Studies of physical and mechanical properties of thickened concentration tailings and artificial rock masses resulting from their disposal in mined-out spaces of open-pits

The article presents the results of studying physical and mechanical properties of thickened concentration tailings, as well as regularities in their changes during the dumping process in mined-out spaces of open-pits. The necessity of experimental studies is explained by the existing discrepancy between the parameters of the artificial hydraulic deposition of soils and the design solutions, in particular, the spreading angles, the lack of a ponding zone created within the rock mass body, as well as the insignificant influence on the intakes of the dewatering plant. The following characteristics of the thickened tailings that define the parameters of the hydraulic deposition technology and the artificial massif formed inside the pit at the design stage were taken as the research objects: density, mineral density, absolute and relative moisture content, storactivity, viscosity, shear stress, flowing angle, and water conductivity. These characteristics were tested using conventional methods. Representative samples were collected at the discharge points of the thickened tailings in the open pit and directly at the discharge point of the thickener No.2 at the paste thickening plant. It was established that as the thickened tailings are transported to the place of their deposition inside the open pit, no changes take place in their density, moisture content, and water conductivity, but the rheological properties, such as viscosity, shear stress, angle of spreading undergo a significant change, which should be taken into account in design solutions. Being familiar with the technology of thickening, transportation and storage of paste mixtures in open-pit mines allows us to consider the mechanical impact on the pulp flocculi and their destruction, consisting in the rupture of the macromolecules, as the main cause of changes in the structure and properties of the thickened tailings.