Numerical analysis of the effect of penetration rate in piezocone tests on silty soils

Resumo

Partial drainage is a relevant effect in piezocone tests (CPTu) performed on geomaterials with
intermediate permeability, such as silts and mine tailings. However, the penetration rates that cause partial drainage
vary for each material. Thus, to investigate the effects of the cone penetration rate on different geotechnical
properties, numerical simulations of cavity expansion were performed. The Cam-Clay model was used, and the
parameters of strength (M), stiffness (κ and λ), and permeability (k) were varied for different cone penetration
rates. The material studied was silt from the Yellow River Delta (China) through the tests performed in centrifuges
by several authors. With the results of the numerical simulations, it was possible to obtain the theoretical drainage
curves of the material, which indicate the penetration velocities that trigger partial drainage. Sensitivity analysis
demonstrated the large effect of the friction coefficient on the drainage curve, the increase in soil stiffness leads to
a decrease in penetration rates and the alteration in the material permeability does not change the magnitude of the
resistance and excess pore pressure generated. The comparison with experimental centrifuge results indicated good
agreement of the numerical analysis.