5. Conclusions
The pressure-dependent multi-yield surface constitutive model was originally developed to capture cyclic mobility and post-liquefaction accumulation of shear strains. This paper presents new updates to the constitutive model to capture the effects of various parameters on triggering of liquefaction including the effects of the number of loading cycles, the effective overburden stress (Kσ effects), and the initial static shear stress (Kα effects). The model has been improved with new flow rules to better simulate contraction and dilation induced by shear strains in soils, thereby more accurate modeling of liquefaction in sandy soils. The model has been implemented in 2D and 3D numerical platforms in OpenSees finite-element, and FLAC and FLAC3D finite-difference frameworks.
The updated model has been calibrated based on design relationships for a range of relative densities for sand. Despite many input parameters that characterize the complex response of the constitutive model, different sets of input parameters are provided for generic response based on simple data available to designers, i.e. relative density of sand. The model parameters are calibrated for typical siliceous Holocene sands with different relative densities and are provided for cases where site-specific experimental data is not available.
This paper describes the basics of the plasticity framework of the model and provides guidelines to calibrate the input parameters of the model to simulate undrained cyclic loading conditions. The model responses under high effective overburden stress (Kσ) and static shear stress (Kα) are compared to expected average behavior published by other researchers showing reasonable agreements. Further developments are needed as new data become available.
