A Comparative Study of Various Empirical Methods to Estimate the Factor of Safety of Coal Pillars

A. K. Verma^1,

¹Department of Mining Engineering, Indian School of Mines – Dhanbad-04, Jharkhand, India

Cite this paper:
A. K. Verma. A Comparative Study of Various Empirical Methods to Estimate the Factor of Safety of Coal Pillars. American Journal of Mining and Metallurgy. 2014; 2(1):17-22. doi: 10.12691/ajmm-2-1-3

Abstract

Design of coal pillars in a coal mine remains a challenge inspite of several theories proposed by several researchers over a period of time. India is heavily dependent on coal availability for supply of electricity to it’s billion of citizens. This has burdened the coal industry to increase the coal production which ultimately has lead to extraction of coal pillars also. Coal pillars are used to support the overlying roof rock to prevent it from falling. The dilemma with coal pillar stability is that On one hand, the size of the pillar should be as small as possible to enable maximum recovery of coal, while on the other hand, the pillar should be large enough to support the load of overlying strata. The stability of coal pillars has fascinated several researchers and hence many empirical equations have been proposed over the decades. In this paper, parameters like height of pillar, depth of pillar, compressive strength of coal, depth of the coal seam have been taken as input to estimate factor of safety of coal pillar from two mines i.e., Begonia and Bellampalli. It is found that Greenwald (1941), Salamon and Munro (1967), Sheorey (1992) and Maleki (1992) method has estimated failed cases correctly while Sheorey (1992) & Maleki (1992) have not predicted stable case of pillar correctly which is an interesting finding as empirical relations proposed by Sheorey (1992) is assumed to have good prediction in Indian condition.

Keywords:
Pillar strength factor of safety Begonia coal mines and Bellampalli coal mines percentage deviation

This work is licensed under a Creative Commons Attribution 4.0 International License. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/

References:

[1]	Bieniawski, Z. T, Balkema (1984): A. A. Rock Mechanics Design in Mining and Tunneling; 272 pp.
[2]	Bieniawski, Z. T. (1992): A method revisited: coal pillar strength formula based on field investigations, proceedings, workshop on coal pillar mechanics and design, Bu mines; p 158-165.
[3]	Bieniawski ZT. (1968): In situ strength and deformation characteristics of coal; Volume 2, 325-40.
[4]	Bunting, D. (1991): Chamber Pillars in Deep Anthracite Mines. Trans. AIME; vol. 42, pp. 236-245.
[5]	Christopher Mark. (1981-2006): Chief, Rock Mechanics Section NIOSH-Pittsburgh Research Laboratory Pittsburgh, PA, USA, The evolution of intelligent coal pillar design.
[6]	Das, M.N. and Sheorey, P. R. (1986): Triaxial Strength behavior of some Indian coals. Journal of Mines, Metals & Fuels; 34 (3). pp. 118-122.
[7]	Hudson, J.A., Brown, E.T. and Fairhurst, C. (1972): Shape of the complete stress-strain curve for rock. In Proc. 131h Symposium on Rock Mechanics, Urbana, Illinois, Edited by E.J. Cording; pp: 773-795.
[8]	Jaiswal, Ashok, Shrivastva, B.K. (2009): Numerical simulation of coal pillar strength, International Journal of Rock Mechanics & Mining Sciences; Volume 46, 779-788.
[9]	Jawed, M., Sinha, R. K. and Sengupta, S. (2013): Chronological development in coal pillar design for board and pillar workings: A critical appraisal, Journal of Geology and Mining Research; Vol. 5 (1): pp. 1-11.
[10]	Mohan, G. Murali, Sheorey, P.R., Kushwaha. A. (2001): Numerical estimation of pillar strength in coal mines, International Journal of Rock Mechanics & Mining Sciences; Volume 38, 1185-1192.
[11]	Mark, C. (1999): Empirical Methods for Coal Pillar Design. Proceedings of the Second International Workshop on Coal Pillar Mechanics and Design. U.S. Department of Health and Human Services, National Institute for Occupational Safety and Health (NIOSH); IC 9448, pp. 145-154.
[12]	Martin,C.D., Maybee, W.G. (2000): The strength of hard-rock pillars, International Journal of Rock Mechanics & Mining Sciences; Volume 37; 1239-1246.
[13]	Maleki H. (1992): In situ pillar strength and failure mechanisms for US coal seams. In: Proceedings of the workshop on coal pillar mechanics and design, Pittsburgh, US States Bureau of Mines; p. 73-8.
[14]	Mukhopadhyay, G., Mukhopadhyay, S. K., Roychowdhury, M and Parui, P. K. (2010): Stratigraphic Correlation between Different Gondwana Basins of India, journal geological society of india; Vol. 76: pp. 251-266.
[15]	Salamon MDG, Munro. A.H. (1967): A study of the strength of coal pillars. J. South Afr. Inst. Min. Metallurgy; 68:55-67.
[16]	Sheorey, P. R., Das, M. N., Bordia, S. K., Singh B. (1986): Pillar strength approaches based on a new failure criterion for coal seams, International Journal of Mining and Geological Engineering; Volume 4: pp 273-290.
[17]	Sheorey PR. (1992): Design of coal pillar arrays, chain pillars. In: Hudson JA, et al., editors. Comprehensive rock engineering, vol. 2. Oxford: Pergamon; p. 631-70.