Abstract

Variable penetration rates during CPTu may impact cone readings through partial consolidation during penetration but also through viscous soil skeleton behaviour. The latter phenomenon is characteristic of dynamic penetrometers during fast penetration in fine-grained materials where tip resistance increases when the penetration rate increases. In this work, the effect of viscosity on piezocone penetration is investigated based on the numerical simulation of CPTu and triaxial tests using the application G-PFEM and a viscoplastic version of the Clay and Sand Model (CASM). The study highlights that the CPTu results are sensitive to the material parameters controlling viscosity, thus requiring careful calibration in order to obtain realistic CPTu simulations.

Abstract

Most natural clays acquire an anisotropic fabric upon deposition. This anisotropic fabric induces differences in the soil mechanical responses, for instance in the undrained shear strength observed in the laboratory. It is unclear how much of that anisotropy is reflected on the responses measured by the cone penetration test. In this work, we use GPFEM to numerically simulate cone penetration tests (CPTu) in undrained, anisotropic clays. The constitutive response is represented by S-CLAY1, a critical state, anisotropic model. Full details of the representative stress path during CPTu insertion are provided. Preliminary numerical results suggest that even a large amount of anisotropy, as described by the model, will have a very small effect on the cone responses. The numerical simulation results also show that the prevailing stress path has strong similitudes with that found during anisotropically-consolidated undrained compression triaxial test.