Page 527 - Moving the Earth_ The Workbook of Excavation

PIT OPERATION

PIT OPERATION 10.33

Dozer push loading is most effective in high banks with a slope steep enough to allow pushing
of large loads and to still allow the tractor to back up easily. Much steeper banks can be used in
clay and hardpan than in loose sand or gravel.
Spoil can be pushed in the same manner into a hopper and conveyor, which may be a light
homemade arrangement such as that in Fig. 10.24(A), or a factory-built, high-capacity belt loader
such as that in (B). In either case, when the material within efficient range is exhausted, the hopper
should be moved.
It is common practice to postpone moving for much too long. Dozer loading on level or slight
grades is inefficient and should be avoided. No part of the push should ever be uphill.
Bulldozers are also used to push bank material within reach of excavators which are stopped
by rock outcrops in the toe, and to keep high banks sloped to prevent undermining and caving.
In “glory hole” excavation, which is usually in rock, a tunnel is driven in from the toe and a
connecting shaft run to the surface. Rock blasted from the sides of the shaft feeds by gravity to a
conveyor, drag scraper, or railcars, which haul it out of the tunnel. A bulldozer is not required
until the pit has widened its slopes so that rock will no longer slide.

FIGURE 10.24 Loading a hopper with a bulldozer.