chapter  90
CPTu-based soil behaviour type of low plasticity silts
ByL.A. Torres-Cruz, N. Vermeulen
Pages 7

The application to low plasticity silts of two CPTu-based soil behaviour type charts proposed by Schneider and co-workers during the last decade is explored. One chart is based on tip resistance and sleeve friction (Q-F), and the other is based on tip resistance and dynamic pore water pressure (Q-U2). CPTu soundings made at two mine tailings deposits with a predominance of silt-sized particles were considered. The results indicate that the mechanical response of the CPT in these low plasticity silts can be indistinguishable from that of sands. As such, it is argued that the potential for misleading classifications can be reduced if the name of the ‘sands’ zone of the charts includes low-plasticity soils in general, regardless of fines content. Additionally, a new boundary for the drained zone of the Q-U2 chart is proposed to enhance the classification of loose or very compressible low-plasticity soils in which largely drained penetration is possible at low values of Q.