Home – Home – Jornals – Journal of Mining Sciences 2023 number 5

The implemented research shows that coalbed gas content in face area is proportional to pyrite content of coal, calculated with respect to iron and sulfur contents determined on X-ray fluorescent spectrometer. These results confirm the hypothesis on methane formation in coal during recovery of carbon oxides in the presence of iron-bearing minerals, in particular, pyrite, and water, and explain different contents of methane in the same rank coals. The obtained inverse proportion between the coalbed gas content in the face area and the sorption surface of coal allows supposing that methane accumulations concentrate mainly in the “solid solution” and in the closed porosity, i.e. in the coal structure. For this reason, it is more difficult and longer to recover such methane from coal than methane accumulated in open pores and fractures, which quickly leaves coal in face area.

The study focuses on the connection between two processes: deformation of proppant under the action of rock pressure and the rock pressure change after injection pressure release. The modeling of proppant deformation (mechanics of granular medium) uses the discrete element method, and the rock pressure redistribution (rock mechanics) is modeled using the earlier developed model of rock as a medium with internal energy sources and sinks, and the finite element method. The numerical modeling shows that depending on the loading history and on the rock mass properties, the mode of deformation can be both stable and unstable. For the stable mode of deformation, the pressure balance is calculated at the created fracture boundary, and the change in the proppant porosity is estimated. In the unstable mode, rock mass experiences dynamic events induced by rock pressure.

The authors investigate the physical and mechanical properties of hornstone, gabbro-dolerite and rich chalcopyrite-pyrrhotine ore subjected to flooding at the Oktyabrsky deposit in the Talnakh ore province. The analysis of the petrography, chemistry and mineralogy of the test samples showed no substantial differences in their properties after flooding. The comparison of the strength and deformation characteristics of rocks from the uniaxial compression and tension testing results demonstrate the decrease of both in water-saturated rocks and the increase in the room-temperature dried samples. The limit strength, elasticity modulus and internal friction angles have smaller values in rocks after drying than in the initial samples.

The authors implemented a series of lab-scale cyclic shear deformation tests of granular medium. The steady-state boundary conditions kept for the hundreds of thousands shear cycles result in the time-varying response of the test medium. The periods of stress fluctuations of the order of tens, hundreds and thousands cycles are observed in the medium. The time-varying response of the medium is connected with periodic formation and deformation of clusters and force chains in the medium. The DEM-based numerical modeling of cyclic shear of a granular medium with the same loading program as in the tests shows the adequacy of the discrete element method and the agreement of the numerical and experimental data.

The article describes the studies on the geomechanical behavior of the large pitwall rock mass using the seismic method. The on-site measurements of elastic wave velocities in rock mass enabled determining the elastic characteristics of rocks, which allowed an inference on the rock mass stability. It is shown that the seismic method provides sufficiently reliable data on the time history of the geomechanical behavior of the large-area pitwall rock mass, and enables the geomechanics and stability control. The long-term experience of using the seismic method to ensure pitwall rock mass stability is presented as a case-study of Zhelezny Open Pit Mine, Kovdor Mining and Processing Plant. The proposed approach is applicable at deep open pit mines.

The authors show that data on characteristics of drill mud penetration zone improve reliability of geoinformation obtained from borehole geology and geophysics. The developed procedure for the data interpretation takes into account the geomechanics and hydrodynamics of drilling. A part of the drill mud penetration zone is represented by mudcake which prevents direct measurement of porosity and permeability. The article describes the experimental studies on growth of the mudcake on the samples of low-permeable sandstone from the Jurassic reservoir rock mass using an original facility. The petrophysical nonuniformity of the mudcake was determined. The repeated measurements revealed the mudding zone.

The article describes the numerical studies on propagation of hydraulic fracture in the nonuniform-stress elastic environment around a cylindrical cavity. The modeling used the extended method of finite elements. The scope of the modeling embraced different variants of the principal stress orientation relative to the cavity and a disk-shaped initiation fracture. The influence of the stress ratio and stress level on the fracture path is described. The main types of the created fractures are shown. The conditions when the created fracture reaches the cavity surface or propagates along it are analyzed. The features of the fracture propagation and opening pressure are described for the fractures of various shapes depending on the volume of the injection fluid.

The article presents the design model and results for the main crack development in closely spaced blasting in brittle rocks. The 3D modeling is described as case-study of crack formation in granite in perimeter blasting of ammonite charges at different spacing and filling of blastholes. The shapes and sizes are determined for the main cracks generated by blasting of single charge and three close-spaced charges. From the modeling results obtained for a specific charge, the method is proposed to determine efficient spacing of blastholes in perimeter blasting to ensure the maximal area of the created crack.

The authors developed the phenomenological model of landslide initiation under multiple seismic effects. The model uses the lab-scale testing data on mechanisms of slope failure under dynamic impacts, the analysis of a large bulk of field data, the instrumental measurements of seismic effects induced by large-scale blasting and the numerical calculations of influence exerted by seismic vibrations on slopes. The rules are formulated for the decision-making in evaluation of potential landslide initiation under seismic impact. Evaluation of slope stability is performed for overburden rock dumps at open pit mines in the Kursk Magnetic Anomaly. It is shown that large-scale blasts in the test open pit mine have no effect on the stability of the dumps, but the damaged drainage and the rising of underground water can result in accumulation of irreversible deformations.

The authors analyze the influence of proppant parameter on the long-term conductivity of hydraulic fractures. Pressing of proppants in fracture walls and proppant smashing was studied using FCMS-V fracture conductivity system, field emission scanning electron microscope, polarization microscope and the sieve method. The correlations between the conductivity, grain size, grain-size composition, proppant concentration and placement technique, closure pressure of fractures and pressure of proppant pressing-in in the fracture walls are revealed. Pressing and smashing of proppant grains of different size under different closure pressure of fractures is discussed. The recommendations on proppant placement during hydraulic fracturing are given as a case study of methane recovery from coal seams in YC site of Ordos Basin in China.

The article presents the optimization design results for impellers of axial fans for main ventilation in mines using the criteria of minimum mass and required stress level in fan assemblies. The design of a single disk impeller is justified. For high-duty fans having the blade tip speed of 200-220 m/s, the topology optimization is performed for the single-disk impeller. The dependence between the design parameters of the impeller components and the speed of the fan rotor is determined. The topology optimization is implemented with SIMP in ANSYS.

The article describes the theoretical and experimental research data on possibility to improve the quality of the end concentrates of float-and-sink, X-ray luminescent, adhesive and froth separation. The method of nitride hardening is proposed for ferrosilicium grain surface with the hardened layer depth in the range of 30-60 nm for reducing ferrosilicium corrosion rate by 2.7 times at the preserved process properties. The necessity of adding the primary float-and-sink flotation circuit with two-stage magnetic separation to decrease the yield of rough concentrates and to improve their quality owing to removal of 29-95% of siderite. The optimized composition of luminophore-bearing modifying agent ensures complete recovery of earlier unrecoverable diamonds in concentrate at the maximum kimberlite yield of 2.5%. The workbench test processing of difficult diamond-bearing raw materials proves the possibility of incremental diamond concentration in adhesive and froth separation (by 14.0% and 12.7%, respectively), and in the cycle of finishing operations in X-ray luminescent separation (by 25.3%) owing to modification of surface properties of diamond crystals using physicochemical methods and energy deposition.

The article presents the laboratory-scale studies on processibility of fine-grained old tailings at Kovdor GOK. Effect of collecting agents represented by fat tall oil acids (FTOA) is investigated. The froth flotation tests show high selectivity of agent Berol-2015 relative to apatite. From the lab-scale tests, it is found that with collector FTOA, the P₂O₅ content of concentrate is not higher than 24.4% despite a high degree of desliming of flotation feed (~ 70.0%). With collector Berol-2015, the concentrate content of P₂O₅ reaches 35.0-37.7% without preliminary desliming.

By means of determining the suspension effect, the authors studied the change in the surface properties of apatite under the action of reagents and ions present in flotation pulp during processing of apatite-bearing ore. It is shown that the ratio of acid-base centers of apatite surface change in interaction with ions HCO₃⁻ , CO₃^2- , HPO₄ ²⁻ , and oleate ions in distilled water and in water after deionization to remove carbon dioxide. The change in apatite surface properties in alkaline water shows up as quantitative superiority of base centers. Such ionization of mineral surface favors adsorption of cations, for example, Ca²⁺, and sets background for more efficient interaction between anion-type agents. The data obtained from the studies of the suspension effect, correlate with the results of infrared spectroscopy of apatite treated by the appropriate agents.

In order to realize the rational utilization of low-grade polymetallic symbiotic mineral resources with low input, typical copper-nickel symbiotic low-grade ores were used as the test object. After careful process mineralogy research on the ore, it was learned that the main valuable elements of the ore were Cu and Ni, and the content of these two elements was 0.16 wt.% and 0.39 wt.%, respectively. The main copper-bearing mineral in the ore was chalcopyrite, and the main nickel-bearing mineral was pentlandite. Useful minerals were finely distributed in ores. Based on the properties of ore, a beneficiation process of one stage grinding → copper/nickel mixed flotation → copper/nickel separation was proposed. A copper concentrate with a Cu grade of 17.08 wt.% and a nickel concentrate with a Ni grade of 4.63 wt.% were obtained by separation. This study provides a low-investment technical solution for the rational utilization of polymetallic paragenetic mineral resources.

The prospects for ecologization of technological paradigm of development in the sector of mineral resources are studied and substantiated with regard to the requirements and constraints, and based on the equal possibilities for the biosphere and technosphere. The notion of the nature-like technologies is structured subject to the coincidence of missions of the content-rich components in the natural and geotechnical systems. The methodology of the homeostatic transformation of the biological system functions into the structure of a cluster on the convergent mining technologies is presented.

The supply of coal-fired thermal power plants with limestone as a sorbent in the flue gas desulfurization process highlights two key issues. Apart from the raw material quality adequate to meet the technological conditions of the installed desulfurization plants in thermal power systems with several potential production and user entities, the question of rational limestone supply arises. The paper presents a multi-attribute ranking model as a possible approach to solving such tasks.

The paper presents the single-criterion modeling of limestone supply under the conditions of the variable structure of the thermal power complex of Serbia. In the end, the paper provides an analysis of the differences between multi-attribute and single-criterion solutions.

As a result of hardware updating of Prognoz-L based on the modern electronic engineering and the accumulated experience, rock mass express-evaluator Prognoz-L.2 has been designed. The test data of the evaluator are presented as a case-study of a rockburst-hazardous mineral deposit.

The article presents the fracture test data of rock samples with the porphyroblastic, granoblastic lepidoblatic and laminated structure. The tests were carried out on lab-scale tester ASI-2. The test samples were subjected to uniaxial compression until discontinuity with synchronous recording of associated electromagnetic emission, load and displacements along the compression axis. The laminated rock samples in fracture show anisotropy of geophysical parameters and electromagnetic emission.