Energy Dissipation in Soil Structures During Uniform Cyclic Loading

Characterization of soil response under cyclic loading is one of the major challenges in evaluating liquefaction triggering. In this paper, we have performed numerical simulations to study dissipated energy and accumulated damage in soil structure at onset of liquefaction. For this purpose, at first, we validated Plasticity Model for Sands (PM4Sand) in capturing soil cyclic response with findings in experiments. Thereafter, the model was utilized to simulate soil behavior during uniform cyclic loading under controlled boundary conditions and stress paths. Simulations were performed on soils with different relative densities and under different confining pressures. The results of this study indicate that energy dissipation is directly related to PWP generation, and is independent of the amplitude, form and frequency of loading. Dissipated energy can be utilized as a versatile metric to characterize soil strength degradation and liquefaction triggering during cyclic loading

Numerical Modeling of Columnar-Reinforced Ground Behavior During Dynamic Centrifuge Testing

Predicting the response of soil profiles during earthquakes is one of the major challenges in geotechnical earthquake engineering. The presence of reinforcing elements such as stiff columns adds further complexity to the problem due to the interaction of these stiff elements with the surrounding ground. This research presents the results of advanced numerical simulations of dynamic centrifuge tests performed on a columnar reinforced model with a loose sandy profile. The model was subjected to earthquake base motions of varying intensities to investigate the reinforcing mechanisms of soil-cement columns. Numerical simulations were performed using the finite element computational platform OpenSees with pressure dependent multi yield (PDMY02) constitutive model. Simulated and measured values were compared for seismic intensity, excess pore water pressure and ground settlement at different locations within soil profile. The calibrated numerical model was able to realistically predict the response of reinforced ground

Simulation of Monotonic and Cyclic Soil Behavior using a Kinematic Hardening Plasticity Model

In this paper we investigate the PM4Sand plasticity model developed by Boulanger and Ziotopoulou in predicting soil behavior under cyclic loading. PM4Sand is a constitutive model based on the earlier Dafalias-Manzari model and builds on critical state soil mechanics theory. PM4Sand uses a two-surface kinematic yield surface in modeling soil behavior and more importantly considers the effect of fabric change and void ratio evolution during loading. The model works robustly over a wide range of loading conditions and stress paths. It was calibrated by Boulanger and Ziotopoulou at different relative densities under a range of confining pressures. In this study, we implemented the model in a MATLAB script and further calibrated it with test data in the literature. Results from earlier experimental studies on Fuji River sand and Sacramento River sand at different relative densities and confining pressures were used in our calibration efforts. Simulated and measured values of number of cycles to liquefaction triggering were compared. The results have shown that PM4Sand can predict the number of cycles to liquefaction with considerable accuracy for a variety of cyclic load levels for these sands at different relative densities consolidated to a wide range of confining pressures

Simulation of Cyclic Soil Behavior using PM4Sand, a Kinematic Hardening Plasticity Model

In this paper we investigate the PM4Sand plasticity model developed by Boulanger and Ziotopoulou in predicting soil behavior under cyclic loading. PM4Sand is a constitutive model based on Critical State Soil Mechanics. It uses a 2-surface kinematic yield surface in modeling soil behavior and more importantly considers the effect of fabric change and void ratio evolution during loading. In this study, we implemented the model in a MATLAB script and further calibrated it with test data in the literature. We simulated the results from earlier experimental studies on Monterey River, Fraser River and Oosterschelde sands at different relative densities and under different confining pressures. Simulated and measured values of number of cycles to liquefaction triggering were compared. The results have shown that, PM4Sand can predict the number of cycles to liquefaction with considerable accuracy for a variety of cyclic load levels for these sands at different relative densities under a wide range of confining pressures