This article shows the interesting results of a pioneer effort by IAG/USP researchers to use ground-penetrating radar (GPR) for humanitarian purposes, guiding the rescue of victims in the tragedy of Brumadinho. The tailings Dam I at the Córrego do Feijão iron ore mine, located in the Brumadinho complex, Minas Gerais State, Brazil, collapsed on 25 January 2019. About 11.7 million m3 of mining mud was spilled from the dam, burying bodies, equipment, structural buildings, buses, and cars along a length of 8.5 km up to the Paraopeba River. Additionally, the contaminated mud traveled more than 300 km along the bed of the Paraopeba River toward the São Francisco River. This work shows the results of a geophysical investigation using the GPR method 17 days after the event. To carry out the geophysical survey, an excavator was used for soil compaction. The data acquisition was performed on the tracks left by the excavator chain using SIR-4000 equipment and antennas of 200 and 270 MHz (GSSI). The GPR studies aimed to map bodies, structural buildings, and equipment buried in the mud. The location of the profiles followed preferably the edge of the slope due to the higher probability of finding buried bodies and objects. The GPR results allowed the detection of subsoil structures, such as concentrations of iron ore and accumulations of sand from the dam filter. The GPR was effective because the iron ore sludge in the mixing process became porous and the pores were filled with air, which provided penetration and reflection of the GPR electromagnetic waves up to a depth of 3.5 m. The results were surprising. Although no bodies or underground equipment were found, the results of this research served to eliminate the studied areas from future excavations, thus redirecting the rescue teams and optimizing the search process. These important results can serve as an additional motivation for the use of GPR in future humanitarian work in areas of tragedies.

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A massa de contaminantes em fase retida e sua distribuição espacial são variáveis relevantes durante a etapa de remediação ambiental. A Análise Exploratória dos Dados em conjunto com a Geoestatística, abordada através da Krigagem Ordinária (KO) e Radial Basis Function (RBF) foram comparadas às técnicas tradicionais de tratamento de dados oriundos de investigações ambientais por baixa e alta resolução com o objetivo de avaliar a diferença na estimativa de massa de contaminantes, volume de solo impactado e indicar melhorias na estratégia de investigação de áreas contaminadas. Foi verificado que os critérios tradicionais de investigação de compostos orgânicos voláteis em fase retida promovem o enviesamento dos dados e redução da confiança da estimativa de massa de contaminantes e de solo impactado. A substituição do método de interpolação tradicional (ABNT NBR 15515-3) pela geoestatística resultou na redução de massa de contaminantes de 62,73 kg para 28,16 kg (KO) e 8,45 kg (RBF), e do volume impactado de 1423,43 m³ para cerca de 525 m³. Recomenda-se a adoção de técnicas como regularização (composite) e a adição de critérios de amostragem aleatória (simples ou estratificada) ou sistemáticos em combinação aos tradicionais.

<p>A Soil Pipe System (SPS) were identified in Candói region, located in the Paraná state, southern Brazil. This region is constituted of intensive agriculture and cattle raising. SPS correspond to a structure associated to an erosive processes stage in downhill slope that tend to increase over time. The growth of the SPS results in instability to the terrain and the possibility of collapse, in this case the collapse can be accelerated by external factors, such as the overload of agricultural machinery and animals that circulate around the site, may leading to the machinery loss, animal’s death or even risk to worker safety. Frequently, the SPS are identified by surface methods that don’t provide parameters such as shape, distribution and depth. In this research, Electrical Resistivity Tomography (ERT) and Ground Penetrating Radar (GPR) were used to obtain a 3D characterization of the SPS identified in a farm in Candói region to estimate the soil cover over the structure, the subsurface channels distribution and identify potential collapse risk portions. Seven ERT profiles using dipole-dipole array and twenty-one GPR profiles of 200 MHz antenna were acquired, covering an area of 900 m². The results were combined in a block diagram, which enabled: i) identify the subsurface channels distribution and direction, ii) estimate the average soil cover thickness, with 1.5 m over the whole structure. The possible connection between subsurface secondary and primary channels has also been suggested in results interpretation through of identification of a channel parallel to acquisition profiles direction. It was verified that in structure portions closer to the river next to the slope, the SPS ceiling has larger dimensions than the walls, suggesting areas with increased vertical tension, which was classified as potential collapse risk areas.</p>