Bearing Capacity Equation for Shallow Foundations on Unsaturated Soils

For shallow foundations resting on unsaturated soils, matric suction increases effective stresses, resulting in enhanced bearing capacity. However, this boost in bearing capacity is ignored in practice for the sake of simplicity, thus compromising economy. That is why this study aims to consider the beneficial effect of unsaturated conditions on bearing capacity. This is achieved by applying limit analysis using the finite element method on unsaturated soils and investigating the problem parametrically for shallow foundations. The suction effect is taken into account in the formulation of the limit analysis based on effective stress principle. The numerical outcomes are verified by comparing them with available experimental data from the literature. The findings from the parametric study emphasize that the influence of suction on bearing capacity is determined by the friction angle. Moreover, the effects of a varying suction profile are contingent on the foundation width. Based on the results derived from the numerical analyses, a modified bearing capacity equation is introduced. This equation showcases a very good coefficient of determination, effectively encompassing the effects of the soil suction profile. Consequently, the proposed procedure can be considered as a convenient yet precise tool for estimating bearing capacity in engineering practice.