Flow Liquefaction Instability as a Mechanism for Lower End of Liquefaction Charts

The state-of-the-practice uses the "simplified procedure" for evaluating liquefaction susceptibility of soils. Based on this procedure, liquefaction charts have been developed that correlate soil resistance to earthquake-induced stresses. These charts are based on case histories of past earthquakes and have proven to be useful while evaluating liquefaction susceptibility at a new site. However, these charts are inherently empirical, which makes extrapolation into regimes with insufficient data difficult. In addition, they do not inform an engineer about the effects of liquefaction. This work hypothesizes that the lower end of liquefaction charts corresponds to soils that are susceptible to unstable flow liquefaction. A numerical investigation is undertaken, the results of which support this hypothesis. This implies that if test data at a new site correspond to the lower end of liquefaction charts, then the site may be susceptible to flow liquefaction. This in turn could provide an engineer with some predictive power regarding the effects of liquefaction. (C) 2017 American Society of Civil Engineers.