Figure 14-25.-Three-level section in cut.
Figure 14-26.-Level section in fill.
In the section shown in figure
14-25, the ground line
across the section is sloping rather
than level. Therefore, to plot this section, you
would need three different elevations: one for the
left slope stake, one for the center-line grade
stake, and one for the right slope stake. If these
three levels are taken, the section is called a three-
level section in cut. If additional levels are taken
midway between the center line and the slope
stake on either side, it is called a
five-level section in cut. Therefore,
it is a section in cut because the
entire cross-sectional area consists of cut.
Level, three-level, and five-level sections are
called regular sections.
14-26 shows a level section in fill;
14-27 shows a
three-level section in fill. The
section shown in figure 14-28
consists of both cut and fill and is
called a sidehill section. When a
more accurate picture of cross sections
than can be obtained from regular sections is
desired, irregular sections are taken and plotted.
For an irregular section you take, besides the
regular levels, additional levels on either side of
the center line. You take these at set intervals and
at major breaks in the ground line.
Cross sections may be preliminary or final.
Preliminary cross sections, from the P-line or
survey base line, are irregular sections
that are plotted before the
finished grade has been determined.
They may be obtained by levels run in
the field or by elevations found on the contour
lines of a topographic map.
Final cross sections are sections of the final
road design. They may be prepared in the same
manner as preliminary sections, or they may be
regular sections plotted from field data obtained
after the finished grade has been set. The term
final cross section is
also applied to as-built
sections taken after construction is completed.
PLOTTING CROSS SECTIONS. Cross
sections are usually plotted on cross-section paper,
which comes either in rolls or sheets. It is ruled
into 1-in. squares with heavy, orange or green