Open-cut mining in NSW

9 Joy 15 S.C. shuttle car. Electrically powered, payloads vary from 4 to 15 tonnes.

The slow emergence of open-cut operations, although shallow coal was known to exist, was no doubt partly due to the fact that the type of equipment suitable to these operations was not available but it was also due to a form of blinkered vision in regard to shafts which were sunk instead of tunnels to very shallow coal measures.

The first attempts to fit the equipment to the task were taken in 1948, when orders were placed by the Joint Coal Board for five two and a half yard shovels and one two and a half yard dragline. Development on a planned basis continued, so that in 1951 three 12 yard walking draglines were in operation, with matching auxiliary equipment. In 1951 open-cuts were producing 1.811 million tonnes of raw coal for the calendar year. About this time underground production was catching up and the open-cuts were used as regulators at about one million tonnes per year until 1966 and then steadily rose to 19.03 million tonnes in 1982 and now the figure is 32.26 million tonnes.

Open-cut mining can be broadly classified as strip mining or open-cast in which the prime mover of overburden is a walking dragline and coal is removed by truck and shovel. Actual operations are carried out over long distances on the strike line and are more suited to single gently dipping seams.

Open-pit mining, which generally refers to non-drag-line mines are more likely to resemble quarries with multiple benching and are predominantly worked by shovel and truck methods, operating to exploit more than one seam with steeper dipping characteristics than is usual with drag lines.

With the exception of the walking dragline, however, the auxiliary equipment, drilling rigs, shovels, trucks, etc., is common to both methods and has evolved on the basis that these are more powerful, speedier and of increasing capacity.

To illustrate this, a list of the major pieces of equipment in operation prior to 1950 is as followers:

Draglines

two and a half cubic yards

Shovels

two and a half cubic yards

Heavy Excavators

one and three quarters to three and a half cubic yards

Medium Excavator

three quarters to one cubic yard.

At the present time the relative capacities of the equipment in use is:

Draglines

Common 46 cu m
Largest 60 cu m

Shovels (excavators)

Range from 14 cu m to 46 cu m

Bulldozers

Up to 10 cu m

Dump trucks

Max 72 t Range from 77 t
Average around 154 t

Australian Academy of Technological Sciences and Engineering