Ventilation of the underground mine

(Figure) The schemes for the ventilation of the underground mines
The schemes for the ventilation of the underground mines:
a - central;
b - winged;
v - grouped;
g - local;

VENTILATION OF THE UNDERGROUND MINE (EN: mine ventilation; DE: Grubenbewetterung; FR: ventilation de mine, aérage de mine; ES: ventilacion de la mina; RU: вентиляция шахты) is the system of the activities, which is directed towards the maintainance of the atmosphere with the parameters, which are necessary for the conducting of the mining works, within all the active mine workings within the underground mine.

The ventilation of the underground mine was known during the 1st century BC (for example, the mines within the Rio Tinto, within the Southern Spain). Later (the 1st century AD), the data about the ventilation of the underground mine have been reported within the "Natural History" by Pliny the Elder; the first systematic description of the methods for the ventilation of the underground mine (the 16th century) has been made by Georgius Agricola. Originally, the ventilation of the underground mine was performed on the account of the natural draft, and subsequently, also on the account of the heating of the outgoing stream. The development of the mining works, and especially the emergence of the methane within the underground mines (the first data were reported during the 16th century), have required the intensification for the ventilation of the underground mine, which was made possible because of the invention of the mine ventilator during the 1832 within Russia.

They distinguish the ventilation for the entire underground mine, in case of which the air, which is delivered from the surface, washes the major mine workings within the underground mine, and the local ventilation. The means of the engineering provision for the ventilation of the underground mine are: the ventilatory installations, the ventilatory built structures within the underground mines, the ventilatory regulators, the ventilatory pipelines (usually for the local ventilation), the mine workings, which are penetrated specially for the ventilation (the ventilatory mine workings), the means for the decreasing of the aerodynamic resistance within the mine workings and of the leaks of the air. The major schemes for the ventilation of the underground mine are: the central scheme, and the flanking scheme; the combination of these schemes is the combined scheme.

In case of the central scheme for the ventilation of the underground mine (see the Figure, a), the air arrives into the underground mine, and exits out of this mine, through the shafts within the centre of the mine field. This scheme is used in case of the limited sizes of the mine field along the strike, and in case of the relatively small productive capacity of the underground mine, and also in case of the conducting of the works at the deep horizons; this scheme ensures the rapid commissioning of the main ventilator, and the creation of the through-passage stream during the construction of the underground mine; this scheme is characterized by the great length of the path for the movement of the air, by the existence of the parallel streams with the pure and polluted air, by the multiple crossings of these streams, and, as the consequence, by the great leaks and depression within the underground mine. The variation of the central scheme is the scheme with the centrally-displaced situation of the ventilatory shaft.

In case of the flanking scheme for the ventilation of the underground mine, the air arrives into the underground mine through the shaft within the centre of the mine field, and exits through the shafts (exploratory shafts), which are situated at the flanks. This scheme is used at the shallow underground mines, when it is not possible or not feasible to maintain the unified ventilatory horizon; this scheme practically excludes the counter-movement of the incoming and outgoing streams; the length of the path for the movement of the air, the leaks, and the depression within the underground mine are lesser, than in case of the central scheme. However, according to this scheme, there are required at least three ventilatory shafts, and usually at least two ventilatory installations; during the period of the preparation of the mine field, the ventilation of the underground mine is hindered. The varieties of the flanking scheme are: the winged scheme, with the unified mine working for the outgoing stream throughout the entire wing (see the Figure, b), the grouped scheme, where the mine workings for the outgoing stream are penetrated for the each group of the places within the wing (see the Figure, v), the local scheme, where the mine workings for the outgoing stream are penetrated at the each place (see the Figure, g).

In case of the underground mine with the small and medium sizes of the mine fields, with he small productive capacity, and with the abundance of the gas, they use the unified schemes for the ventilation of the underground mine. At the large underground mines with the great abundance of the gas, in case of the unifying of several underground mines, and in case of the development of several depositions, which are distanced one from another, using the single underground mine, they use the sectional schemes for the ventilation of the underground mine, in case of which the mine field is divided into the sections, which are ventilated separately. The methods for the ventilation of the underground mine are: the sucking method, the injecting method, and the combined (injecting-sucking) method.

In case of the sucking method for the ventilation of the underground mine, the ventilator sucks the air from the underground mine, thus creating the rarefaction within this mine, as the result of which the clean air is sucked into the underground mine through the mine workings for the delivery of the air. In this case, there is possible the sucking of the air from the surface through the zones of the collapse (in case of the existence of the cracks, which are reaching the surface). This method is used at the underground coal mines, which are abundant with the gas, and at the underground ore mines (to the depth of 1500 metres).

In case of the injecting method for the ventilation of the underground mine, the ventilator injects the air from the surface into the underground mine; this method is used at the shallow underground mines, with the small emission of the gas, with the small aerodynamic resistance of the ventilatory network, with the aerodynamic connection of the mine workings with the surface through the zones of the collapse, with the flanking scheme for the ventilation of the underground mine.

In case of the combined method for the ventilation of the underground mine, one ventilator works for the injection, and another ventilator works for the sucking; this method is used in case of the great aerodynamic resistance within the ventilatory network of the underground mine, in case of the development of the useful minerals, which are prone to the spontaneous ignition (with the aerodynamic connection of the mine workings with the surface through the zones of the collapse), and in case of the flanking scheme for the ventilation.

For the calculation of the consumption of the air for the ventilation of the underground mine (the amount of the air, which is delivered per the unit of time, cubic metres per second, or cubic metres per minute), they use the static method for the calculation, and the methods for the calculation for the separate stopes, and for the entire underground mine.

In case of the method for the separate stopes, the consumption of the air is determined as the sum of the consumptions within the individual places (stopes, chambers, and so on); this method permits to take into account most completely the peculiarities of the ventilation of the underground mine.

In case of the method for the entire underground mine, the consumption of the air is calculated for the underground mine as a whole, according to the generalized indicators (the daily extraction of the underground mine, the consumption of the explosive substances, and so on), with the safety factors for the entire underground mine. This method is distinguished with simplicity, but insufficiently takes into account the specificity of the ventilation of the underground mine.

The static method (the major method for the calculation of the consumption of the air) is based on the assumption of the uniform distribution of the harmful admixtures throughout the entire volume of the flow; this method does not take into account the dynamics of the transfer of the harmful admixtures. The consumption of the air for the ventilation of the individual places is calculated according to the emission of the gas, the greatest quantity of the persons, which are employed during the shift, the consumption of the explosive substances, the dust, heat, and exhaust gases from the internal combustion engines; for the further calculations, there is accepted the greatest of the values, which have been calculated.

One of the problem with the ventilation of the underground mine is the leaks of the air, which proceed through the ventilatory built structures within the underground mine and on the surface, the collapsed rocks, and the broken virgin pillars. These leaks decrease the delivery of the air into the places for the consumption, and may cause the failure of the ventilation of the underground mine. For the compensation of the leaks, they increase the delivery of the air into the underground mine. The fight against these leaks is conducted with the hermetical sealing of the ventilatory built structures, the insulation of the goaf spaces, the usage of the lateral mine workings, of the rational schemes for the ventilation, and with the decreasing of the depression within the entire underground mine. The important goal for the ventilation of the underground mine is the ensuring of the safety of the people in case of the accidents (fires, explosions of the gas and dust, sudden outbursts of the coal and gas), and during the elimination of these accidents. The requirements for the ventilation of the underground mine in case of the accidents are: the prevention of the spreading of the poisonous gases throughout the underground mine; the rapid and reliable reversing of the ventilatory streams; the prevention of the forming of the dangerous concentrations of the explosive gases and so on. The modes for the ventilation of the underground mine in case of the accidents are: the normal ventilation; the decreasing or increasing of the consumption of the air; the termination of the ventilation; the reversing of the ventilation.

The ventilation of the underground mine is maintained by the ventilatory service of the mine, to the duties of which there belong the monitoring of the correctness of the distribution of the air throughout the mine workings, and the compliance with the norms for the delivery of the air to the places of the consumption, the monitoring of the qualitative composition of the air, the performance of the aerial and depression surveys, the repairing of the ventilatory mine workings and built structures. For the improvement of the effectiveness and reliability of the ventilation of the underground mine, they perform the automation of the control on the base of the remote control over the parameters of the ventilation of the underground mine, and they use the computer.