Interpretation of geotechnical data from an upstream dam for preparation of the site response analysis

Abstract

Despite seismic studies in Brazil not being common in the engineering practice as Brazil is a tectonically stable continental region, recent Brazilian regulations require seismic evaluation as supporting studies for decommission and decharacterization projects. Although there exist some critical issues such as limited laboratory data because of sampler processes related to the upstream raised tailings dams, standard tailings and soil foundation characterization, in addition to the field investigation including piezocone (CPTu), seismic piezocone (S-CPTu) and geophysical surveys are the main sources for supporting the characterization of the dynamic properties of the geostructures. This paper presents a brief discussion about the main aspects concerning to the site response analysis carried out for an upstream raised tailings dam (case study), located in Minas Gerais, Brazil. Frequency domain 1-D amplification analyses were conducted by relating local-like representative seismic records and dynamic natural characteristics of the soil profiles to evaluate the seismic response of the case study. Results showed that the maximum accelerations along the profiles are greatly influenced by the presence of the soft foundation tailings layers, and the level of amplification or attenuation is strongly influenced by the tailings layer thickness as well as the frequency content of the applied ground motions. The study pointed out that the site-specific response can support the definition of the appropriate seismic parameters to be used in engineering projects in Brazil.

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