A Mining Method for underground Extraction of thick and steep coal seams of NEC, Assam

Thick and steep coal seams of makum Coalfield, Assam pose serious problems during underground mining of the coal. A number of different underground mining methods have been tried in the past in this area with limited success. Recently, CMRI carried out an experimental trial of chamber method of mining with cable bolt as support for controlled winning of roof coal band at N8 panel of Bargolai colliery of Makum Coalfield, NEC, Assam. Application of cable bolts as roof rock mass reinforcing system and high roof support solved the roof stability problem over the chamber. The aim of this trial was to eliminate timber consumption in addition to arrest the associated strata control problems. Unfortunately, the unavailability of a suitable explosive to win the reinforced roof coal mass of a degree three mine became the bottleneck for the CMRI experiment. This paper first describes the problems encountered during underground mining of the complex coal deposit of Makum Coalfield. Strength and weakness of the CMRI approach is also detailed on the bases of the field observations conducted during the field trial of cable bolt based chamber method of mining