Strata behaviour during depillaring in Blasting Gallery panel by field instrumentation and numerical study
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ORIGINAL PAPER
Strata behaviour during depillaring in Blasting Gallery panel by field instrumentation and numerical study I. Satyanarayana & G. Budi & D. Deb
Received: 26 May 2014 / Accepted: 4 November 2014 # Saudi Society for Geosciences 2014
Abstract Selection of a suitable mining method for economical and safe underground extraction of a thick coal seam is an extremely delicate process and brings a number of geotechnical parameters into consideration. Charbonnage de France (CdF) proposed Blasting Gallery (BG) for the extraction of virgin thick seams as well as developed pillars in thick seams in a single lift. The method was very successful resulting in 85 % of extraction with high productivity. But this method experienced strata control problems during final extraction at East Katras Colliery in Jharia Coalfield, Coal India Ltd., and also at GDK No. 8 Incline, Singareni Collieries Company Ltd. In this paper, the role of different parameters influencing development of mining-induced vertical stress, and maximum roof deformation in a BG 1/12 panel (GDK No. 8 Incline, SCCL) during depillaring in specific geomining conditions was visualized through numerical simulation models using ANSYS software. In this study, extensive field monitoring is carried out using modern instruments such as vibrating wire stress gauges, extensometers, load cells, and telescopic convergence rods to understand the strata behaviour during depillaring in the BG panel. Salient findings of field instrumentation data analysis such as mining-induced vertical stress development over the pillars, load over the support, bed separation at different horizons, and convergence I. Satyanarayana DGMS, Dhanbad 826001, India e-mail: [email protected] G. Budi (*) Department of Mining Engineering, Indian School of Mines, Dhanbad 826004, India e-mail: [email protected] D. Deb Department of Mining Engineering, Indian Institute of Technology Kharagpur, Kharagpur, India e-mail: [email protected]
of roof in rooms with face advance are presented in this paper. The results of induced stress, deformation, and factor of safety of pillar obtained by the finite element method (FEM) analysis are validated with the results of field instrumentation data analysis. Keywords Underground coal mining . Thick seam mining . Blasting Gallery method . Induced stresses . Safety factor
Introduction The bord and pillar system of mining is still the predominant method of mining underground coal in India. Even after the adoption of the longwall method of mining, bord and pillar have an edge due to less roof control problems. Banerjee et al. (Benerjee et al. 2001) stated that longwall technology was not successful in India due to massive and hard roof conditions. About 50 % of coal reserves in India are in seams thicker than 4.5 m, which come under the category of thick seams, the exploitation of which is consistently posing challenges to the mining engineers. The problem is aggravated by the presence of already developed pillars that are estimated about 3000 million tons (Di
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