Home – Home – Jornals – Journal of Mining Sciences 2026 number 4

The authors describe the research findings on cryogenic treatment of a physical model of face zone in a loaded coal seam containing a gas drainage hole. The treatment process included serial injection of liquid nitrogen in a naked hole drilled in the center of the model. Reactions of dry and water saturated coal were tested depending on hydrostatic compression. During the experiments, the change in temperature acoustic emission and permeability of coal was recorded at different distances from the hole. The engineering and methodical solutions used in observations and data processing are described. The influence of coal saturation with water on the velocity of cooling of the model medium and on the increase in its permeability is demonstrated. The utilization efficiency of liquid nitrogen in cryogenic treatment in a naked hole is estimated, based on the obtained results, the recommendations are formulated for the field tests at coal deposits.

The author introduces the concept of the resultant forces. The equilibrium equations of continuum reduce to finite algebraic equations, and the equations of moments-to differential equations. The components of the resultant forces play the role of the stress field potentials. The formulas connecting the stresses and potentials include the volumetric forces, equilibrium equations and the stress boundary conditions. The planar and three-dimensional cases, and the non-Archimedean space generalization are discussed.

The authors focus on probability and time prediction of ground subsidence in the influence zones of underground mining. The relevance of the research is conditioned by limitedness of classical empirical and numerical methods for the assessment of mining safety in complex geological conditions, by deficiency of initial data and by the need of accounting for censored observations, i.e. events of zero ground subsidence in the observation periods. The main tool was the Deep Survival Machines model. Hyperparameters of the model were selected using genetic algorithms. The proposed model allows interpolation of ground subsidence time beyond the limits of a learning sampling and demonstrates an acceptable prediction accuracy (the average absolute error is 10-12 years). The time of occurrence of an event is systematically overestimated due to disbalance of data. two approaches are proposed for eliminating the overestimation: quantile-based interpretation of the survival function and forecast correction based on residual analysis. Modifications of the model allow a substantial reduction of the overestimation risk in the occurrence time of a ground subsidence event at the preserved acceptable accuracy. The approach can be used in estimation of underground mine stability and for decision-making on industrial safety.

Within the framework of pre-mining drainage of coal beds, the method of thermal treatment of coal using hydraulic fractures is substantiated for the gas liberation velocity and volume enhancement. A geomechanical model is developed and implemented numerically to describe the process of heat and mass transfer in a coal bed with regard to empirical dependences of permeability, thermal diffusivity and sorption properties of coal, as well as viscosity of gas on the temperature and pressure. The authors have solved the problem on methane emission from a horizontal coal bed fractured by two orthogonal and vertically oriented created fractures where fluid heated to 70 °C is was pre-injected, which led to an irreversible increase in permeability. Numerical experiments find out that for the typical thermophysical characteristics of a coal bed under such thermal effect, the volume of gas emission can: rise by more than three times; nonlinearly increase with the length of fractures; slightly depend on thermal diffusivity and limit methane content of coal. the obtained results can be used to enhance efficiency of preparation and mining of coal beds with high gas content.

A chain pillar is analyzed in plane deformation under vertical compression. It is assumed that the pillar is initially anisotropic, with variation of all six constants of elasticity. The influence of the initial anisotropic on the critical load in case of the pillar instability is estimated using the Leibenzon-Ishlinsky approach. For different multiplicities of roots of a characteristic equation, depending on constants of elastic stiffness, the values of critical loads when the pillar loses stability are found. In case of the simple roots, the critical load is found from the equality of the forth order determinant to zero. For the multiple roots, an analytical formula is obtained, which connects the critical load with the elastic constants and geometrical parameters of the pillar, generalizing the known relation for the initial isotropic medium by Ishlinsky. The influence of the ratio of all elastic constants to the Young modulus of material under vertical compression on the peak load values is analyzed. The cases when the critical width of a pillar, such that it can lose its stability, is determined at the known height of the pillar and its preset load are discussed. The substantial role of different moduli of the test material in the compression direction and across it is revealed, and the quantitative estimates of the influence exerted by the parameters of the material anisotropy on the critical load values are obtained.

The method and results of numerical modeling of hydraulic fracturing in a medium containing natural fractures and a cavity are discussed. The modified finite element method with additional cohesive elements modeling natural fractures, their growth and fluid flow in them is used. The approach and software tools developed for the approach implementation are described. The results of 2D modeling of hydraulic fracturing in a medium with one natural fracture coming to the surface of a circular opening, with a fractured layer adjoining the opening, and with a system of short fractures distributed all over the model are reported. The influence of the position and orientation of a frac initiator, stress state and properties of the medium on the hydraulic fracturing path is illustrated. The hydraulic fracturing patterns are determined, and the conditions of hydraulic-natural fracture intersection nearby the circular opening are formulated.

The implemented research estimated the influence of multiple freeze-thaw cycles in varied temperature ranges on energy intensity of failure in dolomite from the Internatsionalnaya Pipe and in limestone of the Mokhsogolokh Quarry. It is experimentally proved that freeze-thaw in three-five cycles leads to decreasing energy intensity of failure in dolomite from the Internatsionalnaya Pipe irrespective of the temperature range. The highest decrease from 825 to 600 J/m² (~ 27%) was observed in dolomite under ten freeze-thaw cycles in the temperature range of - 30 ... + 20°С in the samples in water medium. The energy intensity of the air-dried samples under the same conditions decreased from 825 to 700 J/m² (~ 15%). The energy intensity of failure in limestone from the Mokhsogolokh Quarry decreased by 8-11% under five freeze-thaw cycles in water irrespective of temperature, while the energy intensity of the air-dried samples reduced by 1-8%.

Opencast mining of nonferrous and precious metals involves extraction of large volumes of low-grade material which is stockpiled. The scientific literature review and the in-house research shows that fine fractions of low-grade ore are sometimes substantially enriched with useful component. The segregation effect observed in stockpiling using dump trucks ensures concentration of fine fractions at the top of a stockpile. An improved process flow diagram is proposed for the formation of the upper pay layer of a stockpile, that includes differentiation of the low-grade ore mass by the useful component content at an ore control station with the further dumping of two piles using dump trucks. The rational boundary for the low-grade ore separation by the valuable metal content is advised to determine from the condition of impossibility of a pay layer creation in one of the piles. After stockpiling, selective extraction of the pay layer is carried out, with sending the additionally produced mineral raw material to processing together with lean ore.

The article describes the analysis of the parameters of an oblique front bank cut by dredges with the bucket capacity of 250 and 380 l in different geotechnical conditions. The database formation is described using the grapho-analytical modeling. The introduction of a term advance axis offset relative to the front bank center as a parameter linearly correlated with the dredge swing angle is justified. The calculation procedure of dredge productivity is proposed; it is verified by the field observation data. this procedure takes into account the change in the dredge swing angle and in the bucket fill factor. The economic evaluation of the dredging efficiency in the transition to the oblique front bank is carried out. Using the method of the discrete parametric optimization, the conditions are determined for recommending the use of the oblique front bank. A software is designed for the automated choice of optimal parameters for the oblique front bank in dredging in various geological conditions.

The author addressing the problem of selecting a rational underground technology for deep-level mining of flat-lying ore bodies. A mixed-type technology is proposed, with the controlled caving and cemented paste backfill as the mutually complementary components of single stoping flowchart. This solution allows the targeted adjustment of stress distribution in rock mass, decrease of the risk of hazardous deformations and maintenance of the stability of structural elements of stoping at different stages of mining. It is found that the cave zone formation ensures relaxation of backfill and temporal ore pillars, as well as decreases the probability of uncontrollable failure in adjacent rock mass. the technical and economic analysis shows that this mixed-type technology is the most effective in mining low-grade and crude ore at depths where conventional systems with backfill are expensive and cave mining systems become unsafe and inefficient because of higher ore loss and dilution. The mixed-type technology is recommended for deep and flat-lying ore bodies as it ensures safety, completeness and higher quality of extraction, as well as its economic efficiency.

Spotlight is on common patterns in linear parameters of electric and hydraulic shovel implements and biomechanics of higher verterbrates. Using the fundamental composition concept of robotic biomechanical systems, connected with the three-tier structure and stable ratios of their link lengths, proportions of shovel implements were analyzed and their correlation with the human hand is demonstrated. The forms of symmetry, based on prime relations and wurf, are found, materialized in the mechanism irrespective of an engine type and a bucket capacity. The influence of the ratios of link lengths on the technical characteristics of implements and productivity of the machines is shown. the research findings point at the further improvement trends for the mining shovels using the principles of mechanics and physiology of movement of living organisms, and open up new opportunities in the field of geometrical synthesis of shovel implements.

With a view to developing activities aimed at dust reduction in coal mine air, various mechanisms of dust catching with finely dispersed water droplets are discussed. Efficiency of wet dust suppression is estimated theoretically as function of density of dust particles, diameter ratio of water droplets and dust particles, and their collision velocity. The authors determine the minimal velocity of a water droplet to catch a dust particle, as well as the limit velocities of a water droplet relative to a dust particle, when no kickback and fragmentation of water droplets takes place. Dependence of dust suppression along a mine roadway on the parameters of dust particles and air flow is determined, and the start conditions for the secondary dust loss are determined.

As the scope of apatite-nepheline ore extraction expands, the diversity and quantity of complex ores, particularly those from fracture zones, are steadily increasing, which adversely affects ore processing. Research into apatite-nepheline ore revealed differences in the mineral constitution of deposits located in two distinct sections of the main ring-shaped foidolite structure. These differences stem from varying degrees of hydrothermal alteration, specifically in the ore from the Apatity Circus and Rasvumchorr Plateau deposits compared to the Kukisvumchorr and Yukspor deposits, and also from different amounts of finely dispersed secondary minerals, such as zeolites, clay minerals, and hydromicas. Petrographic and electron-microscopic analyses demonstrate that fluorapatite within zones of intense nepheline zeolitization has undergone partial dissolution, recrystallization, and redeposition, resulting in the formation of fine- to very fine-grained aggregates and complex intergrowths with zeolites. Based on these mineralogical and processing characteristics, the apatite-nepheline ore from the Apatity Circus and Rasvumchorr Plateau deposits is predicted to be more rebellious.

The issues of improving gold ore processing technology through the implementation of a crushing technique based on repeated dynamic impacts are examined. This study focuses on a seasonal modular processing plant, in which quartz-vein gold ore from the Maltan deposit is treated. A comparative analysis between the current ore preparation flowsheet with crushers SMD-116 and Barmac B-5000 and a proposed flowsheet with crusher DKD-300 is carried out. Material flows, circulating loads, processing performance, and economic efficiency of the new technology are calculated. The use of crusher DKD-300 reduced the total circulating load and the energy intensity of ore preparation. The crushing resulted in a complete liberation of gold particles coarser than 100 μm, which enabled pre-treatment of the crushed material. The flowsheet upgrade increased end-to-end gold recovery from 75.17% to 83.11%. The high technological and investment attractiveness of crushing by repeated dynamic impacts is confirmed at gold processing facilities.

The microstructural features of compacts made from milled refractory waste of fused aluminous product were analyzed. Structural and morphological changes in compacts when milled with a modifying agent were studied and determined. Test results indicate that compacts produced from modified powder exhibit a more homogeneous structure. The coarsening of subgrains during dry milling with a modifier suggests the formation of dense and strong inter-particle contacts; consequently, compacts made from the modified material will experience reduced surface stresses and strains in roasting, thereby enhancing the quality of finished products manufactured from man-made waste. The findings provide a basis for the development of aluminous waste processing and recycling technologies.

The promising varieties of quartz raw materials from the Southern Urals were processed. The textural and structural characteristics as well as mineral inclusions were studied. Two processing flowsheets were employed: the first involved microwave decrepitation and magnetic separation, while the second utilized thermal crushing. Compared to the first flowsheet, the second yielded more efficient processing results, achieving a 11-24% higher degree of purification in terms of total impurity content. The quartz concentrates produced by thermal crushing contain less than 20 ppm of total impurities, which meets the standards required for applications in the semiconductor, fiber-optic, lighting, optical, photovoltaic, and microelectronics industries.

The results of numerical modeling regarding the formation and atmospheric dispersion of a dust-gas cloud from a large-scale blasting in a quarry are presented. A total explosive mass of 6.500 kg was used. The modeling was divided into two stages: at the first stage, the formation of a blast cloud was analyzed using the Eulerian approach for multiphase media, starting from the time of explosive charges (each weighing 200 kg) detonation in boreholes, and ending with the time when the cloud completed its atmospheric rise. The second stage included calculating the subsequent transfer of rock particles within the dust-gas cloud; the wind speed, gravitational settling, and turbulent diffusion were taken into account. The diffusion was calculated using the Monte Carlo method. Airborne particle concentrations at different times and particle deposition densities at different distances from the pit wall were studied. The extent of dust particle deposition downwind outside the quarry boundaries was estimated.

A test bench is developed to study the stress-strain behavior of rocks under complex loading. The stress state within a cylindrical sample is generated by applying an axial compressive load and a torque. The sequence of application and the ratio between the axial load and the torque can be varied according to the experimental program. During testing, axial strain, circumferential strain, and the angle of twist are measured by novel sensors. Principal strains are determined using specially oriented strain gauges glued to the sample surface. Designed to operate in conjunction with uniaxial compression presses, this test bench enables the study of stress-strain and rheological properties of rocks. The use of rigid presses allows testing under both hard and soft loading conditions.