Cable Bolting based mechanised depillaring of thick and developed coal seams
Based on simple rock mechanics principles, the idea of using a grouted steel rope under tension for supporting a high roof as well as an overlying coal band, and to improve safe span of overhanging strata near the goaf edge for semi-mechanised depillaring of a thick coal seam standing on pillars was first applied at New Chirimiri Ponri Hill (NCPH) colliery of the Chirimiri area of the South Eastern Coal field Limited (SECL). Taking advantage of massiveness of the coal seam and pattern of stress redistribution around a depillaring face, field application of this technique could make it possible to extract full thickness (6.5m) of the No.-3 seam of the colliery (developed along floor with 2.5m gallery height) in single lift. The success of this field trial triggered a number of applications of the technique in many other collieries of India due to its technical superiority over the conventional method for underground extraction of thick and developed coal seams.