Home – Home – Jornals – Journal of Mining Sciences 2023 number 4

The apparatus of nonstationary thermoelasticity is used to estimate the joint and separate effects of gas pressure sorption and gravity on gas drainage and on stress state in the vicinity of underground openings. It is shown that gas flow changes the stress state of coal, and pressure in sorption essentially counteracts pressure in gravity. Ignorance of the latter fact may lead to a poorly substantiated choice of a coal gas drainage technology and to an erroneous prediction of rock strength and stability.

The experimental procedure is developed and tested on a laboratory scale and using layered samples of manmade geomaterials. Within the dual-permeability model, the procedure enables determining parameters that govern fluid flow and poroelastic deformation in fractured porous rock masses, namely, fracture permeability k₁ and mass transfer coefficient β, as well as their dependence on stresses σ. The testing procedure is proposed and implemented. In the procedure, under the stepwise increasing normal stress σ, the stationary flow rates Q₁(σ) and Q₂(σ) are measured in a quasiregular fractured porous sample at the preset pressure difference: using a standard setup (Q₁) and in closed end-face fractures (Q₂). The mathematical model of the experiment is constructed, and the analytical solution of the problem on stationary flow is obtained: pressure patterns in fractures, and stress-dependence of flow rates. The experimental data interpretation algorithm enables calculating k₁ and β by the recorded flow rates Q₁ and Q₂. It is shown that the permeability k₁ is proportional to σ ^-2, and β remains almost unchanged.

The authors analyze seismic and hydrogeological data recorded after a large-scale blast on 22 September 2021 in Lebedinsky open pit mine, Kursk Magnetic Anomaly. In blasting of four groups of blocks, the maximum values of PPV are determined at five observation points arranged at the epicentral distances of 1.7-4.9 km, as well as the amplitudes of the hydrogeological response are assessed in two observation wells in overlying rock mass. The main parameters of the blast-induced seismic effect are used to calculate maximum PPV from the earlier found relation. The divergence of the recorded and theoretical data is observed in the near field of the blast in the first group of blocks, at the reduced distances of 106-198 m/kg^1/3. In blasting in sedimentary rocks at the reduced distances of 405-512 m/kg^1/3, the difference in the wavefield is observed. The research findings can be used in drilling-and-blasting control.

The article presents the results of toothed screw crushing of coal on a laboratory scale. The samples are the marketable coal from different deposits in Russia, Kazakhstan and Kyrgyzstan. From the analysis of change in the quantity outputs of grain sizes, it is found that irrespective of the coal field location and coal grade, the use of a toothed screw crusher in coal preparation for dressing leads to no overgrinding of coal.

The new design of a powered roof support for the controlled longwall top coal caving in thick coal seams contains a special outlet and a reciprocating feeder. The introduction of such technology needs pre-testing and analysis of the outlet modes per the support units, such that to ensure the maximum allowable fill of the longwall conveyor without its overloading and dynamic phenomena. Created in Rocky DEM environment with that end in view, the simulation model takes into account the physical effect of rock mass fracture using the discrete element method, and enables variation in the design parameters and operating conditions of the powered roof support. The implemented experiments make it possible to assess the interdependence of the average velocity of coal outlet to the conveyor, the outlet gate angle and the feeder vibration frequency.

The article describes numerical modeling of sublevel stoping using the discrete element method. The study included development of a modeling procedure, creation and calibration of the numerical models, and the result analysis. The optimal design parameters of structural components of the mining system are found, which are promotive of reduced ore losses in sublevel stoping at the Khibiny apatite-nepheline deposits. Some behavioral patterns of rock mass during sublevel stoping are obtained. The mechanism of ore losses is described.

Compressibility of disturbed-structure strong rocks is determined for predicting land subsidence and stability during operation of transport machines. The plate-bearing tests are carried out on a large bench tester at different normal pressures and different densities of strong overburden rocks. The method to estimate deformability of strong overburden rocks using a plate and a station rod is described. The results were used to assess passability of transport machines during damming and for the damp stability calculation.

The authors developed a pilot project to test different preparations of cemented rock fill, determine the appropriate mix design, and check necessary mix strength. The article presents the required resistance studies and the research method used to determine feasibility, cost performance and increased mine productivity and safety. The study achieved a resistance peak of 1.6 MPa, reduced dilution of the ore, and increased pillar stability.

The authors analyze the control circuit of the work process-related parameters of a hydraulic impactor with the piston retention before the back stroke phase. Retention is implemented via the throttle control of pressure in the hydraulic cell of the slide valve. The physical model of such hydraulic impactor is tested, and its energy characteristics are determined. The tests included re-tuning of throttles and slide homing spring, and variation in fluid flow rate. The article presents oscillograms of the hydraulic impactor dynamics and the slide performance versus throttle parameters, fluid flow rate and the spring pre-tension. The curves of the hydraulic impactor energy, retention pressure and fluid flow rate illustrate the energy adjustability using the proposed performance control circuit. The oscillograms of the slide motion during its work cycle are plotted, the features and shortages of the process are determined. The proposed design of the throttle valve provides the steady-state performance of hydraulic impactors.

The authors discuss the issue of engineering a special gear to change the power fluid pressure in hydraulic fracturing of strong rocks. The article describes the operation of the gear on the basis of implemented laboratory tests, and proposes the ways of eliminating deficiencies. The size and shape of choke grooves for the careful switching of the control valve subject to the power fluid flow rate are determined. The hydraulic circuit of the jet-control slide-type valve is developed. It allows improved accuracy and precision of the valve switching.

The influence of phase transitions in moist and salt-containing soil on freezing process is analyzed. The effects connected with the crystallization heat of pore water under negative temperatures and with the crystallization heat of salt when the eutectic point is reached are discussed. The conclusions on reachability of the eutectic point in artificially frozen strata above saline are drawn. Using a mathematical mode of heat processes in artificially frozen clay containing the common salt solution, the influence of the offset of the eutectic point on the temperature field in the frozen ground is analyzed.

The authors describe the integrated studies into the influence exerted by nonequilibrium low-temperature plasma of dielectric barrier discharge in air under normal conditions and pressure on the acid-base, adsorption and flotation properties of natural iron sulfides (pyrite and arsenopyrite). The studies aimed to correlate the plasmachemical treatment parameters with the physicochemical and process properties of sulfide minerals. Using the Hammet indicator method, it is found that plasma treatment strengthens acceptor properties and weakens electron donor properties of pyrite surface, as well as weakens acceptor properties of arsenopyrite. Adsorptive properties of pyrite relative to the electron-donor butyl xanthate grow, and, as a consequence, flotation activity of the mineral improves. In case of arsenopyrite, the adsorptive properties and flotation activity decrease. It is shown that the low-temperature plasma pretreatment of minerals reduces arsenic yield in flotation froth by 10-11% at the reduced arsenic content of concentrate by 0.71-0.78%.

The authors propose the galena flotation mechanism based on the joint work of chemisorbed collector and physisorbed lead xanthate in molecular form. It is proved experimentally that the products of interaction between xanthate and lead ions possess surface activity dependent on the concentration ratio and on solution pH. In alkaline range, they spread over the gas-water interface and can remove water from the interlayer between a mineral particle and a gas bubble. In sub-acid medium and at the increased mole ratio of lead ions to xanthate anions, the spreading velocity of the interaction products decreases. The physisorption mechanism of the collector has disclosed the causes of high floatability of galena in the alkaline range of pH and the decreased floatability in the sub-acid domain.

The causes of coincidence between pH of a solution of collectors, at which the maximal recovery of a target component is reached, and pH of the solution with minimal surface tension are discussed. Based on the physisorption mechanism of a collector, the floatability connection with the surface tension of the solution is explained. It is shown that extraction of ion-molecular associates from the solution and the presumptive increase in the mineral surface hydrophobicity are not an explanation of the increased recovery. The floatability improvement is achieved via removal of the kinetic constraint of the flotation contact by surface-active species of collectors. The increase in the collecting activity of a blend of collectors is explained by the synergetic effect of the decreased surface tension and reduced induction time. The criterion of flotation activity of a physisorbable collector is proposed.

A new device designed for wet magnetic separation-magnetic hydrocyclone-allows separating magnetic fraction from a fast and curved flow of pulp. The advantages of the magnetic hydrocyclone are the high specific output and the design simplicity which governs reliability of the device. The pattern of calculation of the magnetic hydrocyclonage performance represents an estimation of separability of magnetic fraction depending on the device geometry, variation in the magnetic field parameters, flow velocity and the physical parameters of the particles. The processing performance from calculations is compared with the results of the magnetic hydrocyclone testing. The proposed device is recommended to be included in the processing flow chart for ferruginous quartzite and other types of ore with the pronounced magnetic properties. Inclusion a magnetic system allowing higher magnetic induction up to 5-10 Tl in the flow chart makes it possible to extract weakly magnetic minerals.

The article describes the experiment on the upward percolating mass transfer by water solution according to the natural mechanism of movement of solutions toward ground surface with water evaporation in atmosphere. Useful components settle out from the solutions and concentrate on the evaporation barrier. The experiment simulates a complete cycle of processes for flotation tailings of complex ore: feed of solutions in boreholes from surface to bottom of a tailings body; spreading of the solutions in the tailings body; capillary ascent to the surface; settling out and concentration of useful salts on the evaporation barrier. The usability of this approach and some parameters of the mass transfer process can be found from the relevant research.

Using a laboratory model of a vertical centrifugal breaking machine, the milling efficiency of ore having different Mohs hardnesses is found. The rational structural and operating parameters of the breaking machine are determined for such ore materials. The data are included in the project documentation development for manufacturing a pilot vertical centrifugal breaking machine VTSI-12.

The optical, electron scanning and laser microscopy methods produced new experimental data on the adsorption layer generated by the chelating agent MDTC and hogweed extract on the surface of sulfide minerals in composition of complex ore. It is found that MDTC selectively attaches to chalcopyrite and forms a stable and water-insoluble compound with copper, which uniformly covers the whole surface of the mineral. It is determined for the first time that at the surface of pyrite, intense formation of dark-brown crystals of MDTC oxidation products takes place-dimorpholinethiuram disulfide which is chemically adsorbed at the mineral and is resistant to multiple washing-off in water. Morpholine dithiocarbamate does not interact with the surface of arsenopyrite and scheelite, and does not form stable phases with the components of these minerals. Hogweed extract does not desorb MDTC and is observed on the pre-adsorbed collector in the form of a fine bluish film washable off with water. At arsenopyrite and scheelite, a few separate and fine spots of hogweed are found.

This paper studies the effect of using cationic/mixed anionic collectors in the practical application of quartz sand flotation. The combined use of Dodecylamine(DDA)/sodium oleate(NaOL)/sodium dodecyl sulfonate(SDS) is the innovative point of this paper. This experiment used quartz sand from Hanzhong, Shaanxi Province, China. The results showed that the combined use of DDA, NaOL and SDS was better than the single use. Using DDA/NaOL/SDS mixed collector, the removal efficiency of Al₂O₃ can reach 75.1%, compared with DDA/NaOL mixed collector, the purification effect of Al₂O₃ can be increased by 11.1%. Compared with DDA/SDS mixed collector, the use of this mixed collector can greatly improve the purification effect and recovery rate. And the quartz concentrate has a good recovery rate in practical application.

A brief description of coal resources in Transbaikalia is given. The issues of thermal and hydrochemical modification of coal from Apsat deposit are discussed. The usability of carbonization, gas-steam activation and alkaline treatment of low-caking coal for the improvement of coal adsorption capacity is determined. The proposed technology of Apsat coal preparation and dressing includes crushing, screening, carbonization and steam activation. The characteristics of the initial and treated coal are presented. The main physicochemical properties of the produced carbon adsorbents are determined. The coal modification parameters are identified. The computer-aided modeling of activated carbon adsorbents based on the quantum-chemical interaction of particles is described. The application areas of high-quality adsorbents in mining waste treatment are specified.

By combining the advantages of InSAR, Probabilistic Integral Method and Genetic Algorithm, an improved method for dynamic prediction of probability integral parameters is proposed to realize subsidence inversion and prediction in insufficient mining. Firstly, InSAR is used to obtain the time series information of surface deformation in goaf. Then, a genetic algorithm-based parameter inversion model is constructed to invert the subsidence parameters such as subsidence coefficient and influence radius. After that, a dynamic prediction function is established to obtain the complete surface subsidence pattern and dynamic change trend of the mining area. Taking a goaf in Shanxi Province as the experimental object, Sentinel-1A(S-1A) image as the data source, combined with PIM and InSAR data, the parameter inversion model is used to successfully obtain the dynamic change process of mining subsidence parameters. The results show that the dynamic prediction function can achieve a certain effect on surface prediction in insufficient mining, and the parameter inversion model based on genetic algorithm has a high inversion accuracy, which provides a basis for surface prediction in insufficient mining.