Vol 55 Iss. 1

At the beginning of the current century, P. Wilski, orienting a 1090 m deep mine in Příbram, found that measurements of the adjacent angles at air movement in the shaft and in the absence of this movement give a discrepancy of 11'31”. Based on this and on the data of visual observations of air movement in the shafts, he put forward a hypothesis about the helical movement of air along the shaft, affecting the magnitude of the weight deviation a. He determined the magnitude of the deflection a using the formula ...

Many ore mines that have an active aerodynamic connection of underground workings with the surface through the caving zone are ventilated by the injection-suction method. In this method, by regulating the operation of the suction and discharge fan, it is possible to create in the area adjacent to the caving, the so-called zone of zero depression. In this zone, the effective depression is extremely low, so there should be neither air suction from the surface nor air escape from the mine to the surface. The actual large size of the caving area and the occurrence of local natural draughts do not allow for the complete elimination of air movement through the caving. Air may move upward in one part of the caving and downward in another, but in much smaller quantities than with a single fan. Thus, the zero-depression zone created by the blower-suction method of ventilation serves as a measure to control air suction through the caving zone. At mines in the northern regions, the position of the zero depression zone plays an important role in improving the atmospheric conditions of these mines, reducing the entry of cold air from the surface ...

The Zapolyarny mine widely uses high-performance mining systems with massive ore collapse when mining a thick declivity ore deposit. This is associated with the need to detonate large explosive charges during ore stripping and release and, consequently, with the contamination of the atmosphere of underground workings. For the organization of effective ventilation of treatment blocks is important properly designed ventilation scheme and systematic fight against the causes of deterioration of atmospheric conditions at workplaces ...

Ventilation of hydraulic and transportation tunnels is complicated by a large cross-section of underground excavations, their considerable length and a large volume of blasting operations. Due to low air velocities in such excavations, the most common discharge method of ventilation does not provide rapid removal of harmful gases after blasting. Suction method of ventilation is also ineffective, as in the bottom-hole space is formed, a large volume of slow-moving air ...

Existing work to determine the necessary amount of air for liquefaction and removal of harmful impurities in the chamber-shaped workings are based on the fact that the movement of air entering the chamber, occurs according to the laws of free turbulence. Depending on the configuration of chambers, round or flat free jets are formed in them, acting in a limited space. Distribution of harmful impurities in the volume of chambers and their removal by free jets occurs due to their displacement by the nuclei of constant masses, in which through each cross-section the flow rate maintains a constant value. Proceeding from this basic provision, formulas for calculating the required amount of air at periodic (blasting operations) and continuous (drilling, scraping) sources of formation of harmful impurities are given. Most of the proposed formulas in one form or another clarify the boundaries of application of the known formula ...

At mining enterprises with the use of pneumatic energy may be technically and economically advantageous to ventilate blind faces with compressed air, because for short-term ventilation or with a relatively small amount of constantly supplied air is inexpedient to supply electricity and install a partial ventilation fan ...

In the ventilation network of any mine, part of the total unproductive air flow is lost in the area of the main fan units. This category of leaks always has the greatest negative impact on the mode of operation of fans and the efficiency of ventilation of underground workings. In the harsh climate of the Polar region, sucking of outside air in winter causes intensive freezing of ducts, blocking devices and fan impellers. The applied methods of sealing of ventilation structures do not completely exclude external air losses. Therefore, when choosing the main ventilation fans, these losses must be taken into account. ...

One of the promising areas of high quality coal mining in India is the Jharia basin.Till now in India a significant part of coal is mined by private companies. Creation and development of the state-owned industry implies equipping mines with advanced equipment and introduction of modern mining technology. At the same time, a great role should be played by ensuring safe working conditions, in particular, by improving ventilation of mines. Until 1952, Indian coal mines had no ventilation service. Lack of experience and a sufficient number of qualified personnel makes it difficult to solve the issues of ventilation of underground workings in practice at present. In order to outline measures for its improvement, we at the mines of the Jharia basin investigated the state of ventilation according to the data of air and depression surveys, studied the work of fan installations and developed measures for its improvement, determined the gas content of mines on methane and carbon dioxide, investigated the explosive properties of coal dust and the propensity of coal to spontaneous combustion. Finally, the safety regulations in force in India for coal mines are analyzed, taking into account the experience gained in the Soviet Union ...

At present many potash mines of the GDR are being reconstructed with the aim of increasing labor productivity and reducing the cost of extracted potash salt. In this case, low-productive and labor-intensive endless pumping is often replaced by conveyor delivery and road transport. Sometimes special dump trucks with a load-carrying capacity of 20 tons and an engine capacity of 150 hp enter directly into the mining chambers and are loaded by loading machines. This eliminates scraper delivery of potash salt from the chambers. Motor vehicles are also widely used to deliver people and materials ...

The physical model of thermal processes in mine workings and frozen, thawing and freezing rock mass at the modern level of research can be formulated as follows: the temperature of mine air varies along the length of workings g and in time t as a result of its heat and mass exchange with the rock massif, minerals transported along the workings and ice (water) in the workings, as well as under the influence of “absolute” heat emissions and fluctuations in temperature t0 and relative humidity ф0 at the beginning of the ventilation path. In this case, only the intensity of “absolute” heat emissions can be considered constant in time ...

In mine workings between air and rock massif, beaten coal, as well as settled dust there is a mass and heat exchange. In the cold season, when air is supplied to the mine without heating and humidification, the process of mass exchange is directed from rocks to air. The amount of moisture released into the atmosphere depends on the moisture content of coal, dust and host rocks, the degree of grinding of coal or rocks, the speed of air movement, its humidity and other factors ...

Hygienic standards of dust . air in industrial premises and underground workings, approved by the USSR Gossaninspektsiya, are differentiated by type and composition of dust (SN 245-63). They do not take into account a number of factors that affect the amount of dust penetrating into the human body: different heights of mines and mines, climatic conditions, the degree of severity of the work performed, the duration of human stay in a dusty environment ...

As a rule, mines in the Far North, which develop coal seams in permafrost conditions, are characterized by seasonal fluctuations in the dust content of the mine atmosphere. In January - February, the content of dust in the air during excavation, loading and transportation of coal reaches the maximum value - hundreds and thousands of milligrams per 1 m3, and in summer it approaches the sanitary norm ...

Mining workings during geological exploration works completely or overwhelmingly pass through the oxidation zone, which is of the greatest interest in the study of dust explosiveness. The variety of factors, on which the oxidation process of sulfide deposits depends, does not make it possible to study the explosivity of dust of sulfide ores in this zone at one of any deposits. Explosive properties of sulfide dust are not fully studied, but it is certain that explosiveness is determined mainly by sulfur, and not only the amount of sulfur in the ore, but also the properties of the minerals in which it is contained ....

One of the main factors characterizing the propensity of dust to explode is the volatile yield. Sometimes it is considered to determine the degree of dust explosiveness. There are different opinions about the relationship between the explosiveness of coal dust and the content of volatiles. Some researchers, in principle not denying the influence of volatiles on explosiveness, do not find a strict regularity in it, which would apply to coals of all deposits. Other authors believe that the explosivity of coal dust is a function of volatiles and define it as a linear dependence. The deviation of explosiveness from this regularity, observed by some researchers in the laboratory study of coals, is apparently explained by the influence of oxidation, ash content and partly by the petrographic composition of coals. As our studies of seven coal seams of Kuzbass have shown, dust explosiveness in the first period of oxidation slightly increases and then decreases. It increases, apparently, due to sorption of oxygen ...

When driving preparatory coal workings in mines in the permafrost region, air dustiness after blasting reaches hundreds and thousands of milligrams per 1 m3 of air. The dust formed is the most harmful, because on its surface adsorbed molecules of poisonous gaseous decomposition products of explosives, which have a toxic effect accelerating the development of pneumoconiosis ...

Seasonal fluctuations of air dustiness in mines in the permafrost region are known to be associated with the processes of evaporation and condensation of moisture, which take place in mine workings in cold and warm periods of the year, respectively. The former increase and the latter reduce dust generation during excavation, loading and transportation of coal ...

One of the sources of pollution of mine air in mine workings with conveyor transport is blowing dust from fastenings, soil, conveyor belt, etc. As it is known, dust blowing off the dusty surface occurs under the action of aerodynamic forces of the air stream, when the latter exceed the gravity forces of aerosols and molecular forces of attraction of dust particles with dust particles or dust particles with the dusty surface. Knowing the magnitude of these forces and the nature of the interaction of dust particles with the air flow, it is relatively easy to find the velocity of the ventilation jet, at which the dust disruption begins in these conditions, ie determine the value of the critical velocity of dust disruption ...

The use of cyclones is one of the main directions in solving the problem of improving the atmosphere at the workplaces of drillers. Dust separation in these apparatuses occurs due to centrifugal force, which is received by dust particles when the air stream is fed at high speed tangentially into the cylindrical casing of the cyclone ...

One of the most common measures to prevent sudden coal and gas emissions in longwall faces of single emission-hazardous flat seams, as well as for the preparation workings and opening of emission-hazardous seams in the Donbass is the drilling of advance wells ...

After carrying out a well in the coal bed in the immediate vicinity of it due to redistribution of gas pressure, filtration of gas contained in coal begins. In this case, the intensity of redistribution of gas pressure in the zone of influence of the well depends on the initial gas pressure in the formation, its filtration and sorption characteristics ...

Increased in recent years, the flow of information on the impact of thermal phenomena on the movement of air in the mine during a fire is mainly theoretical in nature. Experimental studies are rare. In the study of phenomena related to the manifestation of thermal depression, the relationship between thermal depression and the amount of air flowing, the temperature in the fire hearth and the location of the fire ... has not received adequate coverage.

In contrast to the previously used in statistical development of the general mine indicator of the number of fires per 1 million tons of production, in this study used the formation fire frequency coefficient, which characterizes the number of fires per 1 million tons of production from a given reservoir. The point is that the all-mine indicator of the number of fires per 1 million tons of production correctly reflects the actual state, provided that the number of fires from the seams developed by the mine is distributed evenly over all seams. In practice, however, such a situation does not happen ...

The intensity of fracture product yield during rock drilling is in direct dependence on the drilling speed. The total yield of fracture products is taken into account when calculating dust removal systems and devices for accumulation of drill cuttings. However, it is known that the drilled fines have a complex fractional composition. The most dangerous for human health are particles smaller than 10 microns. These particles are able to stay in suspension for a long time and, accordingly, to spread to distant distances. Therefore, when evaluating the intensity of dust source from the point of view of its danger, it is necessary to be guided by the content of the smallest fractions in the drilling fines taken out of the well ...

Recently the methods of calculation of methane emission based on the value of natural gas content of coal are becoming more and more widespread. This is the result of numerous studies in the field of methane emission in coal mines carried out in our country ...

The work of limited turbulent flow as a venting factor is associated mainly with turbulent deformation of the gas wave, and the influence of turbulent diffusion of gases in such a flow is insignificant and may not be taken into account in calculations. Let's consider, whether this position remains true for excavations of large cross-section ...