Comportamento dinâmico em barragem de terra: um estudo comparativo de diferentes abordagens de análises sísmicas

Abstract

Seismic loads on earth dams are generally considered to be of short duration; however, such movements can induce significant deformations which, when combined with other triggering factors acting on the dam, may lead to settlements, cracking, reduction of strength parameters, and even liquefaction. This study aims to assess, from a dynamic analysis perspective, the effects of seismic loading on an earth dam built for sediment containment purposes, located in the state of São Paulo, Brazil. For the development of the analyses, general data from dam "X" were obtained, including instrumentation records, field and laboratory investigations, topographic surveys, and the most recent technical documentation. Based on this information, a critical cross-section and the geotechnical parameters for the numerical model were defined. The stress-strain behavior of the soil was modeled using Plaxis software, considering the Mohr-Coulomb and Hardening Soil constitutive models to represent the materials that make up the dam. During the dynamic seismic analysis, Plaxis calculates the propagation of seismic waves through the medium, taking into account reflections, damping, and nonlinear deformations. The software solves the system’s differential equations using step-by-step time integration and incorporates Rayleigh damping to simulate energy dissipation. To represent seismic action, an artificial accelerogram compatible with the probable seismicity of the region was applied at the base of the finite element model. The accelerogram was generated using SeismoArtif software, which applies stochastic modeling techniques to produce seismic records suitable for dynamic analyses. The resulting deformation patterns and safety factors were assessed using the strength reduction method. Finally, these results were compared to safety factors obtained through pseudo-static analyses.