Geotechnical analysis on the erodibility of tailings from the Fundão dam collapse

The collapse of the Fundão dam was responsible for generating numerous environmental impacts. The Gualaxo do Norte River basin was one of the areas most affected by the tragedy, where the deposition of iron ore waste caused a worsening of the erosion processes, especially during rainy periods when water erosion mechanisms intensify. This article aims to analyze the erodibility of tailings through a geotechnical approach that has been little explored in works on rupture, analyzing how physical, chemical and geomechanical properties relate to surface erosion processes. The results of the physical characterization confirmed the high susceptibility to erosion of the tailings, presenting high levels of silt (48%) and fine sand (32%), in addition to a high specific weight of particles (29.5 KN/m³) and low plasticity. The water retention curve showed that the material tends to lose suction quickly when moisture levels rise. Mineralogical analyzes indicated the predominance of quartz, iron and aluminum oxides and hydroxides. Oedometer tests identified low compressibility and collapsible behavior for tensions of 25, 50 and 100 kPa. The loss of shear strength due to flooding was high, reducing the cohesion value by approximately 15 times when compared to the dry condition. The results obtained demonstrated that the tailings from the rupture are highly prone to water erosion, thus contributing significantly to erosion processes and favoring environmental degradation in the basin.