Characterisation of the behaviour of liquefaction triggering in a cyclic undrained simple shear test setting

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The definition of appropriate calibration criteria for liquefaction-simulating constitutive models in sands is essential to properly simulate a liquefied state under seismic ground motions, enabling an adequate estimation of the liquefaction hazard. Therefore, a thorough quantitative characterisation of the behaviour of liquefaction is necessary to define liquefaction-triggering criteria that can describe a liquefied state in terms of stress and deformation. This paper presents a benchmark characterisation study of the behaviour of liquefaction, where liquefaction-triggering criteria, in terms of pore pressure ratio (ru) and shear strain (γ), were determined using two cyclic undrained direct simple shear test databases of Ottawa F-65 sand. The behaviour of liquefaction was analysed considering variations of initial state, confinement pressure (σ’v0) and cyclic shearing (CSR) conditions. The onset of liquefaction-triggering markers was evaluated in terms of moment of occurrence. The research concluded that liquefaction-triggering markers ru ≈ 0.95 and γ = 3% could be used simultaneously to indicate the initiation of liquefaction in loose and dense Ottawa F-65 sand under various initial and cyclic shearing conditions.