Home – Home – Jornals – Journal of Mining Sciences 2024 number 6

The authors theoretically substantiated and, using in-situ measurements, proved the method of determining kinetic characteristics for coal bed gas: content, diffusion factor, mass exchange and rate of desorption. These data are required for the development of technologies of coal mining and methane utilization. The method involves solution of an inverse problem within the framework of a nonlinear model of gas emission from a particle placed in an isolated container, using the data on time change in thermodynamic parameters (pressure and temperature) in a sealed canister with coal chippings. The model analysis shows that ratio of methane concentrations at different moments of time is independent of gas content. This enables development and numerical implementation of a two stage algorithm: first, by solving an inverse problem with time-dependent coefficients, the factors of diffusion, mass exchange and desorption are found; then, with minimization of a special function, the gas content is determined. The in-situ data are obtained using coal chippings from drilling in an operating mine in Kuzbass, by means of measurement of pressure and temperature in five canisters for 10 days. The interpretation of the data made it possible to assess the methane content in the test coalbed site as 4 kg/m³.

The field research of the geomechanical behavior of rock mass was carried out in the neighborhood of an abandoned railway tunnel by means of multi-channel analysis of seismic surface waves. For the interpretation of the results, the spectral dispersion images of waves along the tunnel were selected and analyzed. That made it possible to obtain the velocity patterns of waves in enclosing rock mass, and to identify the low-velocity zones in it. The results prove the applicability of the method of determining structure and condition of adjacent rock mass surrounding underground structures.

Open mining operations generate deep open pits, and the industrial infrastructure and buildings become closely spaced with the open mining zone as a result. The situation requires implementation of integrated monitoring and periodic assessment of pitwall stability considering up-to-date data on properties and condition of rock mass. This article describes an approach to monitoring and assessment of pitwall stability on a hazardous site. The periodic seismic profiling reveals great disruption of the test site. The stability assessment of the test site using the limit equilibrium method shows the slope instability. It is concluded that prediction of failure zones on the test site is advisable to carry out by integrating the field inspection and computational methods of slope stability control.

The static and dynamic wedge indentation resistance tests involved plexiglass and marble samples. The static tests recorded the indentation resistance force as function of penetration depth. The dynamic tests included a rope gravity drop hammer. The tests focused on the dynamics of penetration of a dropping massive wedge into a plexiglass sample. The indentation resistance was determined using an accelerometer mounted on the wedge. Plexiglass as a model material allowed finding the shape and size of the main cracks generated by wedge indentation. The test data on the wedge indentation resistance and on the main crack size were compared with the theoretical values. The comparison showed a good agreement of theory and static experiments with plexiglass samples. In the dynamic tests, the theoretical indentation resistance appeared to be less than the test values by 25% at the most, at a good agreement between the sizes of the main cracks.

The article describes the stability testing and calculation results for a heavy column set on the surface of a granular medium, and for a plate buried in the granular medium. The column and plate were exposed to a pre-limiting static load. The granular medium was subjected to multiple weak impacts. The lab-scale tests determined that under such loading, the granular medium evolved gradually to the critical condition and lost the shearing strength. The rate of approaching the critical condition grows with the number of impacts. The critical number of impacts before failure of the medium obeys the log-normal distribution. The most probable value of the critical impact number increases exponentially with the decrease in the static load. The DEM-based modeling of the stability loss in the plate buried in the granular medium yielded the results that qualitatively coincided with the test data.

It is investigated how the content of basalt fiber with a diameter of 23 µm influences specific energy intensity of failure in concrete D2000 and in light heat-reflecting concrete D1000. The mechanisms of alternating temperature effects on dynamic impact resistance of fiber-reinforced concrete are determined. After 12 cycles (freezing temperature - 50 ± 2 °С), the energy cost of failure in the samples of concrete D2000 at the fiber volume ratio of 2.7% totals 1962 J/m², which is 3.6 times higher than the energy intensity of failure in the samples of non-reinforced concrete. It is found that concrete with a porous absorbing aggregate made of expanded vermiculite possesses higher dynamic impact resistibility than high-density concrete. The energy intensity of failure was 5038 J/m² in vermiculite-containing heat-reflecting concrete and 2326 J/m² in fine-grain concrete D2000. The failure energy intensity in vermiculite-containing non-reinforced concrete after three freeze-thaw cycles drops by 71%, from 5038 to 1473 J/m². At the fiber volume ratio of 2.4%, the energy intensity of failure in fiber-reinforced concrete decreases by 9%, to 4608 J/m². These results can help increase the impact resistibility of shotcrete lining, including situations after the adverse effect of cyclic freeze-and-thaw.

The geodynamic research of coal-rock mass in mines in the Donbas uses composite seismic signals which appear on ground surface during coal mining. The search of regular patterns in geological response of rock mass to seismic waves is based on the main physical principles of elasticity: dependence of the signal energy on the proximity to the vibration source and dependence of P-wave velocity on the density of the medium. The authors of the article discuss the results of seismic monitoring in the mine fields in the Donets-Makeevka region of the Donbas. The energy and spectrum characteristics of seismic signals are correlated with the geodynamic processes and with the geological section parameters. The direct proportional dependence is found between the total thickness of jointed rock mass and an integrated parameter including azimuth of any component of seismic waves. The analysis of spectra of composite signals shows that their frequency characteristics allow differentiating areas of maximal softening and compaction in coal-rock mass and eventually enable delineating faulting influence zones which are the anomalous accumulations of methane.

Density, porosity, P-wave velocity and Leeb hardness were determined for travertine samples from different quarries in Turkey, and the relationship of these properties with uniaxial compressive strength values was evaluated. Exponential relationships were obtained between UCS and physical and mechanical properties of test samples. The strongest relationship was obtained between UCS and the Leeb hardness, at the correlation factor R² 0.91.

Inspection of underground openings in the Taimyrsky Mine, in the previously flooded areas, revealed increased jointing, rock falls in roofs and sidewalls, dome folding in roofs and fracturing of shotcrete lining. The main cause of failures is dissolving of loose material in cracks in gabbro-dolerite rock mass, with its leaching out later on. The complex mode of the Oktyabrsky deposit ore occurrence is revealed within the Taimyrsky Mine field. Mining is greatly complicated by faulting, heavy jointing, low stability of rock mass and dynamic events induced by rock pressure. Condition of mine openings was analyzed, and samples of rocks taken in the flooding zone were tested: in uniaxial compression, the strength, deformation modulus and lateral deformation coefficient were determined; in tension, the strength was determined; the failure curves (cohesion and internal friction angle) were plotted. Stability of rock mass enclosing the Oktyabrsky deposit, including jointing, was estimated. Videoimage endoscopy was carried out in exploration and destressing boreholes in order to detect stratification and fracturing in moist zones in rock mass. The ground penetrating radar inspection of adjacent rock mass was performed. It is found that mine water and mine air have the corroding influence on metal and concrete elements of mine support. The ways of improving the mine support technology in moist rock mass areas are proposed. The recommendations on safe roadheading are made.

The authors describe the methodological approach to formation of geotechnical systems of deep open pit mines with regard to transient processes. Parameters and figures of subsystems of a geotechnical system, and their elements have a great number of interconnections and undergo changes within the space of life of an open pit. Their formation is considered as a set of stable functioning periods and transient processes. The terminological paradigm of structure, components and parameters of the geotechnical system of an open pit mine is described in the context of the open pit mine transport. The concept of adaptation of the technology and equipment subsystems during transient processes is presented as a mechanism of optimal functioning of the geotechnical system. The provision of their dynamic equilibrium is illustrated. Optimization of transportation as the most expensive process in open pit mining is based on integration of computer modeling techniques: geometrical, process simulation and economic mathematical. The key features of pitwall stability estimates in substantiation of the geotechnical system parameters are discussed. The approach to optimization of rock mass preparation by blasting on the basis of real-time adjustment of physical and mechanical parameters of rocks and rock mass data is described.

The geomechanical evaluation of safety is carried out for structural components of a mining system integrating caving and backfilling in extraction of ore reserves under bottom and in pitwall rock mass. It is found that safe distance between drilling and haulage openings in neighbor stopes depends directly on the height of a mining zone. The need of sequential cutting of drilling and haulage openings in the course of extraction of ore reserves from stopes is proved. The advance of heading operations over actual stoping should be not more than one-two mine openings depending on the rock mass quality. Stoping operations should eliminate formation of any pillars across the width commensurable with the stope or smaller. It is shown that operations in undermined or overmined zones are unsafe. The parameters of structural components which ensure safety of mining are determined.

An oil reservoir is simulated by a model composed of two rectangular glass plates. The space between the plates is filled with glass chips of the similar chemical composition as the plates have. The model allows studying fluid flow in the spaced dipole array representing two wells located symmetrically relative to a certain center. The wells are simulated by holes drilled in the upper plate. The experimentation aimed to assess potential oil recovery enhancement in case of using GBK-F composition. The dependences of fluid flow rate on time in the pumping well, and on the water percentage in the overall fluid volume are obtained. The influence of the intermission in the fluid flow on the oil pattern in the reservoir after treatment with GBK-F composition is analyzed. The efficiency of the reagent is proved.

The analysis of rock flow patterns under the cross-effect of contiguous faces uses the 3D discrete element method to reproduce ore drawing processes in underground mining at the Khibiny apatite-nepheline deposit. The study of ore drawing modes revealed the mechanisms of loss formation, as well as the rational designs of structural components of a mining systems and ore draw planograms. The numerical modeling results were verified during in-situ experimental blasting and sublevel stoping in different geological and geotechnical conditions in mines of the Kola Division of APATIT. A conception of sublevel stoping modeling is developed, and the guidelines are proposed for rating ore losses and dilution in underground apatite-nepheline ore mining. The efficiency of the reagent is proved.

The authors identified the cause of loss of diamonds with nonstandard natural luminescence intensity in X-ray fluorescent separation. The technology of adjusting spectral and kinetic characteristics of diamonds is developed as treatment of diamond-bearing kimberlite material by luminophore-bearing reagents including mixture of FL-530-type luminophores and anthracene. For reaching improved stability of luminophore-bearing compositions and for the better attachment of luminophores on diamond surface, it is proposed to enhance their oil receptivity by treating with a hydrophobization agent (potassium butyl xanthate). It is suggested to ensure maximal selectivity of X-ray fluorescent separation through prevention of adhesion of luminophore-bearing composition to kimberlite grains by adding dispergators at concentrations of 1-1.5 g/l. It is shown that hydrophobization of luminophore FL-530 by potassium butyl xanthate and the use of dispergators ensure selective attachment of luminophore at the surface of diamonds with nonstandard natural luminescence, as well as their selective extraction to concentrate. The overall reduction in the loss of diamonds in X-ray fluorescent separation is proved

Composition of collectors is one of the promising avenues in stimulation of flotation efficiency. When using a mix of reagents, their synergetic effect shows up not only at the mineral-liquid interface but at the gas-liquid interface as well. This study aims at connecting the synergetic effect of a cationic / anionic combination collector in reduction of surface tension with synergism of the surfactants in flotation. The tests were carried out to determine surface activity of physisorption in case of combination of these reagents. The results are comparted with the flotation activity and interaction parameter of the components of the combination. The findings can be a framework for the design approach to selecting combinations of collectors for flotation.

It is found that synergism of combination of anionic and nonionic surfactants in reduction of surface tension is connected with their synergetic effect in flotation. These effects have the same nature. The proposed hypothesis of synergism in flotation is based on the mechanism of physisorption of a collector in particle-bubble attachment. The conformity of mole concentrations of surfactants and maximal extraction of useful component to concentrate is experimentally proved. The causes of possible lack of the synergetic effect generated by cationic and anionic collectors in flotation when this effect is observed in reduction of surface tension are discussed. It is found to be necessary to take into account the interaction energy of a collector, mineral and an ambient. The analysis of change in wettability of minerals due to reagents can involve an approach using the Lifshitz theory of Van der Waals force and the acid-base interaction of contact objects. The findings can be used to develop procedures for selecting collectors and efficient reagent modes for mineral flotation.

The authors investigate depression of talc in its monomineral flotation with polymeric anion active reagents: carboxy methyl starch and carboxy methyl cellulose (CMS and CMC, respectively), sulfonates, as well as compounds with polyvalent cations of metals. Sodium polystyrene sulfonate with molecular mass of 10⁶ kg/kmol is more effective in talc depression than sulfonates of smaller molecular mass, but gives way to CMS and CMC. Cations of Mg and Al at concentration of 2.5 mg/l increase efficiency of talc depression with sodium polystyrene sulfonate by 4%. The further rise in concentration of cations of metals weakens depression of talc. Addition of sodium polystyrene sulfonate up to concentration of 250 mg/l changes electrokinetic potential of talc from - 20 to - 32 mV. As compared with CMS and CMC, polymeric sulfonates have lesser adsorption affinity to talc. The authors propose two alternative mechanisms of interaction between polymeric sulfonates and basal surface of talc: without polyvalent cations of metals and with preliminary addition of these cations.

Test flotation of pyrite used potassium butyl xanthate and sodium butyl dithiophosphate as collectors. The study of the influence exerted by the nature of a sulfhydryl collector on the flotation ability of pyrite included pyrite samples -74+44 µm in size. The findings on froth flotation of pyrite with addition of one or two traditional sulfhydryl collectors which display similar collecting action in treatment of pyrite at pH 8 are described. From the analysis of the kinetic curves of pyrite flotation, a new approach to the assessment of flotation activity of thiol collectors is proposed.

Preliminary ultrasound treatment of reagents meant for the flotation of slimes is studied. The study of the influence exerted by the ultrasound treatment applied to water solutions of nonionic collectors for flotation desliming of sylvinite ore focused on the change in characteristics of the generated foams: foam volume and height, foam ratio, moisture content, stability and breakdown rate. It is found that foamability of the solutions, foam ratio and “dryness” increase with the increasing sound power, whereas foam stability drops. The possibility of enhancing foamability and reducing stability of three-phase foams is assessed.

Electric disintegration of spodumene pegmatites is investigated. It is found that treatment with electric pulses ensures partial dissociation of monomineral spodumene, and the best extraction of spodumene crystals, either with or without concretions, takes place when initial rock is ground to a size of 1 to 4 mm. The crystals of spodumene remain unbroken, as in mechanical treatment, and represent whole pieces. The gravity separation later on allows production of spodumene concentrate for the subsequent lithium extraction.

The article presents the method of location of heavily fractured zones in rock mass. The method uses a geophysical model of electromagnetic radiation which accompanies discontinuity of rock mass. It is shown that for the location of a rock mass area with the change in the stress-strain behavior in the neighborhood of mine openings using the electromagnetic radiation method, it is required to assess the power of a source of rock failure by means of recording signals from sensors of electromagnetic radiation. An approach to building a software architecture to predict dynamic events induced by rock pressure is proposed.

The article discusses in-situ seismic tests carried out during operation in the mines Kazakhstan, Abay and Kuzembaev in the Karaganda Coal Basin for studying and predicting geological faults in coal seams. Seismic testing used the methods of reflection survey, transmitted waves, seismic location, as well as their combinations. The practical results of the in-situ seismic testing in complex geological conditions proved the efficiency of the listed methods, and enabled adjustment of the presence, position and stretch of expectable faults, revealed the absence of unpredictable faults, and detected the zones of change in hypsometry of coal seams, as well as other anomalies.