Page 501 - Moving the Earth_ The Workbook of Excavation

PIT OPERATION

PIT OPERATION 10.7

FIGURE 10.6 Stripping with a dragline.

Draglines can load part or all of the spoil into trucks or trains, on the wall or in the pit. They
can dig selectively from the top down, handling different formations in succession from one
stand. This ability makes possible a rough division of the bank into select material to be hauled
away, and waste to be sidecast.
Cleanup bulldozers follow immediately after the dragline and push their loads within reach of
its bucket.
Stacker. Stackers are mobile elevating belts. The belt is carried in a boom which can usually be
raised, lowered, and swung while operating, and may be adjustable in length as well.
The hopper is usually crawler-mounted and self-propelled. It is protected by a grizzly, so that
pieces too large for the belt will be rejected onto the pit floor.
Figure 10.7 illustrates the use of one of these machines in conjunction with a standard-boom
shovel. The shovel digs the bank and dumps in the hopper, from which the belt carries it to the
spoil bank.
Dug soil can usually be moved more economically by a conveyor belt than by swinging a shovel
heavy enough to carry a boom of the same range. However, the stacker is not as flexible and will
not handle as coarse material as a stripping shovel or dragline.
The stacker is also used in the pit for loading trucks up on the bank.