The technical problems which increase very rapidly with depths have become formidable on Kolar Gold Fields where ultra-deep horizons at and below the 113 level (3.2 km) are now being worked. In this paper some of the problems encountered and how attempts are made to find solutions have been outlined. These several problems arising from deep mining in K.G.F. have been discussed in detail under the following heads:
High temperature and humidity,
Dust hazards,
Fire hazards,
Inundation,
Ground control and rockbursts and
Hoisting problem.
Kolar Gold Mines are located in south east corner of Karnataka in India and spread over a strike length of about 8 kms. Shafts have sunk where cumulative depth is a stagqerinq 64 km. Similarly, tunnels driven amount to more than 1320 km, and other connected excavations 190 km. The mines in Kolar Gold Fields have produced about 795 tonnes of gold from approx. 49 million tonnes of one. Total estimated reserves are 10,77,200 tonnes of ore. The extent of mine working have gone up to a depth of 3.2 km from surface. As the working went deeper various problems are encountered giving rise to hostile mine environmental conditions, fatality, loss of surface and underground structures. Some problems arising from ultra deep mining have been discussed here.
Pryore (1923–24) has discussed the geology and mine practice of K.G.F. in detail. The deposits occur in a belt of hornblende schists, after shearing, were intruded by quartz veins which attend into the lode rocks. Subsequently, extensive faulting took place, followed by the invasion of the schists by pegmatites and aplites. Finally wide fissures were opened up by the intrusion of dolemite dykes from below. Out of 26 quartz loads in the field only two, the Champion and Oriental lode are of great economic importance. All the lodes have a strike in north-south direction and dip towards west. The dip varies from 40°-50° at the surface, to nearly vertical at depth. The Champion lode persists through all three mines - Champion, Nundydroog and Mysore mines. The average width of the lode is 1m to 1.2m, but in places where fold occur, the width exceeds 6m. The Oriental lode, which lies west of Champion lode is strongly pyrite. The lode has an average width of 1.2m and at places increases to about 6m. The productive workings terminate both in north and south in a series of faults (Fig. 1). In the vicinity of faults, rich ore shoots such as 43 ore shoot in Mysore mine and Glen's ore shoot in Champion reef mines have been discovered. The Oriental lode is being mined only in Nundydroog mine. The Champion lode extends the working up to a depth of 3200m in Champion reef mine. Bottom stoping is the principal method in Mysore mine. Flat back stoping is used in Nundydroog mine. Stope drive method is practised at depth in Champion reef mine.
