Home – Home – Jornals – Journal of Mining Sciences 2020 number 3

The authors perform numerical modeling of processes which create individual history of mechanics and mechanical condition of salt rocks nearby a roadway. The influence of a sampling point (roof or sidewall) and life time of the roadway on the residual stress level and quality of a sample is estimated with regard to microinhomogeneity. The effect of the specified factors on the mechanical characteristics of a sample in standard compression testing is demonstrated.

The article presents the analysis of seismic observations in mine roadways. The recorded seismic signals are connected with dynamic deformation of rock mass under massive blasting. The source of induced seismicity are dynamic movements of rocks with an amplitude of 3-30 μm along fractures 1-15 m long. These events feature low values of reduced energy, probably, due to shallow depth of mining. Distribution of induced seismicity events in time and space agreed with patterns of larger seismic events due to remote earthquakes, which implies weak probability of nasty geodynamic phenomena in the course of mining in the Korobkov Field.

The author study gas content of coal seams in the face areas in mines of SUEK-Kuzbass. It is found that gas content of coal samples from newly exposed face ranges between 2.4 and 13.5 m³/t and makes 32-60% of natural gas content of studied seams. The coal seams with lower gas content in face area have more ordered microstructure estimated by mean of plotting entropy-structure complexity diagrams based on thousandfold enlarged digital images of coal surface. Coal seams with more chaotic structural arrangement possess both higher natural gas content and gas saturation in face area.

The article discusses feasibility of frozen wall construction supervision in salt rock mine shafts using seismology techniques. Shallow seismic survey locates wakened areas and intense water flows in rock mass near shafts. Borehole seismics, including crosswell shooting and vertical profiling by the common depth point method, allow estimation of frozen rock thickness. The proposed package of seismology techniques aims to reduce risk of emergencies in construction of mine shafts.

The authors examine Kaiser effect in sandstone in nonproportional triaxial cyclic compression tests with stage rotation of an assigned stress ellipsoid through an angle of 90°. The load program consists of three pairs of cycles such that the maximal nominal stress of the second cycle exceeds the first cycle stress by 20 MPa at the constant side support. Cyclic loading is applied to sandstone in three orthogonal directions, with two cycles in each direction. Kaiser effect only appears in the second loading in the same direction, and activation of acoustic emission upon the change in the active loading direction is independent of the earlier reached stress level. This fact points at the orientation-driven nature of Kaiser effect, which means the material remembers its lattermost internal damaged structure.

Blasting still dominates the most suitable and economic processes of exploitation of minerals from the ground. Although there have been many advancements to optimize blasting to inhibit the impacts due to ground vibration caused by it, still there is a long way to go. Some empirical formulas from the past have helped in designing the mining process and served us well in configuring the blast design to minimize the adverse impacts on the surrounding environment. A couple of empirical formulas taken in this study have also proven worthy for predicting the ground vibration with good accuracy, but the reliance of the empirical formulas on only two parameters is their limitation since the beginning. This study aims to find alternatives with the help of various regression models and comparing their competence against the more traditional predictors existing today. The findings of this study suggest that the regression methods can have a better insight into the prediction of the PPV corresponding to the input parameters. The GPRs (Gaussian Process Regressions) were able to predict the ground vibration with much better precision compared to the linear regression methods and also the empirical predictors.

Scaled distance equations used for estimating peak particle velocity have been developed by some researchers. The most widely used equation among these is the equation developed by Duvall and Fogelson. However, the equation has not exactly estimated the peak particle velocity correctly. In this study, peak particle velocity values were measured by a number of blast tests that were conducted in four different sites by using a vibration meter. Scaled distance values for each blast test were calculated according to the equation proposed by Duvall and Fogelson. Subsequently, a new equation that calculates the scaled distance was proposed. The proposed equation gave more realistic values than the equation proposed by Duvall and Fogelson.

The authors perform numerical modeling for the comprehensive stress-strain analysis of roof rocks above powered roof support units in the longwall top coal caving technology. Passive control of top coal prefracture fails to maintain efficient disintegration and well-proportioned flow feed on armoured face conveyor. The relations between the residual and initial strength of coal and the prop of the powered roof support units at different combinations of methods and means of active control are obtained; their ranges of application and the proportioned flow rates are determined.

The article discusses feasibility of secondary mining of natural-manmade sylvinite seam KrII* in the Upper Kama Potassium Salt Field. The full scale tests of large samples were carried out to determine mechanical properties of seam KrII*. Mathematical modeling provides estimates of load exerted on nonuniform safety pillars after secondary mining. The authors propose alternative flow charts for the secondary mining of natural-manmade seam KrII* to ensure safety and reasonable efficiency of production.

The authors study the process of the induced stress field formation in mining with the conventional and nature-like geotechnical systems, including frame and honeycomb mine structures. The rate of change in the natural stress field during mining is estimated using a new index-response factor. Based on the data of experimental mine research, as well as physical and numerical models, with regard to the numerical model calibration, the diagram of influence exerted on the rate of change in the natural stress field by the geometry of stopes in underground ore mining with the conventional and nature-like geotechnologies is plotted. It is found that the highest effect on the size of the induced tensile strain zones is exerted by the mining systems with caving of ore and enclosing rocks. The optimum response factor is a characteristic of the frame mine structure.

The authors discuss the problem connected with insulation of exposed rock surface areas against the aggressive influence of mine atmosphere and rock falls during mining. The lab-scale tests determine the moisture effect on the strength of rocks in the Orlov Ore Field. The tensile strength of samples of isolation membrane as well as their adhesion to rocks and shotcrete is assessed. The technology of preparation and application of polymer membrane insulation layer on the surface of differently damaged areas on the roof and sidewalls in stopes is justified for the Orlov Mine.

The article presents a case-study of mathematical modeling of electromagnetic and electromechanical processes in a downhole vibration exciter EM drive. The authors propose the mathematical model of EM drive on the basis of a double-acting EM machine. This model maintains a wide-range analysis of transient and quasi-stable operating regimes. The algorithm and implementation of the model using the structural modeling methods and means in the Matlab Simulink environment are described. The model verification is carried out by means of comparison of the simulation and physical models of EM drive within the configuration of downhole pulse vibration exciter. The appropriateness of the model is proved. The authors give recommendations on further improvement of the model and its accuracy in calculation of dynamic behavior of drives.

The studies into the mechanism of activation of sphalerite flotation by ions of heavy metals show that neither ion exchange nor electrochemistry explain the experimental facts, namely, activation of flotation of copper mineral by lead ions, activation of sphalerite flotation by zinc, or flotation in the presence of non-conducting surface layer with silver or mercury. The authors put forward the hypothesis of activation due to the effect of physisorption of a collector in elementary event of flotation. It is possible to activate froth flotation by the products of nonstoichiometric interaction between xanthogen and ions of some heavy metals. The influence of the scope of deviation from the stoichiometric relation of concentrations of xanthogen and activation metal salt on the collectability of the interaction products is described. The activation efficiency of the interaction products is estimated using the criterion of ‘surface flow thickness’ of the film of collector derivatives at the gas-liquid interface.

The article addresses processability of old copper-zinc ore flotation tailings. Potential reserves and processability of mining waste are considered in terms of Uchaly Mining and Processing Plant. The mineral composition and chemistry of old tailings are determined. The analysis of modes of interaction between gold and tailings minerals reveals inefficiency of conventional technologies in extraction of valuable components. The authors validate thermochemical processing technology for old tailings with gold and silver recovery using chlorammonium reagents. The thermal study determines the mode of thermochemical interaction of old flotation tailings with NH₄Cl and NH₄Cl - NH₄NO₃ mixture, efficient sequence of tailings processing with chlorammonium reagents and the optimum temperature ranges.

The physicochemical analysis of distribution of useful components in processing of ash and slag of the thermal energy sector plants is performed. The article describes thermodynamics and kinetics of chemical reactions during agglomeration of feedstock and ammonium hydrofluoride at the temperatures of 50-200 °С, sublimation of ammonium hexafluorosilicate in the temperature range of 350-550 °С, production of amorphous silica nanoparticles, alumina particles and red iron oxide pigment, as well as formation of calcium fluoride (Ca, Y)F₂ which is a concentrator of rare and other elements. The efficient technology is developed for processing of electromagnetic fraction of ash and slag with integrated recovery of various useful components.

The article considers extraction of rare elements from monazite and their leaching. In this study, phosphate decomposition process was conducted using alkaline roasting. The results showed that the phosphate decomposition of monazite from Bangka Island increased with increasing temperature and increasing monazite/NaOH mass ratio. Analysis of the decomposition rate on the basis of shrinking core model revealed that the rate could be appropriately expressed by the equation based on mixed control of diffusion through a residual layer and surface chemical reaction.

The author gives methodological ground for the assessment of ecological stability of the mining industry areas based on the mechanism of interaction between the natural and technical subsystems. The list and values of the required ecological stability indicators are presented for the environmental risk classification of industrial facilities.

This study discusses the importance of phreatic layer in the stability of slopes. It describes the development of phreatic layer based on Dupuit and Forcheimmer assumptions in the slope. To understand the water flow behavior through slopes, design of prototype was prepared and later the set-up was fabricated in the laboratory. The set-up includes simulated conventional dump made up of soil type material. The design of experimental set-up resembles the actual scenarios of overburden dumps constructed over the bases having inclination varying from 0º to 5º. The phreatic surfaces obtained in physical models are further compared with numerical models prepared using SEEP/W software.