Probabilistic Post-Liquefaction Residual Shear Strength Analyses of Cohesionless Soil Deposits: Application to the Kocaeli (1999) and Duzce (1999) Earthquakes

Liquefaction of granular soil deposits can have extremely detrimental effects on the stability of embankment dams, natural soil slopes, and mine tailings. The residual or liquefied shear strength of the liquefiable soils is a very important parameter when evaluating stability and deformation of level and sloping ground. Current procedures for estimating the liquefied shear strength are based on extensive laboratory testing programs or from the back-analysis of failures where liquefaction was involved and in-situ testing data was available. All available procedures utilize deterministic methods for estimation and selection of the liquefied shear strength. Over the past decade, there has been an increasing trend towards analyzing geotechnical problems using probability and reliability. This study presents procedures for assessing the liquefied shear strength of cohesionless soil deposits within a risk-based framework. Probabilistic slope stability procedures using reliability methods and Monte Carlo Simulations are developed to incorporate uncertainties associated with geometrical and material parameters. The probabilistic methods are applied to flow liquefaction case histories from the 1999 Kocaeli/Duzce, Turkey Earthquake, where extensive liquefaction was observed. The methods presented in this paper should aid in making better decisions about the design and rehabilitation of structures constructed of or atop liquefiable soil deposits.