Page 49 - Moving the Earth_ The Workbook of Excavation

LAND CLEARING AND CONTROLS

LAND CLEARING AND CONTROLS 1.49

FIGURE 1.39 Getting boulder out of a hole.

If the area is to be finished to a grade, it pays to be liberal in supplying covering soil, for if the
layer is thin, the dozer working on it may hook into freshly buried rocks and turn them into high posi-
tions. They can seldom be put back in place because of soil and other rocks getting under them, and
it may be necessary to knock their tops off with hammers or explosives, or dig them out and rebury
them. Digging a boulder out from among others is very difficult, and is likely to turn them up.
Rocks may be trucked away from the job. They may be loaded by lifting in or on a loader or
dipper shovel bucket, by clamping in a clamshell or grapple, or between a hydraulic hoe bucket
and the stick.
Or a crane may lift them by tongs, chains, or cable slings. Light chains grip well, but are easily
damaged.
Ordinary dump truck bodies may be severely battered by oversize rocks. The floor may be pro-
tected by an extra sheet of steel, a layer of planks, or just a few inches of dirt.

Stone Walls. Stone walls built to dispose of boulders removed from farmland are very common
in some sections of the country, and may include rocks large enough to present a problem to
machinery. The big base stones are often partly or completely buried, interlocked, and bound in
place by tree roots. The smaller stones may be valuable for use in masonry, and may be removed
by hand before or during the wrecking of the wall.
A dozer of sufficient size can walk right through the wall and scatter it around, but an under-
size machine may have to start at a gateway, or find a weak spot to break through and widen the
hole by worrying the rocks out one at a time. If the wall cannot be broken from one side, it should
be tried from the other.
Foundations. Old foundations and other masonry structures usually yield readily to heavy
machinery. High walls should be pulled down, as they might fall on a machine pushing them.
If a foundation is too strong for available machinery, it may be weakened by blasting along the
lines where it meets the floor and other walls, by mudcapping or drilling. Demolishing very heavy
or extensive structures, however, is a house-wrecking job out of the field of this book.