Bearing capacity of plane-strain footings on layered soils

A study has been carried out of the bearing capacity of sand layers overlying clay soils for the case where the thickness of the sand layer is comparable to the width of a rigid foundation placed on the soil surface. A review of previous work is given and a discussion is presented of the dimensionless groups that govern the behaviour of this type of foundation. A parametric study is carried out using both finite element and finite difference methods. This study is based on the use of soil parameters obtained from an assessment of the range of values that might be expected to be appropriate for fun-scale structures. The results of the parametric study are used to illustrate the mechanics of the system and also to develop charts that may be used directly in design. In particular, the results illustrate that the shear strength of the clay has an important influence on the mechanisms of load spread within the fill.