Home – Home – Jornals – Journal of Mining Sciences 2013 number 5

The comprehensive experimental studies into the change in the stress–strain state of rock specimens subjected to uniaxial loading until failure using automated digital speckle photography analysis shows that when stress reaches 50% of the limit strength of the specimens, low-frequency micro-deformation processes begin in the specimens under slow (quasi-static) stiff loading. Amplitude of the deformation-wave processes depends on the level of the pre-set macro-loading. Wave packets are plotted for averaged micro-strains obtained in sandstone and marble specimens under uniaxial compression. Fourier transforms are used to define amplitude–frequency characteristics of four micro-deformation stages: elastic, nonlinearly elastic, post-peak and residual strength regions. Elastic oscillations with frequency of 0.5–4 Hz appear at pre-failure stage and continue at post-peak loading stage.

The authors calculate possible errors in characterization of low-magnitude seismicity sources using the Brune model and methods of seismic event energy class and local magnitude definition. The adequacy of the model has been proved by comparing its results with the recordings of seismic vibrations in the North Ural Bauxite Mine. The errors due to the drastic distortion of emission spectrum become significant at the distance of 1000 m from the emission source and grow as the distance increases. Cases of great deviations from the similarity law are analyzed based on actual seismic monitoring in the North Ural Bauxite Mine, in mines in Poland, Finland and Canada, as well as in water basins. It is shown that phenomena due to physical difference of various size fracturing dynamics do not radically change seismic source capacity. Other causes, due to instrumentation shortcomings or incorrect data interpretation, may result in overestimated seismic energy and scaling-up of low-magnitude seismic events.

The authors have developed and numerically implemented 3D model of evolution of geomechanical and hydrodynamic fields during deep borehole drilling. The modeling exercises showed low-permeable zone of irreversible deformations that appear under definitely interrelated rock strength properties, drilling mud pressure and in situ horizontal stresses in borehole environment. These low-permeable irreversible-deformation zones give rise to angular anisotropy of distribution of water content and drilling mud resistivity in the flushed zone, which greatly affects readings of geophysical logging and must be considered in the logging data inversion.

The article reports the integrated assessment of natural stresses in rock mass in the Nurkazgan Mine. The visual observation of underground excavations and instrumental measurements of effective stresses denote the hydrostatic stress state within the studied minefield. The article shows the deformation-wave behavior of geomechanical processes induced by coal production face advance. The enclosing rock mass response is interpreted as the formation of hierarchy of geomedium elements in the continuum subject to excess elastic energy behind the front of the vertical stress decrease. Parameters of the physical model of the process are given in terms of mine-technical situations.

Based on the constructed geomechanical model of the pneumatic borer and soil body interaction and using the finite element method, the authors solve the problem on the stress state in the soil body inclosing moving pneumatic percussion machine, considering variation of physico-mechanical properties of soil. The experimentally measured and calculated relative accelerations of acoustic field depending on the machine orientation in soil are compared.

The article discusses development of two successive axially symmetric hydraulic fractures in line with well. Shapes of the surfaces of the second hydrofracture that propagates in the stress field initiated by the first hydrofracture are modeled, and the pressure for the second fracture to grow is calculated. The authors assess impact area of the first hydrofracture, analyze options of the second hydrofracture curving and derive formula of the second hydrofracture curving.

The review of laser application in mining is followed by discussion of experimental treatment of carbonate rocks by the continuous fiber-optic yutterbium laser radiation at output capability of 600 W. Local disintegration of carbonate rocks is estimated with a view to show the possibility and practicability of laser-aided means and technologies in mineral mining and processing.

Design parameters of a balanced air sealing device are substantiated. Different design synchronizers are tested with an eye to ensure joint operation of air sealing devices. The article describes laboratory studies of operation modes of an air sealing device and different design synchronizers.

The authors have studied theoretically and experimentally dynamics of mine hydro-pneumatic accumulators and give grounds for a hydro-pneumatic accumulator design for stable and elevated pressure maintenance in a mine compressed air network as compared to a compressed-air plant.

The authors anlyze conditions and factors that influence coal pitwall stability and substantiate applicability of electrical tomography for their exploration. Experimental studies of physico-mechanical properties of the Bikinsky brown-coal pitwall rocks are reported. The article proposes a procedure for electrical tomography exploration of weak layers and lentils within geological column.

The authors illustrate efficient adaptability of aerodynamic characteristics of main mine fans to changes in mine vent modes in the course of mine’s operating life by using fan impellers with replaceable sheet blades of different aerodynamic configurations.

It is proposed to apply nanosized Au and Pt particles to ground mineral particles for the analysis of flotation and adsorptive properties of new reagents. The authors have obtained specimens of pyrite, arsenopyrite and quartz artificially enriched by nanosized gold particles. Reductive adsorption from Na₂[PtCl₆] and Na[AuCl₄] produced pyrrhotine uniformly applied by microsize platinum particles. The article discusses the application range of the proposed techniques and methods of examination of specimens and interaction between reagents and micro- and nanosized gold and platinum particles depending on the conditions of sulfide treatment by the noble metals and properties of host mineral. Advanced integrated analysis of interaction between the nitrogen-bearing reagent MTKh and gold confirmed chemically induced selectivity of MTKh toward gold.

The authors experimentally compared collecting properties of diisobutyl dithiophosphinate (DDP), butyl and isobutyl xanthate, and diisobutyl and dibutyl dithiophosphate relative to pyrite, chalcopyrite and other sulfides. It was found that pyrite adsorption grew in nonfrothing flotation with all the listed collecting agents. The nonfrothing pyrite flotation by DDP showed higher rates of adsorption and flotation as against butyl xanthate. The ratio of DDP and butyl xanthate flotation rate constants was 1.19, which agreed with the ratio of the adsorption rate constants of 1.18 in nonfrothing flotation. The low selectivity of dithiophosphinates toward sulfide ores is explained.

Complexing processes between modified diethyldithiocarbamate (DDC) and copper, iron and gold ions in solution, as well as adsorption of modified solution at auriferous pyrite and arsenopyrite are analyzed using the ultraviolet spectroscopy, scanning electron and laser microscopy. The research shows that modified DDC forms partial water soluble compounds with gold and is selective toward auriferous pyrite and arsenopyrite as compared to xanthate.

The article reports research findings on flotation of apatite from brazilite–apatite–magnetite ore by domestic and foreign manufacture reagents. The agents Phospholan PE65 and Arcomon SO exhibit higher selectivity as compared to saponified tall oil fatty acids.

The authors carried out molecular modeling of clusters of simple structure and ring structure pyrite. It is suggested to analyze bonding of a collecting agent and cluster atom using the collector capacity forecasting index. It is shown that butyl dixanthate more vigorously connects to cluster atoms than thionocarbamates, e.g., Z 200 and IETNC. Analysis of the charge transfer in interaction of pyrite and the listed collecting agents shows that in monodentate bonding the charge is transferred from the mineral to the collector sulfur atoms and in bidentate bonding the classical transfer of the charge from the collector donor to the mineral acceptor is observed. It is supposed that ferrum xanthate decompounding in an acid medium results in inception of dixanthates that govern pyrite flotation. Pyrite oxidation and elemental sulfur formation also favor pyrite flotation and complicate pyrite depression in an alkaline medium.

The articles considers experimental research findings on phase composition of ferrous and nonferrous metal industry slag, morphological structure and physico-mechanical properties of individual phases of slag with the aim to evaluate selectivity of their disclosure along intergrowth boundaries in impact crushing machines. The authors validate disintegration selectivity criterion for slag treatment in centrifugal impact crushers in the form of the ratio of microhardnesses of the slag phases.

In the article, the outcomes of quantitative estimation of adsorption centers of composite backfill components and their alteration by grinding are presented. The derived correlating equation for ferruginous quartzite wet magnetic separation residue confirms the mineral dispersiveness and surface activity association.