Home – Home – Jornals – Journal of Mining Sciences 2014 number 3

The authors offer an approach to estimating parameters of underground voids formed in soil under natural or induced effect. Irreversible deformation of soil is modeled using discrete element method. The formulated inverse problem on geometry and occurrence depth of an underground void by the data on configuration of the subsidence trough has a single-valued solution.

The 3D discrete element approach is used for the computational investigation of the problem on pressure exerted by granular material on the bottom and walls of a cylindrical container. Dry friction between the granular material particles and friction on the container walls are taken into account. The particles have spherical shape with the assigned radial distribution. The authors analyze the effect of filling method on stress state of granular medium. Accuracy of Janssen’s hypotheses is estimated in engineering problem formulation.

It is suggested to assess plastic state of rocks around an unsupported cylindrical excavation by measured displacements of its walls. The problem (overspecified in the viewpoint of classical formulation) has a unique solution that allows calculation of stresses, strains and displacements in the plastic deformation domain, including the elastic-plastic boundary, without addressing the elastoplastic problem.

The authors discuss formulation of boundary conditions in problems on stress-strain state of rocks around an excavation. The classical formulations neglect the presupposition on linearity of stress field in an intact rock mass with depth and disregard the discrepancy of the calculated and actual behavior of rocks. The presented study is based on the linearity of initial stresses and the computational domain boundary conditions that assume stress linearity and unaltered boundary conditions during drivage. The problem on stress-strain state is divided into two problems due to option of formulating accurately boundary conditions for the horizontal boundary and the absence of such option for the vertical boundary.

Stress tensor invariants are determined as average stresses at all possible sites of a volume element. Integration of stresses is performed in the plane of Mohr’s chart. The obtained invariants can be used in formulating criteria of limit stress (failure) in geomaterials.

The authors analyze geoacoustic monitoring data obtained in the rockburst-hazardous Antei deposit and propose an approach to the data processing and interpretation based on the following statistical parameters: wavelet coefficient dispersion, correlation fractal dimension and signal energy distribution. Collated, the calculated parameters and the induced seismicity in the Gluboky Mine have exhibited adequate correlation, which allows considering the parameters as potential indications of accidents.

The article gives the review of the present-day development in the physical kinetics of coal-methane system. The Gibbs thermodynamic potential is derived for this system as the function of methane density (persisting order parameter) and coal jointing (non-persisting order parameter). The authors put forward diffusion-filtration mechanism of gas mass transfer in porous material on two time scales and substantiate the concept of “quick” and “slow” methane. Based on the nonequilibrium thermodynamic potential, kinetic equations are derived for gas pressure and jointing in coal (bed). The first equation solution explains the physical effect of temporal gas pressure growth at the maximum of the external rock (bearing) pressure, the second equation enables generalization of the Griffiths failure criterion for a set of gas-filled fractures. Mechanism of pre-outburst spalling of gas-saturated coal is analyzed.

Under discussion is plastic soil removal in horizontal rotating pipeline by air flow. It is experimentally proved possible to remove soil by batches generated during rotation of the pipeline. The found relationship between soil conveying in the pipeline, the pipeline diameter and air forward pressure is made the basis of determining parameters of the main transporting line in a drilling installation.

In the context of the problem of increase in efficiency of vibro-percussion driving of steel pipes in soil, a pilot model of shock generator with step speed adjustment for the bit and anvil impact is described. The authors report experimental modeling of pipe penetration depending on load of stalk. The influence of the stalk load parameters on the amplitude of generated shock pulses and the pipe penetration rate in elastoplastic soil is defined.

Under discussion are the issues of driving secondary access roadways without pushing ultimate pitwall limits in steep deposits with internal dumping. The calculation scheme and correlation analysis of key elements of the resource-saving technology are presented. Regressional relationships are obtained for length of an open pit mine bottom, specific weight of internal dumping and the open pit mine parameters. The article specifies the effective range of the developed technology.

Existing methods of pushback (phase) design are reviewed in the context of “gap” problems, a term used to describe inconsistent sizes between successive pushbacks. Such gap problems lead to suboptimal open pit mining designs in terms of maximizing net present value. Methods such as the Lerchs-Grossman algorithm, network flow techniques, the fundamental tree algorithm, and Seymour’s parameterized pit algorithm are examined to see how they can be used to produce pushback designs and how they address gap issues. Areas of current and future research on producing pushbacks with a constrainedsize to help eliminate gap problems are discussed. A framework for incorporatingdiscounting at the time of pushback design is proposed, which can lead to minedesigns with increased NPV.

The audit of minerals and raw material reserves in the producing, prepared for production and new areas in the Kuznetsk Coal Basin shows that the use of the available package of coal geotechnologies meant for a relatively narrow range of geological and mining conditions results in depletion of the explored high-processable reserves. It is thought that the Kuzbass development strategy should sidetrack the search of new mining areas with the assigned geological and mining conditions and aim at hunting and elaborating mining and processing technologies that enable extraction of previously proved & undeveloped reserves. Such progression and expansion of the mineral and raw material reserves base of Kuzbass will promote advance in the mining science and engineering and favor to more comprehensive utilization of the available industrial potential, infrastructure and human resources.

The article deals with estimation of snow cover condition and air pollution in areas of fast-paced coal mining. It is suggested to use data of remote earth sounding in winter, and snow cover in this case acts as a survey sheet-indicator of underlying ground contamination. The article exemplifies evaluation of data for a Kuzbass mining area of 100 km² by snow quality.

The authors examine oxidation of sulphide minerals in mining waste storages and the associated ecological problems. The highest environmental hazard is produced by fine-dispersed mill tailings, especially where sulphide content is comparable with nonmetal content of low-chemical activity. In terms of some industrial waste storages in Murmansk Region, it is shown that the eco-hazard source can be not only fine but also coarse particle waste (Allarechensky deposit waste) and ore concentration waste with low sulphide content but highly chemically active nonmetals (Pechenga ore field).

X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy are used to study the change of the surface layers and chemical state of atoms on galena surface after treatment by high-voltage nanosecond electromagnetic pulses. By XPS the induced structural changes of galena surface layer are associated with alteration of chemical state of sulfur atoms, which conditions the change of electrochemical and flotation properties of the semiconductor sulphide mineral: growth of electrode potential creates favorable conditions for adsorption of anion collector and promotes increased floatability of galena.

The authors present a new method of testing wettability of fine coal particles settled on water drops. Ratio of wetted particles is calculated by measured optical density of air and dust mixture. The offered method enables measurements to be taken immediately in the air and dust mixture, without mechanical treatment of coal dust particles, which improves accuracy of particle wettability testing

The effective electrochemical method of saponite and slime removal from recycled water of Severalmaz JSC plants is scientifically and experimentally justified based on the analysis of electric properties of saponite surface. The method consists in utilizing electrophoretic attachment of negative-charge fine saponite particles to anode and electroosmosis and clarified water exudation on cathode. The developed method will allow higher efficiency and regulation of diamond extraction and ecology problem resolution due to closed water rotation and aborted water discharge to the tundra.

The acoustic data measurement system and processing algorithm are developed to position a pneumatic impact machine in soil. The method is based on recording lag time of entry of acoustic signal generated on interaction between the pneumatic impact machine and soil in the receiver of multichannel measurement system relative to reference signal of the machine. The measurement system and the algorithm have been trialed in full-scale conditions.