Advanced numerical modelling of footings on granular soils

Traditionally the analysis of footings on the surface of granular soils using finite elements has been difficult. This has generally led to a noticeable lack of published work in this area, especially for rough footings situated on the surface of granular soils with friction angles greater than 35°. The majority of published work has concentrated on the use of simple elastic perfectly plastic soil models, due to the computational difficulties and run times involved. In the present study a combined multi-surface isotropic & kinematic hardening model is used to study the behaviour of foundations on granular soils. The model gives a much more realistic account of material behaviour and therefore advances the state of the art in this area. The paper confirms the work of De Beer in which a reduction in N? was observed for increasing foundation widths. The paper highlights problems due to the development of singularities adjacent to the footing edge and confirms earlier work, using a simpler model, on the influence of the element depth under the footing on the computed bearing capacity. The paper concludes by presenting the allowable bearing pressures for three different sands as a function of the footing width.