This paper presents geo-mining conditions along with the problems of coal bumps encountered at Chinakuri Mine of ECL (Raniganj coalfield) and Lazy Mine of OKC. Further, the developed and practiced measures at Lazy Mine of OKC to control the coal bump are detailed and analysed to assess their suitability for underground extraction of Dishergarh coal seam of Chinakuri Mine, ECL. It is observed that the conventional techniques, being practiced to release the stress concentrations and to create a network of fissures in the solid accompanying rocks in Indian coalfield, need a complete change. On the basis of this analysis, a suitable method of mining with overlying strata management approach is advised to suit the conditions of the Chinakuri Mine of ECL.
Out of different rock mechanics problems of underground coal mining of deep seated deposits, coal bump/rock burst is identified (CMRI, 1994) as a major hazard during underground coal mining at greater depth. Coal bump/rock burst engage violent and rapid failure of coal/rock in and around an underground excavation. Sudden release of accumulated elastic stain energy from a rock mass in the free face, created due to excavation, is the origin of this phenomenon and is, mainly, related with the geo-mining conditions of the site, characteristics of the coal/rock mass and stress regime of the area. CIMFR undertook an investigation related to this issue (CMRI, 1994) but this investigation remained limited, mainly, to identify different coal seams of the country likely to pose the coal bump/rock burst problems and their causative factors. Some approaches to control the problems of coal bump/rock bursts were also investigated but their field application achieved partial success. However, this study could project characteristics (Table –1) of some the coal seams and found that the Dishergarh coal seam of Chinakuri Mine (Raniganj Coalfield) is one of the most bump/burst susceptible seam in the country. Recently, CIMFR has collaborated with the Institute of Geonics, Ostrava, the Czech Republic for rock mechanics investigations to meet challenges of strata control of deep underground coal mining. During this collaboration, the success of the Czech counterpart in controlling coal bumps/rock bursts during underground visits of Czech mines is experienced. This paper describes the geo-mining conditions of Chinakuri Mine of ECL and the results of investigations taken to characterise the coal/rock mass of the mine.
Chinakuri Colliery 1&2 Pits of ECL is situated in the heart of the Raniganj coalfield on the bank of river Damodar near Asansol city of West Bengal. This is the deepest coal mine in the country, where underground mining is taking place at nearly 700 m depth of cover. Before nationalisation, this mine was owned by M/S. Andrew Yule & Co. and has experienced mining of a number of coal seams by different techniques. However, mining of the Dishergarh coal seam at this mine by bord and pillar and longwall methods of this colliery has always been a problem, mainly due to occurrence of coal bumps.
