Home – Home – Jornals – Journal of Mining Sciences 2023 number 1

The author focuses on complex loading of a granular material at continuous rotation of the principal strain axes. The described testing procedure reveals the stress dependence on the relative velocity of rotation. It is possible to use the velocity of rotation of a unit volume relative to the velocity of rotation of the principal strain axes in the constitutive equations for a continuum.

The plane and axially symmetric 2D numerical modeling of rock mass blasting is carried out using the Lagrangian tensor-based method. The results are compared with the actual direct measurements of rock mass permeability in the near zone of underground nuclear explosion Dnepr-1 in Khibiny in 1972. The post-explosion permeability of hard rocks is assessable at an admissible accuracy using the calculated shear strain intensity. A case-study of rock mass permeability change assessment in the near zone of blasting of a complex configuration charge is discussed.

The gravity flow of granular materials in axially symmetric convergent channels (V-shaped bunkers) is analyzed using the discrete element method. The symmetrical radial flow becomes unstable under certain conditions, and a space-time structure forms in the medium. The flow becomes essentially nonradial and asymmetric - the material is discretized into blocks, and the field of velocities inside the material becomes discontinuous. Further deformation reduces to relative movement of the blocks as rigid bodies.

In this study, the swelling behavior of sand-bentonite mixtures and pure bentonite are investigated by considering different factors, such as bentonite content in the mixture, specimen preparation method by applying different compactive efforts, and varying effective stress levels. Compaction tests were performed on the specimens of the sand-bentonite mixtures with 10% and 20% bentonite contents and pure bentonite. The maximum dry unit weight and the optimum water content of the specimens with 20% bentonite were relatively higher than specimens with 10% bentonite. Pure bentonite specimens had a lower maximum dry unit weight and higher optimum water content compared to sand-bentonite mixtures. Specimens of the swelling tests were prepared at the optimum water content values. Up to a vertical effective stress of 25 kPa, the mixtures showed a swelling behavior. Under the effective vertical stresses of 50 and 100 kPa, it was evident that the specimens behaved in the compression side. It was seen that the application of either 10 or 25 blows by means of compactive effort in pure bentonite specimens had a neglectible effect on the swelling behavior.

The article describes the rotary drilling modeling using the two-mass system of a drill string with a crush-and-shear hybrid drill bit. The head resistance of rocks on the bit is determined non-linearly: the penetration rate is added with the strength loss in the supporting medium under impact. The scope of the analysis embraces the continuous force generated by the rotating bit and the pulsed impacts by the drill strings at the end-points of the bit-bottomhole detachment. The initial conditions of the post-impact process, which define the initial penetration rate and the speed of the bit, are determined with regard to potential stick-slip effects. The numerical modeling proves that, as against the torsional vibrations, the axial-torsional vibrations of the drill string often result in the chaotic dynamics of drilling.

In this paper, the effect of elevated thermal treatment on the physico-mechanical parameters of Chunar sandstone from Mirzapur district of U.P. was investigated. The studied area is represented geologically by the Vindhyan Supergroup from Meso to Neproterozoic age. Sandstone of Chunar area, Mirzapur, U.P. has been granted the tag of Geographical Indication (GI) under the category of natural goods in 2019. Mechanical strength tests (indirect tensile and uniaxial compressive strength) were performed by a universal testing machine. Samples were treated at elevated temperature in the electric furnace at different temperatures for conducting mechanical and physical tests in each sample and results were recorded. The results suggest that for sandstone, high temperature treatment leads to volume expansion, weight reduction and a decrease in density as well as the reduction in the strength characteristics. Up to 200°C there is an inappreciable increase in indirect tensile strength and compressive strength but after 200°C strength gradually decreases. Beyond 400°C, the P-wave velocities showed a sharp decline due to elevated temperature treatment induced cracks in the heated sandstone.

The strength, elasticity and deformability testing of cemented paste backfill is carried out. The test backfill compositions include fine and very fine natural sand with the increased content of clay and dust, and refined with sifted granular blast-furnace slag 0-5 mm in size. The uniaxial compression strength, elasticity modulus and Poisson’s ratio are determined in the test backfill compositions at different stages of curing. The ultimate uniaxial compression strength is correlated with the P-wave velocity and elasticity modulus determined in the static and dynamic tests of the backfill compositions.

In this paper, De Moura and Butt model is extended to the large diameter drilling applications. The model proved to be effective and highly accuracy in predicting drilling performance in 19 distinct RBM and TBM operations even in the presence of datasets with high dispersion.

The authors substantiate the design of an excavator’s end effector for joint rock crushing and loading. The structural layout and parameters of hydroimpactors included in the end effectors of mining machines are described. The physical model of the hydroimpactors is constructed, tested and adjusted. The test data on the dynamics and outputs of the model at different power fluid flow rates are compared. The simulation model of the hydroimpactor is constructed and verified using the test data. The capabilities of the hydroimpactors are calculated for the planned modes of operation. For the excavator’s end effectors, it is proposed to use the hydroimpactor design with the lagged return travel of the piston toward the flexible adjustment of the hydroimpactor performance and to reach the required impact capacity at lower flow rates of power fluids.

It is important to enable remote control of duty cycle of air hammers via external distributors meant to set impact frequency. A new general layout is developed for the air-driven impact impulse generator with smooth adjustment of impact frequency at constant energy in driving construction elements in soil. The experimental model of the machine is designed and tested. Based on the analysis of the impulse indicator diagrams of the machine duty cycle, the impact frequency is correlated with the piston choke cross-section for three configurations of the control unit. The impact frequency control limits are found.

The spotlight is on reversal ventilation in a mine in case of an accident in winter. The inlet of cold air in underground openings endanger the health of miners, and mining equipment suffers from an adverse effect of negative temperatures. In compensatory measures design, the source data is the potentially transient distribution of mine air temperature after airflow reversal. The procedure of air temperature pattern in ventilation shaft during airflow reversal involves mathematical modeling of transient thermal processes in the shaft and in adjacent rock mass. The correct choice of the heat transfer coefficient between the shaft lining and air results from the comparison of the modeling results and the experimental data on the air temperature dynamics in planned airflow reversal.

The article describes the tests of thermal treatment effects on magnetic properties of bauxites and the results of their dry magnetic separation. Under increasing temperature in a muffle furnace to 600 °С, the magnetic susceptibility of treated bauxites decreases. The thermal radiation modification of bauxite by accelerated electrons under the same temperature improves the magnetic properties of the mineral. Magnetic separation efficiency is governed by the thermal treatment conditions. The process parameters to ensure extraction of rare and rare earth elements to the magnetic fraction are found.

In this study, modeling and optimization tests were conducted on enrichment of chromite ore by Knelson concentrator. For this purpose, the three-level Box-Behnken experimental design method was applied. The analysis of variance (ANOVA) was used at 95% confidence interval to test the significance of independent variables and their interactions. In order to estimate the chromite concentrate grade and chromite concentrate recovery with independent variables, quadratic polynomial regression equations were derived. Maximum concentrate grade of 54.77% and concentrated recovery values of 77.1% were reached in 12 l/min fluidization water flow rate, 1124.57 rpm bowl speed, and 21.05% solids ratio. The coefficient of multiple determination (R²) was calculated as 0.996 for concentrate grade and 0.991 for concentrate recovery. This indicates that the proposed model is a usable and effective model.

The monomineral extraction of molybdenite and stibnite is tested and analyzed using non-frothing flotation, adsorption, IR spectroscopy, multiple frustrated total internal reflection and potentiometric measurements. The ionized sulfhydryl collectors tested at concentrations of 10^-4 mole/l in a pH range of 2-12 include butyl xanthate, diisobutyl dithiophosphate, diisobutyl dithiophosphinate and sodium diethyldithiocarbamate. The test nonionized collectors are diesel fuel and O-isopropyl-N-ethyl thionocarbamate. Molybdenite shows higher floatability than stibnite in application of individual collectors in a pH range of 4.5-8.0. Stibnite is better floatable with diisobutyl dithiophosphate, while molybdenite flotation is more active with diesel fuel. The general critical concentration found for the modifiers H₂O₂ and Na₂S₂O₃ is 4.4·10^-3 mole/l-the flotation activity of molybdenite and stibnite is minimal at this concentration of the agents. Different sorption forms of the ionized sulfhydryl collectors are proved by the multiple frustrated total internal reflection infrared spectroscopy. Anisotropism of mineral electrodes Sb₂S₃ and MoS₂ made along and across the crystal lattice cleavage is experimentally confirmed. The ratio rating of grains of low-oxidizable sulfides, broken along the cleavage or in other direction relative to the cleavage, can modify the process properties of molybdenite and stibnite.

The influence of coarseness of magnetite is examined in iron concentrates after wet sieving analysis. The test concentrates are the products of Olkon, Karelskiy Okatysh and Stoilensky GOKs. It is shown that magnetic susceptibility of the concentrates gradually reduces with the decreasing size of magnetite particles in the material < 50 µm and assumes the minimal values in the sieve residue < 8 µm.

The article describes the studies into the mineralogy and process properties of ROM gold-copper-porphyry ore from the Svoboda site of the Malmyzh deposit in the Khabarovsk Krai. The tests and analysis reveal the structure and texture, and mineral composition of the ore, as well as the occurrence forms of gold and silver. The ore characteristics which govern the difficulty of the selective flotation are determined. Efficiency of Cu, Au and Ag extraction in the bulk and copper flotation cycles is described, and the causes of loss of the minerals are discussed. The resultant copper concentrate contains gold and silver, while the presence of Bi, Te, Se and admixture of In, Cd in chalcopyrite add to the value of the concentrate. Magnetite extracted from the bulk flotation tailings contain some platinum (0.5-2.0 µm) and admixtures of Ti, V, Mn, Cr and Cu.

The authors appraise application of milky quartz from the Larino lode deposit in production of high-purity quartz concentrate with the total content of impurities less than 50 ppm. The structure and texture of milk quartz are analyzed using the optical microscopy and ICP-OES spectrometry methods. The elemental analysis data of the preconcentration and deep concentration products are compared. The low contents of the impurity elements in the deep concentration products of quartz from most lodes of the Larino deposit prove the applicability of this quartz material as a feedstock for the production of high-purity quartz concentrates.

The authors discuss feasibility of high-tonnage direct inclusion of overburden in composites for the construction of road layers at mines. It is found that overburden has a strength as per State Standard GOST 23558-94 and the prolonged dedusting effect. The optimal contents of the binder and fly ash are 8 and 10% by mass, respectively. Mechanical activation of fly ash for 1 min enlarges its specific surface by 2 times. The frost-resistant composites modified with mechanically activated fly ash and stabilizer (1% by mass) have the strength grades M20-M40.

The scope of overburden investigation embraces overburden volume, physical state, mineralogy and chemistry, content of toxic elements, hydraulic/thermal/physical/mechanical properties, compositional analysis and potential process flows with a view to manufacturing materials of construction. It is found that the mineral and chemical compositions of overburden in coal mining are the same as the mineral raw material has, and the content of toxic elements is within the allowable concentrations. These rocks are classified as modulus-active and highly active, and are thermally inert. The integrated processing of overburden in coal mining enables using these rocks as a feedstock for the production of heat-insulating, ceramic, binding and road construction materials.