Tailings desiccation process studied in environmental chamber experiment

Abstract

Case studies and numerical simulations show that the long-term stability of tailings dams largely depends on the evolution of their water content. Therefore, desiccation is one of the critical processes influencing the tailing dam's safety. In this work, the air-drying of tailings, starting from a sludge condition, is studied using a fully instrumented column experiment, performed in an environmental chamber with temperature and relative humidity control. Based on the experimental observations, a conceptual model for the desiccation process is proposed. The model consists of the combination of two mechanisms driven by evaporation: shrinkage and capillary rise. The latter is only activated after a granular structure develops (shielding skeleton), capable of sustaining the suction-induced intergranular forces. This evidence explains the tendency of real deposits to develop an unsaturated, dry tailings crust enclosing a body of mud-consistency tailings. In addition, the role of dissolved salts in the desiccation process was observed. Solutes in pore water limit the evaporation rate throughout the test by increasing osmotic suction. Moreover, salt precipitation was observed to cause an interruption of the desiccation process on two occasions during the experiment: first, by the formation of a superficial precipitation crust and later by pore clogging within a shallow layer.

Automatic System for the Study the Interaction Between Porous Media and Atmosphere, Clime Change and Environmental Conditions

“…In addition, in this case the test laboratory also controlled the temperature, an aspect that had not been done before in any of the previous tests [3,4,11]. The sample was prepared according to the methodology described by [3,4].…”

“…The study of the interaction processes between the atmosphere and the porous medium (soils, mine and metallurgical wastes, technosols, etc.) is one of the main lines of research in earth sciences [1][2][3][4][5][6][7][8][9][10][11][12]. Different authors have investigated the process of soil crack formation by desiccation due to interaction with the atmosphere [1][2][3][4]8].…”

“…Different investigations have studied the preferential flow caused by the existence of shrinkage cracks in the porous medium [3,6,10]. The use of sensors for the experimental study of drying pores and the control of the spatio-temporal evolution of certain variables in the porous medium has been developed mainly in the last three decades [3,4,6,11,12,14].…”

Environmental Implications of Saline Efflorescence Associated with Metallic Mining Waste in a Mediterranean Region

“…In this sense, what is decisive is the presence of a variable porosity that allows the capillary movement of water, loaded with mineral salts and metallic sulphates that end up evaporating on the surface and generating secondary mineral deposits [11,17,20]. In this respect, column test studies conducted under laboratory conditions are used to evaluate the desiccation, hydraulic and geochemical evolution of these supergene minerals [14,17,[21][22][23][24][25][26][27].…”

Modelling unsaturated silty tailings and the conditions required for static liquefaction

“…One attained ranging from 10% to 40% across the same depth range and under the same climatic conditions as for a silty tailings which attained a of about 80% (Garrino et al, 2017). Particle sizes and grading have an influence on what may be attained, but so does the presence of salt in the pore water (Garino et al, 2022), as would the type and plasticity of any clay minerals present, and layering -especially the thicknesses and extents and whether they comprise predominantly sand, silt or clay sized particles. Despite many uncertainties there is enough data to suggest that drying may not always result in a that is low enough to prevent the possibility of liquefaction, especially if the tailings are silty and poorly graded.…”