Page 27 - Moving the Earth_ The Workbook of Excavation

LAND CLEARING AND CONTROLS

LAND CLEARING AND CONTROLS 1.27

FIGURE 1.20 Stump pulling.

free it without difficulty. If a number of stumps are being pulled, all of them may be overturned
one way, before pulling the tough ones in the opposite direction.
Half-uprooted stumps are easily knocked out by dozers, and may be left for them to save the
trouble of rerigging.

Resistance. A stump’s resistance varies in different directions. If on a slope, downhill pull is
most effective. Otherwise it should be pulled toward its strongest roots, as these are easier to bend
than to pull apart, and can be dealt with more easily when the rest of the stump is loosened.
The most obvious variable in stump resistance is its height. Greater height means greater
leverage and easier pulling. Limiting factors are difficulty of high cutting and of fastening heavy
chains at a height, and the trunk breaking under pull.
A buried stump is the hardest of all to pull and usually must be dug out. On filled land, two
separate systems of lateral roots may be found, one under the old ground level and the other near
the surface, in which case it may be necessary to cut the trunk below the upper roots, in the same
way as a taproot.
A stump which yields to pull but will not break loose can often be uprooted by moving it as
far as possible, slacking off to allow it to settle back, and pulling again, repeating this process a num-
ber of times. This is most effective if done slowly and smoothly, whether with winch or traction.
This method is very effective with trees, as the trunk will bend with a whipping motion that exag-
gerates the force of both the pull and the snapback.
Chopping the roots on the side opposite the pull, while they are under maximum tension, weakens
the resistance. A moderate amount of digging will generally expose the main lateral roots.
When a stump has been split by blasting, the pieces are most easily pulled away from the center,
rather than across it.

Uprooting Trees. If trees are so large that their stumps will be difficult to remove, it may be
advisable to pull the trees over rather than to cut them down. This gives the opportunity to fasten
lines as high as desired and to make use of the weight of the tree. As soon as the tree is pulled
toward the tractor, its center of gravity shifts to that side and aids greatly at breaking out the roots.
If a large log is chained to its base, on the pull side, the force of the tree’s fall will be more effec-
tive at breaking roots on that side. The log will also serve to prevent the trunk from digging into
the ground where it would be difficult to cut.
If the tree tends to break or split instead of uprooting, additional chokers may be used below
the main pull point to distribute the strain and bind the trunk together. This can be done by pulling
with two or more machines, or with multiple lines and blocks that will be described later.
If the trunk is smooth, a ladder will be needed to get a high grip. The chain may be held from
sliding down by a nail or a notch, when necessary.
Pulling trees is apt to be wasteful of lumber, as the bottom of the trunk may be put under such
strain that it will split when cut.