Home – Home – Jornals – Journal of Mining Sciences 2023 number 3

The authors attempt the numerical modeling of the geomechanical behavior of a rock mass in the course of single unit face longwall mining. The calculation models are constructed for the rock mass geomechanics from ground surface down to mining depth. The model problems are solved in two and in three dimensions. The resultant characteristics of a trough subsidence on ground surface were compared with the data of engineering analysis. The modeling results are verified using actual in-situ observations of check point subsidence. The comparative analysis of the trough subsidence characteristics on ground surface from the geomechanical modeling and engineering analysis show their correlation in case of all test alternatives.

The coal freezing adhesion tests on typical substrates including metal, rubber and plastic substrates were carried out, the steady and separated interfacial structures between coal and substrate surfaces were investigated, and the strength characteristics of coal freezing adhesion on substrates were analyzed in depth. At the stable interface of coal freezing adhesion, the frozen coal slime area is formed in some areas, while the direct contact area as well as the void area may appear between the frozen coal and substrate surface in other areas. The surfaces of metal and rubber substrates have small water contact angle and good wettability, and the separation failure of freezing adhesion occurs at the interior of the frozen coal slime area or the frozen coal itself, thus the coal freezing adhesion strength is reflected by the freezing strength of the frozen coal slime or the frozen coal itself. The surfaces of plastic substrates have large water contact angle and poor wettability, and the separation failure occurs at the bonding interface between the frozen coal slime area and substrate surface, thus the coal freezing adhesion strength is reflected by the bonding strength. The coal freezing adhesive strength on plastic substrates is 4-12 time less than on metal and rubber substrates.

In this study, the rebound hardness values (Shore-Schmidt-Leeb) were calculated for 12 different carbonate rocks using three different devices. The relationships between hardness values and rock cuttability properties (specific cutting energy and noise level) were investigated by simple and multiple regression analyses. It is determined that the Leeb hardness of the rocks can be an alternative to the Shore hardness and Schmidt hardness and that both the specific cutting energy and the noise level can be estimated with the Leeb hardness values.

This study examines the usability of concrete wastes generated from buildings demolished for various reasons in shotcrete. The strength properties of shotcrete produced from recycled aggregates (RA), cylinder specimen and plate specimen were tested. it was observed that as the ratio of RA used instead of natural aggregate increases, the strength of the cylinder specimen decreases, ultrasonic pulse velocity increases. The toughness value has increased in the concrete samples prepared by replacing the natural aggregate with 50% or more RA. It was observed that the fiber amount and load carrying capacity were proportional in fiber reinforced plates prepared using RA. As a result, it has been observed that the interaction of RA with fiber is positive and it can be used in shotcrete. It has been revealed that RA can contribute to the reduction of environmental pollution caused by construction and wreckage wastes and can be presented as an alternative to natural aggregate.

The authors discuss the mechanisms of gas transfer in exposed coal on the strength of the phenomenology of coal gas content. The phenomenon of gas transfer is divided into flow and diffusion, and the major characteristics of these processes in the overall gas travel are revealed.

The authors make a geomechanical assessment of undermined rock mass before and after formation of a sinkhole on ground surface during blind orebody mining on Podruslovy site. The geophysical surveys allowed finding the pillar size dynamics above the mined-out void. The borehole gravity measurements in integration with an orthophotomap made it possible to determine the boundaries of the mined-out void and the parameters of the sinkhole. The mathematical modeling estimated the zones of stress concentration and fracture in enclosing rock mass in the neighborhood of the test boreholes. The safety precautions are designed for the further mining operations on Podruslovy site at Sheregesh deposit.

The usability of salt mine water with high content of chloride-ions in preparing cemented paste backfill is studied. The rheological and mechanical properties of experimental backfill mixtures at different cement consumption are analyzed at uniform and compound aggregate hydrated with tap and mine water with the content of chloride-ions up to 0.75% of the mass of cement. The strength, elasticity modulus and Poisson’s ratio are calculated in cemented paste backfill with tap and mine water after curing for 28, 60, 90 and 360 days. It is found that the strength, elasticity and deformation characteristics of the test cemented paste backfill made of mine water change similarly to the backfill made of tap water, at deviation of ± 10% and ± 4% in terms of strength and deformation, respectively. Chloride-ions contained in mine water have no adverse effect on rheological properties of backfill or hydrated cement, and on dynamics of development of strength in the mixture.

It is examined how convergence of roof and floor affects condition of temporary roadways during extraction of coal series in Kuzbass. The geological and geotechnical factors that can cause deformation in roadways are identified. Roadways are classified in terms of their location relative to a coal seam being mined and a coal seam being overmined in a coal series. The parameters and phases of deformation of rocks are analyzed as primary and secondary convergence of roof and floor rocks in temporary roadways. The primary convergence is observed in temporary roadways located in parallel to the mined-out void and driven in the bottom layer of a thick coal seam being overmined. The secondary convergence takes place in temporary roadways in the abutment pressure zone induced by the earlier mined-out extraction site.

The authors perform the aerodynamic design of axial fans with impeller and inlet guide vane to reverse air flow direction via killing rotation of the impeller while putting the guide vane into rotation. This approach can substantially enhance fan efficiency in reverse mode. The newly developed blade angle analysis procedure allows finding air flow parameters in reversal. The parametric regions in aerodynamic designs of axial fans, where the proposed approach of reversal is effective, are delineated. Design of a fan having similar aerodynamic characteristics in the forward and reverse air flow is undertaken. The swirl ratios of flow in the guide vane are correlated with the axial velocity ratios toward geometrical similarity of blade profiles of impeller and guide vane at an average radius.

A brief review of machines for pit wall scaling is given. The inertial impact technique is compared with the surface miner operation. The authors describe an inertial impact machine with a hammer rotor for pit wall scaling. The procedure and data of the numerical and lab-scale testing of the machine are presented. The tests produced the rational range of lip angles for hammer plates and the preferable impact frequency, which ensure the minimized energy intake of the rotor motor and the least counterforce of rock mass to the bearing seat of the rotor at the preserved efficiency of fracture process.

The found interaction mechanism between a mineral-diamond mixture and a modifying agent includes the stage of adhesive attachment of luminophore at grains of diamonds and kimberlite. The selected compositions of modifying agents and the modification process parameters ensure efficient attachment of luminophore-bearing compositions at diamonds. The proposed criterion of selective action of modifying agent on spectral characteristics of diamonds enable choosing modes of recovery of weak and high luminous diamonds from kimberlite ore in X-ray luminescence separation. The rational variation parameters are determined for the organic collector composition, water phase of a modifying agent and for the process of modifying treatment of diamond-kimberlite products before the X-ray luminescence separation. The test of the selected compositions of modifying agents and the diamond-bearing product treatment modes proved almost complete extraction of weak and high luminescence diamonds to concentrate at minimized yield of kimberlite.

The literature review discloses preferability of using the time of induction rather than the wetting angle as a criterion of coal floatability. The authors analyze kinetics of coal flotation as function of surface properties of heteropolar collectors relative to the gas-liquid interface. The correlation between the spreading velocity of collectors on water surface and the coal flotation kinetics is determined as a case-study of fat coal slurries. Justification is given for using the time of displacement of the boundary between three states of aggregation as the time of induction. From the correlation of the spreading velocity of a collector, displacement time of the contact line (induction time) and the flotation velocity, it is found that flotation activity of the collector is governed by its properties relative to the gas-liquid interface.

The article proves the promising nature of joint roasting of rebellious oxidized and sulfide lead-and-zinc ore from Ozerny deposit at the stage of ore preparation for flotation. The joint roasting of lead-and-zinc ore and sulfide ore initiates generation of sulfur-containing agents and sulfidation of rebellious oxidized lead and zinc. It is experimentally proved that selective oxidation of pyrite proceeds together with disintegration of lead and zinc along the interphase boundaries. The main products of such interaction are ZnS, PbS, Fe₃O₄ and Fe₂O₃, which can greatly facilitate flotation later on. This method of complex ore processing can potentiate commercialization of oxidized lead-and-zinc ore and rebellious sulfide ore, can prolong service life of mines and mitigate the environmental impact of the industry. The produced samples are analyzed and described using the X-ray phase analysis, differential scanning calorimetry, optical microscopy, chemical analysis, Rietveld refinement and program TOPAS.

Consumable supplies in mines (explosives and explosive devices, oil, lubricants, rubber, protective devices, spare parts for machinery and equipment, flotation reagents, etc.) should be sufficient for stable production. However, for mining operations, supplies are burden costs, as storing supplies increases operating costs. The logical question is how to achieve the balance between mine production stability and minimization of costs of supplies, that is, how to optimize supplies. The paper presents a quantitative model of stochastic supplies optimization as a possible answer to this question. The application was demonstrated in the specific case of polymetallic ore lead, zinc, copper, and silver mine flotation with value indicators.

The authors discuss the mineral resources and mineral reserves of the Russian Far East in terms of their volume and production of certain minerals. The key challenges of subsoil use, which complicate advancement in the mining sector at the present time, are identified. The growth prospects of the mining sector can build on the processing industry and on the transition from mineral extraction to mineral production at high degree of conversion. The economic efficiency of subsoil use depends on the professional corporate management, transportation and power generation infrastructure, sound scientific grounding and on the development of the processing industry which uses products of the mining industry. The main trends of the spatial development in subsoil use are proposed. The large infrastructural projects are described, which can promote social and economic progress in the Far East Federal District of Russia. Emphasis is laid on improvement of personnel potential and on introduction of scientific supervision in the mining and processing industry in the region.

The authors present a multi-factor algorithm for making provisions for geological/geotechnical constraints and operation timing criteria subject to availability of resources. The algorithm enables embracing a variety of possible combinations of heading or stoping conditions at each specific underground mine facility. The algorithm is a part of the digital tool of automated underground mine production planning in geological and mining information system MINEFRAME.

The authors examine the present-day hydrogeological situation and its post-mining phase forecast in the Chelyabinsk Coal Field. Geotechnical facilities in the areas of Krasnaya Gornyachka Mine and Kopeisk and Korkino Open Pit Mines are discussed. The problems to arise during flooding are identified. The hydrological forecasts and an action plan to prevent underflooding in the study areas are presented.

The article presents the case-study of properties of domestic binders in dust suppression at tailing storage facilities at a mining and processing plant in the Murmansk Region. The strength development dynamics of the binder-formed blankets and the change in the strength in the wetting-drying mode are determined, the impact of chemical agents on water permeability of treated tailings is estimated, and leaching of polymerized concentrates in weakly acid and alkaline media is carried out. The authors emphasize essentiality of an integrated research for the well-founded choice of a binder.

In the study, the particulate matter (PM) measurements were carried out during several blasting operations using a portable Cascade Impactor with eight particle size fractions. The particle mass size distribution was characterized for each blast shot. The PM dispersion trend equations were established for using the measurements collected from various distances in the downwind direction and classified for different fractions (respirable, thoracic, and inhalable) to assess the health risks. As an outcome of the study, the amount of dust generated in the blasting source was specified according to the blasting theory. The PM dispersion trends were established by evaluating measurement results. It was concluded that, PM decreases from gram to milligram grades in the first 100 m distance. All of the PM fractions ultimately settles at an approximate distance of 535m and not spread out of the quarry pit. Regarding particle mass size distribution studies, blast-induced PM is classified as fine particles. The study has preceded features regarding both PM sampling during a blasting event and revealing PM fractions close to the blasting point. The context also provides a detailed comparison of the amount and characteristics of dust caused by blasting with other activities.

The authors investigate geophysical parameters of water-saturated and frozen rock samples, and compare the results with the data of natural rocks. The samples were subjected to dynamic loading, an acceleration signal was recorded and a spectral density was calculated. On this basis, later on, the authors determined the longitudinal vibration velocity, the logarithmic decrement of damping, the internal friction factor and the acoustic Q-factor. The water-saturated and frozen rock samples demonstrated the increased velocities of longitudinal vibrations. The samples, which had the high acoustic Q-factors in the frozen conditions, fractured under much higher loads. The degree of water saturation affected the strength of the test samples: their strength reduced with the higher water saturation. Freezing of the samples generated microseismic vibrations in the region of high frequencies. In the uniaxial compression tests to failure of the samples under critical loading, a high frequency signal was recorded during initiation of an extension fracture, and the signal spectrum shifted toward lower frequencies as the fracture grew.