The relation between the state indices and the characteristic features of undrained behaviour of silty sand

Abstract

The characteristic features of a series of isotropically and K0-consolidated undrained triaxial compression behaviour of a silty sand were investigated for a range of initial void ratio (e) and mean effective confining stress (p′). The silty sand used in this study contained about 10% natural fines. The critical state line (CSL) of K0-consolidated specimens, K0U was slightly lower than the CSL for isotropically consolidated specimens, CIU. The respective CSLs for K0U and CIU were used to define state indices, such as state parameter (ψ), state index (Is), state pressure index (Ip) and modified state parameter (ψm), within critical state soil mechanics (CSSM) framework. It was found that each state index exhibit a unique relation with liquefaction potential, irrespective of consolidation type, however different relationships were observed between state indices and the stress ratio at the triggering of liquefaction, ηIS or the liquefaction resistance, qIS. The correlation of characteristic features of undrained shearing (i.e., liquefaction potential, ηIS and qIS) and drained shearing (maximum rate of volume change, dεv/dεamax) with state indices were compared statistically in terms of root mean square deviations (RMSD). All characteristic features of undrained shearing generally showed the best correlation with Ip in term of RMSDs, however ψ showed comparatively wider scatter for the specimens showing flow and limited flow behaviour.