Home – Home – Jornals – Journal of Mining Sciences 2017 number 5

The article presents physical modeling of geomechanical processes in outer zones of coal beds with the main roof caveable with difficulty. The scope of the modeling embrace the effect exerted on gas release by gas temperature and pressure variation during stage-wise outlet of gas from a pressure bomb, which simulates cyclical mechanical impact on a coal bed in the zones of a gas pocket. It is found that the low-frequency (2.0-4.5 Hz) attenuating vibrations generated in the main roof can induce both secondary rock mass disintegration as well as methane desorption and decomposition of gas hydrates (if present) accompanied by an increases in gas pressure and in number of gas-dynamic events in outer zones of coal beds.

The author proposes a new analytical approach to the description of statics, kinematics and dynamics of interaction between mine support and enclosing rock mass in the course of stoping. Inclusion of the static component suggests the classical construction of a probable line of fracture. The kinematic aspect means accounting for the influence of the overlying rock weight on the process of failure. The dynamics of failure during growth of mined-out area is illustrated in terms of a unit event of production heading advance. These components of the damage accumulation process in rock mass allow more accurate monitoring of destructions due to rock pressure.

Mechanisms of change in the spectra of acoustic emission in specimens of mineral coal from Kuznetsk and Pechora Basins are experimentally determined in uniaxial and triaxial (Karman scheme) compression tests. It is shown that at the pre-failure stage in a specimen under uniaxial compression, the spectrum pattern of acoustic emission changes considerably, the amplitudes of low frequencies grow while the amplitudes of high frequencies reduce. Under the Karman scheme loading of specimens, the amplitudes of the low-frequency signals grow without the decrease in the high-frequency amplitudes, which is connected with the prevented opening of fractures under the influence of the hydrostatic pressure in the horizontal plane.

The object of the numerical study is the travel of pendulum waves in a blocky medium under nonstationary impact of deep-seated charge blasting on the surface of the expansion chamber. The blocky model is simulated by a two-dimensional lattice of masses connected by elastic springs along the axes and diagonals. The displacements and velocities of the masses at different half-space points are calculated using the finite-difference method.

The article describes the theoretical and experimental research into the strength of cylindrical specimens made of layered and anisotropic geomaterials exposed to axial compression and lateral pressure. The tests used INSTRON 8802 versatile servohydraulic fatigue testing system. The experimental results are the relationships between the ultimate strength and bedding angle in specimens of an artificial material, meta-siltstone and shale. The experimental data agree well with the theoretical calculations.

Fracturing efficiency of fluids in specific mining processes depends on reliability of data on structure and state of rocks, on pre-setting the location of fracturing origin, on choice of a fluid and its injection regime, as well as on the accepted engineering solutions. Fracturing by fluids are the processes that alter properties, structure, composition and state of rocks. Investigation of such processes offers a deeper insight into the multi-phase media (earth crust) and promotes advancement in nonconventional mining technologies.

In focus of the studies is the influence exerted by the radial displacement of the hammering unit on the air distribution in the air hammer drill with the ring-shape elastic valve. The minimal allowable volume of the backstroke chamber at the frontmost position of the hammering unit when it contacts the anvil is calculated with regard to the limited maximum pressure in the impact stroke chamber at the moment of the blow. In the capacity of the air hammer drill efficiency criterion, it is suggested to use the length of the powered closure of the elastic valve, that compensates rotation of the hammering unit in the body when the radial clearance between these parts grows. The parameters of the air distribution system are estimated for all sizes of air hammer drills with the ring-shaped elastic valves.

The article presents the procedure and algorithm for selecting basic characteristics of a positive-displacement hydraulic hammering system. The procedure is based on the dimensional analysis of equations of the system, selected similarity criteria and calculations of output characteristics in the space of the similarity criteria. The program offers a user the options of setting initial parameters and characteristics of hydraulic impact systems in the form of values and constraints and, then, table values for the dimensionless characteristics to be inserted in the similarity formulas for the selection of a hydraulic impact system. For a selected system, geometry of the hammer head is calculated. The Java-based program has a graphical multi-window interface, including menu, toolbox, windows for setting parameters, and limitations, input of source data and calculated data, computation of hammer head sizes and output of plotted dynamic characteristics of limit cycles of the hydraulic system.

The review of accidents connected with explosions in gently dipping and inclined coal bed mining with mechanized equipment is presented. It is shown that the most probable cause of the explosions is inflammation of methane-and-air mixture induced by the sources of coal self-ignition in mines. The explosion wave brings burning gas in the production heading and adjacent tunnels and causes blasting of coal dust. The mechanism of coal self-ignition in edge areas in inter-panel pillars exposed to high rock pressure is described.

The complicated geology and geomechanics in Tashtagol, Sheregesh and Kaz mines induce geodynamic events during transition to deeper level mining. Mining advance from the higher stress concentration areas from the hanging wall of a fault towards the lower stress concentration areas contributes to the reduction in rockburst hazard. The use of the self-propelled equipment allows higher volume of preparatory driving per 1000 t of ore production by 10-20% as compared with the portable equipment. The mechanism of rock mass movements in deeper level stoping is revealed. High mining depth and high strength of enclosing rocks are favorable for starting extraction of ore reserves left in pillars. The combination of these factors and the efficient mining system design enable mining of blind ore bodies without backfill and allows extraction of ore reserves from pillars under the rivers and ground surface infrastructure.

The methods and means of dumping overburden at open pit coal mines in Kuzbass are reviewed. Specific features of dumping are highlighted, and the dependence of dump stability on geological conditions and physical properties of overburden is determined. The priority lines of development in the dumping technology are aimed at efficient utilization of mined-out areas in open pits and idle hydraulic fills. The issues of the environmental safety of dumping are addressed.

The article gives testing data on the effect exerted by energy impacts (ultrasonic, electrochemical and thermal) on the recovery of zirconium and rare earth elements from eudialyte concentrate to pregnant solution by acid leaching. An original installation is developed for the implementation of leaching. Based on the research findings on the kinetics of acid leaching of eudialyte concentrate and on the change in the concentrate micro-structure and phase composition, the mechanism of the influence of integrated energy impacts on the efficiency of recovery of zirconium and rare earths in pregnant solution is substantiated.

The interaction of fatty acid sodium oleate collector and higher isoalcohols in liquid phase and on the surface of separated minerals of scheelite and calcite is investigated. The research findings on monophase calcite and scheelite are presented with their X-ray patterns and IR spectra. The experimental data show the contribution of the intramolecular interactions in combinations of differently ionizable oxyhydryl collectors on the increase in the contrast between floatabilities of scheelite and calcite. The IR spectroscopy states that the maximum strength of the intramolecular hydrogen bridges between oleate and isoalcohols in the range of 300-3200 cm-1 fits with the molar ratio 2. Isoalcohols in the surface layer of scheelite neutralize hydrophilic behavior of oleate micells by means of generation of heteromolecular associates through hydrogen bridges, loosen hydtrated layer and enhance air bubble attachability; adhesion of isoalcohol drops improves floatability of scheelite; higher isoalcohols reduce flotation activity of calcite. The maximum contrast in flotation properties is observed in slimes at oleate concentrations fit the micelle formation process.

The experimental research into intensification of copper-nickel ore concentration by flotation and magnetic separation shows that pre-treatment of ore before milling by accelerated electrons results in the increased yield of - 0.071 mm size and in enhanced recovery of useful components in the concentrate. Magnetic separation improves complexity of use of mineral raw materials.

Mine water at some mineral deposits in Transbaikalia contains valued metals commercially recoverable from solutions using zeolite rocks. Experimental impregnation of metal-bearing mine water from Sherlovaya Gora and Bom-Gorphon areas with sodium and ammonium kinds of clinoptilolite rocks from Shivyrtui deposit has been carried out. In the laboratory conditions, metals adsorbed by zeolite rocks are extracted by means of displacement by concentrated ammonium salts with the further calcinations of the filtrate up to 500 °С. The metal content of the obtained cakes is conditioned by metal concentrations in solutions, by methods of impregnation and by the eluents applied. Saturation of ammonium types of zeolites with mine water solutions from the Sherlovaya Gora lake and the further extraction of adsorbed metals by ammonium acetate yields the recovery of lantanoids of 73%. The obtained results, considering multiple recycling of the sorbent, can be used in development of an efficient technology for extraction of rare earth elements from mine solutions.

The article describes features of ore reserves and development of processing technologies at Mikhailovsky MPP. New approaches to disintegration of ore and to improvement of dry magnetic separation of unoxidized ferruginous quartzite are evaluated. The scope of the discussion embraces the process of finishing magnetite concentrate, extracted from unoxidized ferruginous quartzite by wet magnetic separation, using the flotation flow chart with the closed and open circuits, as well as the reverse cation flotation of hematite concentrate from tailings of wet magnetic separation. The authors present process solutions aimed at designing energy-saving conveyor roasting machine MOK-1-592 and the technologies of production of different purpose iron ore pellets.

A Stefan problem is analyzed for the case of rock freezing during shaft sinking, It is shown that the rate of thermal diffusion in rock mass is comparable with the velocity of the boundary between different phases. The Stefan problem is solved for a single shaft using the finite difference method. The procedure for the generalization of the calculation data on thickness of an ice-and-rock shield in a single shaft for the case of many shafts is improved. The ice-and-rock shield thickness forming around freezing pipes is calculated in terms of shaft 1 in the mine of Petrikovsky Mining and Processing plant of Belaruskali.

The authors propose to assess air pollution in mining regions using the integrated instrumental monitoring, calculation and remote sensing. The algorithms for experimental data processing for the calculation and remote monitoring of snow cover pollution as a universal indicator of the pollution distribution in air are substantiated. The article presents the integrated monitoring data on the induced load in the air in the large mining industry cluster in Kuzbass.

The authors propose the approach to validation of the surveying control accuracy in safety monitoring of earth dams in terms of liquid waste receivers at mines. Based on the system structuring of types of earth dams and their elements, estimation of influence of loads and effects exerted to these structures, as well as the analysis of accident The article presents the installation meant for the determination of gas permeability of rock specimens placed in a testing cell with the adjustable axial and lateral compression. The installation includes a measurement system for the automated long-term investigation of rock permeability in accordance with the preset program. It is also possible to test specimens with a fracture filled with a propping material. The reported data of the permeability tests of porous quartz-containing material and coal demonstrate the capacity of the installation and the experimentation specificity.

The article presents the review of the current methods used in Russia and abroad to predict accidents in underground mines based on the monitoring of stresses, strains and seismic and electromagnetic events. The phenomenon of emission of submicron particles is reveled in rocks and the submicron particle emission under compression of rock specimens is modeled physically. A conclusion is drawn on the possibility of developing a new method and equipment for the prediction of accidents during underground mining.

The method of the empirical model decomposition and its application to the analysis of data obtained using a laser strain meter is described. The issues of adaptation of the method to the real data are discussed. The method enables identification of a monotone trend and a slow component of deformation process much more efficiently than the conventional techniques. The method shows reliable operation in cleaning of signals from noise and high frequencies.