Page 348 - Moving the Earth_ The Workbook of Excavation

ROADWAYS

8.10 THE WORK

FIGURE 8.6 Checking a slope.

Grade. Grade stakes show the distance that the ground surface is above or below a desired ele-
vation or grade. Vertical distances to grade are marked on the stakes in feet, inches, and eighths
of inches, or in feet, tenths, and hundredths of feet. Figures are preceded by the letter C, for cut,
if the ground is high and must be cut or dug away, or by F if it is low and must be filled.
Cuts and fills may be figured from the base of the stake (ground level), from its top, or a line
drawn on it. Any basis except ground level is confusing to operators and may cause serious mistakes.
However, ground level should be marked in case soil falls away or is added without disturbing
the stake.
If the fill is less than the height of the stake, the grade may be marked directly on it with crayon.
It is an excellent practice to tie a rag around the mark to make it readily visible to the operator.
Shallow cuts may be marked temporarily with rags a specified distance, such as 1 or 2 feet,
above grade, so that operators will not have to dismount to read the figures.
A great number of rags can be made of one old sheet by tearing it in narrow strips. If none is
available, unsterilized 1-inch bandage can be bought quite cheaply for the purpose. These cloths
are easily dyed.
Original centerline stakes are usually marked to show finish grade, that is, the surface of the
pavement, since it is the line that forms the basis for engineers’ calculations. The letter G indicates
that reference is to finish grade.
Subgrade is the surface of the native soil after cutting, filling, grading, and compaction. See
Fig. 8.7. It is lower than finish grade by the thickness of the pavement and any pavement-base
and/or subbase that may be required. The combined thickness of these layers may be almost noth-
ing, if the surfacing is to be oil or cement stabilization of native soil; or 3 or more feet for very
heavy construction.