Stefanovich L.I., Molchanov А.N., Кamchatniy А.А., Sobolev V.V., Bilan N.V. Impedance spectroscopy of gas-saturated coal bed under conditions of its slow unloading

Details

Parent Category: Geo-Technical Mechanics, 2018

Category: Geo-Technical Mechanics, 2018, Issue 142

Geoteh. meh. 2018, 142, 13-24

https://doi.org/10.15407/geotm2018.142.013

IMPEDANCE SPECTROSCOPY OF GAS-SATURATED COAL BED UNDER CONDITIONS OF ITS SLOW UNLOADING

StefanovichL.I., Molchanov А.N., Кamchatniy А.А., SobolevV.V., BilanN.V.

Authors:

Stefanovich L.I., Doctor of Physics and Mathematics, (D.Sc.) (Phys.-Math.) (IPMP, NAS of Ukraine)

Molchanov A.N., Doctor of Technical Sciences (D. Sc), Senior Researcher (IGTM, NAS of Urraine) (IPMP, NAS of Ukraine)

Kamchatniy A.A., Master of Sciences (M.Sc.), junior researcher (IPMP, NAS of Ukraine)

Sobolev V.V., Doctor of Technical Sciences (D.Sc), Professor (NTU “Dniprovska Polytechnica”)

Bilan Nataliya Valerievna, Candidate of Geology and Mineralogy (Ph. D), Associate Professor (NTU “Dniprovska Polytechnica”)

UDC 622.2, 537.31

Language: Russian

Abstract. In this paper, the theoretical possibility of using impedance spectroscopy methods to determine the degree of fracturing of fossil coal inside the face in the process of coal excavation with taking into account the intra-layer pressure of gaseous fluids filling the crack cavities is analyzed. For certainty, a coal bed of horizontal bedding containing a system of parallel but randomly distributed cracks is considered. The situation is analyzed when mechanical loading is released relatively slowly - at a speed of the face driving. A crack initiation curve is built, which determines a region of the main crack stability. It is shown that the evolution of main cracks occurs in three stages. The first stage corresponds to the "swelling" of cracks due to an increase in its gap. The second one corresponds to the rapid propagation of the crack due to the growth of its length with unchanged gaps and, finally, the third stage of the crack slow ripening when both the crack length and gap simultaneously grow. With taking into account the fact that, on the one hand, gas-filled cracks provide additional active resistance to DC and, on the other hand, conduct AC due to the polarization properties, it is shown how it is possible, with the help of methods of impedance spectroscopy, to trace evolution of coal fracturing near the bottom face at its driving. An analytical expression for the coefficient of coal fracturing is derived, which connects it with electro-physical characteristics, which can be found by the methods of impedance spectroscopy. It is shown that coal fracturing inside the face as a result of the slow release of the coal bed is several times greater than its fracture measured in the laboratory. The technique developed in this article can be applied to the experimental determination of the fracture coefficient of a gas-saturated coal bed in order to prevent sudden outbursts.

Keywords: impedance spectroscopy, fracture coefficient, intra-bed pressure, electrophysical characteristics, gas-saturated coal bed.

References:

1. Stefanovich, L.I., Sobolev, V.V., Molchanov, A.N., Bilan, N.V., Kamchatniy A.A. and Pronskiy, E.A. (2017), “Application of impedance spectroscopy for determination of gas-saturated coal beds fracturing in real condition of backwall”, Fiziko-tekhnicheskie problemy gornogo proizvodstva, vol. 19, pp. 91–105.

2. Feldman, E.P., Stefanovich, L.I., Vasilenko, T.A. and Kirillov, A.K. (2015 ), “Impedance spectroscopy as a method of determining the coal cracking. I. Dry example, ”Fizika I tekhnika vysokikh davleniy”, vol. 25, no.3/4, pp. 122–132.

3. Feldman E., Kalugina N. and Chesnokova, O. (2017), "Evolution of cracks in selvedge of the coal bed during its stationary working", Mining of Mineral Deposits, vol. 11, issue 2, pp. 41-45.

https://doi.org/10.15407/mining11.02.041

4. Sneddon, I.N. (1955), Preobrazovanie Fur'e [Fourier Transformation], Inostrannaya Literatura, Moscow, Russia.

5. Griffith, A.A. (1921), "The phenomena of rupture and flow in solids", Phil. Trans. of the Royal Soc. of London, vol. A221, pp. 163-198.

https://doi.org/10.1098/rsta.1921.0006

6. Feldman, E.P., Vinnik, E.A., Granovskiy, Ya.I. and Kalugina, N.A. (2011) "Electrical resistance of conductive material containing cracks", Fiziko-tekhnicheskie problemy gornogo proizvodstva, no 14, pp. 54-59.

7. Salganik, R.L. (1974), "Transfer processes in solids with a large number of cracks", Inzhenerno-fizicheskiy zhurnal, vol. 27. no. 6, pp. 1069-1075.

https://doi.org/10.1007/BF00863006

8. Аmmosov, I.I. and Yeryomin, I.V. (1961), Treshchinovatost uglya [Coal Fracturing], Nauka, Moscow, Russia.

9. Slyusarev, V.V. (2007), “Structure and properties of anthracite under pressure up to 2 GPa”, Abstracts of International Conference “Functional materials”, Partenit, Ukraine, October 1-6, pp.284.

10. Paffengoltz, K.N., Borovikov, L.I., Zhamojda, A.I. [et al] (1978), Geologicheskiy slovar [Geological dictionary]: in 2 volums in. (ed), Nedra, Mosscow, Russia.

About the authors:

Stefanovich Leonid Il’ich, Doctor of Physics and Mathematics, (D.Sc.) (Phys.-Math.), Deputy Director of the Institute for Scientific Work, Institute for Physics of Mining Processes NAS of Ukraine (IPMP, NAS of Ukraine), Dnepr, Ukraine, This email address is being protected from spambots. You need JavaScript enabled to view it. .

Molchanov Alexandr Nikolaevich, Doctor of Technical Sciences (D. Sc), Director of the Institute, Institute for Physics of Mining Processes NAS of Ukraine (IPMP, NAS of Ukraine), Dnepr, Ukraine, This email address is being protected from spambots. You need JavaScript enabled to view it. .

Kamchatniy Alexei Anatol’yevich, Master of Sciences (M.Sc.), junior researcher, Institute for Physics of Mining Processes NAS of Ukraine (IPMP, NAS of Ukraine), Dnepr, Ukraine, This email address is being protected from spambots. You need JavaScript enabled to view it. .

Sobolev Valeriy Victorovich, Doctor of Technical Sciences (D.Sc), Professor National Technical University “Dniprovska Polytechnica” MES of Ukraine (NTU “Dniprovska Polytechnica”), Dnepr,Ukraine, This email address is being protected from spambots. You need JavaScript enabled to view it. .

Bilan Nataliya Valerievna, Candidate of Geology and Mineralogy (Ph. D), Associate Professor of National Technical University “Dniprovska Polytechnica” MES of Ukraine (NTU “Dniprovska Polytechnica”), Dnepr,Ukraine, This email address is being protected from spambots. You need JavaScript enabled to view it. .

• < Prev
• Next >