Undrained shear strength for liquefaction flow failure analysis

Abstract

An important factor in evaluating the stability of hydraulic fills against flow sliding is the undrained steady-state strength mobilized in the field. This paper proposes an empirical relationship between three factors: the undrained strength back-calculated from fills that failed by flow sliding, equivalent clean sand normalized blow-count values, and soil-specific parameters from steady-state laboratory testing. It is shown that S_uo, which is a reference value of steady-state strength at maximum void ratio, is an important soil parameter. The proposed method offers an explanation for the performance of many artificial sand islands in the Beaufort Sea, indicates the extreme sensitivity of S_uoto soil type and the usefulness of S_uofor assessing the potential strength loss of soils for use in safety assessments of existing hydraulic fills. Key words : undrained strength, liquefaction, sand, field, case-histories, analysis.