Design of shallow footings on heavily overconsolidated clays

This paper presents an integrated bearing capacity–settlement approach to the design of shallow foundations on heavily overconsolidated clays by alterations of the “modified Cam clay” (MCC) model. The bearing capacity of soils and their settlements from loads imposed on shallow footings have been studied extensively. Yet, there is no consensus on a method that provides both reliable load-bearing capacity and settlement predictions. Current methods treat the soil under shallow footings as different ideal materials for the purpose of calculating the bearing capacity and settlement. The method proposed in this paper treats the soil as a single ideal material for both bearing capacity and settlement. The MCC model is tailored by adding Hvorslev’s findings on overconsolidated clays and delineating stress states that bring the soil to tensile failure from those that cause it to yield or behave elastically or to show discontinuous response. A limiting stress surface is established as defining a limiting bearing capacity. A heavily overconsolidated clay is assumed to behave elastically if its stress state is below the limiting stress surface. Predictions from the method proposed in this paper compare favorably with model tests and field test results. Examples are provided illustrating how to use the proposed method.