Home – Home – Jornals – Journal of Mining Sciences 2018 number 3

The classical solution of elasticity problem on deformation of a plane weakened by a mathematical cut under wedging by constant forces is analyzed. The ill-posedness of the classical failure mechanics statements for problems with angular points is demonstrated. The approximate solution is constructed for deformation of continuum in the vicinity of a cut under small strains.

Rock is considered as a medium containing a load-bearing skeleton and a pore space. The two-dimensional closed deformation model under construction takes into account plastic strains and local bends of grains. The model describes the medium capacity to accumulate energy of internal self-balancing stresses.

A device is developed for loading granular materials by shearing with air flow driven through the material without its pseudo-liquefaction. Internal stresses and dilatancy of a sample are measured depending on shearing angle. It is shown that shear modulus, characterizing material capability to resist shearing as air flow rate is increased, lowers while dilatancy grows.

Interaction between an open-end pipe and a soil plug is studied using Coulomb’s law of friction. The scope of the study embraces different models of soil and pipe. The finite difference solutions obtained for all models and the analytical solutions derived for some models describe the elastic process of the pipe and soil interaction. Agreement of the numerical and analytical solutions is shown. Results of different model calculations are compared, and the validity limits are determined for the models. The influence of Coulomb friction on pipe and soil movement is investigated.

In order to ensure accurate hole-making in soil, it is required to adjust motion path of pneumatic puncher by deflecting its rear body relative to longitudinal axis. The structural layout of the path control mechanism, which allows upgrading series-production pneumatic punchers, is presented. The solution of problem on forces required to change the pneumatic punch path in soil is given. Soil body is considered as a rigid-plastic medium, and the deflector is assumed as a nondeformable body. The problem is solved in two stages: penetration of the deflector in soil and motion of the pneumatic puncher with the rear deflected at a certain angle in soil. The loads applied to the rear for changing pneumatic puncher path in soil and the turn radius under deflecting force are determined.

Two model approaches to estimation of lifetime of supporting mining machines are described, one of which is based on the theory of reliability and the other-on the principle of cost. While on service, reliability of machines reduces and operating cost grows. These indexes of opposite trends define machine serviceability, and make a framework for decision-making on the expediency of further operation, maintenance or replacement of machines. In terms of bulldozer as one of the most high-usage machines in supporting operations in open pit mines of the Electric Power Industry of Serbia, the application of both model approaches is compared, as well as the estimations and conclusions are made.

The problem of oil flow in model reservoir is solved at the preset harmonic time variations in differential pressure at the model sides. Hysteresis effects of capillary pressure upon the change in direction of fluid expulsion are considered. The influence of water level fluctuations on removal of possible capillary blockage by water from wellbore zone is estimated. The action of alternating pressure pulses on oil-filled formation is analyzed. It is shown that harmonic change of water pressure promotes removal of immobile water blocked in capillaries from wellbore zone. The results of full-scale experiments on wave action on wellbore zone and oil recovery enhancement are presented.

The approach to further development in engineering geologic mapping of mineral reserves with respect to quality levels based on geoinformation models of deposits is substantiated. The algorithm and methods for delineation of clusters in the area of a seam using a vector index composed of simple indicators characterizing useful and harmful properties of coal are explicated. The results of new software trial are presented in the form of distribution of coal reserves for coking and power generation by quality levels and visualization of delineated clusters by means of plotting quality maps.

Theoretical aspects of studying stability of natural systems depending on investigation purposes are briefly analyzed. Applicability of the watershed/landscape concept of nature management to study transformation of geosystems disturbed by gold placer mining is substantiated. In terms of a model site within the limits of the Ket-Kap cluster of placers, the data on the degree of such transformations are given, and mid- and large-scale landscape mapping is performed using the modern remote sensing techniques. The qualitative indicators of transformation degree under placer mining are given for valley nature systems depending on watershed order. The relevance of the remote sensing in estimating the degree of transformation of natural systems at objects of gold placer mining at regional and local levels is demonstrated.

Airflow disorder in inlet shafts and related crossheadings, caused by local natural ventilation pressure, is a complicated thermodynamic phenomenon. The conception of local natural ventilation pressure is proposed based on a simplified ventilation system. Airflow disorder principle is analyzed theoretically and verified by similar simulation experiment and in-situ study. Research results show that local natural ventilation pressure will form when average temperature difference or density difference of air-column exists among inlet shafts in an underground mine with exhaust ventilation. When changing in a large range, local natural ventilation pressure will cause airflow disorder in inlet shafts or related crossheadings. The research results have guiding significance for promoting the stability of ventilation system and improving the working environment of underground mines.

Organic and inorganic luminophores having similar parameters of luminescence as diamonds are selected. Based on the excerpted luminophores, indicators are synthesized. Spectral and kinetic characteristics of luminophores are experimentally determined for deciding on optimal compositions to ensure maximum extraction of diamonds in X-ray luminescence separation owing to extra recovery of non-luminescent diamond crystals. As the components of luminophore-bearing indicators, anthracene and K-35 luminophores are selected as their parameters conform with the luminescence parameters of diamonds detected using X-ray luminescence separator with normal settings.

Activation of sulphides by heavy metal ions is discussed. A brief analysis of modern ideas on mechanism of activation of sphalerite, pyrite and galena by copper sulfate and lead nitrate is given. It is shown that the current technology insufficiently conforms with the experimental and practical data on activation of minerals. A new mechanism of mineral flotation activation is proposed based on the action of physical adsorption species of collecting agents, which allows explaining suppression of flotation under increased concentrations of activator and flotation of sulphides without collectors. The new mechanism integrates the action of mixed potential, activation of minerals by heavy metal ions and the collectorless flotation into a common theoretical framework.

The research findings on efficiency of hardly soluble low-hydroxyethylated iso-nonylphenols as regulators of selective flotation are presented. The methods for increasing their solubility are developed, which are based on using unsaturated carboxylic acids as wedding agents for alkaline salts. It is shown that addition of such wedding agents to ethoxylated iso-nonylphenols makes it possible to obtain stable aqueous micellar solutions or emulsions under much lower temperatures, as well as ensures permanence of the process and efficiency of regulating agents in selective flotation of phosphorus-bearing ores with fatty acid collector. Efficiency of the developed methods is proved by in practical application of one of them, which improved ore dressing performance, reduced labor content, energy input and preparation time of solutions, and provided considerable economic effect.

The recovery and rate of galena flotation depending on galena grain size and butyl potassium xanthate concentration are studied at the laboratory scale. It is found that the recovery and flotation rate decrease with galena grains smaller than 38 μm and with the lower concentration of the collector. Galena grain size has larger influence on the recovery by flotation than the collector concentration. These findings are the result of analysis of multivariable correlations between the galena recovery in flotation, collector consumption and galena grain size since partial correlation coefficient and general correlation coefficient point at close relationship between these parameters.

Tin-bearing tailings of the Solnechny Mining and Processing Plant (MPP) in the Khabarovsk Territory are studied with a view to producing tin and copper concentrates. The features of the material constitution of tailings and their influence on the process flow diagram development are described. Processability of the Solnechny MPP tailings is tested, and PFD is developed using the modern methods of disintegration, including cavitation and ultrasound. The semi-commercial-scale implementation of the proposed PFD has allowed production of copper concentrate at copper content of 18.28% and recovery of 60.48%, tin concentrate at tin content of 11.35% and recovery of 50.88%, and rejects with the tin and copper contents of 0.139 and 0.154%, respectively. The recovery of tin and copper has made 46.66 and 38.45%.

The study data on mineralogy and process properties of magnetite ore of the Poperechny deposit (Maly Khingan) are presented. The mineral composition, structure and texture of the ore are analyzed, and signs of its contact-metasomatic nature are determined. Two generations of magnetite are revealed. Extractability of iron at recovery of 93.39% is proved experimentally, including 78.72% to concentrate and 15.67% to middlings. Iron recovery of rougher concentrates is 40.74-42.74%. It is found that the ore contains noble metals: gold is represented by free grains 0.05-0.2 mm in size; platinum and platinoids (Os, Ir, Ru) are revealed as micronodules in magnetite jaspilite and dolomite in concentrates.

The timely character of using digital satellite observation data at regional and local levels for operational quantitative assessment of nature condition in the areas of mineral mining and processing activities is validated. The qualitative ecological estimates of impacts in time intervals by biota response in the area of location of several mines with different production infrastructure are presented and analyzed.

The mathematical model of heat flow and transfer in roof rocks of underground gas gasifier during coal gasification is developed and tested. In terms of geological conditions in the Olkhovo-Nizhnee site (industrial region in Donbass), in Mathcad environment, convective and conductive components of heat flow from reaction channel to upper-lying aquifer are determined. The change in the heat flow from the reaction channel and in the ground water temperature is estimated depending on impermeable layer thickness and water well yield. It is found that after underground coal gasification, water-bearing sandstones accumulate more than 60% of heat migrating from gasifier to enclosing rock mass. It is shown that withdrawal and use of water heated during underground coal gasification will enhance efficiency of the process by 18-25% subject to thickness of partition layer.

The study is devoted to the methane hazard in hard coal mining. This hazard occurs in almost every coalfield in the world. Ensuring maximum work safety under methane hazard conditions is based, among other things, on reliable, fast and frequent determinations of methane content in a coal seam. The existing methods are time-consuming, and determinations must be performed in laboratories. Indirect methods such as desorbometric methods are burdened with high measurement uncertainties. The study presents a model of methane release from granular coal samples and a device (AMER) developed for measuring methane content in a coal seam under in situ conditions. Measurements are performed in a fully automatic way and preliminary results, based on the approximation of the Crank model, are available within several dozen minutes from the beginning of the measurement. Also, the use of the unipore diffusion equation and a proper software of the device allowed to determine the values of the effective diffusion coefficient. Results of measurements performed with the AMER desorbometer are highly consistent with the results of the measurements performed in the laboratory using a traditional method.