Page 126 - Moving the Earth_ The Workbook of Excavation

ROCK, SOIL, AND MUD

3.20 THE WORK

FIGURE 3.12 Road subgrade covered by geotextile. (Courtesy of Hoechst Celanese Corporation.)

cable, spikes, or lag bolts. Such fastenings are important when the road surface is well above the
ground, where the mud will not act to hold it in place.
Drainage ditches may be dug on one or both sides to remove standing water. These should be
kept from 3 to 10 feet away so that mud will not flow into them from under the logs. In very thin
mud their use is inadvisable.
When a drainage channel or small stream must be crossed, the stringers can be increased in
number and strength and set on sleepers on each side of the channel so as to serve as a log bridge.
If clearance is doubtful, metal pipe may be used to carry the water under the stringers.
Corduroy roads are quick and fairly easy to construct if logs are on the site and usually are very
strong. However, their surfaces are extremely rough, and it is advisable to cover them with gravel
or other surfacing if they are to have much use. This saves damage to both machinery and road.
A corduroy road made of oak, cypress, or other strong and rot-resistant wood may have a very
long life. Some softwoods, such as poplar, will rot out in 2 to 3 years. If mixed species must be
used, the inferior ones will give their best service as stringers or sleepers.
Saplings or brush may be wired into tight bundles and used instead of logs for light corduroy.

Plank Roads. Plank road constructions are shown in Fig. 3.14. These are usually more expen-
sive than corduroy, but are easier to lay and provide a smoother surface. Rain or mud may make
them very slippery so that sanding will be required.
Nails should be driven diagonally from the sides of the tread planks, as in (B), to prevent them
from working up and puncturing tires. Even with this precaution, frequent inspections for nails and
splinters should be made. If the wood is hard, nails should be soaped or greased before driving.
Splitting may be reduced by making thin pilot holes with an electric drill.

Surface Protection. A wet soil with good load-bearing qualities, which might be readily churned into
mud, may be protected by a few inches of gravel, spread before traffic uses it. Two feet of broken rock
with a skin of gravel may carry heavy traffic for a while over almost any mud. Brush mats or pole cor-
duroy under the rock gives added stability. Between these extremes is every type of condition and cure.