Sub-level stoping with consolidated rockfill is the main method for
mining steep dipping baryte and fluorite veins in Germany. Drifting is
fully mechanised using drill jumbos, LHD units and shotcrete support.
Stopes have heights up to 50 m with sub-level distances up to 15 m.
Winning of the pillars between sub-levels is done by longhole blasting in
slices of 3-5 m length on strike. Mucking is done on the lowermost level
by LHD units. After each blast rockfill with binder (cement and/or fly
ash) is dumped into the scope from the uppermost level. Economic success depends on both geological and technical
parameters and factors, eg vein thickness and dip, ore grade, size and
distance of sub-level drifts. Of particular influence are ore loss in pillar
winning and dilution both in drifting on vein and in pillar mining. A
comprehensive computer program has been developed for calculating the
total cost per tonne run-of-mine ore respectively per tonne of concentrate
for a single stope. The cost model includes development, longhole
blasting, mucking and haulage to the mill, milling and ventilation. All
costs (labour, energy, supplies, maintenance, depreciation and capital
cost) are taken into account. Dilution and recovery are both considered. The program can be used to estimate the cost of mining a particular
stope. It can also be used to investigate the influence of relevant
parameters and factors on the economic result. By this way it should be
possible to optimise the technical design of a stope.