Modelling the static liquefaction of sand with low-plasticity fines

Abstract

There have been significant advances in understanding of the effect of fines content, fc, on the mechanical response of sand with fines. The concepts of equivalent granular void ratio, e*, and equivalent granular state parameter, ψ*, which were developed for sands with fines, can be used in lieu of e and ψ to provide a unifying framework for characterising the undrained response of sands with low-plasticity fines, irrespective of fc. In addition, a recently developed constitutive model was able to capture the influence of both density, using e, and stress states on the stress–strain responses of clean sand under drained or undrained shearing with one set of parameters. This was achieved by rendering dilatancy and peak-failure stress ratio functions of ψ. The present work combines these two powerful unifying propositions, and by merely substituting e* and ψ* for e and ψ into the equations of the aforementioned model for clean sands, obtains a constitutive model for sand with fines that can capture the influence of fc, irrespective of density and stress states. The model-specific parameters were obtained from a few drained tests at a single fines content. Undrained responses for a range of fc and densities, with particular emphasis on liquefaction behaviour, were then predicted. For flow behaviour, the predictions agree well with experimental observations over a wide spectrum of initial conditions. The quality of the predictions reduces for limited flow behaviour. For non-flow behaviour, significant deviations were observed.