Estimating the Severity of Liquefaction Ejecta Using the Cone Penetration Test

Abstract

A cone penetration test (CPT)-based procedure to estimate liquefaction-induced ejecta severity is developed. The liquefaction ejecta demand parameter (LD) captures the amount of upward seepage pressure that can produce artesian flow due to elevated excess hydraulic head, and the crust layer resistance parameter (CR) captures the strength and thickness of the nonliquefiable crust layer. The procedure is examined using 176 well-documented field case histories consisting of thick, clean sand, and stratified silty soil sites in Christchurch. LD tends to increase systematically as ejecta severity increases at the thick, clean sand sites, and low LD values are estimated at stratified soil sites that did not produce ejecta, which resolves the apparent overestimation by other liquefaction indices at stratified soil sites. CR improves the reliability of the procedure by differentiating the performance of sites with and without a competent crust layer overlying a thick liquefiable layer with a high LD value. The proposed LD–CR liquefaction ejecta severity chart separates cases with severe or extreme ejecta, which have high LD and low CR values, from cases with minor or no ejecta, which have low LD and high CR values.