Piezocone Penetration Rate Effects in Transient Gold Tailings

Abstract

The drainage conditions during cone penetration is a critical factor in the assessment of tailing properties, as the sedimentation process produces deposits that are spatially variable, and often include materials in the intermediate permeability range. This paper provides evaluation for the parameters linking the rate of piezocone penetration to drainage effects in gold tailings. Cone soundings performed at penetration rates from .3 to 57 mm/s are compared and results are interpreted in a space that correlates dimensionless velocity, V, to piezocone normalized resistance, Q, and normalized pore pressure, U. A nonlinear poroelastic model conceived to capture the transient flow effects of the soil around an expanding cylinder has assisted in analyzing the measured behavior. Cone data from variable penetration rate soundings from other reported tests are also analyzed within the same framework to demonstrate that significant errors can occur in the interpretation of soil properties for soil conditions represented by normalized velocities, Vh, in the range of .1–1.. In tailings, a practical recommendation is to perform tests at different penetration rates in the same location, which allows appropriate nonstandard penetration rates to be selected according to these empirical observations and mathematical models.