Page 272 - Introduction to Mineral Exploration

Incline
Vertical
11: PROJECT EVALUATION 255
shaft shaft
Abandoned
open pit

Adit
portal
Waste dump Adit portal
Ore
stoped
out and
space
filled
with
waste

Haulage drift or level
Shaft pillar
Ore
Sub-level bin Loading
station
Development from ore
raise bin Shaft
Stope Development station
raise with
Broken ore sump
Raise below
Main haulage level
Winze
Unbroken Unmined
ore ore

FIG. 11.1 Mining terminology. Ore was first extracted at the mineralized outcrop using an open pit. Later an
adit was driven into the hillside to intersect the ore at a lower level. An inclined shaft was sunk to mine from
still deeper levels and, eventually, a vertical shaft was developed. Ore is developed underground by driving
main haulage and access drifts at various levels and connecting them by raises from which sublevels are
developed. It is mined from the lower sublevel by extracting the mineralisation upwards to form a stope.
Broken ore can be left in a stope to form a working platform for the miners and to support the walls against
collapse (shrinkage stoping). Alternatively, it can be withdrawn and the stope left as a void (open stoping) or
the resultant space can be filled with fine-grained waste rock material brought from surface (cut-and-fill
stoping). Ore between the main haulage and sublevel is left as a remnant to support the former access until
the level is abandoned. (From Barnes, 1988, Ores and Minerals, Open University Press, with permission.)

FIG. 11.2 Development of an open pit mine. During
the early stages of development (a–a′) more ore is
removed than waste rock and the waste to ore ratio
b a a' b'
is 0.7:1. That is, for every tonne of ore removed 0.7
tonnes of waste has also to be taken. The waste rock
is extracted in order to maintain a stable slope on
the sides of the open pit, normally between 30 and
45 degrees. Obviously the greater the slope the less
the waste rock to be taken, and the lower the waste
to ore ratio. As the pit becomes deeper the ratio will
increase; at stage b–b′ it is 1.6:1. (From Barnes 1988,
Ores and Minerals, Open University Press, with
permission.)