Home – Home – Jornals – Journal of Mining Sciences 2021 number 6

The article presents a geomechanical model of a tunnel with rock bolt support. The numerical modeling is performed in ANSYS. The effect of the rock bolt support on the tunnel stability is analyzed with regard to the rheological properties of rocks. The loading and functioning of rock bolts are actualized owing to joint deformation of the rock bolts and enclosing rock mass during their interaction with each other and with the anchoring grouting. The authors discuss feasibility of loss of the load-bearing capacity by the rock bolts because of their fracture. The algorithm of timing of a rock bolt to keep functioning and damage localization is described.

The article discusses application of the deep-level stress determination method developed for modeling stress redistribution in rocks and in backfill as mining operations are advanced. It is suggested to take into account elastoplastic properties of rocks and backfill using the stiffness matrix of intact rock mass. The illustrative calculations are presented.

A study was conducted to uncover the possible correlations among mechanical and index properties of sandstones from formations of Salt Range area, Punjab, Pakistan. For this purpose, sandstone block samples were collected from seven formations of the Salt Range. The samples were prepared for rock testing according to the guidelines set by International Society of Rock Mechanics (ISRM). Defective samples were discarded and those meeting the ISRM specifications were tested for sonic velocities, dry density, porosity, uniaxial compressive strength, tensile strength and elastic constants. Results obtained were then statistically analyzed to find the predictive relationships. The analysis revealed that correlations exist between two groups of tested rocks. The predictive relationships were determined between porosity and static mechanical properties of rocks and between porosity and dynamic mechanical properties.

The paper concerns an analysis of the causes of the rock burst that occurred in 2019 in one of the underground hard coal mines in the Upper Silesian Coal Basin (Poland). This incident occurred in the area of an active longwall with complex mining and geological conditions. The operation was linked to natural hazards, with seismic (rock burst) and methane hazards predominating. The recorded seismic activity in the course of the operation was at a high level. Commonly used methods of assessing the state of the rock burst hazard are characterised by the difficulty in predicting the occurrence of tremors which may result in dangerous incidents (rock bursts or relaxation). There is therefore a need to constantly improve methods of forecasting the state of such hazards. The paper presents selected results of the applied analytical and empirical methods, which made it possible to determine the causes of the rock burst and to determine the principles of further exploitation in the area covered by the study.

The paper discusses the direct and Brazilian tensile strength testing data in terms of the mechanical properties of rocks. The statistical correlation factors by categories of rocks only offer rough estimates of the direct strength in tension using the Brazilian tensile strength test data. It is suggested to compare the two methods using models which include the structure of a material. It is shown that when the analysis includes the biaxial stress field, which leads to a decrease in the strength by the Brazilian test as compared with the strength value from the direct tension, as well as when the analysis includes the nonuniformity of the tensile stresses, which brings an opposite effect, the tensile strength values of the two methods are correlated more accurately.

The authors describe the numerical studies into hydraulic fracturing in an isotropic elastic medium with a fracture initiator set at the hole bottom. The influence of individual factors, including the setting depth of the fracture initiator, its distance from the hole bottom, the bottom shape, the strength and elasticity of the medium, on the shape of the created fractures and on the fracturing pressure is determined. The application of the revealed dependences in optimization of the technology and equipment of the directional hydraulic fracturing is illustrated.

The article presents the theoretical and experimental results on propagation of hydraulic fractures in the neighborhood of an extended cylindrical cavity in an isotropic elastic medium under the hydrostatic stress and in the triaxial stress field composed of unequal components. The influence exerted on the curvature and volume of the created fractures by the fracture initiator and cavity spacing, as well as by the strength and compression of the medium is illustrated. The main types and conditions of the created fractures are described. The physical simulation and the full-scale experiment prove the numerical research reliability and the applicability of the program and method solutions in design of hydraulic fracturing at short distances from underground openings and structures.

The analytical model and numerical program are developed for solving 3D elastic problem on wedge tool penetration resistance in brittle rock mass with regard to the main crack growth. The program testing is described. Its efficiency is proved by comparison with the analytical solution of a problem on equilibrium propagation of a disc-shaped crack in the elastic space with pressure applied in the center of a circle of limited radius. Such solution is a good approximation of the problem on wedge penetration and can be used to estimate the wedge penetration resistance depending on the wedge geometrics, penetration depth and characteristics of the medium.

The authors discuss the lab-scale studies into sub-horizontal effect of a low-frequency seismic wave on a slope. Acceleration transducers enabled tracing relative slope sliding even in case of invisible straining. It is found that if the maximum acceleration in the momentum is below a certain value governed by the soil strength, the slope keeps stable even at high displacement velocities. A single impact at high acceleration but low mass velocity is also incapable to initiate landslide. However, in this case, residual strains arise, accumulate and can make the slope unstable. Under multiple impacts, the critical parameters are markedly lower as compared with the single impact. This is particularly true for steep slopes having small stability factors. The parameters of vibrations generated by different-magnitude earthquakes which initiate slope failures in the form of landslides are analyzed.

The article presents a package of engineering solutions to ensure an essential increase in overall extraction of useful components in development of structurally complex ore deposits. The efficiency criterion of such mining using mixed-type process flows of ore extraction and processing is proposed to be the highest NPV of extraction and processing of high-grade ore, low-grade ore and mining-and-processing waste within the overall period of mining. The use of this criterion allows setting optimal ranges for cut-off grade to identify the ore types and qualities. Extraction blocks are distinguished by geological types determined based on the texture, structure and material constitution of ores. In a structurally complex extraction block, zones of super rich, rich, crude, poor and super poor ore are delineated. Super rich ore is extracted in the first place and is forwarded to pressure leaching or to leaching-and-adsorption. After disintegration by blasting, the other above-listed ore grades are sent to a processing plant or to heap leaching. This technology enables enhanced overall metal recovery from an extraction block.

The authors substantiate applicability of type-design practice of geotechnical facilities by their complexity with a view to determining structure and contents of deformation monitoring. It is suggested to exercise the type-design practice using particular characteristics of geological, hydrogeological and geotechnical conditions of mineral mining. Based on the existing regulatory documents and considering the modern scale of open pit mining and the current dimensions of open pits, the system of particular characteristics is shaped for the assessment of open pit mining conditions. The multi-criterion analysis of influence exerted by the particular characteristics on the resultant complexity estimate of an open pit is presented. The deformation monitoring procedure for open pits depending on their mining complexity is proposed. The procedure is tested at Tsentralny open pit mine at the Khibiny apatite-nepheline deposit on the Rasvumchorr Plateau.

The ore dilution is generally defined as the degradation of economical and valuable ore with the addition of the unwanted host rock, failed backfilled material and or ore material considered below the cut-off the grade. The importance of ore dilution on the profitability of a mining operation is very well known and also well documented, since, it adds to the cost of mining, hauling, transportation, milling and processing etc. It also differs from one mining operation to another, the ore type being extracted, the type of the host rock present and type of mining method applied, type of backfilling method and material used, including other mining parameters. The ore dilution is generally expected at all stages of mining operation including the very first step of stoping in the case of hard rock mining, where, the low-grade ore is extracted un-intentionally or intentionally to insure the safe mining environment including excavation stability and or towards the easy movement of men and machineries. It is well known that the numerous parameters including mining and rock mechanics influence the occurrence of ore dilution in the case of underground hard rock mining. Herewith, through review study, the problem of ore dilution, various factors affecting dilution, its measurement and possible control measures is discussed.

The effect of various parameters (S:L ratio, duration, temperature and intensity of ultrasonic treatment) on recovery efficiency of zirconium and rare earth elements (REE) in dissolution of silica gel is investigated. The leaching process optimization is performed using the method of Taguchi L9 orthogonal array and the analysis of variance (ANOVA). The recovery of zirconium and REE from silica gel to pregnant solution at the optimized dissolution parameters is 47.95 and 56.17%, respectively. The ANOVA method shows that contribution of ultrasonic treatment in the recovery of zirconium and REE equals 89.6 and 59.6%.

Tecflote non-ionic organic agents are investigated as potential flotation collectors for copper-nickel sulfide ores. Adsorbability of four Tecflote agents having different-structure alkyl radicals and different numbers of functional groups is analyzed. The efficiency of the agents toward copper- and nickel-bearing minerals is estimated in non-frothing flotation of ore samples treated with chalcopyrite and pentlandite-pyrrhotine. The behavior specificity of Tecflote agents as compared with sulfhydryl collectors is illustrated. Tecflote agents are more active relative to nickel-bearing minerals. The flotation tests prove that inclusion of Tecflote collectors as additives to standard flotation regime enhances efficiency of the process. Partial replacement of xanthate favors higher recovery of copper and nickel in flotation froth at lower recovery of nickel in flotation tailings.

The article describes the studies into the mineralization kinetics of air bubbles with non-activated and activated sphalerite particles 74-100 µm in size in brackish solutions of sulfhydryl collectors. The test collectors were isopropyl potassium xanthate and isopropyl sodium dithiophosphate (Aeroflot), and the test activator was copper sulfate. The tests provided new data on the mineralization kinetics of air bubbles with sphalerite particles in brackish solutions. The mineralization kinetics test procedure and the new data on the air bubble mineralization rate and intensity can be a framework for the science-based selection of flotation agents (collectors, activators, etc.).

In view of rapid digitalization in the mining business, the authors highlight some associate problems. The definition of a digital twin is explained, and the difference of a digital twin of a solid mineral deposit from the other digital twins in the industry is described. The key function of a digital twin of a mineral deposit consists in updating of the deposit representation and in the use of the updated data in reasoned decision-making concerning mining development. A digital twin is formed using a set of automation tools. The mining and geological information system MINEFRAME integrates and structures the geology and geotechnology data a solid mineral mining in a unified digital space and, thereby, generates a mining plan based on the actual geological information. The methods of geological and geotechnical modeling, including digital twins, enable enhancement of occupational safety and optimization of mining strategy.

The article presents the studies into accumulation, distribution patterns and concentration conditions of radioactive elements in natural coal. The distribution patterns of radioactive elements in coal as function of its grade are also found. The application range of radiation properties of coal and barren rocks is substantiated for identifying the coal-barren rocks interface in longwall top coal caving with gravity coal flow to AFC. The working capacity of the nuclear geophysics method with metallic shielding of a responsive indicator is proved experimentally.