Engineers Australia

Rate effects in centrifuge piezocone penetration on dilatant silica silt and subsequent dissipation

Marcelo F. Silva

Abstract

Centrifuge testing on industrial silt-sized silica particles was performed to investigate the possibility of using variablerate piezocone tests to gain additional data in soils. In order to perform partially to fully drained piezocone tests in the saturated silica samples, a careful combination of penetration rates, probe diameter and coefficient of consolidation of the centrifuge samples was assigned. The piezocone tests were then performed at 50g with a 12-mm diameter piezocone at different penetration rates. Measurements of excess pore pressure ∆u in the samples allowed the assessment of the radial distribution of pore pressure during penetration, where the tendency for the silica flour to dilate was observed. In general, negative values of ∆u were measured near the piezocone, whilst positive ∆u values were measured in the far field. The data were then used to describe the behaviour of dilatant soils with increasing penetration rate of the probe, and its shortcomings in the soil penetration.