2022 H. Bolton Seed Memorial Lecture: Evaluating Liquefaction Effects

Abstract

The potential effects of soil liquefaction at level ground sites should be evaluated through examining soil element responses of the individual soil layers and system responses of the soil deposits they form. The cyclic responses and postliquefaction volumetric strain of uniform clean sand, sandy gravel, nonplastic silty sand, and nonplastic silt at the element level can be captured in a unified manner using relative density or the state parameter. The depositional environment should be characterized because geologic details, such as soil fabric, which can be discerned through detailed logging of high-quality continuous sampling, are important in evaluating liquefaction effects. Effective stress analysis enables soil system responses that govern the effects of liquefaction, including the formation of ejecta, to be investigated. A calibrated cone penetration test (CPT) procedure employing the liquefaction ejecta demand parameter captures key aspects of system response and provides an estimate of ejecta-induced building settlement. A probabilistic CPT-based procedure for estimating postliquefaction ground settlement is developed using laboratory and field case history databases. Correlations are developed to estimate Dr or ψo to enable use of the laboratory-based volumetric strain models. Adjustment factors enable the procedure to capture field observations of postliquefaction ground settlement. The proposed ground settlement procedure is combined with shear and ejecta-induced settlement procedures to estimate liquefaction-induced building settlement.

Topics & Concepts