Home – Home – Jornals – Journal of Mining Sciences 2016 number 5

The effect of a small added mass on the frequency and shape of free vibrations of a thin shell are studied using shallow shell theory. The proposed mathematical model assumes that mass asymmetry even in a linear formulation leads to coupled radial bending vibrations. The interaction of shape-forming waves is studied using modal equations obtained by the Bubnov-Galerkin method. Splitting of the bending frequency spectrum is found which is caused not only by the added mass, but also shell wave-formation parameters. The ranges of the relative lengths and shell thicknesses are determined in which the interaction of bending and radial vibrations can be ignored.

An electromagnetic viscoelastic problem is solved for piecewise-homogeneous plates. The problem is reduced to solving a sequence of problems of electromagnetoelasticity with complex potentials. General representations of approximation functions for multiply connected domains and the boundary conditions for their determination are given. An analytical solution of the problem for a plate with one inclusion and an approximate solution to the plate with a finite number of inclusions are obtained. The change in the electromagnetoelastic state is investigated numerically as a function of time, the properties of the plate and inclusion materials, and the distance between the inclusions.

The influence of hydrogen on the strength and ductility of 30KhGSA and EI659 steels in quasi-static and shock-wave tests was studied experimentally. The sensitivity of the steels to hydrogenation in air under normal pressure or in hydrogen at a pressure of 25 MPa was determined from the results of tests of samples in the initial state and samples pre-hydrogenated at a temperature of 773 K and a hydrogen pressure of 50 MPa for 24 h. It is found that EI659 steel doped with tungsten and vanadium is less sensitive to to hydrogen than 30KhGSA steel doped with manganese and chromium.

A mathematical model is proposed which describes the interrelated processes of unsteady elastoplastic deformation of stacks of woven metal wire meshes and wave processes in pore gas in a two-dimensional axisymmetric approximation. The nonlinear equations of the dynamics of two interpenetrating continua are solved numerically using a modified Godunov scheme. The problem of explosive loading of a multilayer shell with an internal permeable deformable layer is solved. The results of numerical solutions are compared with experimental data. The influence of the gas-permeable layer on the shell deformation is determined.

The effect of the position of a passive porous coating on natural disturbances in a hypersonic boundary layer is studied experimentally. The experiments are performed in the flow around a sharp cone aligned at a zero angle of attack with the free-stream Mach number M_∞ = 5,8, stagnation temperature T₀ = 370±5 К, and unit Reynolds numbers Re_1∞ = 2,6 x 106, 4,6 x 106, 6,6 x 106, and 10⁷ m^-1. The wave characteristics of the boundary layer are calculated with the use of the linear stability theory for flow parameters corresponding to experimental values. A comparison of experimental and predicted results shows that the presence of a porous coating in the region where the second mode is unstable leads to reduction of its amplitude at the measurement point, whereas the presence of a porous coating in the region of second mode stability leads to enhancement of the amplitude.

The structure of a swirl flow in a vortex chamber is studied. Distributions of the azimuthal and axial components of velocity are obtained almost in the entire volume of the chamber. A pattern of streamlines of this flow is constructed, and the mechanism of the emergence of a reverse flow directed toward the closed end face of the chamber is identified.

The temperature field formed in the process of laser cladding of worn teeth surfaces of the gear shaft is simulated by the finite element analysis software. Isothermal lines are inside the tooth are obtained. Simulated results are compared with experimental data. Recommendations are given on improvement of the cladding technology to provide a durable continuous coating.

The effect of the arc-cone liner configuration parameters on explosively formed projectile (EFP) flight stability is studied experimentally. The effect the liner edge structure on the EFP formation is computed numerically. The results show that an EFP formed by a liner whose thickness is 0.046 times the charge caliber has improved flight stability and can perforate a steel armor 0.5 times the charge caliber thick in the case of large stand-off distances. A good tail skirt EFP can be formed by choosing appropriate parameters: the liner-to-charge diameter ratio in the interval 0.96÷0.98, the liner edge thickness equal to 0.0020÷0.0025 times the charge caliber, and the liner edge chamfer of 45÷50°.

An investigation has been conducted on the MHD Casson fluid and heat transfer over an unsteady stretching sheet with viscous dissipation effects. With suitable dimensionless variables, partial differential equations are reduced to ordinary differential equations, which are then solved by the homotopy analysis method. Dependences of flow characteristics on various parameters involved into the equations are obtained.

The goal of the present paper is to examine the magnetohydrodynamic effects on the boundary layer flow of the Jeffrey fluid model for a non-Newtonian nanofluid past a stretching sheet with considering the effects of a heat source/sink. The governing partial differential equations are reduced to a set of coupled nonlinear ordinary differential equations by using suitable similarity transformations. These equations are then solved by the variational finite element method. The profiles of the velocity, temperature, and nanoparticle volume fraction are prese graphically, and the Nusselt and Sherwood numbers are tabulated. The present results are compared with previously published works and are found to be in good agreement with them.

A magnetohydrodynamic flow of the Casson fluid over a stretching surface in the presence of the slip condition, heat transfer, and thermal radiation is considered. The effects of the skin friction coefficient and local Nusselt number on flow parameters are analyzed numerically. The present results are compared with the existing limiting solution.

A numerical study of a steady two-dimensional double-diffusive free convection boundary layer flow over a vertical surface embedded in a porous medium with slip flow and convective boundary conditions, heat generation/absorption, and solar radiation effects is performed. A scaling group of transformations is used to obtain the governing boundary layer equations and the boundary conditions. The transformed equations are then solved by the fourth- and fifth-order Runge--Kutta--Fehlberg numerical method with Maple 13.The results for the velocity, temperature, and concentration profiles, as well as the skin friction coefficient, the Nusselt number, and the Sherwood number are presented and discussed.

A simple microchannel model with submillimeter-scale geometries is proposed for studying capillary flows and investigating the dynamics in the channel. The finite element method incorporating surface tension and two-phase flow characteristic is applied. Velocity and pressure fields in the microchannel are presented. It is shown that the capillary-phase front in the microchannel is stirred, suffering small oscillations and retreating from the previous position before traveling again. Such a phenomenon is caused by nonlinear interaction of the capillary flow, surface tension, and boundary conditions.

Heat transfer characteristics of an incompressible viscous fluid past a plate embedded into a porous medium with a convective boundary condition are obtained by using the Darcy-Forchheimer-Brinkman model. The governing partial differential equations are reduced to nonlinear ordinary differential equations, and similarity solutions are obtained. The similarity equations are solved numerically. With increasing convective parameter, the surface temperature increases. The rate of heat transfer increases as the Prandtl number increases.

The problem of a fully developed MHD mixed convection flow in a vertical channel with the first-order chemical reaction is analyzed. The dimensionless governing ordinary differential equations are solved numerically by using the Maple 18 software. It is observed that dual solutions exist for both velocity and temperature.

The article focuses on seismic monitoring of causes of landslides. Such studies are of great importance in open pit mining in permafrost rocks. Extensive mining-induced impact in combination with natural thawing of permafrost as a consequence of the planet warming may end in catastrophe. The authors describe a procedure for plotting velocity profiles of seismic waves along slopes in the presence of extremely contrast discontinuities conditioned by permafrost rocks. The presented approach enables studying slip surfaces of landslides and detecting potential failure zones where wave velocities are lower due to extensive jointing. The processed field data obtained in the area near Chagan-Uzun settlement in Kosh-Agach district of the Republic of Altai are reported.

The article considers applicability of non-Archimedean analysis to multi-scale rock mass modeling based on the concept of dissipation function. In the capacity of coordinates, the author introduces non-Archimedean lines of infinite hierarchy. Basic definitions of univariate analysis are generalized for a two-dimensional case.

The article describes a proved method to calculate stress state of support and surrounding rock mass, considering roof and wall rocks displacement until the contact with the support. The method is based on the use of the intact rock mass stiffness matrix formed prior to mining. Modeling of drivage using the method of initial stresses allows splitting the problem into two subproblems: the first subproblem is on mechanical state of rock mass during roof and wall rocks displacement, the second subproblem describes joint deformation of roof rock, walls rocks and support. The cases of stress calculation for rocks and support, considering support installation conditions, are described. The stress behavior depending on the value of roof and wall rocks displacement until the contact with the support is determined. The features of the method application in case of greatly different mechanical characteristics of rocks and support are discussed.

Actual physical models and discrete element method are used to analyze stress state of broken rocks at the moment when an apron feeder starts discharge from floor storage. It is shown that designs of discharge units of floor storages fail to eliminate broken rock dilatancy which is a determinant of the peak load on the feeder at the moment of its actuation. Based on the investigation results, the authors propose an approach to filling floor storages with broken rock and a structural layout for the storage discharge unit. The offered engineering solutions enable preventing from dilatancy-induced impact on stress state of broken rock flow and, as a result, elimination of peak loads on feeders.

Based on the tests of packings of calibrated glass balls with a diameter of 1 mm, it is shown that multiple point impacts improve waveguide characteristics of the medium-conducting paths composed of force “chains” emerge in the test material. The further quasi-static alternating shears change the packing of particles, break the chains and reduce conduction. If continued onward, the multiple impulsive loading results in recovery of the “chains” and in better conduction of the paths.

Experiments allowed finding regular patterns in propagation of supersonic elastic P-waves in specimens of black coal exposed to uniaxial compression and tiaxial compression by von Karman. It is shown that in case of uniaxial compression, the largest information content is ensured by translucence in perpendicular to bedding and loading axis of coal specimens. Such translucence exhibits four stages of deformation of a specimen. The information content of translucence under triaxial compression reduces with the increase in the lateral pressure that prevents from disintegration of a coal specimen. Four deformation stages are best identified with the lateral pressure of 2.5 MPa, while only stages of specimen consolidation and failure are traced at the pressure of 10 MPa.

The author reports test data on disc-shaped specimens of rocks and model media with a hole drilled through the center of the specimens loaded along the diameter. The test data processing uses non-local failure criteria. The calculated destructive forces are compared with the measured destructive loads. Based on the tests of specimens with the central through holes, the tensile strength algorithm is presented.

By the data on measured displacements at the boundary of a cylindrical underground opening (mine shaft), in the model of a perfectly plastic body, the authors assess deformation of rock mass around the opening and find the elastic-plastic boundary and displacements in the plastic deformation zone.

Gravity-induced lateral stress in rocks is assessed in the framework of physical simulation using a flexible thin-walled cylinder. Compression of loose geo-materials changes diameter of the cylinder, which allows estimating lateral stress. The observed dependences with various compacted geo-materials are then theoretically approximated based on characteristics of porosity, rock deformation modulus and Poisson’s ratio. The obtained relations are applicable to estimation of gravity-induced lateral stress in an intact rock mass.

Based on the developed procedure, experimental regularities are obtained for the formation of submicron particles under rock failure. The experiments involved explosion load on rock specimens and their uniaxial compression with the concurrent control over size and amount of particles until failure using laser spectrometry. It is found that most of all particles are formed in the size grade of a few microns irrespective of the kind of loading. Dynamics of the formation of particles depends on structural characteristics of specimens and on the value of the compression stress. The authors emphasize the promising nature of the experimental results usable both in the environmental monitoring and for disaster prediction in the course of mining.

The article reports data on continuous indentation of different rank black coal and anthracite. The test specimens are specially prepared, and their faces are differently oriented relative to their bedding planes. Different mechanical behavior of coal and anthracite microcomponents in different planes relative to bedding is identified, and relevant values of elasticity modulus and hardness are determined. The measurements exhibit spatial anisotropy of microlevel mechanical properties of vitrinite and inertinite.

Under discussion is the experimental estimate of an actual power variation range of pneumatic hammer with a ring-type elastic valve arranged in exhaust unit of back-drive cell in order to lock mechanically this cell until exhaust stroke at various values of the hammer travel. The variation ranges of the valve channel cross-section are found to ensure sustained operation of the pneumatic hammer and the minimized air flow rate irrespective of the hammer weight and position (vertical or horizontal) and the ratio of the hammer power-stroke to the hammer power-stroke cell diameter.

The article presents the remote monitoring systems for operation of high-voltage substations and shovels, designed at the Karaganda State Technical University and introduced at Shubarkol-Komir open pit coal mine. The systems measure power consumption parameters (high-voltage substations and shovels) and controls power consumers and electrical protection. The high-voltage substation monitoring systems transmit data via rf modem, the shovel operation monitoring systems use GPRS modems to transmit data via Internet to a central operator office. In the course of trial operation of the remote monitoring systems, it was succeeded to save power owing to elimination of idle operation of heavy-duty mining machines; moreover, the scope of the continuous control covered power consumption and electric protection at substations and on shovels.

The authors present the schematic circuit of the new-generation compression/vacuum impact machine (CVIM) and its operation using an adjustable magnetic lock, which allows varying the machine power performance and extends the machine capacities in mining, construction and seismic exploration. The operational cycle of CVIM is tested. The authors determine technical parameters of the machine and mechanisms of interaction between the lock, striking unit, air reserve tank and compressed air source. CVIM unit blow energy is estimated at different space positions of the machine. The field trial has assisted in denoting ways of further improvement of the machine.

The authors develop a version of a compound technology with consolidating backfilling and caving for thick flat body of polymetals. Numerical evaluation shows that the technology with the cover caving above consolidating backfill ensures higher safety of mining.

The described technology and equipment enable eliminating drilling-and-blasting in open pit mining. The authors also discuss usability of transfer bins with vibrating discharge in combination with intermodal transport and adaptability of vibratory machines to dump truck-aided stockpiling.

The authors give basic design procedures for two-level rock bolt support in underground mining in permafrost regions. The use of rock bolting in combination with heat insulation on a test site in Dzhebariki-Khaya Coal Mine is studied.

Under discussion is the particle and bubble interaction in froth flotation. Water flow from an interlayer between the particle and the bubble under effect of hydrophobic component of wedging pressure is studied. It is assumed that for a mineral to be extracted, electrostatic interaction slightly influences the particle and bubble contingence and the liquid interlayer thinning. For this reason, particular attention is given to the effect exerted by mineral particle surface hydrophobicity on water flow rate from the interlayer. It is found that water flow rate under influence of hydrophobic component of wedging pressure is less than water flow rate under physical adsorption of a reagent. The authors hypothesize that hydrophobization creates areas on the mineral particle surface, where the reagent species active relative to gas-water interface attach in accordance with the polarity equalizing rule. Physically adsorbed reagent species pull out water from the interlayer after the interlayer rupture and, thus, remove the kinetic constraint of the particle-bubble attachment.

Placer gold mining waste may be assumed an important source to replenish mineral and raw materials supply of the gold mining industry in Russia’s Far East. The tests are carried out on samples of placer gold mine waste of gravel size and fines. The article gives mineralogical and petrographical characteristics of the samples. Admixtures of platinum, silver, titanium and iron are traced in the sample composition. Results of the gravity concentration with the preliminary magnetic separation of the samples are reported. The yield of magnetic fraction makes 39.77%, and it is found that magnetite contains titanium. Gold recovery in the gravity concentrate is 91.6% with 0.06 g/t content of platinum and 57.7 g/t content of silver.

Laser diffraction analysis and dynamic light scattering method are used to study highly dispersed particles generated during milling of lead-zinc ore (Gorevskoe deposit), rich sulfide and impregnated copper-nickel ore (Norilsk and Kingash deposits), as well as Gorevskoe Pb concentrate and Sorskoe deposit Cu and Mo concentrates. Zeta-potentials of particles are measured in clarified (colloid) solution above precipitation; surface composition of ores and their fine sizes is analyzed using X-ray photoelectron spectroscopy. The highest yield of particles under 5 μm size grade (to 3 total percent) was observed in case of Kingash ore; moreover, zeta-potential of these particles was positive at pH 9.5 and surface compositions of precipitation and colloid particles were nearly the same. Comparatively high content of ultra dispersed fractions was observed in case of Gorevskoe ore and Pb concentrate. Clarified solutions contained mostly aggregates of nano-size particles, first of all, Si and Mg minerals, with the hydrodynamic diameter of 500-1200 nm, which shows little changes with time. Sulfide component of hydrosols contains many nano-size particles of minerals that better resist oxidation (sphalerite, molybdenite, pentlandite, chalcopyrite) and, in particular, can transfer metals in the ambient medium.

The article illustrates feasibility of prediction of change in energy content and reactivity of scheelite concentrate after mechanical activation based on the data of X-ray structure analysis under onward low-temperature (under 100°С) sodium leaching. The complex nature of change in the energy content and reactivity of mechanically activated scheelite under influence of structural changes in mineral particles is determined. It is confirmed that energy accumulated in the form of surface energy and micro-deformations during mechanical activation affects performance of further leaching. The procedure and criteria developed to estimate efficiency of mechanical activation of scheelite make a technical background for energy-saving technology of scheelite concentrate treatment directly at mining and processing plants.

Integrated development of Volkov copper-iron-vanadium deposit is impossible without heap leaching of copper from old oxidized and mixed ore stock pile. The current condition of the stock pile imposes risks of pollution on the Lai River water and on the topmost aquifer groundwater. The natural protection barrier between the groundwater and the old oxidized and mixed ore stock pile is rather good. Permeability of the upper layer of the stock pile, determined by the standard procedure in accordance with the construction norms and regulations, is classified with ambiguousness. For final decision-making after geological engineering survey, permeability characteristics of the upper layer were analyzed using different concentration sulfuric acid solutions to simulate heap leaching conditions.

The entropy analysis is used to study composition of trade effluent in the Kemerovo Region. A number of clusters of pollutants are detected in organic and metal-bearing water solutions (aniline, fats, oils, oil products, phenols, synthetic surfactants, silicon, fluorine, chromium, cyanides, aluminium, vanadium, iron, magnesium, copper, nickel, lead, zinc, nitrates, nitrites, ammonia nitrogen). The evolution of population of the pollutants in surface water bodies in 2008-2013 is illustrated. It is found that water quality of most water bodies in the discussed mining region is beyond standard.

The scope of the discussion embraces main definitions of a constituent of the geoecology-environmental mineralogy. The main research areas, objectives and subjects of the environmental mineralogy are specified. It is highlighted that yet no regulating documents are available for mineralogical analyses during environmental appraisal of mineral mining objects.

The down-the-hole unbalance vibration exciter with the pneumatic drive is designed to treat face zone in the seismic frequency range. The modular-type source consists of a vibration generator with the automated stepped static moment variation, a hold-down unit and an in-built pneumatic percussive device to advance the facility in uncased holes. The article gives pilot test data on R&D model of the vibration exciter, and amplitude-frequency characteristic and spectral content of the excited signal.