Dams are built to contain water or mining tailings and provide several benefits to society. The safety and stability of these structures are essential since eventual accidents can generate catastrophic damage. The main cause of ruptures is associated with abnormal seepage, which can progress to an internal erosion process. To assess the stability and safety of dams, periodic inspections are carried out, which typically include visual inspections and geotechnical instrumentation. Some geophysical methods have the potential to assist conventional geotechnical instrumentation using non-destructive and rapid acquisition investigations. The present study applied a finite element forward modeling to evaluate the percolation conditions and water stability in an earth dam of a decommissioned uranium mine in Brazil. The dam is the final structure of the contention system of mine water treatment. The electrical resistivity data were acquired using electrical resistivity tomography (ERT) and Schlumberger array. The results were presented from the inversion of data in 3D models. The data were processed by open-source software (modeling and inversion of geophysical data). The results indicate the presence of water in the vertical filter located in the crest area. The different levels of investigation indicated water infiltration in the rock mass of the dam foundation. These results are supported by structural surveys carried out in the area that indicate a fracturing pattern in the rock mass of the mine area. The results of the study were satisfactory for the desired purposes and demonstrate that geophysical methods constitute an important complementary tool for the geotechnical monitoring dams.

In rapidly growing urban areas of developing countries, inappropriate urbanization practices near water bodies lead to significant environmental degradation, including deforestation, soil impermeabilization, and direct waste discharge into rivers and streams. This not only compromises water quality and ecosystem health but also exacerbates flood risks for nearby communities. Dumpsites, common in these regions due to inadequate waste management infrastructure, pose significant environmental threats, including soil and groundwater contamination. Our study employed a frequency-domain electromagnetic survey on an inactive dumpsite adjacent to one of Brazil’s major rivers. This geophysical method provided critical insights for geoenvironmental investigations, facilitating the collection of soil and groundwater samples to understand leachate behavior. We found that the shallower electrical conductivity map aligned with the waste disposal area's boundaries, verified by on-site surveys and excavations. Historical aerial images supported this interpretation and helped explain conductive electrical anomalies in the deeper conductivity map, linked to old irregular housing and waste disposal around the dumpsite. Moreover, the electrical conductivity maps revealed NE-oriented percolation at depth in the study area. Groundwater monitoring wells and soil analyses identified chemical elements exceeding standards set by Brazilian and international environmental agencies in this flow direction. These findings highlight the importance of using investigation techniques with superior spatial resolution compared to traditional environmental monitoring approaches. Electromagnetic methods prove effective in enhancing understanding and management of contamination in dumpsite environments.

The application of non-destructive methods of investigation in dams, such as refractive seismic method and Multichannel Analysis of Surface Waves (MASW) are increasingly effective from the point of choosing the best dam site, as well as in the phases of construction and maintenance of the structure. The objective of the research was to apply geophysical methods in the structure of the dam to detect the internal flow of fluids, the presence of voids, find possible fracture zones and variations in the level of saturation of the massif, characteristics related to permeability and directly linked to the stability of the dam. In this way, geophysical methods have proved to be excellent tools, because, unlike instrumentation traditionally used in this type of monitoring, such as piezometers and water level indicators, they can cover a large study area quickly. This paper aims to present the results of the correlation between the MASW method and the S-wave seismic refraction method in two small earth dams in the countryside of the State of São Paulo, Brazil, more precisely in the cities of Cordeirópolis and Ipeúna. The main goal was to obtain the depths of the rocky top and the saturated/unsaturated zone of the earth dams using seismic tests under conditions of lack of information about the construction of the dam. The application of geophysical methods in dams that do not previously have important information (presence of drainage blanket, vertical/horizontal filters, for example) proves to be a very interesting non-destructive investigation technique.Keywords: geophysics in dams, MASW, seismic refraction, dam investigation. Investigação Não-Destrutiva em Barragens de Terra de Pequeno Porte usando Métodos Geofísicos: Análise Multicanal de Ondas Superficiais (MASW) e Sísmica de Refração TomográficaRESUMO. A aplicação de métodos não destrutivos de investigação em barragens, como o método da sísmica de refração e a análise multicanal de ondas de superfície (MASW), são cada vez mais eficazes desde a fase de escolha do melhor local para a instalação da barragem, bem como nas fases da construção e manutenção da estrutura. O objetivo da pesquisa foi aplicar métodos geofísicos na estrutura da barragem para detectar o fluxo interno de fluidos, a presença de vazios, encontrar possíveis zonas de fratura e variações no nível de saturação do maciço, características relacionadas à permeabilidade e diretamente ligadas à estabilidade da barragem. Desta forma, os métodos geofísicos se mostraram como excelentes ferramentas, pois puderam cobrir uma grande área de estudo com rapidez, diferentemente da tradicional instrumentação utilizada neste tipo de monitoramento, como piezômetros e indicadores do nível d'água. Este trabalho tem como objetivo apresentar os resultados da correlação entre o método MASW e o método sísmico de refração com ondas S em duas pequenas barragens de terra no interior do Estado de São Paulo, mais precisamente nas cidades de Cordeirópolis e Ipeúna. O objetivo principal foi o de obter as profundidades do topo rochoso e da zona saturada/insaturada das barragens de terra fazendo uso de ensaios sísmicos em condições de ausência de informações a respeito da construção do barramento. A aplicação de métodos geofísicos em barragens que não possuem previamente informações importantes (presença de tapete drenante, filtros verticais/horizontais, por exemplo) mostra-se como uma técnica de investigação não destrutiva bastante interessante.Palavras-chave: geofísica em barragens, MASW, sísmica de refração, investigação em barragens.