Page 363 - Moving the Earth_ The Workbook of Excavation

ROADWAYS

ROADWAYS 8.25

On small areas, topsoil may be held by adding straw, and holding it with chicken wire firmly
pegged down. Horizontal wood slats are sometimes used. Placing and tamping cut sod in drainage-
ways, in horizontal strips on slopes, or on the whole surface are very effective, but the cost is high.
Rock Faces. Rock cuts can be left with very steep or vertical faces, and occasionally are
allowed to overhang. Such faces usually cause a hazard of rockfalls to the roadway, but the
expense of cutting rock back to completely safe slopes can seldom be justified.
Some rock formations tend to break up into gravel or small stones at the face because of tem-
perature changes, and will at times subject the road to an almost continuous bombardment. Such
faces should be cut back sufficiently to permit a wall or fence to be put beside the road, with space
behind to catch falling stones.
More massive cliffs may present the danger of occasional falls of larger rocks or of whole sec-
tions. These may be checked in the danger season by a worker with a bar, supported by a rope held
at the top. Loose pieces can be pried out.
Long expansion bolts, similar to those used to secure tunnel roofs, can be placed to fasten a whole
slope into a solid and safe unit. They are particularly efficient in shale beds parallel to the slope.
Vegetation tends to break up rock faces, so artificial planting should not be attempted.

THROUGH CUTS

A through cut has a high wall on each side, as shown in Fig. 8.17, so that little or no material can
be excavated by sidecasting.
If it is on a sidehill, one edge will be higher than the other. The part of the cut which is above
the low wall is actually a sidehill cut, and may be handled as one or as a through cut.
Through cuts are seldom used in building pioneer roads, except where borrow is needed to
cross a ravine. When roads are narrow, and the sharpness of curves is not an important consider-
ation, sidehill work is faster and less expensive.

FIGURE 8.17 Cross section of scraper cut. (Courtesy of
U.S. Army Engineers.)