Page 206 - Moving the Earth_ The Workbook of Excavation

DITCHING AND DEWATERING

5.8 THE WORK

FIGURE 5.5 Wide-dragline ditch.

large boulders by widening the trench as much as necessary, and dragging them up the slope
toward itself. The ditch can be easily curved around boulders too large to lift or pull.
The clam is a slower machine but is able to dig to any depth desired, and can work close to
obstructions, except those that are overhead.

OTHER DITCHERS

Ditching Machines. Continuous-type ditching machines offer great advantages in areas where
hard bedrock and boulders are rare. They dig by continuous picking and sidecasting, rather than
the dig-and-dump cycle of the hoe.
These machines excavate rapidly; make a neat ditch, usually with a curved bottom which is help-
ful in lining up pipe; can work with less headroom, and do not need space to swing. They can dig
certain classes of homogeneous soft rock which a shovel cannot, and seldom tear up banks in shale.
Medium and large machines have a number of small buckets mounted on wheels or double
chains, that dump on sidecasting conveyors. Small units have a single chain, fitted with teeth that
cut soil and drag it to a surface auger that sidecasts it.
Buckets may be much narrower than in hoes, and drag chains may cut slots only 4 inches wide.
Some machines may be fitted with a carbide-toothed wheel that can chew slowly through boulders
and bedrock.