Page 339 - Moving the Earth_ The Workbook of Excavation

Source: MOVING THE EARTH

CHAPTER 8

ROADWAYS

Roads are of many kinds, from cart tracks to superhighways. The importance of the simpler types
is often overlooked. They are essential in their own places, and they show principles that are basic
to the more elaborate highways.

ROAD TYPES

Pioneer Roads. Pioneer roads are access roads built along the route of a highway, pipeline, or
other heavy construction project to allow the movement of equipment to and between different
sections of the job. If such a road is required, it should be the first work undertaken; and any
delays in cutting it through will slow the starting of the job and may keep workers and equipment
idle.
It is best to locate it sufficiently to the side that it will not be blocked or cut off by the main
work, and if it must cross the construction strip, it should do so where it is close to subgrade.
The importance of the pioneer road decreases as sections of the main road become passable for
trucks, but it often retains at least emergency or detour value until the job is finished.
If it is to be used only for moving in equipment, it may be narrow, crooked, and steep for the
sake of economy or haste. Specifications written, and the route surveyed or walked through for it,
serve as guides rather than instructions, and the job supervisors are usually given wide latitude in
altering them for the sake of speed or economy.
Pioneer roads are most often needed in mountainous and timber country where severe obstacles
hinder cross-country travel. Where fill is available, trees are cut flush and the stumps buried; other-
wise they are uprooted and the holes graded in. Topsoil is handled as fill.
Rock is avoided as much as possible in the layout of the road, and when found is often buried
instead of blasted. If an excessive amount of rock must be moved, it may be economical to place
the pioneer road in the route of the highway, as the cost of the separate blasting may outweigh the
advantage of the independent road.
Grades follow the land contour as closely as possible. The maximum grade will depend on the use.
Shovels, tractors, and lightly loaded trucks should be able to negotiate grades up to 30 percent,
but serious delays can be caused by stalling of weak units, or as a result of skidding. Ten to 15
percent grades are more practical.
Curves should be wide enough to enable the longest units to get around them somehow, and
the machines in steady use should be able to make them without backing. Attention should be paid
to the lane width needed, so that inside rear wheels will not run off the road. Width requirement
increases with length of wheelbase and sharpness of turn.
The road width is determined by its intended traffic, construction problems, and haste. It is
desirable that it be two lanes wide, but often this is not practical. On steep slopes, two one-way
roads may be constructed, one above the other.
Two-way traffic on one lane will require turnouts at 100- to 500-foot intervals. It is best to
make these of two-lane roads the length of two vehicles, but deadend turnoffs may be easier to

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