1D Effective Stress Site Response Analysis; Using Stress Based Pore Pressure Model and Plasticity Model

The accumulated stress based porewater pressure (PWP) generation model is a simplified model using the concept of damage parameter. The only input of this PWP model is liquefaction resistance curve (CRR-N). The model is very useful since the CSR-N curves can be developed empirically from in-situ penetration tests measurements. In this research work the estimation of excess PWP development during seismic loading by using stress based PWP generation model is compared with a rigorous plasticity model. One dimensional (1D) effective stress nonlinear site response analyses were conducted in DEEPSOIL and Opensees using the stress based PWP model and PressureDependentMultiYield02 (PDMY2) model, respectively. The site response analysis were performed on a sand column 30 m in depth comprises of a low density liquefiable layer in between two dense non-liquefiable layers. Three bed rock outcropping motions with peak ground acceleration (PGA) level of 0.11 g, 0.124 g and 0.357 g were used as input motion in the analysis. The maximum r u profiles computed from the two models were compared and analyzed. The r u time histories at the center of the non-liquefiable layers and liquefiable layer were also compared. The comparisons revealed that the two models used in this study compute most comparable r u values. The computed r u is also found in line with density of soil and the PGA of the input ground motions where the r u increases with increase in the PGA and decreases with increasing density.