Influence of material damping characteristics on the seismic behavior of rockfill dams

Multi-dimensional nonlinear ground response analyses are slowly becoming the norm in earthquake engineering practice. However, they require advanced cyclic models that can reproduce the soil’s dynamic behavior with high accuracy. In this study, a nonlinear cyclic model, developed by combining and modifying the formulations of existing nonlinear cyclic models, is introduced. The model is capable of taking any desired damping and shear modulus reduction curve as input parameters. An example of simulation is presented in which a set of reference curves is used to perform a 2D dynamic analysis to study the seismic behavior of a rockfill dam. The simulations are also performed with input curves obtained from the Masing rules to investigate the effect of material damping characteristics and investigate the limitations of Masing-type models. Results indicate that the damping curves generated by the Masing rules produce lower amplification in PGA for strong earthquakes, because Masing rule induce higher damping at large strains. Using the Masing rules and attempting to modify the shear modulus reduction curves to generate damping curves closer to the reference curve resulted in softer material, which significantly reduced the PGA amplification in the dam.