. In the current study, a three-dimensional finite element model (3D-FEM) was utilized. Hypoplastic sand model has been used to simulate sand behavior. It can effectively simulate the compression and shear behavior of sands over a broad confining pressure and density range. The model has been validated using experimental centrifuge and one element tests available in literature. Critical friction angle ϕcr has been considered as a shear strength parameter that is independent on pˊ and Dr. Further research is done using parametric analysis. The main objective is to assess the expected bearing capacity factor Nγ of various sand characteristics and to offer a solution that can be valid for a wide range of sand properties.