Fig. 46. Longituainal section of Kherti mine, showing principal shafts, main levels and stoping areas

Blasting is by ANFO, with the priming using anodets and 20 g primer cartridges plus PETN booster charges in the column.

Recently large diameter blast hole stoping has been successfully introduced in Kolihan mine using a Mission Mega-drill to put in 150 mm/l64mm diameter holes in an open stoping method which eliminates the need for sub-level development. This has enabled a 40% reduction to be made in necessary development, and brought about a 30% reduction in stoping costs and a 50% reduction in stope preparation time. The method is likely to be progressively introduced throughout both mines.

Broken ore from the sub-level stope is extracted through cross-cut draw points, using rocker shovels on tracked levels and LHD's on trackless ones.

In Kolihan mine, small footwall ore-shoots are worked by a sub-level top-slicing method using jackhammers and remote controlled Cavo loaders.

Overall extraction оf ore is 70%, the balance being left in crown, sill and stope pillars. Dilution is 5%; the stopes are worked to an assay contact, but some over-drilling is practiced in the hanging wall to reduce ore losses in blast-hole toe sockets.

Shafts at the Kherti and Kolihan mines

Mine		Kherti		Kolihan
Shaft	Production	Service	No: 3: Inckline	Production/Service
Collar clevation (m) Depth (m) Cross-section Use Levels served Loading levels Skips Cages Guides Shaft lining Hoist type Hoist kw	390 475,5 5,5 m dia Ore hoist/Vent. return - 0 m 2 x 14 t - 8 ropes Concrete Koepe winder 2,870	370 388,4 6,1 m x 4,93 m Waste hoist/Vent.intake/Services 300, 240, 180, 120, 60 180,0 - 2 x 2 deck Rails Concrete Double-drum winder 1,600	374 194 - Waste hoist/Services 350, 300, 240, 180 300 1 x 2 t - Track Uneined Single-drum winder 150	424 270 5,90 m dia Ore/Waste hoist/Vent. intake/Services 306, 246, 229, 200, 184 246, 184 2 x 6 t 2 x 1 deck Rails 300 mm concrete Koepe (skips) Double-drum 2,900