Ground motion modeling and site response analyses
Due to the complex behavior of soil, a proper constitutive model is needed which should be capable of accumulating volumetric strain and consequently capable of modelling liquefaction. The parameter selection and the use of numerical tools play a significant role in this type of analysis.
Calibration of the constitutive model with insitu testing data (CPT, SPT, Vs30) is a promising path leading to mechanics-based regional liquefaction assessment. Once the correlation is built, evaluation of liquefaction-induced damage using FEM at local sites could be made. This could be integrated with random field models to predict regional liquefaction hazard. For example, Monte Carlo method and random fields could be combined to generate random and spatially variating soil properties and then conducted finite element analysis at site-specific scale with these random material. The consideration of material randomness and inhomogeneity is important since strength of a soil is affected by both the degree and orientation of anisotropy. This could also be true with liquefaction instability simulations since soil liquefaction is such a complex phenomenon-a multiscale, multiphysics problem, originating at the pore scale level but rapidly propagating to the particle cluster and specimen scales. Pioneering works in numerical analysis of the effects of soil heterogeneity on liquefaction resistance have been presented decades ago. Owing to restrictions imposed at the time by computational resources, only a small number of samples were used in the Monte Carlo simulations, and the studies were usually limited to one single earthquake intensity. Recent years, with improved computation abilities, researchers started to analyze the effects of spatial variability on soil liquefaction for a wide range of earthquake intensities. For example, one of my ongoing works is trying to analyze soil liquefaction accounting for full earthquake possibilities. A future work is to integrate the developed finite element model with multiscale random field framework for regional assessment of liquefaction hazard.