College of Mining, NUST MISIS, Moscow, Russia:

P. V. Nikolenko, Associate Professor, Candidate of Engineering Sciences, petrov-87@mail.ru
V. L. Shkuratnik, Professor, Doctor of Engineering Sciences
M. D. Chepur, Student

The authors discuss feasibility of roof control in underground mines with a new method based on effects of acoustic emission in composite materials in deformation and failure. The laboratory research objects were specimens of composites made of epoxy resin with filler represented by aluminum powder or dispersiondistributed carbonic fibers. All specimens were subjected to uniaxial cyclic tension to failure. In the course of loading, activity of acoustic emission and complete wave forms of all emission events were recorded. As a result, it has been found that all specimens show stress memory effect in acoustic emission. The Felicity Ratio is higher in the specimens reinforced with carbonic fibers. In such composites, acoustic-emission strain sensitivity (characterizing interconnection of acoustic emission level and deformation rate of a specimen) is also higher. The analysis of separate acoustic emission signals in the course of brittle failure of specimens shows that such signals essentially differ from background signals, both in amplitude and spectrum composition. This allows distinguishing such signals and locating a fracture to the accuracy up to 5 %. The regularities revealed in the acoustic emission can be the basis for development of methods to control roof conditions in mines. In one of the proposed methods, a sensitive composite element installed in a measurement borehole detects excess of tensile stresses over a preset threshold in roadway roofs. The other method allows locating zones of spalling in roofs. Both methods enable continuous roof monitoring.
This study was supported by the Russian Science Foundation, Project No. 17–77–10009.

1. Kasparyan E. V., Kozyrev A. A., Iofis M. A., Makarov A. B., Kulikova E. Yu. Geomechanics : Textbook. Murmansk : MGTU, 2016. Part I. 272 p.
2. Kurlenya M. V., Baryshnikov V. D., Gakhova L. N. Experimental and analytical method for assessing stability of stopes. Journal of Mining Science. 2012. Vol. 48, Iss. 4. pp. 609–615.
3. Deng E., Yang W., Lei M., Yin R., Zhang P. Instability Mode Analysis of Surrounding Rocks in Tunnel Blasting Construction with Thin Bedrock Roofs. Geotechnical and Geological Engineering. 2018. Vol. 36, Iss. 4. pp. 2565–2576.
4. Zhang C., Yu L., Feng R., Zhang Y., Zhang G. A numerical study of stress distribution and fracture development above a protective coal seam in longwall mining. Processes. 2018. Vol. 6, Iss. 9. DOI: 10.3390/pr6090146
5. Shabanimashcool M., Li C. C. Analytical approaches for studying the stability of laminated roof strata. International Journal of Rock Mechanics and Mining Sciences. 2015. Vol. 79. pp. 99–108.
6. Cherdantsev N. V. Stability of anisotropic rock massif with two adjisent square cross-section openings system. Bulletin of Research Center for Safety in Coal Industry. 2016. No. 3. pp. 6–13.
7. Zhao X. G., Ma L. K., Wang X. Y., Qin X. H. Hydraulic fracturing in-situ stress measurements in the Jijicao rock block of the Beishan area, China. Transit Development in Rock Mechanics: Recognition, Thinking and Innovation : Proceedings of the 3rd ISRM Young Scholars Symposium on Rock Mechanics. Xi’an, 2014. pp. 21–26.
8. Linhai Bao. In-situ stress measurement and surrounding rock stability analysis of The Gaoligong Mountain tunnel. Applied Mechanics and Materials. 2014. Vol. 501–504. pp. 1766–1773.
9. Luo C., Li H., Li W., Gao Z. Study on stress field and modulus measurement of surrounding rock masses in Meihuashan tunnel of Ganzhou-Longyan railway. Chinese Journal of Rock Mechanics and Engineering. 2014. Vol. 33, Iss. 9. pp. 1880–1886.
10. Yokoyama T., Ogawa K., Hirayama N., Funato A., Sanuki T. et al. Rock Stresses Measurement with High Stiffness Hydraulic Fracturing System in ILC Kitakami Site. ISRM International Symposium – 8th Asian Rock Mechanics Symposium. Sapporo, 2014. pp. 2371–2378.
11. Ermolov I. N. Theory and Practice of Ultrasonic Control. Moscow : Mashinostroenie, 1981. 240 p.
12. Li Q., He J.-J., Li C.-X. Relationship between the ultrasonic velocities and strata pressure of the coalbed methane reservoir in qinshui basin by rock physical testing. Wutan Huatan Jisuan Jishu. 2013. Vol. 35, Iss. 4. pp. 382–386.
13. Bobrenko V. M., Kutsenko A. N., Rudakov A. S., Acoustic Tensometry. Testing. Diagnostics. 2001. No. 4. pp. 23–29.
14. Shkuratnik V. L., Nikolenko P. V., Kormnov A. A. Estimation of ultrasonic correlation logging sensitivity in crack detection in excavation roof. Gornyi Zhurnal. 2016. No. 1. pp. 54–57. DOI: 10.17580/gzh.2016.01.11
15. Jiang H., Zhang J., Jiang R. Stress evaluation for rocks and structural concrete members through ultrasonic wave analysis: Review. Journal of Materials in Civil Engineering. 2017. Vol. 29, Iss. 10. DOI: 10.1061/(ASCE)MT.1943–5533.0001935
16. Lavrov A. The Kaiser effect in rocks: principles and stress estimation techniques. International Journal of Rock Mechanics and Mining Sciences. 2003. Vol. 40, Iss. 2. pp. 151–171.
17. Wang H.-J., Tang L., Ren X.-H., Yang A.-Y., Niu. Y. Mechanism of rock deformation memory effect in low stress region and its memory fading. Yantu Lixue. 2014. Vol. 35, Iss. 4. pp. 1007–1014.
18. Hardy H. R., Zhang D., Zelanko J. C. Recent studies of the Kaiser effect in geological materials. Proceedings of the 4^th Conference AE/MA in Geologic Structures and Materials. Clausthal-Zellerfeld : Trans Tech Publications, 1989.
19. Amann F., Gonidec Y. L., Senis M., Gschwind S., Wassermann J. et al. Analysis of acoustic emissions recorded during a mine-by experiment in an underground research laboratory in clay shales. International Journal of Rock Mechanics and Mining Sciences. 2018. Vol. 106. pp. 51–59.
20. Nikolenko P. V., Shkuratnik V. L. Acoustic emission in composites and applications for stress monitoring in rock masses. Journal of Mining Science. 2014. Vol. 50, Iss 6. pp. 1088–1093.
21. Nikolenko P. V., Nabatov V. V. Interference protection in geoacoustic control of critical stresses in rocks. Gornyi Zhurnal. 2015. No. 9. pp. 33–36. DOI: 10.17580/gzh.2015.09.06