Rock burst represents a very dangerous phenomenon in deep underground mining, as well as for underground structures in unfavourable conditions (great depth, high horizontal stress, proximity of major tectonic structures, etc.). The rock burst problem relates to the natural and mining conditions of the rock mass. The evaluation of rock burst is becoming increasingly important as mining activities reach greater depths. In the literature, rock burst assessment challenge was tackled by many researchers using various methods. However, no study providing review and comparison of different rock burst assessment methods is available. In this paper, rock burst classification is briefly summarized. This includes a classification based on rock burst type, and another classification based on rock burst severity. As an important method for rock burst prevention, some novel energy-absorbing bolts were developed. These bolts demonstrate constant resistance under both static and shock loads and large elongation ability enabling them to withstand large deformations of rock masses under rock burst-prone conditions. Among the novel energy absorbing bolts, Modified Cone Bolt (MCB) and Constant Resistance at Large Deformation (CRLD) Bolt are selected to be presented in this paper.

Providing a reasonable forecast of the required properties of intermetallic compounds (hereinafter also referred as intermetallides or IM) is an important scientific and commercial problem, which may be solved by focusing scientific researches and permanent generation of knowledge in this field. To date, researches in chemistry and physics of IM have been developing empirically for a simple reason, due to the complexity of describing the relationship between the crystal structure and chemical bonds, and, therefore, between all the properties of IM. IM is mainly characterized by metal type of chemical bond, as well as specific metallic properties. At the same time, among IM, there are also salt-like compounds with ionic bond, i.e. valency compounds formed from elements of different chemical nature, being stoichiometric compounds. The examples of such compounds are compounds with intermediate bond type, i.e. ionmetal and covalently-metal, as well as covalent bond types (e.g., NaAu). In the series of compounds of Mg with elements of the IV subgroup, along with decreasing the difference in the electrochemical characteristics of the components, the change in the IM properties is observed, from those peculiar to ionic compounds (for example, Mg2Si, Mg2Ge) to the properties typical of metals (Mg2Pb), etc. Due to the fact that lanthanides form the largest group of elements of the periodic system occurring in nature, and Mg is a relatively active chemical element in terms of IM formation (for example, it forms three IM with cadmium - Mg3Cd, MgCd and MgCd3), its oxides in slag provide decreasing average silicon content and increasing the stability of the silicon content in iron, being an important process indicator in the course of physicochemical reactions occurring in a blast furnace (for example, in the process of iron production). The presence of Si impurity (along with O, Au, Ti, V, Zr) produces the greatest effect on efficiency of solar cells, etc. [1–3]. Based on the foregoing, it is very important to study the state function, i.e. enthalpy of magnesium-lanthanide systems, rich in magnesium, and, based on the results of computer simulation, taking into account molecular dynamics method and other similar studies [4–8], to model regularities of changes in melting enthalpy of IM of the mentioned systems. The issue of modeling the pattern of change in melting enthalpy of IM of magnesium-lanthanide (Mg-Ln) magnesium-rich systems is considered based on systematic analyzing melting enthalpy of IM of Mg-Ln magnesium-rich system, including Mg2Ln, Mg3Ln and equimolar compound MgLn, implemented using semi-empirical method developed by N.S. Poluektov.

The findings of review of promising methods and techniques providing increasing effectiveness of degassing of coal seams containing methane in the process of their underground mining are presented. Based on the review findings, traditional methods and techniques of degassing were identified, the effectiveness of which is 12–25 %, as well as unconventional methods providing methane degassing of up to 40%. As a classification feature of the unconventional methods and techniques of gaseous methane liberation, a condition of decreasing pressure and increasing temperature of coal matrix containing solid gas hydrate has been adopted. The conditions for methane transition from gas hydrate to free gas taking into account actual mining and technogenic conditions of the mines have been identified. Given the difficulty of supplying additional thermal energy into a coal seam, as the main way to reduce pressure in the seam, unloading of the rock mass relative to the initial stress state, and disruption of coal and rocks in the course of transition from their elastic deformation to elastic-plastic and out-of-limit deformation are accepted.

For analyzing the dependence of face equipment failure on its length, two groups of elements are commonly considered. The first group includes all elements of shearer-loaders: conveyor drives, elements of pumping stations of powered supports, supports of face junctions with strikes and others. The second group includes all elements of powered support sections, linear sections of pan lines and scrapers of face scraper conveyors, electric cables of shearer-loaders, main pipelines of powered supports, etc. It is noted that the constancy of number of the first group elements linear variability of number of the second group elements do not uniquely determine the constancy or variability of the failure factor of the aggregate of the same type elements of the first or the second groups [1]. The plot of mean-time-between-failures (MTBF) of SL-500S stoping complex as function of face length is presented. Besides, the curve of the face (complex) length-dependence of average recovery) time (after failure of the SL-500S stoping complex time is shown. Analyzing the dependence of availability factor of stoping complexes on the face length showed that the length of stoping complexes is not a factor determining decrease in the MTBF and increase in the average recovery time. The plot of recovery time (after failure) of the SL-500S stoping complex as function of face length is shown. A formula is presented for assessing the cumulative effect, on the MTBF of SL500S stoping complex, of its length and potash ore cuttability. The plot of correlation between the MTBF of SL500S stoping complex and the face length/the potash ore cuttability is presented, which demonstrates that the complex length followed by the thickness of the extracted layer produce the greatest effect on the MTBF. The plot of the number of failures per day as a function of the maintenance factor of the SL-500C shearer-loader is presented. The plot demonstrates that the average number of failures of the SL-500C shearer-loader per day reaches a minimum and practically stabilize at values of the maintenance factor of 0.9–1.0, which correspond to three-shift production with one 6-hour maintenance shift per day.

Intensification of coal mining from mine seams of 0.55–1.20 m thick requires increasing efficiency of loose coal loading that may be achieved by selecting the optimal parameters of auger operating device of a shearer. The most reliable way to determine effect of the auger parameters on the energy parameters of the shearer operation is experimental research in actual operating conditions. As the subjects of the research, we selected up-to-date UKD400 and UKD200-500 shearers, operating in representative conditions of the Krasny Partizan mine of SE SVERDLOVANTRATSIT and Ternovskaya mine of DTEK PAVLOGRADUGOL PJSC. An adaptive method for specific mining operating conditions is proposed for determining the specific energy consumption of the shearers on material disruption and loading for thin seams in actual operating conditions based on fixing the values of currents of the cutting drive motors. Based on processing of the experimental data, an indicative dependence of the power for rock mass loading on the feed rate and the effective width of the operating device is determined. Increasing the auger effective width results in increasing the loading power and specific energy consumption. At the same time, the higher the shearer feed rate, the greater the growth of the loading power and specific energy consumption. This is due to the beginning of the process of loose rock mass circulation, and the larger the auger effective width, the more intensive the circulation process, and at the lower feed rate of the shearer the process starts. A method is proposed for selecting the auger optimum effective width based on the criteria of minimum specific energy consumption and maximum commercial productivity.

It is known that conveyor operates in chemically aggressive and abrasive environments; for this reason the drive drum of belt conveyor wears out rather rapidly. It is noted that the lining of the conveyor drum increases coefficient of friction between the conveyor drum and the conveyor belt, reduces the belt wear rate, and also protects against corrosion and abrasive wear. The plot of the PU-60 polyurethane wear rate as function of load when rolling on steel is presented. It is noted that increasing the load increases the strength of adhesive junction between steel and polyurethane rollers; friction wear causes fatigue failure of surface layers of the materials. Besides, the plot of the PU-80 polyurethane wear rate as function of load when rolling on steel is presented. The plot of the polyurethanes wear rate as function of hardness of polyurethane is presented, which shows that the lowest wear rate is demonstrated by the hardest polyurethane, PU-80. The bar chart of static friction coefficient for PU-60 and PU-80 polyurethanes demonstrates that the optimal material for lining the drive drum of a conveyor belt is PU-80. The plot of the rubber wear rate as function of load at a speed of 1 m/s is presented. The plot shows that the wear rate increases with increasing the load. This is due to the effect of two factors: growing contact deformations of the surface layer of the rubber and increasing the contact area of mating parts. It is noted that IRP-1347 rubber is less susceptible to wear than "REMAGRIP" rubber. This allows using IRP-1347 rubber in aggressive environments. The bar chart of static friction coefficient for the rubber presented in the paper shows that the investigated IRP-1347 and REMAGRIP rubber grades have the required value of static friction coefficient for use as lining material for the drive drum. The plot of the wear rate as function of the rubber hardness and as function of the polyurethane hardness is presented. In practice, it is proved that the best material for lining the drive drum is PU-80.

Conveyor transport at a modern coal mine is the main link that determines the overall performance of the enterprise. For safe operation of belt conveyors, it is important to ensure that shift output per face doesn’t produce average and maximum minute material flows, which exceed strength margin of the belt, power margin of the drive, and receiving capacity. Such situation, as a rule, may arise due to the strive of workers to compensate for underproduction caused by long downtimes of a face for any reason. In the paper, a method is proposed that enables determining the maximum shift output per face. According to the technique described in the “Basic Provisions for Designing Underground Transport of New and Existing Coal Mines,” the average minute material flow, which determines the operational load on a belt conveyor, depends on the material feed time factor. Accepting the assumption that a coal shearer works the entire shift in a face, the limiting value of the material feed time factor is equal to 1. To determine the actual value of this factor, it is proposed to determine the face operating (production) time using actual planogram. The shift time is spent for preparatory and finishing operations, the face equipment and conveyor line troubleshooting and failure recovery, auxiliary service operations and, finally, operational and organizational downtimes. On the actual planogram, these time intervals are displayed by straight-line portions. Thus, the shift time minus downtime for any reason, represents the face production time. The ratio of these values represents the operation factor. Applying the operation factor allows to determine the maximum limiting face production, not only taking into account the volume of coal mined per cycle, but also based on coal cuttability and technical specifications of the face equipment. This enables us to determine the face production load that ensures safe operation of the belt conveyor.

Electric energy is the most common and universal form of energy. It can be produced in large quantities near energy sources, transmitted to large distances, easily distributed between consumers and converted into mechanical, thermal, and light energy. Ensuring reliable and economical quality electric energy supply to mining enterprises with the optimal use of energy resources is one of the most important tasks facing the country's energy sector. In the Russian Federation, high degree of concentration of generating capacities at power plants has been achieved. The main capacities are concentrated in power plants with installed capacity of more than 1 million kW. High importance of the electric power industry is determined by the infrastructural nature of the industry and the direct relationship between the country's economic growth and the level of its development effectiveness. One of the most pressing problems of modern electricity supply is the problem of ensuring the quality of electric energy. The main reason for the deterioration in the electricity quality is widespread non-linear loads that create non-sinusoidal currents and voltage unbalance during their operation. The voltage unbalance is most often caused by the presence of an unbalanced load. Unbalanced load currents flowing through the elements of the power supply system cause unbalanced voltage losses in them. This results in appearance of unbalanced voltages on the terminals of electric apparatus. The voltage deviations at electric apparatus overdriven phase may exceed the normally acceptable values, while the voltage deviations at electric apparatus other phases may remain within the normal limits. In addition to the deterioration of the voltage mode at electric apparatus under the unbalanced voltage conditions, the operating conditions of both the electric apparatus and all the network elements are significantly worsened, and the reliability of the electrical equipment and the power supply system as a whole decreased. The paper considers the issues of reducing the voltage losses in power supply networks by improving quality of electric power.