Page 157 - Moving the Earth_ The Workbook of Excavation

ROCK, SOIL, AND MUD

ROCK, SOIL, AND MUD 3.51

HYDRAULIC BACKHOES

Hydraulic backhoes sink in mud just as readily as other excavators, but they are much better able
to get themselves out.
If any solid anchor is within reach, it can be gripped with the bucket teeth, the bucket crowded
in to pull the shovel toward the anchor, and down pressure used to raise the near ends of the tracks
as they move.
If there is no anchor, or ground firm enough to act as one, poles or other supports may be placed
close to the tracks (or wheels). The back of the bucket is placed on them, and down pressure exerted
to raise the machine high enough to put supports under it.
The bucket may also be placed against a bank, the ground, or artificial helps, and forced outward
to move the shovel back.
If the carrier is a tractor or a truck, the working end of the machine can be moved sideward by
forcing the bucket down to raise it, and then swinging. This may also be done with a crawler if
the end opposite the bucket is not deeply buried.

FREEZING DOWN

Frozen Mud. Mud may cause serious difficulty when it freezes, as it sets like concrete and any-
thing in it is likely to stay there. Crawler machines are particularly vulnerable, for if they are
muddy, tracks, track wheels, and chassis are liable to be combined into one immovable unit. If
they are clean, they are still apt to freeze to the ground.
Precautions to be taken are to clean all mud from the tracks and wheels at the end of the shift, and to
park the machine on rock, metal, or wood, with as much of the track length as possible in the air. Mud
should be at least scraped off with a trowel, screwdriver, or stick, but it is safer to wash it with a hose also.
Frozen mud is hard, heat-resistant, and tough, particularly when very cold. However, the bond
between mud and other materials may be a film of brittle ice, which will resist pull or twist but
shatter at a quick blow.
Breaking Loose. If the tracks are frozen down but the track wheels are free, the machine can often
be broken loose by rocking it forward and backward with clutch and gears. Jerky clutch action is much
more effective than smooth, but also much harder on the machine. Moving forward tends to loosen the
rear pad; backward, the front. The hardest part of the job is getting the first crack in the frost; after that
the additional movement makes the breaking away progressively easier. It is sometimes advantageous
to apply power to one track at a time, using the steering clutch to disconnect the other.
If there is frozen mud holding the wheels, it is unlikely that the machine can break loose with
its own power, and the mud must be chipped or melted away. Chipping is very tedious and often
impossible because of lack of space to work. Heat is usually more practical, but if the weather is
extremely cold, very large amounts are required.
Melting Out. A blowtorch—the larger the better—is the usual tool for this work. The flame is
moved back and forth over the mud surface, and the thawed material scraped off. The wheels,
tracks, and other metal parts will conduct heat to the mud effectively, so that chunks can be under-
mined and broken off; but care must be taken not to heat the metal enough to take out its temper.
If the temperature is very low, a small section should be worked at a time; if it is near or above
freezing, the flame may be moved back and forth over the whole area.
Hot water is effective if available in large quantities, as it will wash off the mud particles as
they are thawed, exposing new surfaces to the heat. However, it may freeze on other sections of
the machine while draining off. A portable heater may be used to blow a current of warm air on
it, preferably under a tarpaulin. A flexible tube may be used to conduct hot engine exhaust.
More drastic measures are to erect a tent, or tarpaulin shelter, over the machine and thaw it
with a stove; or to drag and push it with locked tracks into a heated building. But often the most
practical method is to leave it until a thaw occurs, clean it off, and make good resolutions.