Developing a Constitutive Model Considering Fabric Anisotropy Under Monotonic Undrained Loading

Developing a constitutive model for granular material under undrained condition is becoming more popular nowadays because granular materials behave differently under different loading conditions. There have been many studies on the current soil material model. However, most of these soil constitutive models have some drawbacks such as that these soil models can describe the granular materials under certain loading conditions, input parameters used in the model must be adjusted, and the fabric anisotropy evolution is not developed properly. In this study, a soil material model is developed based on an effective and popular constitutive model and focuses on overcoming the obstacle where the Poisson’s ratio is adjusted from experiments to fit the laboratory loading curves and the fabric anisotropy in the model is not evolved properly. This developed model will use the actual Poisson’s ratio of the soil, and the fabric anisotropy evolution will be developed. By comparing the simulation results of the original model and the developed model with the experimental results, we observed that when using the experimental value of Poisson's ratio, the developed model can overcome the underestimation of the dilatancy under undrained condition. These results play an important role in the development of a constitutive model of granular behaviours, allowing researchers to further improve the developed model to be able to simulate other granular behaviours.