Page 311 - Moving the Earth_ The Workbook of Excavation

LANDSCAPING AND AGRICULTURAL GRADING

LANDSCAPING AND AGRICULTURAL GRADING 7.5

originally pleasing appearance degenerates badly in a year or two. Effects are bad when a level or
evenly sloping lawn settles into humps and hollows, and are worse when game courts, stone walls,
or paved drives are involved. See Fig. 7.2.
Trench backfill can be compacted by hand; with air, gasoline, or mechanical hammers; or with
electric vibrators. If ample time will elapse before grading, ditches can be loosely filled then pud-
dled by flooding with water. Full shrinkage will not occur until they have dried out, a process
which takes a few days with porous soils and weeks with heavy ones. While wet, a puddled ditch
is a dangerous trap for machinery.
Fills should be compacted by rollers or trucks. If trucks are used, each fill layer (preferably not
higher than 10 inches) should be thoroughly rolled, first empty and then loaded. Running a loaded
truck on loose fill puts a severe strain on its power train.
A medium-textured fill is more satisfactory for most purposes than either very porous or very
clayey soils.
Lawns should not be perfectly flat for any appreciable distance. The maximum slope which it
is convenient to mow is about 1 on 6 for long grades, and 1 on 3 for short terraces that are hand-
cut. Steeper grades may be left in long grass; planted with vines, shrubs; or fixed as rock gardens.
Old Walls. In New England and many other sections of the United States, utilizing or disposing
of old stone walls is a common problem in landscaping. They often contain huge stones which are
so buried and bound that they are a problem to any but the largest machinery. For this reason, and
because of the beauty of many of them, it is advisable to leave them in place when possible.
If the wall is to be removed, an attempt should be made to sell it. Weathered field-stone in small
sizes is often in demand. Boulders can occasionally be used in deep fills, stream bank riprap, or break-
water construction. Prices obtained for large stone seldom more than repay the expense of handling.
If there is no market for stone, an attempt should be made to bury it. The bulk can be roughly cal-
culated by measuring the length and the average height and width of the wall, including the under-
ground part. If no gully or other natural disposal point is available, a hole or holes should be dug to
contain somewhat more than the calculated yardage, allowing for a foot or more of fill over the top.

FIGURE 7.2 Irregular settlement after grading.