Analysis of Roof Failure at the Intersections on a Coal Mining
- 1 Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil
- 2 Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil
Abstract
The objective of this paper is to understand the behavior of the roof and the cause of roof failure of a coal mining. Eleven roof falls occurred in the mine section in sequence. All the roof falls were surveyed, and the geological features were determined which include rock type, mechanical properties, and thickness. The immediate roof thickness was interpolated to determine the cause of the roof failures which was the inappropriate roof support where the immediate roof is thicker. The average thickness of the immediate roof was determined by the drilling log in 1.2 m (3.9 ft.). The roof support was design based on the average thickness, and the bolt length is 1.5 m (4.9 ft.) in suspension. The challenge was to estimate where the immediate roof gets thicker and to design the support considered to maintain the regular bolt length. This is because the cost and productivity of support operation could increase if the bolt length changes as the roof thickness changes. The idea was to adjust the support for beam building with a fully grouted bolt and rearrange the bolt geometry to keep the roof stable. It means, with the same bolt length the type of roof support would change from suspension to beam building depending on when the roof gets thicker. Two empirical approaches were considered to design the roof support: 1) CMRR and 2) RMR. The entry width is 5 m and the roof support was designed with four bolts per row. Where the roof support must change to beam building, the number of bolts per row changes to five or six. The results of the design and application on underground showed that the approach keeps stable.
- Torres, G.A. (2018) Análise de rupturas do teto imediato em mina de carvão, camada Barro Branco. Dissertação para obtenção do título de Mestre em Engenharia, Universidade Federal do Rio Grande do Sul, Porto Alegre, 112 p.
- Unal, E. (1986) Empirical Approach to Calculate Rock Loads in Coal Mine Roadways. 5th Conference Ground Control Coal Mines, West Virginia University, Morgantown, 11-13 June 1986.
- Bieniawski, Z.T. (1989) Engineering Rock Mass Classifications. John Wiley & Sons, Hoboken, 251 p.
- Mark, C.E. and Molinda, G.M. (1996) Rating Coal Mine Roof Strength from Exploratory Drill Core. In: Peng, S.S., Ed., Proceedings of the 15th International Conference on Ground Control in Mining, Colorado School of Mines, Golden, 415-428.
- Zingano, A.C., Koppe, J.C., Costa, J.F., Felipe, C.L.J. and Peng, S. (2008) In-Situ Tests and Numerical Simulation about the Effect of Annulus Thickness on the Resin Mixture for Fully Grouted Resin Bolt. Effect. Proceedings of the 27th International Conference on Ground Control Morgantown, Morgantown, June 2008, 284-290.
- Laubscher, D.H. (1977) Geomechanics Classification of Jointed Rock Masses—Mining Applications. Transactions of the Institutions of Mining and Metallurgy, 86, A1-A8.
- Mark, C. (2000) Design of Roof Bolt Systems: New Technology for Coal Mine Roof Support. U.S. Department of Health and Human Services, Public Health Service, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, DHHS (NIOSH) Publication, Pittsburgh.
- Molinda, G.M. and Mark, C. (1993) The Coal Mine Roof Rating: A Practical Rock Mass Classification for Coal Mines. In: Peng, S., Ed., Proceedings 12th Conference on Ground Control in Mining, West Virginia University, Morgantown, 92-103
- Peng, S.S. (2008) Coal Mine Ground Control. John Wiley & Sons, Hoboken, 600 p.
- Mark, C. and Molinda, G.M. (2003) The Coal Mine Roof Rating in Mining Engineering Practice. In: Aziz, N., Kininmonth, B., Eds., Proceedings of the 4th Underground Coal Operators’ Conference, Australian Institute of Mining and Metallurgy, Carlton.
- Unal, E. (1983) Design Guidelines and Roof Control Standards for Coal Mine Roofs. PhD Thesis, Pennsylvania State University, State College, 355 p.