Influence of drainage conditions and monotonic preloadings on the monotonic behavior of Karlsruhe fine sand

This article presents the results of an experimental program aimed at evaluating the difference between undrained and drained maximum mobilized friction angles at identical initial densities and initial mean effective stress states, as well as the influence of monotonic preloadings on the monotonic behavior of Karlsruhe fine sand. For this purpose, a series of monotonic triaxial tests was performed considering different initial densities, preloading types and drainage conditions, such as drained, undrained and combinations of these within the same test. The experimental results suggest that under triaxial conditions, the drained maximum mobilized friction angle is up to \(10^{\circ }\) larger than the corresponding undrained maximum mobilized friction angle. Furthermore, the results reveal that monotonic drained preloadings lead to significant differences in the subsequent undrained monotonic response. The capabilities of two advanced constitutive models for sands to reproduce the experimental observations were evaluated. With this aim, the models were calibrated using conventional monotonic and cyclic triaxial tests. Without any parameter adjustments, the model predictions were then inspected for samples subjected to monotonic preloading or shearing under different drainage conditions.