In a stipulated hard rock situation, drilling and blasting costs per tonne in open cutting or underground operations are comparable. In open cuts the drilling and blasting costs per tonne of ore are multiplied by the waste ratio._x000D_
Conventional underground loading and haulage practices are so batch-oriented that the cost per tonne of ore handled is a large integral multiplier of open out costs per tonne loaded and hauled._x000D_
If underground costs are to be reduced to compare favourably with open out costs then loading and hauling practices underground must be converted to a non-batch continuous system. This can be achieved by utilising gravity to control ore to mobile crushers feeding conveyors running direct to surface.