Large Deformation Analysis of Strip Footing on Layered Purely Cohesive Soils

The bearing capacity of footings on layered soils has already received significant attention of researchers, however, most of the reported studies are limited to footings resting on the surface of soil, and are based on the assumption that the displacement of the footing is very small. In this paper, an approach developed by Hu and Randolph (15), which combines the Arbitrary Lagrangian Eulerian (ALE) approach and the finite element (FE) method, is adopted to allow the large penetration analysis of footings on layered soil. The FE configurations and ALE approach were verified by comparing the FE small deformation analysis results with available analytical and semi-empirical predictions, and the results of ALE large deformation analyses with available solutions for homogeneous soil.

Large deformation analyses of strip footings on strong-over-weak layered cohesive soils were carried out. The load-displacement curves and the bearing capacity factors predicted by the large deformation analysis are given in the paper. It is shown that during footing penetration, both the increased bearing resistance from the soil above the footing base and the decreased bearing resistance from the weaker bottom soil affect the overall bearing capacity. Bearing capacity factors are given for various cases of different layer thickness and different cohesion ratios for the two soil layers. Unlike the small deformation analysis for cohesive soil, it is found that the soil self-weight can have a significant effect on the bearing capacity in large penetration problems.