Home – Home – Jornals – Journal of Mining Sciences 2021 number 1

The samples of anthracite and bituminous coal are studied in cyclic freeze-thaw at different water contents. In the freeze-thaw cycles, the samples were subjected to continuous ultrasonic sounding. It is found that different contents of water have an essential influence on the spectrum of recorded signals. Regarding the water-unsaturated check samples, the spectrum change is reversible, and the freeze-thaw treatment results in no failure. An increase in the water content of the samples fosters the irreversible change in the spectra of the signals against the background of macro-cracking along stratification planes. Anthracite exhibits higher persistence to freeze-thaw damage than bituminous coal.

The authors construct an exact solution to the problem on the stress-strain behavior of rock mass at the boundary of an underground excavation of an arbitrary geometry if the vectors of the Cauchy stresses and displacements are assigned simultaneously at this boundary. All explicit components of stress and strain tensors, as well as the components of rotation vector are determined as functions of the elastic characteristics of rocks, values of the preset functions and differential properties of the boundary.

The article discusses the mathematical modeling results on formation of concentration zones of failure stresses in annular space of a well during hydraulic fracturing of productive formations from vertical or nearly vertical boreholes. The rigid connection between the cement lining and rocks fails because of a thin clay layer in-between, which leads to unsealing of the annular space and to various troubles, including environmental implications. To prevent annular space unsealing during hydraulic fracturing, it is proposed to ream out borehole in the area of contact with the productive stratum roof, and to install a bow springs centralizer on this level then.

The article presents the experimental data of seismic and acoustic monitoring in a fully mechanized longwall mining face. The predictors of the rock mass behavior are selected to be the acoustic emission activity and the increase in the pulse recurrence rate at the same time in the neighbor roof support unit. Crack formation in the longwall mining face zone is calculated.

The authors analyze the influence of the semi-autogenous (SAG) mill parameters on the mill grinding efficiency, energy consumption and the tangential cumulative contact energy. This paper provides a new liner parameter design and optimization method, which offers theoretical guidance for the optimization design of liner parameters.

Uniaxial compression test of outburst coal was conducted to explore the mechanical characteristics of coal with outburst tendency in low gas pressure environment. The mechanical properties of coal were analysed, the surface crack morphology of coal was obtained and the energy characteristics of coal during loading were determined. Results are as follows. In the pressure range of 0.03-1.0 MPa, the uniaxial compressive strength and elastic modulus of coal show a negative exponential relationship with pressure, and both decrease with the increase in pressure. With the increase in gas pressure, the angle between the failure surface and horizontal surface of coal body increases gradually. With the increase in gas pressure, the fracture morphology of coal failure tends to be complex. When the gas pressure is low, the coal can store a large amount of energy, and its ability to resist damage is greatly improved.

In deeper level mining in Tashtagol deposit, during extraction of ore reserves from safety pillar, the stresses and inelastic strain zones increase 2-4 times. In safety pillar in Sheregesh deposit, the tensile stress zones, where failure of undermined rocks intensifies, enlarge as mined-out stoping void grows. During mining in the Eastern and Northwestern sites of Tashtagol deposit, at the tunneling speed of 2.0-2.5 m/day and more, rock bumps of energy class 5-6 are recorded. In mining of Podruslovy and New Sheregesh sites, the decrease in the energy class of rock bumps is achieved at the tunneling rate of 0.4-0.6 m/day. The feasibility and sequence of safe extraction of ore reserves from safety pillars established under the Kondoma and Bolshaya Rechka rivers are justified. The backfill options in extraction of ore reserves from safety pillars in Tashtagol and Sheregesh deposits are discussed.

The mining of iron ore, an essential raw material for iron and steel industry, is of prime importance among all mining activities undertaken by any country. Therefore it is important that the iron ore mining should be environment-friendly and sustainable. Ripper Dozer combination is one of the most commonly used excavation methods in Iron ore mines of Goa because of the presence of soft and friable rock mass and also it can bring the mining project more productivity, accuracy, safety and the additional option of selective mining. Improper selection of ripper dozer and unscientific deployment can lead to high production cost. So, performance prediction is an important issue for successful ripper application which deals with exposed rock mass properties and ripper machine parameters. Ripping production prediction using multiple linear regression analysis (MLR) and artificial neural network (ANN) is performed to estimate ripper production in the lateritic rock formation.

Large-scale mining methods are taking over the leading role in exploitation of low-grade and deep mineral deposits considering its high productivity, low cost, and satisfying ore recovery and ore dilution. In order to improve properties of existing block and sublevel caving methods, researches were carried out in laboratory conditions on physical model of similarity. Results of the research, the determination of optimal parameters and indicators for the new variant of the caving mining method is discussed in this paper. Experiments were based on ore drawing for the case with two and three one-sided lateral loading chambers and they were performed in order to determine the best combination between variable parameters of block width and spacing between loading chambers that would give the most optimal results for ore recovery and ore dilution.

The experience of high-frequency pneumatic hammer design to run on increased compressed-air pressure is reviewed. Arrangement of a coupled shock-pulse generator composed of two pneumatic hammers is described, and its stable operation conditions are determined. The synchronized operation of the hammers in the coupled generator is implemented through smooth percussion frequency control of one of the hammers. After the accomplished research into interaction between soil and some prototype models with two percussion masses, a fully phase- and frequency synchronized machine has been designed.

The mechanism of change in the surface morphology, physicochemical properties, adsorbability and floatability of eudialyte concentrate as a result of exposure to high-power nanosecond pulses and dielectric barrier discharge in air under the atmospheric pressure is analyzed. The research methods were the Fourier-transform infrared spectroscopy, analytical electron microscopy, atomic force microscopy, confocal laser scanning microscopy, microhardness testing, flow potential determination and other techniques. The rational parameters of energy deposition and reagent regimes toward enhanced efficiency of complex eudialyte-bearing ore flotation are found.

The action of the arbitrary physisorbed species of a collector at a mineral is compared with the theoretical evidence on particle-bubble attachment. The lack of the correlation between the hydrophobic behavior, characterized by the wetting angle, and the floatability of minerals, as well as the correlation between the inductance time and the mineral recovery are discussed. The causes of disagreement between the collectability sequence of xanthates, dithiophosphates and dithiocarbamates and the sequence of boost in energy of chemical bond between these reagents and cation of mineral lattice are exposed. Collectabilities of frothers and residues of the collectors are explained. The ways to increase flotation performance are shown, namely, the mineral recovery and the concentrate quality can be improved by means of adjustment of the chemisorbable /physisorbable collector ratio.

The capacity of novel selective dithiocarbamate collectors, namely, morpholine dithiocarbamate (MDTC) and S-cyanoethyl N, N-diethyldithiocarbamate (CEDETC) to form complex compounds with gold on the surface of sulphide minerals containing fine gold under conditions of flotation is experimentally proved. MDTC adsorption at the surface of chalcopyrite without gold takes places due to formation of morpholine dithiocarbamate copper. At chalcopyrite and arsenopyrite containing gold fines, MDTC-Au and CEDETC-Au compounds are formed. MDTC and CEDETC improve floatability of gold-bearing sulphides as against gold-free minerals, which is beneficial for the production of Au-Cu concentrates with lower content of As and Fe by flotation.

In this article, the recovery of the Y, La, Nd, and Ce rare-earth elements (REE) from apatite concentrate by acid leaching and digestion-water leaching processes were studied. The maximum REE recovery of 62% in the acid leaching process with sulfuric acid was obtained for La in the condition of 12 M acid concentration, leaching time of 4 h, process temperature of 25℃, and a liquid to solid ratio (L/S) of 1:5. In the optimal conditions in terms of process (220℃, 3 h and L/S (1:2)), the digesting process in the presence of sulfuric acid led to the recovery of La, Ce, Nd and Y at 93.92, 92.22, 92.04 and 91.00%, respectively. In contrast, the aqueous leaching process in the optimum conditions, including a leaching time of 5 h, at 80℃ and L/S of 1:10 ended up recovering the La, Ce, Nd, and Y at 89.50, 88.45, 92.20 and 94.0%, respectively.

The authors compare the effect exerted by copper ions and sulphide copper nanoparticles on flotation of Gorevskoe deposit sphalerite using potassium n-bytul xanthate and in reagent-less regime. Covelline-like colloid particles 4-8 nm in size, obtained in interaction of copper (II) and sulfide ions in aqueous solutions, are characterized using the methods of dynamic light scattering, electron microscopy and diffraction. Sphalerite surface after reaction with copper ions and CuS dispersoid solutions are described by zeta-potential measurements and X-ray photoelectron spectroscopy. It is found that sphalerite flotation after activation with nanoparticles is lower than with copper ion solutions of the same concentrations, and improves with increasing duration of activation and flotation processes. The mechanism of CiS nanoparticles consists in creation of active centers for the collector to attach to, which intensifies the hydrophobic behavior and adsorption of the collector. Moreover, CuS nanoparticles promote formation of a special microrelief of the solid-liquid interface, which ensures rupture of liquid film and attachment of sphalerite particles to air bubbles when they collide.

The subcool zone length is determined in lining of an extra-long railway tunnel subjected to deep influence of piston effect. The air temperature distribution in the outer air-tunnel lining contact zone is determined as function of the velocity of train and the outdoor temperature in the cold season. The authors review the de-icing methods of tunnel lining: warming-up using a self-tuning heating cable; arrangement of an unheated access gallery and heat insulation. The distribution of the hourly average air temperature in an extra-long railway tunnel is analyzed against of sites of fan heaters. The heat power patterns in the tunnel are estimated by the criterion of the required temperature conditions. It is shown that the most efficient arrangement of fan heaters to maintain the required air temperature in the tunnel is their uniform distribution along the length of the tunnel in combination with installation of warm air curtains at the tunnel faces.

The experimental version of a bidimensional measurement facility allows recording displacement of rock blocks in the normal direction relative to a fault and their shear displacement relative to one another. In 2020 the facility was deployed at Zarnitsa open pit diamond mine, and was included in the long-term geodynamics monitoring in the zone along a fault which cuts the open pit. It is found that displacements of rock blocks in the normal direction to the fault are periodic at the maximum amplitude of 3.5 mm, while the shear displacement is reversal at the maximum amplitude of 1 mm.