Aging simulation of the tailings from Stava fluorite extraction by exposure to gamma rays

Abstract

Tailings storage facilities are disposal systems for storing the waste products of the mining industry consisting of a slurry mixture made of soil, rock and water that remain after the mineral values have been removed from the patent ore. Tailings dams are supposed to last forever, so after their deposition, tailings can experience aging processes with physical and chemical changes depending on the interactions between local conditions and source mineralogy. The consequences of these aging processes are increased interlocking of particles and oxidation processes, sometimes making previously safely held contaminants available and mobile. Among the long-term aging processes, the natural ionizing radiation (from radioactive isotopes of the soils, cosmic rays, and also ultraviolet rays from the sun) can be considered, as proposed in the current research. Furthermore, in many countries, tailings are beginning to be re-used as backfill, landscaping material or feedstock for cement and concrete. So if any, the long-term physical and chemical modifications could affect the hydraulic and mechanical behaviour of tailings with relevant economic consequences. For these reasons, wet and dry silty samples of tailings spilled out after the failure of the Stava tailings dam (Trentino Alto Adige, Italy) were exposed to gamma rays, as an accelerated aging technique to simulate the natural ionizing radiation, and then characterized. The modifications on physical and chemical properties were observed and, despite certain chemical stability, some physical changes were observed, particularly in terms of size particle distribution, inner porosity of the particles and specific surface.

Hydro-Mechanical Behaviour and Critical State Conditions of Unsaturated Silty Tailings

“…Its grain size distribution is given in Fig 1, while liquid limit (wL=27.4%) and plastic limit (wP=18.0%) show a medium-low plasticity soil (PI=wL-wP =9.4%) with 8% in weight of clay size material ([3]- [4]). The specific gravity GS=2.828 and permeability k=10 -7 m/s of the silt fraction allows to define the soil as a medium-low permeable, heavy tailings predominantly made of quartz, with significant amount of calcite and fluorite, as resulted by X-ray diffraction analysis ([5]- [6]).…”

A Preliminary Insight into the Effects of Tailing Wastes Addition on Metakaolin-based Geopolymers

“…For these reasons the storage of tailings became difficult, leading to considering other storage destinations such as storage in piles and their use as raw materials for other manufacturing chains, such as backfill material, aggregate in road construction, or fine aggregate for cement and concrete paving as shown in the Fig. 2 ([5]- [6]- [7]). ICGRE 109-2…”

Numerical Investigation on Tailing Dams Stability: a Preliminary, Parametric Analysis of some Key Factors

“…Furthermore, tailing basins are subjected to many external actions and phenomena affecting their operation, i.e., surface runoff, infiltration and consolidation process, capillary rise or chemical reactions that generate additional products, such as acids, that can more easily leach into waterways. Failures of such structures can have deleterious consequences on the environmental, society and even impact areas miles away far from the collapsed dam ([3]- [4]- [5]- [6]- [7]) as proved from the high rate of recent collapses in several countries (Fig. 2a).…”