A Calibration Procedure for Sand Plasticity Modeling in Earthquake Engineering: Application to TA-GER, UBCSAND and PM4SAND

Abstract

A generalized element-test based calibration methodology is developed. The calibration is based on best matching the response in terms of (a) the liquefaction resistance (CRR) curve as a function of the relative density of sand and the equivalent number of uniform cycles required to trigger liquefaction, and (b) experimentally derived shear modulus and damping ratio curves commonly used in practice. Regarding the first part of the calibration procedure, the correlation for the reference cyclic resistance ratio CRRMw=7.5, σv0΄=1atm from SPT data by Idriss & Boulanger was combined with (a) the empirical formula of Seed & Idriss that relates the earthquake magnitude to the equivalent number of uniform cycles of the seismic motion, (b) the magnitude scaling factors (MSFs) proposed by Idriss that associates the reference cyclic resistance ratio with the actual one and (c) the correction factor for overburden stress Kσ suggested by the NCEER workshops. The developed calibration process is applied to three constitutive models available in the literature. Namely: (a) the TA-GER, (b) the PM4SAND and (c) the UBCSAND. For the last two models both the finite element code PLAXIS 2D and the finite deference one FLAC 2D were used in the calibration procedure. Despite the generally satisfactory performance of all models, re-adjustment of the recommended calibrated parameters may be required in boundary value problems.