Bearing capacity of strip footings on layered sands

In this paper we investigate the bearing capacity of strip footings resting on the top of a relatively thin layer of dense sand, which overlays a weaker sand layer. We use the Finite Element Limit Analysis method to calculate the collapse load and identify the geometry of the failure mechanism, as well as how this geometry changes with varying problem parameters. Results are benchmarked against published experimental data and methods used in practice for the design of working platforms for tracked plant, based on the punching shear model. The observed discrepancies are attributed to the development of a transitional mechanism when the bottom layer is rather dense, and the increase in the shear strength at the interface of the two layers is not abrupt. To cover this gap, we propose a new factor to calculate the bearing capacity in cases where a transitional mechanism will govern failure of the footing.