The authors describe the results of leaching of Cu, Ni, Fe and S from copper–nickel ore mill tailings. The lab-scale testing conditions simulated in-situ capillary rise of solutions to ground surface. The leaching agents were water and water solutions of hydrogen peroxide at concentrations of 0.5, 1.0 and 10.0
The article studies a mining system with stoping under open pit bodies at steeply dipping ore bodies of small and medium thickness using rubble concrete and dirt fill as ground control. The technology assumes upward mining on the levels at the total downward sequence of stoping. The limit variant of stoping in various geomechanical conditions is studied for a geotechnical situation of mining on three levels including two mined-out levels. The mining system parameters are substantiated using 3D FWEM-based mathematical stress–strain modeling. The dependence is revealed between the geotechnology parameters and the stress behavior, and between the stability of rocks in the structural components of mining and in adjacent rock mass. The areas of possible rock fracture are identified. The safety of the mining system is governed by the integrity of rubble concrete pillars and by the stability of the crown pillar.
The generalized stress deviator is introduced as a difference between a stress tensor and a unit tensor multiplied by an average normal stress non-reducible to an octahedral normal stress in a general case. From the condition that the average normal stress of the generalized deviator should be identically equal to zero, a functional equation of the relative average normal stress is obtained. The solution of the equation is given; it depends on one of the functions of two variables. The class of the limiting state criteria formulated relative to the relative average normal stress and the second invariant of the generalized stress deviator is discussed. It is shown that the von Mises–Schleicher and Mohr–Coulomb criteria belong in this class. Some intermediate cases are also discussed.
The accomplished review of the geological and geomechanical conditions at the Tashtagol and Sheregesh deposits shows that the operating mine fields contain small- and medium-amplitude fractures, faults, dikes and ore–rock interfaces. It is revealed that during heading and stoping, geodynamic phenomena arise mostly in the neighborhood of these planes of weakness. The mathematical modeling was used for the stress–strain analysis of rock mass at different slope angles of faults approached by development headings. It is found that in case of a fault 1 to 3 m wide, the shear of the fault edges along the fault plane at the fault slope angle of 65° can happen when an approaching roadway is at a distance not less than 10 m, at the slope angle of 45°—at a distance not less than 20 m and at the slope angle of 15°—at a distance not less than 40 m. For the faults 5 to 10 m wide, at the fault slope angle of 65°, no shearing takes place, at the slope angle of 45°, shearing can happen when a roadway approaches the fault at a distance not less than 5 m and at the slope angle of 15°—not less than 30 m.
The article describes the lab-scale tests of permeability of long-flame coal from the Mokhovsky Coal Mine in Kuzbass depending on the intensity of cyclic treatment of coal with liquid nitrogen. The freezing effect on jointing was assessed by the change in the gas flow and in the ultrasound velocity. It is found that permeability of the test coal in compression rises up to commercially significant values. To reach this effect, it is sufficient to implement three–four cycles of treatment with liquid nitrogen. The treatment decreases the ultrasonic P-wave velocity by up to 6
The article describes the lab test data on the structure and permeability of sand reinforced with elastic polyurethane. The electron microscopy reveals the spatial patterns of hard polyurethane, voids and mineral particles in reinforced sand. The permeability of the test samples is investigated under conditions of uniform triaxial compression. The response of permeability of reinforced rock to freeze–thaw is analyzed depending on moisture content, specific consumption of chemical reagents and reinforcement method. The stability values of the insulating properties of sand are compared for the cases of sand reinforcement by its mixing with polyurethane resin and through creation of a low-permeable inclusion (injection simulation). The advantage of injection over mixing is shown—the consumption of polymer composition is smaller and the stability to seasonal temperature fluctuations is higher.
The authors reviewed the known methodical approaches to the determination of strength characteristics of rocks using their testing results. Some shortages of the approaches are revealed, and the common shortage is their empirical nature consisting in reduction of strength of rock mass in proportion to degradation of its quality. The proposed procedure to determine rock mass strength takes into account the rheological alteration of rock mass. The procedure better represents physical processes in mine openings due to rock pressure.
The authors revealed the dependence of the dehydrating activation energy parameters in rocks on the phase ratio of β -quartz to α -quartz. In rocks with the predomination of β -quartz ( β -quartz / α -quartz >1 ), rock falls are observed and the ratio of the dehydrating activation energies of crystallization water (chemically bound) and adsorbed water (physically bound) is less than 1. This is reflective of the build-up of free and physically bound water which penetrates defects in rocks due to the phase transition of quartz, and leads to an increase in their dehydrating energy.
The authors present the results of development of a powered roof support control system included in the machine group of top coal caving to a longwall conveyor. The methods of measurement of the conveyor loading by a swinging feeder, recording of changes in the quantity of dirt in total rock mass, as well as the integration of the newly developed system in the powered roof support control are described. For determining loading of the longwall conveyor by the swinging feeder, it is proposed to use the algorithms and methods of machine vision, added with a camera of projection of light marker net on the rock mass surface. The method of detection of variation in composition of rock flow is proposed to be implemented through automated measurement of gamma radiation in rock flow and comparison of the measurement with the control value. The concept of a versatile adapter is developed, and the control system architecture and automated operation algorithm are presented for the longwall top coal caving technology.
The article describes the method to estimate sensitivity of local seismic monitoring networks in two underground mines at the khibiny massif: kirovsk and rasvumchorr. The method uses empirical data of induced seismicity monitoring. At each monitoring station, based on the behavior of seismic waves and the distance to epicenters of seismic events, detection probability diagrams were plotted for seismic events and different ranges of seismic energies. The diagrams were used for plotting the probability of detection maps for a seismic event and a certain energy range. this approach has a few advantages. First, the input data may be records of production blasts and other sources rather than natural seismic events. Second, the method allows using the averaged probability diagrams for the decision-making on deployment and expansion of monitoring networks in mines. It is shown that monitoring networks ensure reliable recording probability (95
Flotation involves two forms of sorption using both a collector or a composition of collectors. Effect of the two forms of sorption of a collector can be assumed as a synergy of two reagents–collectors. In this case, flotation runs under conditions of hydrolysis of the reagent or its dissociation. Selection of a reagent mode means creation of condition for the two forms of sorption on a mineral surface. Activation of flotation by cations of metals, catalytic oxidation of xanthate form a sorption layer represented by the chemically or physically adsorbed reagents or by their derivatives. Each form of sorption plays a part in particle–bubble attachment. The first form of sorption aims at enhancement of hydrophobic properties of a mineral to be recovered, and the second form removes the kinetic constraint in the particle–bubble attachment. The strategy of selecting combinations of collectors to reach their synergetic effect in flotation is developed and proposed. Each collector performs its function in the particle–bubble attachment. Enhancement of hydrophobic properties of a mineral, or increase in the density of adsorption of a reagent at its surface results from the fulfilled condition of either chemisorption or physisorption of a reagent or a composition of reagents. It is shown that the properties of the second form of sorption are determined from the mechanism of work of a physically adsorbed collector.
Some criteria are justified for selecting coal waste dumps suitable for heat recovery as a case-study of solid mine waste accumulated in the Donbas. These criteria involve geodynamics—position of a dump relative to the boundaries of an active geodynamic zone, as well as air dynamics—gas permeability of rocks in this zone and methane concentration in air entering the dump. It is shown that young and medium-age dumps situated within the boundaries of closed unflooded mines can contain mixture of air and gas with an explosive concentration of methane. The model of changing the role of mine methane in generation of the heat field in a self-heating dump is described. The model uses the idea that methane can both reduce the oxidation rate in coal waste and intensify their combustion efficiency. It is proposed to undertake geodynamic and gas dynamic ranking of coal dumps to determine their suitability as heat generators. The justified criteria can be used to develop a heat recovery technology for coal dumps.
The authors discuss the influence exerted by reagents–regulators on selective modification of spectral–kinetic characteristics of unrecoverable diamonds with anomalous luminosity to ensure their complete and selective recovery in X-ray luminescence separation. The parameters of kinetic stability are determined in emulsions of luminophore-bearing modifiers, and the reagents–regulators that cause no worsening of attachment of the modifiers at the surface of diamonds are found. It is shown that reagents–regulators of different classes (derivatives of alkyl/aryl phosphonates, aliphatic alcohols, bifunctionally modified derivatives of carboxymethyl cellulose, ionic and non-ionic nitrogen-bearing polymers, short-chain aliphatic amines, complex reagents) substantially decrease attachment of luminophores at the surface of hydrophobic minerals of kimberlite and prevent thereby their recovery to separation concentrate. The influence of reagents–regulators on the spectral–kinetic characteristics of the applied luminophore-bearing modifiers and treated diamonds is determined. The reagents–regulators suitable for the use in the modification technology without subsequent unwanted correction of spectral characteristics of diamonds are selected.
The modified surface of sulfide minerals (arsenopyrite and antimonite) after bio-treatment with bacteria Pseudomonas Japonica is studied using electroacoustic spectrometer Dispersion DT-310, scanning electron microscope Tescan Vega II SBH, digital technologies and DSA20 EasyDrop unit. It is found that bio-treatment leads to substantial hydrophilization of the mineral surface, which is confirmed by an increase in the wetting angle by 40–50° and in the work of adhesion by 2 times. It is found that the electrochemical properties of the mineral surface also change, including the sign reversal of the ζ -potential and the increase of the electric conductance by an order of magnitude. The scanning electron microscopy proved adsorption of the bacterial cells at the mineral surface. The proof tests confirmed efficiency of the bio-treatment and showed reduction in flotation of sulfides by 15–17
The objective of this study is purifying kaolin ore collected from Djebel Debbagh deposit, situated in eastern Algeria by the utilization of a multigravity separator. The chemical, mineralogical and microscopic analyses were carried out. These analyses reveal that the kaolin ore contains kaolinite as the main mineral contaminated with manganese considered as an impurity in this case. This last reduce significantly the quality of this kaolin and consequently limit its use as raw material in several industries. Three variables, namely, drum velocity, wash water flow rate, and shake amplitude of the Mozly multigravity separator were chosen for the analyses of their influence on the content, yield and recovery of manganese in mill tailings. The Box–Behnken designs and the response surface methodology were used. After optimization of the process variables, the maximal values of Mn content, yield and recovery were obtained. The predicted results were consistent with the experimental data, confirming the model correctness and the effectiveness of the parameters adjustment in MGS for manganese removal from kaolin.
The practical application of manmade geochemical barriers in treatment of waste water in the mining industry is described. The studies of efficiency of natural and modified minerals in reduction of concentrations of heavy metals in mine waste water and in model solutions have positive results. The technical aspects of creation of manmade geochemical barriers are examined, namely, materials, sizes and designs aimed at enhanced efficiency and extended service life of the barriers. The geochemical barriers can be integrated in process flowsheets of operating mines, and are suitable for the independent use in closed mines where the cost of sophisticated waste water treatment systems is too high.
The research focuses on processing of copper–nickel alluvial sand wastes at the Verkhnee deposit, Norilsk Industrial District. In the sand wastes, the size category of –100 μ m is chosen, with the nickel and copper contents of 0.32 and 0.22
The authors assess prospects for recycling of carbonate–fluorite ore processing waste in the Voznesensky ore district in the Primorski Krai. The main factors that can influence processing of slime are determined. The flotation-based recoverability of fluorite from low-grade (11.56–13.12 μ m is demonstrated. A rational process flow sheet to produce concentrates with CaF2 content more than 93
The article analyzes efficiency of safety and support of underground excavations at great depths in potassium salt rock masses as a case-study of the Starobin and Petrikov deposits. Various protection technologies are discussed. It is found that owing to formation of block structures and cohesion loss zones nearby the perimeter of mine excavations, the balance holes can have both beneficial and adverse influence on excavation stability. The relaxation excavation technology allows a great reduction in the dimensions of limiting state zones in rock mass surrounding mine openings. The model of block movement is proposed, and it is shown that mutual displacements of blocks by more than 1–2 mm in the vicinity of an excavation perimeter can be a cause of the dynamic failure of blocks into mined-out areas. It is recommended to install rock bolting as soon as cohesion loss is detected on sliding surfaces.
The article analyzes interaction of a hydraulic fracture and a permeable crack nearby a void in a uniform medium under triaxial compression. 2D modeling used the finite element method. Possible paths of the created fracture are set as cohesive layers composed of elements which can deform and fail depending on an applied stress. A fluid flow is modeled by additional points with crossflow of fluid from the created fracture into the permeable crack when they intersect. The numerical studies are presented for the nature of the hydraulic fracture–permeable crack interaction depending on the: distance between their interaction point and the void; stress state; strength and internal friction factor of the medium; fluid viscosity. On the basis of the obtained results, for the creation of an antiseepage screen, it is recommended to perform hydraulic fracturing in the vicinity of a void at a distance equal to the void radius.
