Features of the thermal regime formation in the downcast shafts in the cold period of the year

In the cold period of the year, to ensure the required thermal regime in underground mine workings, the air supplied to the mine is heated using air handling systems. In future, the thermodynamic state of the prepared air flow when it is lowered along the mine shaft changes due to the influence of a number of factors. At the same time, the processes of heat and mass exchange between the incoming air and its environment are of particular interest. These processes directly depend on the initial parameters of the heated air, the downcast shaft depth and the presence of water flows into the mine shaft. Based on the obtained experimental data and theoretical studies, the analysis of the influence of various heat and mass transfer factors on the formation of microclimatic parameters of air in the downcast shafts of the Norilsk industrial district mines is carried out. It is shown that in the presence of external water flows from the flooded rocks behind the shaft lining, the microclimatic parameters of the air in the shaft are determined by the heat transfer from the incoming air flow to the underground water flowing down the downcast shaft lining. The research results made it possible to describe and explain the effect of lowering the air temperature entering the underground workings of deep mines

Multi-Criteria Assessment of Ergonomic Conditions of Work. Case Study

The supervision of OHS conditions (working conditions and the realization of work tasks) is one of the basic obligations of the employer. The number and variety of describing elements (and thus being subject to assessment) means that synthetic measures (measures that are one-dimensional images of complex phenomena) are more and more frequently applied to solve problems of that type. Although the methods of multivariate statistics used for this purpose differ in the way they treat assessment criteria (defining mutual dependency thresholds, unifying the field of compared criteria), the final effect of their application always offers the option to replace the entire set of features describing a given object with one variable (aggregate). The article presents a potential applicability of one of the so-called discrete multi-criteria decision-making methods (Simple Additive Weighting), which allows to determine a linear combination of normalized elements of the decision matrix and the elements of weight vector. As part of the article, the working conditions at 5 workstations were assessed (a miner’s workstation in 5 underground mine workings being excavated), taking into account 8 assessment criteria (6 were cost criteria and 2 – criteria of qualitative character). In effect of the application of the Simple Additive Weighting method, we could determine the ranking vector R, which allowed to order the examined objects and to carry out a comprehensive assessment of OSH conditions occurring in them.

Research into technology of fastening the mine workings in the conditions of unstable masses

Purpose.Determination of the rock stability along the strike of the mass, where the drift mining of the horizon -480 m is conducted, considering the possibility of using the improved types of supports in the conditions of the 10th Anniversary of Kazakhstan’s Independence mine at the Khromtau field with the substantiation of using the effective type of fastening that increases technical and technological, operational and economic indicators of the mine. Methods. Numerical modelling of the stress-strain state of the rock mass applied at the mine have been performed using the RS2 software in a two-dimensional formulation. The rock mass state, as well as the physical-mechanical properties of mine rocks are determined according to building codes and regulations (SNiP II-94-80), depending on the category of the rock stability. Findings. It has been revealed that the combined supports from rock bolts and shotcrete are the most rational type of fastening in the studied mine. The efficiency and prospects of using the combined supports have been determined, which ensure a decrease in their material consumption and cost while increasing the reliability of mine workings and the labor productivity of miners. The use of combined support allows to increase the economy of materials for support by 1.7 times, as well as to increase the drifting rate by 1.6 times in comparison with the metal support. Originality.The paper proposes a new approach to substantiation of an effective fastening method by comparing the costs when driving horizontal underground mine workings in the mining-and-geological conditions of the 10th Anniversary of Kazakhstan’s Independence mine. Practical implications.The research results can be used when planning mining operations, in particular, stable fastening methods at the 10th Anniversary of Kazakhstan’s Independence mine of the Khromtay deposit, as well as other mining enterprises with similar mining-and-geological conditions.

Transport of Aerosols in Underground Mine Workings in Terms of SARS-CoV-2 Virus Threat

This paper presents a method of implementation and the results of aerosol dispersion tests in underground mine workings. Numerous tests were carried out to determine the potential risk of SARS-CoV-2 coronavirus infection in the underground environment of the mines. The influence of selected parameters of mine air on the possibility and method of aerosol transmission through ventilation routes was experimentally determined in real conditions. The concentration of additional aerosols in the class of ultrafine and fine aerosols increased with the distance from the generator, while the concentration of coarse particles decreased. Assuming the consumption of the solution with which aerosols were generated, even at a small level of 1 cm3/min., the number of additional aerosols was several hundred particles in one cubic centimeter of air at a distance of 50–70 m from the generator. The concentration of ultrafine particles in the range of 40–20,000 nm increased from 122 particles/cm3 to 209 particles/cm3 at air temperature of 12 °C and relative humidity of 95–96%, and from 90 particles/cm3 to 243 particles/cm3 at air temperature of 17 °C and relative humidity of 76–82%, with the increasing distance from the generator (10 m to 50 m).

Determination and verification of the calculated model parameters of salt rocks taking into account softening and plastic flow

The article suggests using a combination of the modified Burgers model and the Mohr – Coulomb model with the degradation of the adhesion coefficient and the increase in the friction coefficient to determine the parameters of salt rocks. A comparative analysis of long-term laboratory tests and field observations in underground mine workings with the results obtained using a calculated model with certain parameters is carried out. The parameters of the Mohr – Coulomb model with the degradation of the adhesion coefficient and the increase in the friction coefficient were obtained from the statistically processed data of laboratory tests, and the parameters of the modified Burgers model were determined. Using numerical methods, virtual (computer) axisymmetric triaxial tests, both instantaneous and long-term, were performed on the basis of the proposed model with selected parameters. A model problem is solved for comparing the behavior of the model with the data of observation stations in underground mine workings obtained from borehole rod extensometers and contour deformation marks. The analytically obtained coefficients of the nonlinear viscous element of the modified Burgers model for all the analyzed salt rocks did not need to be corrected based on the monitoring results. At the same time, optimization was required for the viscoelastic element coefficients for all the considered rocks. The analysis of the model studies showed a satisfactory convergence with the data on the observation stations. The comparative analysis carried out on the models based on laboratory tests and observations in the workings indicates the correct determination of the parameters for salt rocks and the verification of the model in general.

A new potentially large uranium district in Russia (Far East)

Research subject. The aim was to justify the prospects of uranium deposits in the Tyrminsk area of the Far East, which were briefly studied over 60 years ago. These deposits are highly similar to those located in the Streltsovsk mega uranium district. Materials and methods. The materials were geological data on uranium deposits in the promising Tyrminsk district and in the largest Streltsovsky district in the Far East. The research method was a comparison of the available information about the geological features of uranium deposits and ore areas as a whole. Results. The uranium ore regions under study are localized in Mesozoic volcanogenic calderas, within Paleozoic granites. Specific uranium deposits are formed at intersections of multidirectional faults, most frequently in the vicinity of volcanic caldera boundaries. The deposits formed within a contrasting geological section are represented by steep vein-like and stock-like bodies, as well as by gently sloping formation-like bodies under the screens of layers of dense sandstones and siltstones. In addition, deposits are found in favourable layers of conglomerates and effusives breccia. The length and thickness of ore bodies comprise 0.2–1 km and 1–80 m, respectively. Uranium ores belong to the fluorine-molybdenum-uranium type; near-ore rocks are represented by mudstones and hydrosludites. Some fields in the Tyrminsk district are opened by wells to a depth of 80– 160 m from the surface, while the fields in the Streltsovsk district are explored by wells and underground mine workings to a depth of 1.5 km from the surface. Conclusion. The extent of uranium deposits in the Tyrminsk district is predicted to reach a depth of 500–700 m, with their resources being estimated as “large” based on the high similarity of localities in the areas under study. As the most promising uranium area in the south Far East, the Tyrminsk district is recommended as a priority exploration site for uranium.