Page 312 - Moving the Earth_ The Workbook of Excavation

LANDSCAPING AND AGRICULTURAL GRADING

7.6 THE WORK

Excavation is done in the same manner as for a basement. Topsoil should be stripped off the
area that is to be dug and regraded. The hole should be deep rather than wide, and might well be
dug by a backhoe rather than a dozer, if one is on the job. A backhoe may dig a trench close along
the wall, followed immediately by a dozer pushing the stones into it and regrading.
A backhoe is often more efficient than a dozer at breaking up a stubborn wall, as it can work
out one stone at a time. However, it cannot transport the stone readily.
The rocks can be trucked away if burial is impractical because of shallow soil, trees, or land-
scaping. A front-end loader, a backhoe, or a big clamshell can break up the wall and load it.
Trucks should preferably have bodies built to carry rock, or be so old and beat-up that damage
will not matter.
Loading a wall is slow work. Even small stones may be hard to dig out when in groups, and
big ones are hard to get securely in the bucket. Production in yards per hour may be pitifully low.

Retaining Walls. Masonry walls are frequently used to separate different ground levels. They may
be required where the slope is too steep for plain earth, or used largely for the sake of appearance.
In the first case, the wall may make up only part of the required rise, and an earth slope is con-
tinued from its top. Such walls must be strong and well founded if they are to give good service.
They are subject to very heavy pressure from the dirt behind them, particularly if it slopes up from
the top of the wall, and if it becomes saturated. Freezing will cause a push against the top of the
wall and disruptive forces inside it. Tree roots can act to lift and overturn it.
Some cross-sections of retaining walls are shown in Fig. 7.3. The foundation must be adequate,
or the wall will fail. If the ground under it is unstable because of its nature, recent placement with-
out proper compaction, or frost heaves, the wall will break up or lean outward. It is therefore

FIGURE 7.3 Retaining-wall sections.