Home – Home – Jornals – Journal of Mining Sciences 2014 number 1

The paper presents results of numerical experiments performed to evaluate the effective viscosity of a fluid-proppant mixture, used in hydraulic fracturing. The results, obtained by two complimenting methods (the particle dynamics and the smoothed particle hydrodynamics), coincide to the accuracy of standard deviation. They provide an analytical equation for the dependence of effective viscosity on the proppant concentration, needed for numerical simulation of the hydraulic fracture propagation.

The article reports the geomechanical assessment of rockburst-hazardous Khingansky manganese ore body (Poperechny extraction site) at the early stage of development. The researchers accomplished geodynamic zoning of the ore body, analyzed mining-and-geological and mine-technical conditions, and estimated parameters of physico-mechanical properties of host rocks and ore. Using numerical modeling, the stress state of the ore body and rock mass at various mining stages is assessed, and the bottom part of the Khingansky ore body is considered rockburst-hazardous.

The stress-strain state in rocks around an excavation is assessed by the values of stresses “at infinity”, i.e., it is required to know stress distribution in an intact rock mass. The authors propose a new method of the stress-strain state assessment for an arbitrary cross-section excavation based on direct measurement of displacements of the excavation walls, using the Kolosov-Muskhelishvili formulas. Under analysis are the excavations shaped as circular and elliptical cylinders.

The authors present the results of underground excavation lining examination aimed at detecting inhomogeneities in the lining (reinforcement metal, voids, weakening) and recommend on selecting the lining sites to be optimal for measurement hole drilling based on field observations.

In focus is the problem of mathematical modeling of zonal disintegration of rocks around a deep-level excavation. In the framework of the elastic model of isotropic material, the author analyzes the two-dimensional case on stress field in rocks around a circular cross-section excavation. The acting compressive stresses at infinity depend on the depth of the excavation occurrence. The shear stress analysis has shown that in rocks around the excavation, the increased shear stress circle zone appears at the distance from the excavation center. The increased stresses come before the rock mass disintegration and create conditions for next destruction circles. The author dwells on probable influence of initial hydrostatic stress on the disintegration law. In modeling, the zonal disintegration circles appear at larger distance from the excavation center than in the experiment, due to the idealization of the classical problem formulations in rock mechanics.

The processes of free and absorbed coal gas filtration and diffusion are described using the earlier offered mathematical model in the form of the set of nonhomogenous parabolic equations. Movement of such medium is considered in the form of a progressive (shock) wave, i.e., the self-similar approximation. It is proved that the problem reduces to the plane boundary value problem of the quality theory of the regular differential equations. The effect of the gas sorption relaxation time on the shock wave structure is quantitatively estimated.

The general regular patterns in focalization of deformation at pre-failure stage in rocks under compression are found and analyzed (sylvinite, marble sandstone). Applicability of speckle-photography methods in problems on rock deformation and failure is proved. The authors define the self-sustained behavior of the focalized plastic deformation in rocks under compression, due to effect of various plastic micromechanisms. The self-sustained structures in rock specimens under compression propagate at a rate of ~ 10-5 ÷ 10-4 m/s (0.3-3 km/yr), which is close to slow motions induced in the earth crust by an earthquake or a rockburst. The ratio of the experimental and calculated failure times is correlated with the coordinates of the failure points in the test rock specimens.

Under consideration is the stress-strain state in the edge area of a bed when mine faces approach a vertical fracture. The author illustrates the stress-strain state analysis using the previously derived analytical solution for a single pillar located symmetrically in a mined-out void. Comparison of the analytical and numerical results shows their admissible precision.

The authors have revealed features of local methane concentration minimums in undermined degassing holes and causes of their zonality. The offered hypothesis on methane emission in underground wells accounts for zonal disintegration of rock mass around a stope.

It is known that under certain conditions, the structural geology, seismic, design and technology factors do not inhibit increase in the inclination of the limit pitwalls in deep open pit mines. The evaluation of the limit pitwall stability is made by the pitwall stability index, considered in ideal case. In practice, , which flattens pitwalls, expands the open pit mine limits on the surface and expands stripping. Therefore V.N. Sytenkov has proposed to construct a convex pitwall with the depth-wise decreasing stability index. It is assumed that when an open pit mine reaches its design depth and depletes its design reserves, the open pit mine stability coefficient cannot exceed 1. The article shows that this approach has both economical and physical preconditions.

The article reviews analytical methods of studying heat transfer processes running in the conditions of resource-saving underground coal processing, heat drying in processing facilities and in the course of heat accumulation and emission in caved rocks. The author considers problems with boundary conditions formulated at the moving boundary of the heat transfer domain.

The developed procedure for selecting parameters of positive-displacement hydropercussion systems has two stages. The first stage is the picking of the key parameters; the second stage is the engineering design of the system, adjustment of the selected parameters using the multivariate optimization procedure and the improvement of the system performance.

Based on the mine investigations of directional hydraulic fracturing using the bidirectional sealing device, aimed at weakening of a dirty band in a coal bed, the researchers have refined the valve synchronizer and eliminated detected vibration defects. The article presents the laboratory analysis of the KS-1 valve synchronizer operation and validates its efficient performance parameters.

The authors analyze excitability of polyharmonic vibrations in a single-body vibration machine. The developed mathematical model of the vibration system accounts for an elastic component element included in the design of the unbalance vibration exciter drive. The operating limits, frequency content and effect of the main design factors on the flow data of the vibration machine are examined. It is found that superharmonic vibration greatly contributes to the polyharmonic spectrum at certain frequencies, depending on the stiffness of the elastic component element of the clutch connecting the vibration exciter and the rotary drive.

The article gives analytical review of the mining and dressing waste situation and the experience gained in the waste exploration and reprocessing in Russia. The authors offer a new procedural approach to the appraisal and calculation of the mining and dressing waste accumulations with intent of their re-processing. The approach has been tested under conditions of diamond-containing mining and dressing waste sites.

The developed technology for thick and very thick flat ore body mining combines a number of mining methods using various ground control techniques. The regular patterns of stress distribution in the geotechnology elements are found. Analysis of rock mass stability yields the safe application range for the proposed geotechnology.

The upside potential of an underground mine ventilation by return air systems is analyzed in the article. It is shown that subsidiary air supply depends on the ratio of the pressure head of a recirculating draught producer to the mine depression at the recirculating draught producer site. By calculation of the actual example, the authors prove that air leaks can cause emergencies due to drastic reduction of fresh air supply in working areas.

The article discusses a new approach to implementation of the geoinformation environment for the mining geoinformation science problem solution using cloud technologies. In focus are the types of the cloud service as applied to the distributed geomonitoring networking for the wider range problem handling in mining. The authors describe specific structures of software support of the offered approach and exemplify problem solution in various spheres of mining geoinformation science.

The timely character of the digital space data utilization for regional and local day-to-day assessment of the environmental situation in the area of surface / underground mines and processing plants is proved. The natural environment situation is analyzed in terms of the Sorsky copper-molybdenum opencast mine (Republic of Khakasia, Russia).

By the analysis of oleinic acid flotation of fluorite and hematite, it is inconsistent to use thermodynamic approach to explain the flotation effect by the chemical adsorption of the reagent only. The authors propose a hypothesis that collecting ability of a flotation reagent relates with the activity of its physical adsorption at the air-liquid interface. The hypothesis is supported with the data on flotation of rutile, zircon and fluorite. Capability of surface pressure of film generated by molecules or ion-molecule associates as the criterion of collecting ability of a flotation agent is defined.

The authors describe experimental research findings on chemical-electrochemical leaching of gold from rebellious minerals. A laboratory-scale plant has been designed for studying the leaching kinetics. Rational parameters of chemical-electrochemical leaching are specified (duration of the process, electrode current density, NaCl concentration). The researchers analyze the changed microstructure and phase composition of arsenopyrite surface after the leaching and substantiate the leaching improving practices.

The studies into the fine-ingrained high-carbonate fluorite ore concentration show that increasing of pulp dispersion uniformity results in higher selectivity of flotation. The researchers find out availability of quality fluorite concentrate in processing of low-grade ore with carbonate index less than 1 CaF ₂ recovery up to 70%.

The actual safety regulations elide dynamics of air and gas conditions and their probabilistic nature, which results in underutilization of options of the advanced air and gas control in mines. The article proposes the decision-making using statistics filters, based on estimations of amplitude and duration of blow-outs. The authors derive relations for calculating the rational discrete intervals of explosimetric sensor sampling.