Abstract
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.
Highlights
THE ground motions and surface response are significantly modified Excess porewater pressure (PWP) generation during earthquake shaking [1, 2], suggesting that effective stress nonlinear site response analysis should be performed for seismic design
The generated excess pore pressure values are higher in low density liquefiable layer and smaller in dense non-liquefiable layers in all the cases. ru is in line with the bed rock input motion peak ground acceleration (PGA) where it increases with increase in the PGA level
One dimensional effective stress nonlinear site response analysis are always performed to estimate the ground surface response, development of excess PWP and liquefaction potential of saturated soil strata subjected to strong earthquakes
Summary
THE ground motions and surface response are significantly modified Excess porewater pressure (PWP) generation during earthquake shaking [1, 2], suggesting that effective stress nonlinear site response analysis should be performed for seismic design. Effective stress nonlinear site response analysis are performed to estimate the excess PWP development and liquefaction potential of soil strata subjected to strong ground motions. The PWP models are incorporated in site response analysis programs to predict the buildup of excess porewater pressure during dynamic loading. Simpler PWP models have been developed which predict the buildup of excess PWP based on the accumulated shear strain, but the rarely performed undrained strain controlled cyclic tests data are always needed to select the input for these models. Which is one of the reasons in selecting input parameters inconvenient for the strain based PWP models and is responsible for the rarely use of effective stress dynamic analysis in practice. One dimensional nonlinear effective stress site response analysis was performed in DEEPSOIL using the stress based PWP generation model and in OpenSees using PDMY2 (PressureDependentMultiYield). OpenSees (Open System for Earthquake Engineering Simulation) is an open source finite element software which provide a platform for modeling the dynamic response of geotechnical structural systems [7]
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