Gornye nauki i tekhnologii = Mining Science and Technology (Russia)

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Vol 7, No 2 (2022)
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93-99 304
Design and operation of auxiliary underground workings in coal mines involves substantiation of parameters of coal pillars and requires development of new approaches to substantiate their geometrics. On the one hand, sufficient stability of a “rock mass – working – coal pillar” system should be ensured. On the other hand, the parameters of “frozen” coal reserves in the pillars should be justified. The joint solution of these two problems requires accurate forecasting based on modern digital models of a rock mass. In this study, a model of rock mass and mine workings with different dimensions of a coal pillar is presented with the use of Flac3D software. The simulation findings showed that when developing sloping coal seams, the volume of coal extraction in a longwall has an effect on the stress-strain state of the enclosing rock mass. During the study different factors having effect on geometrics of a coal pillar were analyzed, and their influence on the field of stresses and shear of inclined layers in a rock mass was studied, and the size of the plastic deformation zone around an auxiliary mine working was also determined. The study findings are also of practical importance in terms of substantiating the parameters of a working support design. The size of coal pillar is also connected with the support type. It should be taken into account that bolts should be of sufficient length to ensure firm fixing and located in the zone of intact rocks. The research showed that a coal pillar should be 10 to 15 m wide in order to ensure optimal mining conditions and safety.


100-110 242
Sn-W multimetal mineralization in the Dong Van region, North-Eastern Vietnam was studied using statistical and multivariate approaches based on 890 samples of stream bottom sediments collected for assaying for 27 elements. The findings of frequency analysis demonstrated that Pb, As, Bi, Li, Sn, W, Ta, Ce, Ag, Sb, and Be have close ties with multimetal ores, implying that these elements can be used as prospecting indicators for multimetal mineralization. In addition, correlation matrix and dendrogram studies were also applied to subdivide the elements in the stream bottom sediment samples assays into two groups: associated with multimetal mineralization (Be-Sn-W-Bi, and, to a lesser extent, Li-Pb sub-groups) and not associated with the mineralization: (As-Cd-Sc-Cr-Ce-La, Co-Ni-V, and Ga-Ge-Ba sub-groups). Sn and W were found to be the best indicator elements for the mineralization, according to the findings of geochemical modeling and location of their anomalies in the region. Furthermore, extensive Sn and W anomalies were identified in the Dong Van region (using threshold values (mean ± 3 STD), providing the most important indications for multimetal mineralization prospecting in the region. The studies also suggest genetic ties between the region’s multimetal mineralization and the northwest-southeast fault system and concealed granitoid blocks. Finally, the performed statistical analyses (with the use of threshold values) of stream bottom sediments assays allowed revealing indicator elements and their geochemical anomalies and using them as an effective tool in further prospecting and exploration for multimetal mineralization in the region.


111-125 352
PM2.5 air pollution is not only a significant hazard to human health in everyday life but also a dangerous risk to workers operating in open-pit mines OPMs), especially open-pit coal mines (OPCMs). PM2.5 in OPCMs can cause lung-related (e.g., pneumoconiosis, lung cancer) and cardiovascular diseases due to exposure to airborne respirable dust over a long time. Therefore, the precise prediction of PM2.5 is of great importance in the mitigation of PM2.5 pollution and improving air quality at the workplace. This study investigated the meteorological conditions and PM2.5 emissions at an OPCM in Vietnam, in order to develop a novel intelligent model to predict PM2.5 emissions and pollution. We applied functional link neural network (FLNN) to predict PM2.5 pollution based on meteorological conditions (e.g., temperature, humidity, atmospheric pressure, wind direction and speed). Instead of using traditional algorithms, the Hunger Games Search (HGS) algorithm was used to train the FLNN model. The vital role of HGS in this study is to optimize the weights in the FLNN model, which was finally referred to as the HGS-FLNN model. We also considered three other hybrid models based on FLNN and metaheuristic algorithms, i.e., ABC (Artificial Bee Colony)-FLNN, GA (Genetic Algorithm)- FLNN, and PSO (Particle Swarm Optimization)-FLNN to assess the feasibility of PM2.5 prediction in OPCMs and compare their results with those of the HGS-FLNN model. The study findings showed that HGS-FLNN was the best model with the highest accuracy (up to 94–95 % in average) to predict PM2.5 air pollution. Meanwhile, the accuracy of the other models ranged 87 % to 90 % only. The obtained results also indicated that HGS-FLNN was the most stable model with the lowest relative error (in the range of −0.3 to 0.5 %).
126-136 303
Mine planning involves selecting an optimal mine layout. At the same time key factors, including those influencing mining safety, should be comprehensively taken into account. A developed rock burst forecasting technique taking into account mine workings of an extraction area and a mine goaf enables determining the safe direction of a coal face. The proposed technique also takes into account all faulting/joint systems, occurring beyond a mine field. The distribution of specific potential energy in an intact rock mass is proposed to be used as the basis of the input data required for rock burst forecasting. The forecast is carried out via estimating the Lode-Nadai coefficient at different directions of coal face advancing. The stress (intensity) coefficient is proposed to be used as a criterion in order to determine a safe direction. We determined the safety criterion is equal to 10 in the Komsomolskaya Mine conditions. Besides, the safest direction of a coal face advance to mitigate the risks of rock burst was determined for this mine. The direction between 138° and 128° counter-clockwise from the north direction was identified to be the safest for the Komsomolskaya Mine conditions for any values of deformation modulus and Poisson’s ratio.


137-149 416
Controlling blast action, in order to increase its energy efficiency in a production blasthole is quite an important issue. This is because it enables the formation of broken rock mass with preset coarseness parameters. Increasing the blast pressure and the time of the blast impact on a rock mass is traditionally recommended as one of the ways to improve the blast action on the rock mass, thus reducing the oversize yield in open pits. One device which enables this approach to a certain extent is a turbulator. The turbulator is fabricated of aluminum plate twisted in a helical fashion around its longitudinal axis. It is mounted in a production blasthole according to a specially designed scheme. The methodology developed to study the stress and strain state of a rock mass when using a turbulator in a blasthole explosive charge allows the size of radial fracture zone and the radius of rock fragmentation to be defined. A method was developed to initiate blasthole charges in a pit blasting block. It includes drilling blastholes, filling them with explosive, installing downhole blasting caps, and blasting using non-electric initiation system. A blasting block is divided into two equal parts (sections), which in turn contain three series of blastholes for short-delay blasting. Blasthole charges are initiated simultaneously in the two parts of the block based on a trapezoidal blasting pattern, thus ensuring meeting detonation waves. In the first series, instantaneous blasting of blastholes located on both ends of the blasting block and forming a trapezoid (in plan view) is carried out. Then after 42 ms, the second series of blastholes (also forming a trapezoid) is detonated. After another 42 ms, the remaining blastholes are detanoated along the perimeter of the blast block in the third series. Implementation of this design with the effect of turbo-blasting for rock fragmentations by blasthole charges at the Kalmakyr deposit of JSC “Almalyk Mining and Metallurgical Complex” has led to the reduction of consumption of explosives, volume of drilling, secondary fragmentation costs, and increased productivity of excavators and mining safety.


150-160 197
Despite innovations in ALROSA’s (PJSC) mining and processing complexes under the updated strategy for economic development, practice shows that in recent few years the operating costs of the section pumps at the Udachny underground mine’s main drainage have increased significantly. Such an increase could be the result of a concentration of mechanical impurities in the mine water. This study is aimed at the integrated assessment of the impact of mechanical impurities concentration in mine water on the performance of the Udachny underground mine’s main drainage section pumps. It is also aimed at studying the feasibility of sinking additional inclined clarifying working-reservoirs. The target goal was achieved by means of visual, analytical, statistical, and other types of research in determining the impact of the concentration of mechanical impurities in mine water on the performance indicators of section pumps of the kimberlite mine’s underground drainage facilities. The integrated studies showed that the concentration of mechanical impurities in mine water is the key factor in determining the overhaul life and electricity demand of pumping equipment. The Udachny underground mine’s main drainage section pumps overhaul life can be calculated as a linear function of their delivery rates at the moment of taking-down for overhaul. This function is reliably described by empirical expression Q = –7.5X6 + 326.67, where X6 is the averaged mechanical impurities concentration in the mine water. Calculations showed that reducing the concentration of mechanical impurities in mine water from 17 to 4 g/l would decrease the annual operating costs of the Udachny underground mine’s main drainage section pumps by 100 million rubles.
161-169 195
The practice of using units with milling-type operating devices showed their insufficient reliability, which leads to deterioration of the units’ performance. The reasons for this are high dynamic loads in structural members, which are caused by external resistance forces on a milling cutter. They have random, sharply variable nature due to structural heterogeneity of a peat deposit, its random physical and mechanical properties, the presence of wood inclusions in it, as well as periodic interaction of blades with the deposit, and many other factors. In this case, the parameters of actual milling cutter, due to manufacturing and installation errors, differ from those specified in the “ideal” design. In addition, wear and irreversible deformations of cutting elements (blades) occur during operation. As a result the position of blades in a cutter body differs from the “ideal” positioning pattern. The purpose of the paper is to develop a model of section moment on a milling cutter when interacting with a peat deposit in the process of technological operations, taking into account the influence of the error of blade positioning on a cutter body. Expressions for calculating the moment spectral density were obtained. Its characteristic features were analyzed. Errors in positioning of cutting elements on a cutter body lead to changes in the magnitude and nature of the load and its frequency content. In this case, new, additional components appear at frequencies multiple of the cutter’s angular velocity, enriching the load spectrum and increasing its variance. Their magnitude is determined by the cumulative value of the errors. As an example, an analysis of the influence of the error in positioning cutting elements on the spectral density for the operating device of MTP-42 deep milling machine is given. The study results are of practical value and should be taken into account in the calculation of dynamic loads in designing structural members of milling units, especially if their operating devices have a large number of blades, use fine feeds, and when the natural frequencies of the structural members are equal to or multiple of the angular speed of a milling cutter.
170-179 287
Belt conveyors are widely used in mining industry in open-pit and underground mining for moving bulkload in horizontal and inclined directions to the sites of processing. In order to create the best conditions of frictional contact between a belt and a drum, various methods of drive drum lining are used. The main lining material is rubber of different grades, providing proper coefficient of friction of a belt with a drum (within the range of 0.6–0.62). A drive drum lining material must have high wear resistance, thermal resistance, mechanical strength, ability not to accumulate electric charges on the surface and not to generate dangerous concentrations of toxic components (for example, chlorine gases, carbon monoxide) when heated. The use of ceramic lining opens up great opportunities for increasing lining durability and useful life of high capacity heavy-duty conveyors. The paper presents the results of the study of stress-strain state of belt conveyor drive drum ceramic lining plates. We used Solid Work Simulation environment in the study on the basis of the accepted analytical model of plate-belt contact for drive drum with diameter D = 1250 mm, belt width L = 1000 mm, and the belt entering branch tension value Se = 25400 daN with regard to the value, direction, and nature of the acting loads. On the basis of stress-strain analysis of alumina ceramics lining plates, the favorable geometrical parameters of the plate cleats (projections) and the required properties of lining material ensuring the proper load-carrying capacity at the contact with the belt rubber facing were found. It was established that a plate cleat diameter for heavy duty conditions should be not less than 4.5 mm and its end round R should be within the limits of 0.5–0.6 mm, and, in the base, 0.3–0.4 mm at a cleat height of 1.0–1.4 mm in order to prevent stress concentration in hazardous sections. It was also established that alumina ceramics bending strength must be no less than 350 MPa for effective functioning of rubber-ceramic lining. Simulation of a plate stress-strain state on exposure to alternating loads made it possible to identify characteristic areas with maximum stress concentration, which were foci of crack nucleation. Thus, it became possible to predict lining useful life.


180-187 617
Personnel working at mining enterprises must be prepared to overcome professional difficulties and to possess the professional competencies required not only for the implementation of processes, but above all their safety. Modern digital modeling technologies used in mining activities expand the boundaries of practical training not only for future mining engineers, but also for working specialists. As part of the training process, it is important that the simulation of the mining environment be of a high quality almost indistinguishable from the actual environment. In this context, the development of process solutions based on virtual and augmented reality (VR/AR technologies) is most relevant. Process automation in the conditions of large-scale digital transformation laid the foundations for the development of VR/AR in mining industry. Data analysis shows that VR/AR technologies are the major consumer of IT solutions. They are in fact the integrator, or the highest “IT-transformation”, which in practical terms create digital parallel production objects and processes. Further developments in this area may also change some of the existing traditional entities or create new ones, in the training system as well. An example of such an entity, on which the digital future will depend, is the emerging “digital culture”. As such it will be applicable not only in the corporate, industry, but also nationally. Despite the diversity of areas in the development of VR/AR technologies, the maximum effect of their implementation is manifested in the development of special skills of personnel in equipment operation. This clearly relates to the need to ensure the efficiency and reliability of technological operations and processes. The interaction between the consumer and producer of VR/AR solutions together with universities allows a number of problems related to the formation of competencies in the future generation of specialists to be resolved. These include: training of university graduates; creation of specialized courses in educational programs; individual higher educational programs; professional development and retraining courses for specialists in the field of VR/AR technologies in mining; involvement of the academic community representatives in the development of practical tasks based on VR/AR solutions, including researchers of different specializations (geology, geophysics, geotechnics, geoinformatics, aerology, geotechnology, mining machinery and equipment, automation, etc.). Other key areas include the dissemination of the best practices of VR/AR usage in the interests of future customers; creation of a common method to assess the effectiveness of VR/AR projects to determine their investment attractiveness; as well as prediction and creation of future technologies.

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ISSN 2500-0632 (Online)