Figure 14-36.-Determining cut or fill from grade rod and
ground rod.
3. Compute the difference between the HI
and finished grade; this vertical distance is called
grade rod.
4. Read a rod held on the hub top or ground
point for which the cut or fill is desired. This rod
reading is called ground rod.
5. Determine the cut or fill by adding or
subtracting the grade rod and the ground rod,
according to the circumstances, as shown in figure
14-36.
6. Mark the cut or fill on the stake.
During the final grading, you will most likely
be working with hubs called BLUE TOPS (fig.
14-31). These hubs are driven into the ground until
the top is at the exact elevation of the finished
grade as determined by the surveying crew. When
the top of the stake is at the desired finish grade
elevation, it is colored with blue lumber crayon
(keel) to identify it as a finished grade stake. Other
colors may be used, but be consistent and use the
same color keel throughout the project so as not
to confuse the Equipment Operators. Blue tops
are normally provided with a guard stake to avoid
displacement during construction work. The
guard stake usually shows the station and the
elevation of the top of the hub. The elevation and
station markings may be required only at station
points; otherwise, all that is needed is the blue top
and the guard stake with flagging.
The procedure for setting blue tops lends itself
primarily to final grading operations. It is carried
out as follows:
1. Study construction plans and center-line
profiles for each station to determine (1) the
exact profile elevation and (2) the horizontal
distance from center line to the edge of the
shoulder.
2. Measure the horizontal distance from the
center line to the shoulder edge at each station,
and drive a grade stake at this point on each
side. Sometimes it is advisable to offset these
stakes a few feet to avoid displacement during
construction.
3. Set the top of the stake even with the grade
elevation, using both the level and the rod. This
is accomplished by measuring down from the HI
a distance equal to the grade rod (determined by
subtracting grade elevation from the HI). The
target on the rod is set at the grade-rod reading;
the rod is held on the top of the stake; and after
a few trials, the stake is driven into the ground
until the horizontal hair of the level intersects the
rod level indicated by the target. Color the top
of a stake with blue crayon (keel).
4. Where the tops of stakes cannot be set to
grade because grade elevation is too far below or
above the ground line, set in ordinary grade stakes
marked with the cut or fill as in rough grading.
However, for final grading, it is usually possible
to set mostly blue tops.
Where grade stakes cannot be driven, for
example, in hard coral or rock areas, use your
ingenuity to set and preserve grade markings in
a variety of conditions. Markings may often be
made on the rock itself with a chisel or with a keel.
SETTING SLOPE STAKES.– SLOPE
STAKES are driven at the intersection of the
ground and each side slope or offset a short
distance; they indicate the earthwork limits on
each side of the center line. The minimum areas
to be cleared and grubbed extend outward about
6 ft from the slope stakes.
14-37
