Page 156 - Moving the Earth_ The Workbook of Excavation

ROCK, SOIL, AND MUD

3.50 THE WORK

their way down into soft earth, particularly at the load end. If there is a thin layer of sod or hard
soil overlying unstable material, the top will give an appearance of solidity, but if it breaks
through, will let the machine sink rapidly. Ordinarily, slight sinking can be ignored or checked by
poles under the tracks, but if it causes the shovel underparts to rest on a stump, it is a more tick-
lish situation.
The underparts of a shovel, between the dead axles, are more vulnerable to damage than any
part under a tractor. In mud there is often nothing to do but to get out in any way possible and hope
for the best; but if possible, any projection reaching up into this vulnerable area should be care-
fully watched during rescue work.
The power shovel may be freed from an obstruction by anchoring the bucket and hoisting, or
by walking it up on logs, or by using a plank bolted to the tracks, or even by using a long cross-
cut saw to cut off a stump while still under it.

Counterbalancing. If a shovel sinks so far on one side that it is in danger of overturning, the
boom should be swung to the high side and lowered as much as practicable, the bucket extended,
and weighted or anchored, then raised to serve as a counterbalance. This should prevent further
tipping and may make it possible to shore it up.

Overturning. If a shovel is overturned or so steeply tipped that it cannot be operated, the swing
lock should be set, a line should be attached to the top of the A-frame and to any available anchor
on the high side, and drawn taut to prevent further settling. If this line can be attached to a power
source of sufficient strength, the shovel may be pulled upright, but this should be done slowly,
with careful attention to any tendency toward bending the A-frame or other parts.
If no adequate power is available, a platform must be laid or constructed on the ground, and
the shovel raised with jacks and blocks. The best and cheapest blocks are old railroad ties, but
any sort of beams or heavy planking may be used. The actual raising of a shovel is so intricate,
so dependent on the position and construction of the machine, and so liable to result in severe
damage if done improperly that it cannot profitably be described here. The best method is to hire
people who specialize in rigging and machine moving, work with them, and remember their
methods.
If a shovel starts to tip during a swing, the bucket and load should be dropped, if possible.

Counterweight. If a shovel is heavily counterweighted to carry a long boom, and the boom is
removed to install another attachment, the shovel has a tendency to turn over backward. Removing
counterweight is usually too much work to be practical. The shovel may be walked slowly to its other
attachment, with a high heavy sawhorse or some other support dragged or pushed along under its tail
as shown in Fig. 3.41. Or a line may be rigged from its A-frame to a tractor or heavy truck moving
ahead, and kept taut, a device which can be used not only to steady it but also to pull it upright if it
does “sit down.” Another system is to bring the attachment to the shovel.

FIGURE 3.41 A basic shovel is tail-heavy.