INVeSTIGATION INTO CROwN STABIlITy AT uNDeRGROuND leAChING Of uRANIuM OReS Purpose. Determination of influence of various factors on crown stability at underground block leaching of uranium ores. Methodology. Mathematical modeling applying the finite element and analytical methods is used to investigate into the impact of the ore body dip angle and crown workings on changes in the crown stress-strain state and stability. On this basis, dependencies of the above factors' influence on the crown stability are determined enabling their adequate consideration when specifying the appropriate crown thickness. Laboratory studies allow estimating influence of the reagent used at block leaching of uranium ores on their hardness for the purposes of determining safe crown parameters. findings. The dependencies of the ore body dip angle impact and the degree of crown disturbances caused by workings on crown stability as well as uranium ore hardness decrease resulted from application of the acid solution enable adjusting the appropriate crown thickness in determining safe parameters of the technology at the stage of the design work execution. Originality. Scientific novelty consists in determining dependencies that consider the impact of the ore body dip angle and the degree of crown disturbances caused by workings on crown stability. For the first time, influence of the sulfuric acid solution used in underground block leaching of uranium ores on changes in their hardness has been studied. Comprehensive consideration of the effect of these factors and the determined dependencies enables specifying safe thickness of crowns and ensures their integrity. Practical value. Possibility of adjusting crown thickness considering the ore body dip angle, the degree of disturbance caused by workings, and the acid solution impact will allow specifying the appropriate crown thickness at the stage of designing. This will allow avoiding possible failure of crowns caused by negative impacts of the above factors and ensuring safety of works.
Purpose. Determining the possible level of air dustiness during the bucket hoisting of uranium ores along the shaft "Holovnyi" of the mine "Novokostiantynivska", SE "VostGOK".
Methods.To determine the level of air dustiness, a physical modelling of this process under laboratory conditions was used. Physical modelling of the dust formation process has been performed on a laboratory bench, which consisted of an AT-2K-250/500 wind tunnel with non-return-flow and a closed working section, as well as an aspirator with a drive and hoses for sampling and filtration of air. The granulometric composition has been determined for modelling: the parameters of large-sized fractions -by the linear method (i.e., measurements of the geometric dimensions of the separate pieces and their weighting), and the composition of fine-sized fractions (-15 + 0 mm)by sieve analysis and weighing.Findings. The granulometric composition of the rock mass has been determined, which is planned to get out by a bucket hoisting method along the shaft "Holovnyi", and the dust formation process has been modelled on a laboratory bench. It has been set that the level of air dustiness during the rock mass hoisting will be significantly influenced by its humidity or the additional binding of ore fines in the upper layer if to treat the surface with acting agents. Moreover, it is influenced by the uniformity of these fines distribution within the bucket volume, which, in turn, will depend on the way of its loading. It is recommended to use the vibrating feeder for loading the bucket. Thus, the sufficient natural moisture of the rock mass (more than 4%) will ensure the level of dust content of the emitted air below the normative indicators.Originality. It has been determined that the dust content in the air depends on the moisture of the rock mass and the presence of moisture in the ore to more than 4% reduces the level of dust in the air to 0.4 -0.45 mg/m 3 , which is 0.67 -0.75 of the existing safe dust concentration for such conditions. Practical implications. The result obtained confirms the possibility of using the bucket hoisting method along the shaft "Holovnyi" to the daylight surface of uranium ores mined at the mine "Novokostiantynivska" (provided that the proposed recommendations will be observed) without exceeding the existing safe dust concentration of air supplied to the mine.
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