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

This paper investigated cone penetration test end resistance under various drainage conditions in mixed soils through numerical simulations and piezocone experiments in laboratory testing chambers. The soil samples used in the laboratory tests contained various proportions of kaolin, silt, and sand. The piezocone tests were performed using a 10 mm diameter cone in consolidated soil samples. The measured variations of cone resistance and pore pressure at cone velocities varying from 0.005 mm/s to 30 mm/s are presented, which covered the full range from drained to undrained conditions. The cone resistance was evaluated using the spherical cavity expansion limit pressure predicted in Finite Element (FE) analyses that employed the NorSand (NS) constitutive model. The experimental and numerical findings allow assessment of the suitability of the normalised velocity (V) term, proposed by others, to unify cone resistances measured at variable rates.