V.V. Senkus’s research while affiliated with Kemerovo State University and other places

The paper discusses the main disadvantages of strip and underground mining methods and possibilities of eliminating the disadvantages through introducing a combined technology of coal deposit mining. Combined coal mining technology is the method comprising elements of several geotechnologies, for example, underground and strip mining, as well as, possibly, underwater mining, borehole and other techniques of deposit mining. The combined coal mining technology provides for unified layout for opening, development, production and processing of reserves for the whole LoM on the basis of general technological solutions made in advance. Such complex solutions for opening and development of deposit reserves within the opencast and underground mining contour allows minimizing the volume of openings and reducing the time for commissioning, investment costs, as well as decreasing the costs for aerage, drainage, rock mass hauling and land reclamation. Substantiation of deposit opening options should comprehensively take into account technical, organizational, and economic factors [34–37]. Analysis of the options as exemplified by the Makar’evskoe coal deposit development in Kuzbass allows to conclude that the combined method is promising and promotes increasing optimal volumes of coal production, while reducing the deposit development time by about 15 %, and increase the net present value compared to underground and opencast mining options more than 5 times.

Assessment of accident rate in mines was carried out in the form of the post-event analysis and identification of a trend making it possible to detect the deterministic component of the time series, the adequacy of which was governed by the value of the correlation factor. The most significant external factors influencing the rate of accidents are the technical and economic performance of a coal mine. Based on the results of the analysis of the approaches to methane risk assessment and their deficiencies, another method is proposed, which takes into account the influence exerted on methane hazard by temporary roadheading, booster fan modes, as well as by filtration and diffusion of methane in air flow. The list of characteristics is proposed to account for the influence exerted on methane hazard in temporary roadways by operating modes of booster fans and by diffusion and filtration of methane in air flow. In order to assess methane risk, it is required to determine concen-tration of methane in face area of temporary roadways, methane concentration in fresh air flow, coefficient of eddy diffusion of methane in air, thickness of coal at the contact with air, period of relaxation during edge coal drainage through exposed surfaces, average rate of advance of temporary roadheading, initial gas release rate, time from the start of roadheading to the moment of methane risk assessment, time from the completion of temporary roadway construction, density of broken coal, coal gas content in face area, residual content of gas in coal under atmospheric pressure, average size of broken coal fragments, consumed power of booster fans, aerodynamic resistance in ventilation duct, booster fan efficiency, coefficient of air leakage from ventilation duct and average concentration of methane at outlet of temporary roadways.

Ventilation of surface and underground mines in hybrid mining obeys common principles and has peculiar features of combination and interaction of open pit and underground mining technologies. Specificity of ventilation of underground excavations in hybrid mining is conditioned by the fact that these excavations are driven from the pit walls and bottom, which are the production areas of open pit mine. Air in such work areas contains much dust and vehicle exhaust gas at concentrations exceeding MAC values. Ventilation induces mixing of air flows and is complicated by the basin-like shape of open pit mine. The function of underground mine ventilation in hybrid mining method reduces to air feed from the windward side of the open pit using booster fans or stationary fan installations and outlet of return air to the mined-out area of open pit where pollution of air with gas is very high. The independent ventilation of underground excavations requires drilling of air holes on the sides or in the center of excavations as air feed pressure and velocity is such air holes are unconstrained under safety regulations. The side air inlet holes need installation of many low-head fans to ensure pre-set air flow rates in development and production headings. Such fans are not produced in lots. Thus, hybrid mining operations require a combination ventilation circuit with air holes equipped with suction pumps to discharge mine air in the atmosphere beyond the limits of open pit mine.

Analysis of change in the number of gas molecules in an elementary volume of rock mass shows that as a consequence of collision of gas molecules and rocks and owing to sorption–desorption reactions between them, the phase-space distributions of molecules of free and adsorbed gas are statistically interrelated, and, for this reason, in conformity with the principle of local equilibrium for an arbitrary point in rock mass, the deviation of the distribution function of free gas molecules from the Maxwell distribution will be insignificant. At the same time, due to desorption, the second group will drag in molecules which fall beyond the first group at a given time. The analytical equation is obtained to describe gas transfer in coal beds and enclosing rocks at the molecular scale in pursuance and entailment of the fundamental provision of the theory of kinetic equations. The equations of gas flow in a porous gas-adsorbing medium disregard dispersion of macroscopic fields of true density of free gas and fluctuation due to the irregularity of the transfer velocity field, while the kinetic equation of distribution function of free gas molecules in phase space takes this specificity into account. Going from the distribution function to the first order moment allows localization of the equation and mathematical model of gas flow process with the unknown quantities represented by macroscopic characteristics of density or pressure of free gas. The mathematical model of gas transfer in a gas-adsorbing porous medium, to be suitable for the scientific substantiation of applied problems, should contain generally accepted macroscopic characteristics of thermodynamic state of gas. Thus, it is required to find connections between the effective characteristics of seepage transfer and density field of free gas.

The article gives geological characteristics of the Makarievsky coal site in Kuzbass and offers mining scenarios using open pit, underground and hybrid methods. Based on the net profit criterion, it is found that over the period of mining, money flow makes 143.4 billion rubles and net profit totals 20.1 billion rubles. The analysis of money flows and net profits in the alternate scenarios shows that in the open pit and hybrid mining methods, production efficiency is enhanced by 20–30% and mining period is cut down by 15–20 years, while land reclamation using traditional techniques nullifies net profit. Therefore, land reclamation requires hydraulic or mechanical/hydraulic engineering which ensures cost saving by 30–45%.

This article presents a method and a mechanized crushing and screening plant designed to sort loading of raw coal into gondola cars, in which the ROM is separated by size, thus allowing for a mechanical waling of rock and separate loading of coal, first small and then large grades to prevent floating the coal away from gondola cars during movement, and protecting the environment from pollution, it also presents quality design characteristics serving to calculate the performance of the complex providing the given performance and the crusher energy saving.