This paper presents a computational sand model based on the well-known pressure dependent multi-surface constitutive model to solve the necessity of employing a separate set of model parameters for each soil relative density change. The proposed model correlates the original model parameters with the soil relative density through critical-state-based soil mechanics formulations to provide a single set of model constants that adapt to different soil states. Model formulation updates are performed for the flow rules, material moduli calculations, and the computation of stress ratios at the phase transformation and failure stages. The model parameters are calibrated for Ottawa F-65 sand against cyclic soil element tests with different stress levels and various soil densities. Thereafter, numerical simulations are conducted for centrifuge experiments of gently sloped grounds to validate the proposed model. Throughout numerical simulations, the proposed model accurately replicates the sand cyclic undrained behavior as similar to laboratory-measured responses for different soil relative densities with a single calibrated set of model parameters and provides reliable numerical predictions in finite element simulations of the engaged centrifuge experiments. Overall, the proposed model robustly simulates the saturated sand seismic response, which can improve the numerical prediction accuracy of liquefaction-induced damage in different engineering applications.

This chapter presents a summary of the calibration exercises (i.e., element test simulations) submitted by nine numerical simulation teams that participated in the LEAP-ASIA-2019 prediction campaign. The standard sand selected for the campaign is Ottawa F-65, and researchers have developed several efforts to increase the database of laboratory tests to characterize the physical and mechanical properties of this sand (Carey TJ, Stone N, Kutter BL, Grain Size Analysis and Maximum and Minimum Dry Density of Ottawa F-65 Sand for LEAP-UCD-2017. Model tests and numerical simulations of liquefaction and lateral spreading: LEAP-UCD-2017. Springer, 2019; El Ghoraiby MA, Park H, Manzari MT. Physical and mechanical properties of Ottawa F65 sand. In: Model tests and numerical simulations of liquefaction and lateral spreading: LEAP-UCD-2017, Springer, 2019; Ueda K, Vargas RR, Uemura K, LEAP-Asia-2018: Stress-strain response of Ottawa sand in Cyclic Torsional Shear Tests, DesignSafe-CI [publisher], Dataset, https://doi.org/10.17603/DS2D40H, 2018; Vargas RR, Ueda K, Uemura K, Soil Dyn Earthq Eng 133:106111, 2020; Vargas RR, Ueda K, Uemura K, Dynamic torsional shear tests of Ottawa F-65 Sand for LEAP-ASIA-2019. Model tests and numerical simulations of liquefaction and lateral spreading: LEAP-ASIA-2019, Springer, 2023). The objective of this element test simulation exercise is to assess the performance of the constitutive models used by the simulation teams for simulating the experimental results of a series of undrained stress-controlled cyclic torsional shear tests on Ottawa F-65 sand for two different relative densities (Dr = 50% and 60%) (Ueda K, Vargas RR, Uemura K, LEAP-Asia-2018: Stress-strain response of Ottawa sand in Cyclic Torsional Shear Tests, DesignSafe-CI [publisher], Dataset, https://doi.org/10.17603/DS2D40H, 2018; Vargas RR, Ueda K, Uemura K, Soil Dyn Earthq Eng 133:106111, 2020; Vargas RR, Ueda K, Uemura K, Dynamic torsional shear tests of Ottawa F-65 sand for LEAP-ASIA-2019. Model tests and numerical simulations of liquefaction and lateral spreading: LEAP-ASIA-2019, Springer, 2023). The simulated liquefaction strength curves demonstrate that majority of the constitutive models are capable of reasonably capturing the measured liquefaction strength curves both for Dr = 50% and 60%. However, the simulated stress paths and stress-strain relationships show some differences from the corresponding laboratory tests in some cases.