Flow Liquefaction Assessment of a Sensitive Glaciolacustrine Deposit in Northern Ontario

ABSTRACT: Loose, saturated non-plastic silt is known to be susceptible to flow liquefaction. The Cone Penetration Test (CPT) is widelyused to evaluate the state parameter and to check the flow liquefaction susceptibility of natural soil or tailings. In this study,a series of field investigations consisting of CPTs, Seismic Cone Penetration Test (SCPT), and boreholes was carried outto check the flow liquefaction susceptibility of a saturated, non-plastic, and highly sensitive glaciolacustrine deposit in thefoundation of a tailings management facility dam in Canada. The critical state line (CSL) of this deposit was determined bycarrying out a series of triaxial tests. The flow liquefaction potential of the silt deposit has been assessed using sevendifferent methods that interpret the CPT basic parameters and a method that considers soil water content test results. Ofthe methods developed for the CPT basic parameters, two methods are based on CPT cone resistance only, while the fiveother methods use both CSL parameters and CPT cone resistance. The method developed based on water content testresults uses both CSL parameters and in-situ water content, which correlates with void ratio. NORSAND constitutive modelcalibration and CPT widget calculations were performed to determine CSL parameters. The state parameter was estimatedfor all seven methods that utilized the CPT basic parameters as well as the water content method and the results werecompared. Excess pore water pressure generation due to CPT advancement was also considered and compared for thevarious methods. The liquefaction assessment indicates that, while results of some methods are reasonably close, therecan be considerable differences between the results of some other methods. Accordingly, liquefaction assessments thatconsider one or two methods only, may result in an unconservative or overconservative geotechnical design. The findingsof this paper highlight the importance of using engineering experience and judgment to correctly assess the soil flowliquefaction potential in geotechnical projects.