Fabric Effects on Strip Footing Loading of Anisotropic Sand

Abstract

The effects of sand fabric anisotropy on the response of vertically loaded rigid strip footings were numerically investigated with the use of a bounding surface constitutive model developed within the premises of anisotropic critical state theory. In agreement with pertinent centrifuge test results that were successfully simulated, this paper showed that if the strip footing rests on a sand with a horizontal deposition plane, smaller footing settlements, higher bearing capacity and a wider and deeper failure mechanism are observed, compared with those that appear if the same sand (at the same relative density) has its deposition plane rotated to the vertical direction. Anatomy of the experimentally verified numerical analyses revealed that these differences in footing response are governed mostly by the anisotropic behavior of the sand located under the footing, which is significantly stiffer and more dilative under vertical load when its deposition plane is horizontal rather than vertical. Regardless of initial fabric anisotropy, the development of a distinct failure mechanism is progressive and requires significantly more footing settlement than that for the ultimate (maximum) bearing capacity. In practice, neglecting fabric anisotropy effects may lead to significant overestimation of the ultimate bearing capacity of footings on sand.