Estimating the Severity of Liquefaction Ejecta Using the Cone Penetration Test

A cone penetration test (CPT)-based procedure to estimate liquefaction-induced ejecta severity is developed. The liquefaction ejecta demand parameter (L-D) captures the amount of upward seepage pressure that can produce artesian flow due to elevated excess hydraulic head, and the crust layer resistance parameter (C-R) 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. L-D tends to increase systematically as ejecta severity increases at the thick, clean sand sites, and low L-D 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. C-R 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 L-D value. The proposed L-D-C-R liquefaction ejecta severity chart separates cases with severe or extreme ejecta, which have high L-D and low C-R values, from cases with minor or no ejecta, which have low L-D and high C-R values. (C) 2021 American Society of Civil Engineers.