Blast-Induced Caving from Surface over Continuous Miner Panel at a 110m Cover in an Indian Mine

Continuous mining is a most popular mining method in USA and Europe. Nearly 60% of coal mining in the West is through continuous mining process in underground mines. Continuous miner technology, which has of late been introduced in India, is able to extract 65-74% of the coal in a panel depending upon the seam parameters as against 50-60% by semi-mechanized Bord and Pillar system of mining with SDL/LHDs, which is popular in India. The rate of extraction by the continuous miner being high is able to create larger panels, and thus, reduces the coal loss in barrier pillars. Presently, efforts are being made to introduce this technology on a larger scale in underground coal mines of Coal India Limited in India. When the first depillaring panel started its operation in November 2009 at Jhanjra, the panel was stopped after extraction of nine pillars by the Indian regulatory body (Directorate General of Mines Safety, DGMS, GOI) as the geological conditions of the overlying strata gave trouble of non-caving. The anticipated roof fall did not take place. The exposed roof area reached 10,400 m(2), which was equivalent to 46,800 m(3) of the void volume posing a threat of air blast. Since all the attempts to induce caving by underground blasting failed, an attempt was made from surface to induce the caving by destress blasting. This paper deals with the design of blasting parameters and execution of destress blasting keeping in view the safety and sentiments of nearby villages.