Bearing Capacity of Square Footing Resting on Layered Soil

Abstract

The prime focus of this article is to analyze the bearing capacity of a ring footing resting over sands, which is underlain by fully cohesive strata. The analyses are performed by using the axisymmetric lower bound limit analysis in conjunction with finite elements and non-linear optimization. The results are presented in the form of efficiency factor (ɳ); where, ɳ is defined as the ratio of bearing capacity of ring footing in presence of sand layer to the bearing capacity of ring footing placed over clayey layer alone. A rigorous investigation has been performed to understand the impact of the material strength, geometrical configuration, load magnitude and soil footing interface on the development of ɳ. It is found that even an inclusion of thin sand layer between the footing and clays improves the bearing capacity significantly. The detailed design charts are provided considering the footing roughness and the external surcharge pressure. Failure patterns are drawn for several cases.