Evaluation of Internal Erosion Potencial Due to Dipersive Fine Soil Used as Construction Material in the Chasqueiro Dam – Arroio Grande/RS: Geotechnical and Geophysical Methods

Objective: The objective of the study was to assess the potential for internal erosion in the Chasqueiro Dam, in southern Brazil, considering the possible use of dispersive fine soils in its construction. Theoretical Framework: Key information is highlighted regarding internal erosion, soil dispersibility, and the inductive electromagnetic method, offering a solid foundation for understanding the context of the investigation. Method: The methodology identified the probable location of the quarrier exploted for the dam construction using historical aerial images and records from the basic project. This analysis was corroborated by fieldwork. Subsequently, soil samples from these quarries were collected for geotechnical characterization. Finally, the Inductive Eletromagnetic Method (IEM) was applied to assess the apparent electrical conductivity of the soil, validating the results obtained in the laboraty. Results and Discussion: The precise location of the quarry used for the dam construction was identified, even nearly five decades after the dam's completion. This allowed the collection of representative soil samples, which demonstrated low susceptibility to dispersion. The electrical conductivity maps corroborated this finding by revealing predominantly uncontaminated areas, ruling out the possibility of significant saline contamination and refuting the hypothesis of internal erosion caused by the use of dispersive soil. Research Implications: The study provides significant theoretical and methodological contributions by integrating geotechnical and geophysical approaches with the analysis of historical aerial images, establishing a multidisciplinary framework for evaluating the stability of earth dams. Methodologically, the research demonstrates the effectiveness of combining non-invasive techniques with geotechnical characterization to assess soil properties without compromising the structural integrity of the dam. Originality/Value: The study innovates by integrating geotechnical and geophysical methods with the use of historical aerial images. Its relevance lies in offering a multidisciplinary approach to the monitoring of earth dams, while also contributing to the technical literature on the use of dispersive soils in engineering works.