Simplified probabilistic state concept characterization of sandy soils and application to liquefaction resistance assessment

Abstract

Probabilistic relationships are developed for the simplified characterization of a sandy soil’s state within the state concept framework. The relationships require knowledge of conventional geotechnical characterization parameters (i.e., median particle diameter, fines content and particle shape) and in situ field data (i.e., SPT N1 values). The salient features of the proposed relationships are illustrated by comparing the reference and in situ states of Toyoura sand, obtained in laboratory tests, with those obtained from the simplified relationships. Sensitivity analyses are utilized to understand the uncertainties in the simplified relationships which have the most significant impact on common problems of flow liquefaction and cyclic mobility resistance of sandy soils. The presented results illustrate that uncertainty in the position of the steady-state line at zero confining stress is the most significant uncertainty in flow liquefaction assessment, followed by in situ void ratio, and slope of the steady-state line. Analyses using the simplified state concept relationships within an elastic-plastic constitutive model illustrate that the in situ relative density is the key uncertainty in cyclic liquefaction resistance. Finally, it is shown that the uncertainty in cyclic liquefaction resistance due to uncertainty in situ void ratio is largely consistent with that obtained from empirical predictions of cyclic liquefaction resistance.