This paper reports an experimental study and subsequent constitutive modelling focused on the stress-strain and volumetric response during deviatoric stress application of a partially saturated clayey-silt. The material was statically and isotropically compacted at constant water content towards a pre-defined pre-consolidation stress. A series of strain-controlled triaxial compression tests on a state-of-the-art device and isotropic experiments are presented and discussed. All of the experiments started at the same stress state (i.e., identical matric suction and mean net stress) and were conducted at the same constant suction. Several stress paths under isotropic conditions (i.e., drying/wetting, loading/unloading and wetting/drying) were followed to induce different over-consolidated states before shearing the specimens. The test results are initially interpreted using the elastoplastic Barcelona Basic Model (BBM). Independent tests were selected to determine the model parameters associated with the volumetric behavior of the soil. The BBM was not able to capture the dilatant behavior observed during shearing in all the samples. An enhancement of the BBM is proposed in this work, which consists in including a more general hardening law and sub-loading concepts. Main capabilities and limitations of original BBM and enhanced model are discussed and compared. The modified BBM was able to handle the dilatancy features observed in the experiments and provided a more realistic description of the experimental stress-strain behavior.

Peer Reviewed