Numerical Simulation of Seismic Energy Dissipation caused by Liquefaction

Seismic energy in free field soil is mainly dissipated due to the plastic response of the soil and due to the relative movement of the soil particles to the pore fluid of the soil material. While the viscous damping is usually considered to be of less significance and is omitted it can be of important role in the case of saturated soil and especially in the case of soil liquefaction. Furthermore, the plastic response of soil can dissipate great amount of the propagating seismic energy. The plastic energy dissipation and viscous energy dissipation mechanisms are the main concern of this study.;This thesis uses numerical simulation tools to implement the porous mechanics theory through the u-p-U finite element formulation as well as constitutive models in order to quantify the dissipated energy from each mechanism separately and coupled. The u-p-U formulation is based on the porous mechanics theory of Biot, and is used in order to estimate the viscous damping caused by the relative movement of the solid particles u and the fluid particles U. For the estimation of the plastic energy two constitutive models are used, the von Mises model with Amstrong Frederick kinematic hardening rule and the Dafalias-Manzari model.;Moreover, the input energy in a closed soil volume due to seismic wave propagation is estimated and compared to the dissipated energy. A parametric analysis of the influence of the porosity in the seismic energy dissipation is also conducted.;From the analysis results several conclusions have been made. The numerical analysis done in elastic porous material, showed that the porosity has great influence on the amount of the viscous dissipated energy during the earthquake motion as well as on the time needed for the oscillation to seize. In addition, from the analysis in both elastic and elastoplastic porous material seems that in some cases there exist a porosity value for which the energy dissipation becomes maximum.