Application of limit analysis in unsaturated soils: Numerical and experimental study of bearing capacity

Computational Limit Analysis (CLA) is a tool that has found significant application in conventional geotechnical engineering. This paper presents work in progress that extends the CLA method, Discontinuity Layout Optimization (DLO), to account for the effects of partial saturation on strength, by adopting an effective stress equation that accounts for suction and degree of saturation. The modified analysis is then used to model a simple bearing capacity problem and is compared with laboratory model tests. These tests provided load-deflection data for a range of soil saturation scenarios and also soil displacement data using Particle Image Velocimetry (PIV). The experimental results demonstrated that 3-fold changes in bearing capacity could be achieved across the modelled water levels. Comparison of the numerical and experimental data shows reasonable agreement indicating that the bearing capacity strength enhancement first rises as suctions in the soil increase but then subsequently diminish as the degree of saturation starts to fall.