Saint-Petersburg Mining University, Saint-Petersburg, Russia:

V. V. Nikolin, Senior Researcher, Candidate of Engineering Sciences, nikolin.vic@gmail.com
A. N. Shabarov, Prorector, Doctor of Engineering Sciences
G. I. Korshunov, Head of a Chair, Professor, Doctor of Engineering Sciences
L. V. Bugaenko, Researcher

It was noticed in the early 20^th century that temperature of coal lowers in the course of cutting. The further studies showed that the rate of coal cooling was governed by the liberated amount and desorption velocity of methane. In addition, the temperature in the coal seam face area is influenced by the induced change in rock pressure – the temperature grows in the higher rock pressure zones and lowers in the rock pressure relief zones. On the whole, alongside the other factors, temperature is assumed a self-consistent index for the assessment of gas-dynamic state in the coal seam face area. However, the attempts to its application in prediction of hazardous zones failed due to the problems connected with the measurement data interpretation and with the hazard/nonhazard distinction. As a consequence, it was decided to solve the opposite problem, namely, to assess the degree of rock pressure relief and the rate of the coal face area degassing based on the temperature index using the STT. U5 equipment meant for the contactless measurement of not the absolute but the relative temperature in a coal face area at a distance of 1–1.5 m. Four measurement stations arranged in a test site in a longwall concurrently measured the face area temperature at five points and determined the safe relief zone size based on the dynamics of the initial velocity of gas liberation from holes. The measurement results reliably proved the regular increase in the face area temperature (390 measurements) with the enlargement in the size of the relief zone (112 measurements) Physically, it means that the zone of natural degassing of coal in front of the face grows with the size of the pressure relief zone. In the meanwhile, the zone of the most intensive relief and degassing, i.e. zone of endogenous processes, moves depthward the rock mass. If host rocks and coal have essentially different temperatures, the said processes improve heat exchange between host rocks and coal in the face area and, thus, the face area temperature grows. It is known that at the longwall ends adjacent to mined-out voids in the neighbor longwalls (panels, levels, shafts), the zone of coal relief and degassing forms. For this reason, these sites were used as the test grounds to find basic parameters of the method on limits of safe zones in different geological and geotechnical conditions. The additional comparative research was carried out at two experimental sites at the longwall ends adjoining intact rock mass using the analogous procedure. The antithetic results of the two test series confirmed the validity of the physical sense of the phenomenon under analysis.

1. Chernitsyn N. P. Ore gas, its liberation conditions, its properties and methods of struggle. Petrograd, 1917. 186 p.
2. Ettinger I. L. Gas content of fossil coal. Moscow : Nedra, 1966. 223 p.
3. Ettinger I. L., Maevskiy V. S., Radchenko S. A. Control of gas-dynamic state of layer’s well face. Ugol. 1983. No. 5. pp. 8–9.
4. Rozenbaum M. A., Elchaninov E. A., Shor A. I. Effect of stress and deformation changes on coal layer temperature dynamics. Ugol. 1977. No. 2. pp. 27–31.
5. Radchenko S. A., Soloveva E. A. Influence of gas-kinetic properties of coal on working safety provision. Gornyy informatsionno-analiticheskiy byulleten. 2008. Special issue No. 4. Metahne. pp. 248–258.
6. Ettinger I. L., Lidin G. D., Shulman N. V., Radchenko S. A. Change of coal layer temperature as an indicator of physical and physical-technical processes. Fiziko-tekhnicheskie problemy razrabotki poleznykh iskopaemykh. 1984. No. 5. pp. 65–69.
7. Guidance for safe mining operations on the layers, prone to sudden outbursts of coal (soil) and gas. RD 05-350-00. Moscow : NTTs «Promyshlennaya bezopasnost», 2000. 160 p.
8. Walker P. J. L., Mahajan Q. P. Methane diffuision in coal and chars. Analytical Methods for Coal and Coal Products. New York : Academic Press, 1979. Vol. 1. Ch. 5. pp. 163–188.
9. Smith D. M., Williams E. L. Diffusion models for gas production from coals: application to methane content determination. Fuel. 1984. Vol. 63. pp. 251–255.
10. Barker-Read G. R., Radchenko S. A. Methane emission from coal and associated strata samples. International Journal of Mining and Geological Engineering. 1989. Vol. 7, Iss. 2. pp. 101–126.
11. Barker-Read G. R., Radchenko S. A. An experimental investigation of coal/air heat transfer. Great Britain : University of Leeds, LUMA, 1990. pp. 193–202.
12. Radchenko S. A. Forecast of gas-dynamic phenomena in mines for the change of coal substance temperature. Inzhenernaya fizika. 2007. No. 3. pp. 59–62.
13. Zabigaylo V. E., Shirokov A. Z., Kratenko L. Ya., Lukinov V. V., Stovas G. M. Geological conditions of outburst hazard of coal layers in Donbass. Kiev : Naukova dumka, 1980. 189 p.
14. Vasyuchkov Yu. V. Forms of connection of methane with coal matrix and gas drainage efficiency. Gornyi Zhurnal. 2016. No. 10. pp. 82–87. DOI: 10.17580/gzh.2016.10.17
15. Saghafi A., Pinetown K. L. A new method to determine the depth of the de-stressed gas-emitting zone in the underburden of a longwall coal mine. International Journal of Coal Geology. 2015. Vol. 152. pp. 156–164.
16. Haifeng W., Yuanping C., Lei W. Regional gas drainage techniques in Chinese coal mines. International Journal of Mining Science and Technology. 2012. Vol. 22. Iss. 6. pp. 873–878.
17. Maevskiy V. S., Rubinskiy A. A., Topalov O. V. New way in the control of structural disturbance of outburst hazard coal layers. Bezopasnost truda v promyshlennosti. 1990. No. 4. pp. 17–19.
18. Babkov S. V., Kremenev O. G., Maevskiy V. S. Thermoelectric temperature alarm STT.U5. Ugol Ukrainy. 1989. No. 8. pp. 29–30.
19. Nikolin V. V., Shabarov A. I., Korshunov G. I., Yasyuchenya S. V., Kokoev S. G. Method of definition of boundaries of protected areas of coal layers. Patent RF, No. 2542068. Applied: 05.02.2014. Published: 20.02.2015. Bulletin No. 5.
20. Guidance for safe mining operations on the layers, prone to sudden outbursts of coal (soil) and gas. Moscow : IGD imeni A. A. Skochinskogo, 1989. 192 p.
21. Shcherban A. N., Kremnev O. A. Scientific basis of calculation and regulation of thermal regime of deep mines. Kiev : AN USSR, 1959. Vol. 1. 430 p.
22. Voropaev A. F. Thermal conditioning of mine air in deep mines. Moscow : Nedra, 1979. 192 p.
23. Bobrov A. K., Nikolin V. V., Topalov O. V. Assessment of the grade of outburst hazard of the bottomhole part of formation for the change of radiation temperature of hole surface. Methods and means for creation of safe and healthy working conditions : collection of scientific proceedings. Makeevka : MakNII, 1990. pp. 203–209.
24. Nikolin V. V., Zablotskiy V. P., Topalov O. V. Industrial testings of method of defi nition of non outburst hazard area sizes in the upper part of steeply inclined layers, adjacent to goaf. Mineral deposits mining : republican interdepartmental scientific-technical reference book. Kiev : Tekhnika, 1992. Iss. 92. pp. 55–59.