Page 499 - Moving the Earth_ The Workbook of Excavation

PIT OPERATION

PIT OPERATION 10.5

FIGURE 10.3 Bulldozer stripping. FIGURE 10.4 Stripping shallow overburden with scrapers.

In Fig. 10.4 the high wall is smoothed off and the outcrop of the pay formation covered by bull-
dozers working down the slope. The scrapers then dig the high wall, working downhill, and build
their fill on the full width of the empty pit.
Lengthwise digging is well adapted to combined operations. If only part of the overburden
were to be removed by the scrapers, and the balance by shovels, a narrower fill would be made.
The scraper work would thus serve to reduce the depth to be handled and the distance it would
have to be thrown.
Scraper cuts are frequently made to dispose of loose or soft overburden on rock which requires
blasting. This reduces the drilling footage, eliminates the need of casing large blast holes, and permits
use of wagon drills on the exposed rock.

Front Shovel. For sidecasting work, front shovels are equipped with extralong booms and
sticks to increase reach. These are compensated by extra counterweight and power or smaller
buckets.
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Crawler-mounted stripping shovels are made with buckets from 2 ⁄ 2 - up to 140-yard capacities.
In strip work they are generally used for sidecasting, but except in the largest sizes they may also
be used for loading trucks or trains that stand in the pit or on comparatively low walls.
Small- and medium-sized stripping shovels are generally more or less standard units that can
be readily transported from job to job. Large ones are likely to be custom-made, shipped to the
job in pieces, and erected at considerable expense. Their high cost is only justified when enough
work is available in one area to repay it.