Cherdantsev N. V. Framing the solution to the problem of coal seam state by the methods of the mechanics of granular materials. Izvestiya vysshikh uchebnykh zavedenii. Gornyi zhurnal = News of the Higher Institutions. Mining Journal. 2019; 7: 68–76. DOI: 10.21440/0536-1028-2019-7-68-76

Introduction. It is essential to reliably estimate the geomechanical state of marginal zones at a mineable coal seam in order to ensure mining balance and safety. Research aim is to build the model of the state of a coal seam in its marginal zone based on the fundamental methods of the mechanics of granular materials, make calculations within the framework of the model, analyze the results and compare them with the results obtained by the well-known methods.
Methodology. The problem of the stressed state of coal seam marginal zones is implemented by means of numerical solution of three boundary value problems of limit equilibrium theory for a range of typical areas situated in these zones. The criterion of limit state beginning is concurrent compliance with Coulomb–Mohr stratum condition and Mohr–Kuznetsov condition along the contact with rock wall.
Results. It has been shown that the components of stress field change non-monotonically along the seam roof. Sections with constant stresses are changed by sections with stresses nonlinear increase. With distance from the marginal part into the depth of the massif, the size of sections with constant stresses decreases. The obtained stress results have been compared with the results obtained with the use of voltage change exponential formula. The dimensions of seam marginal zone have been determined with rather close results of two approaches.
Summary. Polynomial approximation of the obtained graphs allows accurately replace the results of numerical solution to the limit state problem by analytical functions and simplify the solution to the problem of the enclosing rock stressed state.

Key words: rock mass; coal seam; mine; limit stress seam zones; Coulomb–Mohr and Mohr– Kuznetsov strength criteria.

REFERENCES

1. Petukhov I. M., Linkov A. M. The mechanics of rockbursts and outbursts. Moscow: Nedra Publishing; 1983. (In Russ.)
2. Chernov O. I., Puzyrev V. N. The forecast of coal and gas outbursts. Moscow: Nedra Publishing; 1979. (In Russ.)
3. Zhang C., Canbulat I., Tahmasebinia F., Hebblewhite B. Assessment of energy release mechanisms contributing to coal burst. Int. J. Rock Min. Sci. Technol. 2017; 27: 3–7.
4. Shadrin A. V. Static and dynamic outburst hazard of coal seams. Bezopasnost truda v promyshlennosti = Occupational Safety in Industry. 2018; 4: 42–48. (In Russ.)
5. Fisenko G. L. Limit state of rock around mine workings. Moscow: Nedra Publishing; 1976. (In Russ.)
6. Napier J. A. L., Malan D. Simulation of tabular mine face advance rates using a simplified fracture zone model. Int. J. Rock Mech. Min. Sci. 2018; 109: 105–114.
7. Guo H., Yuan L. An integrated approach to study of strata behaviour and gas flow dynamics and its application. International Journal of Coal Science & Technology. 2015; 2 (1): 12–21.
8. Guo W., Xu F. Numerical simulation of overburden and surface movements for Wongawilli strip pillar mining. Int. J. Min. Sci. Technol. 2016; 26: 71–76.
9. Khristianovich S. A. Continuum mechanics. Moscow: Nauka Publishing; 1981. (In Russ.)
10. Ruppeneit K. V. Some issues of rock mechanics. Moscow: Ugletekhizdat; 1954. (In Russ.)
11. Gao W. Study on the width of the non-elastic zone in inclined coal pillar for strip mining. Int. J. Rock Mech. Min. Sci. 2014; 72: 304–310.
12. Sokolovskii V. V. Granular materials statics. Moscow: Nauka Publishing; 1990. 272 с.
13. Cherdantsev N. V., Cherdantsev S. V. The analysis of the state of a coal mass with an in-seam working and fracture. Izvestiia RAN. Mekhanika tverdogo tela = Mechanics of Solids. 2018; 2: 110–121. (In Russ.)
14. Cherdantsev N. V. Solution to the problem of soil rock layer heaving in the in-coal working. Izvestiya vysshikh uchebnykh zavedenii. Gornyi zhurnal = News of the Higher Institutions. Mining Journal. 2016; 8: 32–39. (In Russ.)
15. Cherdantsev N. V. Solving a problem on ejection of a dirt seam from the coal seam floor in the in-seam working. Gornyi informatsionno-analiticheskii biulleten (nauchno-tekhnicheskii zhurnal) = Mining Informational and Analytical Bulletin (scientific and technical journal). 2017; 5: 369–381. (In Russ.)
16. Klishin V. I., Klishin S. V. Mineral mining technology: Coal extraction from thick flat and steep seams. Fiziko-tekhnicheskie problemy razrabotki poleznykh iskopaemykh = Journal of Mining Science. 2010; 2: 69–81. (In Russ.)

Received 16 May 2019