Page 48 - Moving the Earth_ The Workbook of Excavation

LAND CLEARING AND CONTROLS

1.48 THE WORK

FIGURE 1.38 Pushing oversize boulder.

direct blows of the blade or bucket, it should come out. It is sometimes very difficult to get a grip
on smooth sloping surfaces, so that an excessive amount of digging must be done just to get a hold.
When a grip is obtained with a dozer blade, the rock may be raised and pushed. The engine
clutch should be slipped, or the converter-equipped engine throttled so as to supply just enough
forward pressure to keep the blade in contact with the rock while it lifts it vertically, and, when it
is high enough, rolls it out. The rock may slip back into its hole at any time, and it is good to have
a helper throw stones or logs under it so the blade can be dropped and a fresh grip obtained. If no
helper is available, the operator can lock the brakes to hold pressure against the stone and do the
hole filling himself or herself.
If a big stone is rolled out without blocking, it may leave such a large hole that the tractor may
be damaged if it falls in it. The danger is more serious than with stumps, as rocks leave sharper-edged
and harder holes.
A rock should be pushed from all angles before digging it out, as it may be susceptible to pres-
sure from only one direction. If it is to be dug out, a bowl-shaped crater of considerable size is
excavated, working on three sides, if a good grip is available at the top, or all around it if the top
is smooth. When it is finally loosened, it may be found that it is so heavy that the dozer cannot get
it up out of the hole.
It probably can be pushed out by following the procedure outlined in Fig. 1.39. The dozer
builds a ramp out into the crater, shaped so that the machine will be pitched downward when its
blade meets the rock. With gravity assisting, it should be able to push the stone a short distance
up the opposite slope. The ramp is then built out, and another push made until the stone is out of
the hole.
Loose boulders may be pushed out of the work area and scattered, piled, or arranged in walls;
or they may be buried, being either used as a fill or wasted in holes. Holes may be dug to bury them.
Where many boulders are pushed into a hole they afford unsafe footing for a bulldozer and
may pile up above the desired grade. A moderate amount of dirt, either scraped off the bank or
trucked to the spot, will allow the dozer to fill in the holes and stabilize the rocks so that it can
walk across them in pushing other boulders to their resting place.