Dams are structures that dam rivers and streams for a variety of purposes. These structures often need to be sturdy to withstand the force of the impoundment and the high values of accumulated water load. The constant maintenance of these structures is essential, since a possible accident can lead to damage of catastrophic proportions. This research presents an alternative cheap and quick application for investigating water seepage in earth dams, through the application of the DC resistivity geophysical method from the electrical resistivity tomography (ERT) technique in Wenner array. Three ERT lines were placed parallel to the longitudinal axis of a dam formed by clay soil from the decomposition of diabase. The data are presented in 2D and pseudo-3D geophysical images with electrical resistivity values modeled. Based on the physical principle of electrolytic conduction, that is, decrease in electrical resistance in materials or siliceous minerals in moisture conditions as compared to the material in the dry state, the results revealed low-resistivity zones restricted to some points, associated with water infiltration in the transverse direction of the dam. The absence of evidence as water upwelling on the front of the dam together with geophysical evidence indicate saturation restricted to some points and low probability at the present time, for installation of piping processes.

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The implementation of open pit mines promotes alterations on geological and hydrogeological processes, mainly on natural streamflow patterns. Drainage system tries to reach its equilibrium due to modification on slope profiling water flows through new pathways contributing to erosion and leaching processes. One of the impacts related to mining is the generation of acid mine drainage (AMD), which occurs as a product of sulfide minerals exposure to oxidizing environment and, in contact to water, favors the formation of sulfuric acid. Thus, a low pH promotes a higher mobility of heavy metals and radionuclides, which become a source of contamination. In order to understand the hydrogeological dynamic in rock masses that contribute to AMD production, this paper aimed to subsidize mitigation programs in fractured aquifers using a structural analysis and geophysical survey for the reduction of acid drainage generation. The study was carried at the four mining fronts that compose the mine pit of Osamu Utsumi Mine, named according to its cardinal position (NE, SE, SW and NW). Local structural survey indicated that fractures attitudes are mainly N20E/80NW and N55 W/75NE, with intersections between them. Evidence of water flows, like whitish kaolinite stains and small vegetation growth, was identified in fronts NE, SW and NW, in addition to water springs at the base of the slopes. The flows arise mainly in areas that coincide to intersection between fracture systems in an orthogonal arrangement and the fracturing pattern indicated that at all fronts most of the fracture planes project into the open pit area, which favor the water channeling to the center of the mine as a water catchment basin. Moreover, the relationship between the persistence and spacing among the discontinuities enables a good hydraulic conductivity within the rock masses and the water upwelling on the slopes surface. The geophysical data corroborated with the structural survey, which identified the fracture planes as linear structures associated with low resistivity zones. DC resistivity method showed a strong contrast between saturated zones, differing natural from acidic water. Delimitation of linear features in the inversion models indicated that water flows are channeled through fracture planes and promote an expressive weathering process inside the rock masses, observed at depths of up to 70 m.

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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.