Home – Home – Jornals – Journal of Mining Sciences 2016 number 3

The article puts forward a procedure to determine structure and physico-mechanical properties of near-surface cohesive soil based on seismic surveying. The backbone of the approach is the use of distribution of P- and S-waves obtained from combination of the seismic refraction technique modification and the multi-channel surface wave analysis. The recovery of the physico-mechanical properties uses correlation dependences. The authors give an example of field data processing. The field research covered a section of a motor road where groundwater level is determined and zones subjected to washout and deformation are detected.

The authors model deformation and mass transfer in jointed and porous rock mass around a production well. The modeling based on the concept of a continuum with double porosity uses an original method with finite difference solution of mass transfer equations and analytical solution of pore elastoplasticity equations. From the numerical experiments, dimensions of irreversible straining zones in the well bore zone grow with the parameter Bio. The estimate of the reservoir permeability decline in the course of operation, obtained from the pore elasticity and pore plasticity models, qualitatively agrees with the in situ observation data.

The practical calculation of rock mass deformation around an underground opening accounts for the weight of rock mass by solving a complimentary problem on “weightless” rock mass. A domain with an opening is bounded by a plane with the preset zero vertical displacements, which enables taking into account difference of pressure along the height of the opening. This solution, with the adequately selected boundary conditions, is added with stress field of an intact rock mass and offers zero boundary conditions at the future opening perimeter, however, the issue on the validity of setting boundary conditions at the lower boundary of the calculation domain remains yet to be handled. This article presents a phenomenological model of rock mass deformation to answer the set question. It is taken into account that action of roof rock weight coincides with the orientation of tensile stresses at the opening perimeter and differs from it in the floor. The author thinks it is required to add the class of inverse problems of rock mechanics with the problems directly accounting for rock weight.

The authors present studies into geomechanics of Berezitovoe gold-polymetal deposit at the stage of transition from open pit to underground mining. The authors have carried out geodynamic zoning and evaluated parameters of modern stress field. Rock mass ratings are used to assess physico-mechanical properties of rocks. Rock mass stress state at various stages of mining is examined using numerical modeling, and underground mining system parameters are evaluated using Mathews procedure and analytical relations.

The author offers a new deformation criterion for the compressive strength of salt rock specimens. The limiting principal strain is a function of stress parameter in the form of a ratio of hydrostatic pressure and stress intensity. The safety factor based on the deformation criterion is defined. The numerical modeling of experimental compression of various geometry specimens produces the deformation criterion for sylvinite and carnallite of Upper Kama deposit. The offered criterion is applicable to assessment of load-bearing capacity of stopes in salt rocks.

The scope of the discussion covers the issues of open pit mining efficiency and safety with dry overburden dumping over clayey alluvium. The stress analysis of a dump at Kedrovsky open pit mine uses finite element modeling of linearly deformable medium based on geotechnical, surveying and hydromechanical data. The modeling produces the field of displacements of the dump and its base and the distribution of the Mohr-Coulomb strength criterion. The clayey rock breakout-hazardous areas are revealed, and displacements of the growing dump are predicted. The developed model enables operational forecasting of strength loss at dumps.

Based on the analysis of qualitative interaction between rocks and a rock-breaking tool, a new coefficient of the tool efficiency is proposed. This coefficient makes it possible to estimate the quality of the tool impact on broken rocks and to predict energy input of rock breaking and, consequently, productivity of mining machines in specific geotechnical conditions.

The authors analyze numerically growth of a cross fracture between two existing fractures under multiple directional hydrofracturing using chemically active mixtures. The scope of the studies embraces effect exerted by problem parameters, such as value and orientation of external compression field, rate of healing of fractures, size and intermediate spacing of fractures, on deviation of a fracture from its initial orientation. The results are meant for optimization of the local hydrofracturing method for steam-distribution and producing wells in low-gravity oil reservoirs.

Under analysis is electrohydraulic crushing of rocks under electric charge using nanosecond high-stress pulses to optimize ore pretreatment. A nanosecond high-voltage generator of pulses at a capacity to 500 MW is designed and tested. A flow-through discharge cell at a voltage to 550 kW is developed. The new method of mineral crushing is highly efficient and enables designing commercial plants for electrohydraulic rock processing.

The authors report and discuss the experimental results on an air drill hammer with an elastic valve installed in the backstroke exhaust line for mechanical closing. It is approved that such air hammer is capable to ensure the wanted blow capacity at fixed blow energy by varying blow frequency through adjustment of cross section choke coupling the backstroke and front stoke chambers of the hammer. With larger cross section of choke coupling, the maximum blow frequency is achieved and remains the same later on.

The article presents a calculation procedure for limiting rotation frequency of an axial main mine fan rotor. The calculations are made for fan model VO-21. The suppositions that make the calculations simpler without considerable errors of the results are evaluated. The calculations use the finite element method and ANSYS software. The critical frequencies are determined from the Campbell diagrams plotted for the estimates with and without regard for the stiffness of the bearing assemblies of the rotor. The effect exerted by the rotor bearing assembly stiffness and by the gyroscopic moment of the fan impeller on the frequency of free bending vibrations of the rotor shaft under direct and back precession is illustrated. The estimated critical frequencies are compared with the analytical data obtained based on discrete two-mass models. For the preliminary engineering estimation, it is possible to use a discrete two-mass model of the fan rotor without regard for the yielding of the bearing assemblies and for the influence of the gyroscopic model; in the design model, it is required to replace the transmission shaft by the point mass. The calculation error will not exceed 7%.

The structural layout is presented for a hybrid unit for directional hydrofracturing with the description of operating principles of the unit in the mode of drilling and slotting. The kinematic parameters of the movable parts of the unit are calculated.

A formalized approach is proposed to evaluating design loads on shovels with compound kinematic chains, based on numerical estimates of response of primary structural members to unit forces. The practical implementation of the approach uses structural layout of a mine shovel with electromechanical push-bars of pressure and uplift drives.

The authors give theoretical and actual evidence of reduction in absolute methane release under higher rates of advance of production face in coal mines. The parabolic relation between methane release, feed speed and productivity of cutter-loader is evaluated.

The experimental studies allow determining efficient parameters of a technology meant for formation of pay zones in gold mine waste dumps. The technology is applicable to developing gold mine waste early assumed unprofitable.

The analytical research has yielded differences in composition of mineral species on the surface of natural diamonds of hyperaltered kimberlites under conditions of diamond ore occurrence and processing. The classification of the mineral species is based on the mineral origin, properties and attachment on the diamond crystal surf.

Under discussion is collectability of ethyl and butyl xanthate species resulted from non-stoichiometric interaction with oxidizer. It is visually proved that solution contains fine micro-drops stabilized by negative charge. The size and ζ-potential of micro-drops are determined together with the spreading velocity of emulsion over water surface. The mentioned velocity is higher than the spreading velocity of products of non-stoichiometric interaction between xanthate and heavy metal salt. The products of interaction between xanthates and oxidizers, at the moment of rupture of water film between mineral particle and air bubble, can detach from particle surface and attach to air-water interface (desorbable species DS). Spreading of a DS over the interface forces water out of the film. The forces applied to liquid in the film from the side of DS of ethyl and butyl xanthates are evaluated. The volume-flow rate of water from the film is related with the surface pressure of reagent species active at the air-water interface. The surface pressure of dixanthogen-xanthate emulsion is evaluated as a function on initial concentration of xanthate. Collectability of a reagent depends on the surface tension of solution of its DS and is governed by the structure of hydrocarbon fragment of the agent.

The authors report studies into adsorption of tannin and cow-parsnip extract components on stibnite, arsenopyrite and chalcopyrite using UV spectroscopy, scanning laser microscopy and measurement of air bubble detachment from mineral particle. It is found that tannin and the organic reagents are selectively adsorbed on the surface of the listed sulfide minerals and exert selective effect on adsorption of sulfhydryl collecting agent, which, in its turn, may result in efficient recovery of the minerals in the proper concentrates under complex gold ore flotation.

Under analysis is low efficiency of drum mills when dissociating higher strength aggregates of rebellious ore. It is shown that the main reason is insufficient destructive force. The structural-chemical characteristics of mineral aggregates and the role of defects in their dissociation are described. The author evaluates principles of estimating required energy input to dissociate aggregates composed of minerals with different types and values of interatomic and intermolecular bonds under high-power and high-velocity free impacts in disintegrators. By way of example, velocities of collision between minerals and disintegrator tools in dissociation of aggregates of sulfide and rare-metal ores and coal are given.

Experimental evaluation is given for mineral preconcentration in a bed of a sorption collector in percolation of low concentration useful components from aqueous solutions of salts. Sorption collectors represented by interlayers of lignite, peat, marble and vermiculite are included in an evaporation barrier installed in subsurface zone of rock mass aeration. Storage properties of such geochemical sorption barriers are examined. Migrating solution was aqueous solutions of salts of cobaltous and nickelous nitrates. It has been found feasible to shape beneficiation zones under up-going capillary permeation of the solutions through the sorption barriers in the zone of aeration in rock mass.

Parameters of porous structure of different rank Kuzbass coal and gas- and mass-exchange processes under coal heating are analyzed. The main part of volatile matter is dissolved in the volume of coal layers. For all coal specimens, it is typical that mass fraction of methane and ethane decreases with temperature while mass fraction of hydrogen, carbonic oxide and ethane increases. The latter gases can be the sources of violent burning of coal beds. UHV pyrolysis of bituminous coal reveals physical balance and composition of gaseous products. The results permit coal rating based on carbonization, enable recommending using inert gases in underground fire fighting and allow estimating temperature level in fire source zones in coal beds based on chemical composition of emitted gases.

The 3D mathematical model of temperature conditions in salty rock mass at shaft mouth takes into account parameters and modes of freezing unit operation, temperature of ambient air and air in the shaft, as well as nonuniformity and rate of salinity of enclosing rocks. The model allows dynamics of temperature variation in rocks around the shaft and load-bearing capacity of each pole of head frame foundation depending on rock mass temperature and salinity. Different variants of freezing unit operation are considered to select the variants to ensure the required load-bearing capacity of the head frame poles and the diamond shaft lining safety.

The article discusses the case study of temperature behavior prediction in permafrost rock mass before and after blasting at Kangalass lignite deposit. It is illustrated how the blasting period is related with the temperature behavior in the disintegration of broken rocks. The results are the basis to predict dragline productivity in different seasons and to select efficient scheme for blasted rock removal.

A down-the-hole tool has been designed for gas-dynamic research of coal. The tool is manufactured based on the layout of a straddle packer with an adjustable interval. The tool design is suitable for hydrofracturing and gas-dynamic researches using the methods of indicator diagrams and pressure drop and recovery curves in package with relaxation of coal and rock mass by means of radially symmetric loading of hole walls in the hydrofracture interval.