Current Science

Open Access Open Access  Restricted Access Subscription Access

Prediction of Rock Load Emphasizing Excavation Damage of in situ Rocks Caused by Blasting in Coal Mines


Affiliations
1 CSIR-Central Institute of Mining and Fuel Research, Dhanbad 826 015, India
2 Department of Mining Engineering, IIT Indian School of Mines, Dhanbad 826 004, India
3 Formerly at CSIR-Central Institute of Mining and Fuel Research, Dhanbad 826 015, India
 

Roof failure in coal mines is strongly related to the frequency of laminations and their movement when the load acts upon them. Detachment of roof bolts from mine roof due to improper estimation of extent of weak zone is one of the major problems in underground coal mines, thus affecting the safety and productivity of workings. The most popular and practised method for roof support design in Indian coal mines is the Central Mining Research Institute-ISM geomechanical classification system. Irrespective of such an established system of support design, accidents due to roof fall still persist. Here we review various available classification systems for rock load estimation and identify their limitations. The study has been extended taking into consideration the case study of KTK-6 incline of Singareni Collieries Company Limited by proposing a modified rock mass classification system based on seismic wave velocity as a key descriptor. A modified rock mass rating (RMR) system (RMRdyn) with inclusion of seismic velocity as one of the parameters is proposed for the estimation of rock load. Enhancement in rock load by 20% has been found for RMRCMRI-ISM values less than 40 according to the new rock load relation. This resulted in under-supporting of the roof and thus might have caused failures. For cases with RMRCMRI-ISM values more than 60, the earlier equation overestimates rock load by about 25% resulting in over-supporting. Thus, estimation of rock load from the proposed new equation appears to be more rational as it takes into account the actual damage zone.

Keywords

Blasting, Coal Mines, Excavation Damage, Rock Load.
User
Notifications
Font Size

  • Paul, A., Singh. A. K., Sinha, A. and Saikia, K., Geotechnical investigation for support design in depillaring panels in Indian coal mines. J. Sci. Ind. Res., 2005, 64, 358–363.

  • Paul, A., Singh, A. K., Rao, D. G. and Kumar, N., Empirical approach for estimation of rock load in development workings of room and pillar mining. J. Sci. Ind. Res., 2009, 68, 214–216.

  • Paul, A., Singh, A. P., John, L. P., Singh, A. K. and Khandelwal, M., Validation of RMR-based support design using roof bolts by numerical modeling for underground coal mine of Monnet Ispat, Raigarh, India – a case study. Arab. J. Geosci., 2011; doi:10.1007/s12517-011-0313-8.

  • Scott, D. F., Williams, T. J., Denton, D. K. and Friedel, M. J., Seismic tomography as a tool for measuring stress in mines. Min. Eng., 1990, 51, 77–80.

  • Singh, K. K. K., In-seam seismic application for detecting in homogeneities in coal seams – a review. J. Min. Met. Fuel, 1994, 42, 49–54.

  • Ritter, W., Die static der tunnelgewolbe, Springer, Berlin, Germany, 1879.

  • Terzaghi, K., Rock defects and rock loads on tunnel supports. In Rock Tunneling with Steel Supports (eds Proctor, R. V. and White, T. L.), Scientific Research, Academic Publisher, 1946, vol. 1, pp. 17–99.

  • Mandal, A. and Sengupta D., Fatal accidents in Indian coal mines. Technical Report No. ASD/99/33, Applied Statics Unit, Calcutta, 1999.

  • Deere, D. U., Technical description of rock cores for engineering purposes. Rock Mech. Eng. Geol., 1964, 1, 17–22.

  • Priest, S. D. and Hudson, J. A., Discontinuity spacing in rock. Rock Mech. Min. Sci. Geomech., 1976, 13, 135–148.

  • Palmstrom, A., The volumetric joint count – a useful and simple measure of the degree of the rock jointing. In Proceedings of the 4th Congress, International Association of Engineering Geology, Delhi, 1982, issue 5, pp. 221–228.

  • Bieniawski, Z. T., Engineering classification of jointed rock mass. Trans. S. Afr. Civ. Eng., 1973, 15, 335–344.

  • Bieniawski, Z. T., Rock mass classification in rock engineering. In Exploration for Rock Engineering, Proceedings of the Symposium, (ed. Bieniawski, Z. T.), Balkema, Cape Town, South Africa, 1976, vol. 1, 97–106.

  • Barton, N. R., Lien, R. and Lunde, J., Engineering classification of jointed rock mass for the design of tunnel support. Rock Mech., 1974, 6(4), 189–239.

  • Laubscher, D. H. and Taylor, H. W., The importance of geomechanics classification of jointed rock masses in mining operations. In Exploration for Rock (ed. Bieniawski, Z. T.), Balkema, 1976, vol. 1, pp. 119–128.

  • Laubscher, D. H., Planning mass mining operations. In Comprehensive Rock Engineering (ed. Hudson, J. A.), Pergamon Press, Oxford, UK, 1993, vol. 2, pp. 547–583.

  • Cummings, R. A., Kendorski, F. S. and Bieniawski, Z. T., Caving rock mass classification and support estimates. USBM contract report I0100103, Engineers International Inc, Chicago, USA, 1982.

  • Venkateswarlu, V., Ghosh, A. K. and Raju, N. M., Rock mass classification for design of roof support – a statistical evaluation of parameters. Min. Sci. Technol., 1989, 8, 97–108.

  • CMRI, Geomechanical classification of roof rocks vis-à-vis roof supports. S&T Project Report, 1987.

  • Ghosh, C. N. and Ghose, A. K., Estimation of critical convergence and rock load in coal mine roadways – an approach based on rock mass rating. Geotech. Geol. Eng., 1992, 10, 185–202.

  • Sheorey, P. R., Application of modern rock classification in coal mines roadways. In Comprehensive Rock Engineering, Pergamon Press, Oxford, UK, 1993, pp. 411–431.

  • Mark, C. and Molinda, G. M., The coal mine roof rating engineering practices. In Coal Operator’s Conference, University of Wollongong & the Australian Institute of Mining and Metallurgy, Australia (ed. Aziz, N.), 2003, pp. 50–62.

  • Marinos, P. and Hoek, E., GSI: a geologically friendly tool for rock mass strength estimation. In Proceedings of the Geological Engineering 2000 at the International Conference on Geotechnical and Geological Engineering, Melbourne, Australia, 2000, pp. 1422–1446.

  • Suresh, R. and Murthy, V. M. S. R., Seismic characterization of coalmine roof for rock load assessment. In First Indian Mineral Congress, Dhanbad, 2005, pp. 31–46.


Abstract Views: 173

PDF Views: 90




  • Prediction of Rock Load Emphasizing Excavation Damage of in situ Rocks Caused by Blasting in Coal Mines

Abstract Views: 173  |  PDF Views: 90

Authors

Avinash Paul
CSIR-Central Institute of Mining and Fuel Research, Dhanbad 826 015, India
Vemavarapu Mallika Sita Ramachandra Murty
Department of Mining Engineering, IIT Indian School of Mines, Dhanbad 826 004, India
Amar Prakash
CSIR-Central Institute of Mining and Fuel Research, Dhanbad 826 015, India
Ajoy Kumar Singh
Formerly at CSIR-Central Institute of Mining and Fuel Research, Dhanbad 826 015, India

Abstract


Roof failure in coal mines is strongly related to the frequency of laminations and their movement when the load acts upon them. Detachment of roof bolts from mine roof due to improper estimation of extent of weak zone is one of the major problems in underground coal mines, thus affecting the safety and productivity of workings. The most popular and practised method for roof support design in Indian coal mines is the Central Mining Research Institute-ISM geomechanical classification system. Irrespective of such an established system of support design, accidents due to roof fall still persist. Here we review various available classification systems for rock load estimation and identify their limitations. The study has been extended taking into consideration the case study of KTK-6 incline of Singareni Collieries Company Limited by proposing a modified rock mass classification system based on seismic wave velocity as a key descriptor. A modified rock mass rating (RMR) system (RMRdyn) with inclusion of seismic velocity as one of the parameters is proposed for the estimation of rock load. Enhancement in rock load by 20% has been found for RMRCMRI-ISM values less than 40 according to the new rock load relation. This resulted in under-supporting of the roof and thus might have caused failures. For cases with RMRCMRI-ISM values more than 60, the earlier equation overestimates rock load by about 25% resulting in over-supporting. Thus, estimation of rock load from the proposed new equation appears to be more rational as it takes into account the actual damage zone.

Keywords


Blasting, Coal Mines, Excavation Damage, Rock Load.

References





DOI: https://doi.org/10.18520/cs%2Fv118%2Fi1%2F123-132