Page 387 - Moving the Earth_ The Workbook of Excavation

ROADWAYS

ROADWAYS 8.49

FIGURE 8.36 Center and side profiles.

Distances measured from the road line to the ground line will indicate the depths of cut and fill
required to establish the road grade. If topsoil is to be stripped, its depth should be added to the
fills and subtracted from the cuts.
If the ground does not slope across the line of the road, this type of profile, shown in Fig. 8.36(A),
should give a reasonably accurate picture of the relative volume of cuts and fills, and the distances
they are to be moved. However, to obtain yardages, cross sections usually must be calculated, as
described below.

Side Profiles. If the road is laid out on side hills, side stakes and slope stakes may be set. The
side stakes may be at the edge of the pavement, at the outer edge of the shoulder, or the far side
of the gutter, if any. In general, the shoulder or the gutter locations are preferable. Slope stakes
are placed where the intended cut in a bank reaches its top, or at the outer, base edge of a proposed
fill. These are not placed until cross sections are calculated.
If the side stake elevations are plotted in the same manner as the centerline, two additional profiles
can be drawn, as in (B). These will give additional information about the bulk of material to be moved,
but since they often do not include cuts for gutters, and cannot show the volume which must be dug
or filled for side slopes outside the road lines, they are not an adequate basis for careful calculation.
Cross Sections. A cross section is a profile taken at right angles to the line of the roadway. It is
at least long enough to include the full width that will be graded. Such profiles are sometimes
taken with hand or string levels. They may be taken at each 100-foot station, plus points where
the ground surface changes, or, in smooth terrain, less frequently.
This cross profile is also drawn on cross-section paper, preferably on the same vertical scale
as the center profile. Horizontal scale may be the same as vertical, or at any convenient propor-
tion to it. The cross section of the road subgrade is drawn in.
A number of such cross sections are shown in Fig. 8.37, together with the cut and fill for each.
Wherever the ground line is above the road line, there will be a cut; and where the road line is
higher than the ground line, there will be a fill. If topsoil is to be stripped and saved, it may be
advantageous to lower the ground line by the depth of the topsoil to save confusion.
Figure 8.38 shows a sample cross section with the arithmetic involved in computing its area.
The road and gutter surfaces have been simplified in the calculation, as this reduces the work
without introducing too large an error for rough figuring. The problem is also simplified by a hor-
izontal ground surface.