definitions of some terms that you are likely to use when
preparing the working plans for a road:
1. CUT. Has two connotations: (1) an excavation
through which the road passes and (2) the vertical
distance the final grade is below the existing grade.
2. FINAL, OR FINISHED, GRADE. The
elevation to which the road surface is built.
3. SURFACE. That portion of the road that
comes into direct contact with traffic.
4. EXISTING GRADE. The undisturbed earth
before construction begins.
5. FILL. Has two connotations: (1) earth that has
been piled up to make the road and (2) the vertical
distance the final grade is above the existing grade.
6. SUBGRADE. The foundation of a road which
can be either undisturbed earth (for a cut) or material
placed on top of the existing grade.
7. BASE. Select material (crushed stone, gravel,
etc.) placed in a layer over the subgrade for the purpose
of distributing the load to the subgrade.
8. TRAFFIC LANE. That portion of the road
surface over which a single line of traffic traveling in
the same direction will pass.
9. TRAVELED WAY. That portion of the
roadway upon which all vehicles travel (both lanes for
a two-lane road).
10. SHOULDERS. The additional width
immediate y adjacent to each side of the traveled way.
11. ROADBED. The entire width (including the
traveled way and the shoulders) upon which a vehicle
may stand or travel.
12. ROADWAY. The entire width that lies within
the limits of earthwork construction.
13. ROADWAY DITCH. The excavation, or
channel, adjacent and parallel to the roadbed.
14. DITCH SLOPE. The slope that extends from
the outside edge of the shoulder to the bottom of the
ditch. (Sometimes called front slope or side slope.)
15. BACK SLOPE. The slope from the top of the
cut to the bottom of the ditch (Sometimes called cut
slope.)
16. FILL SLOPE. The slope from the outside edge
of the shoulder to the toe of the fill. (Also, sometimes
called front slope or side slope.)
17. TOE OF SLOPE. The extremity of the fill
(where the existing grade intercepts the fill).
18. INTERCEPTOR DITCH. A ditch cut to
intercept the water table or any subsurface drainage.
Also, a ditch cut along the top of fills to intercept surface
drainage.
19. WIDTH OF CLEARED AREA. The width of
the entire area that is cleared for the roadway.
20. SLOPE RATIO. A measure of the relative
steepness of the slope, expressed as the ratio of the
horizontal distance to the vertical distance.
21. CENTER LINE. The exact center, or middle,
of the roadbed.
22. BLANKET COURSE. A 1- or 2-inch layer of
sand or screening spread upon the subgrade to prevent
mixing of base and subgrade.
23. CROWN. The difference in elevation between
the center line and the edge of the traveled way.
24. SUPERELEVATION. The difference in
elevation between the outside and inside edge of the
traveled way in a horizontal curve.
25. STATION. A horizontal distance generally
measured in intervals of 100 feet along the centerline.
26. STATION NUMBER. The total distance from
the beginning of construction to a particular point (for
example, 4 +58 is equal to 458 feet).
SURVEY
When it is decided that a road is needed through a
particular area, the first and logical step is to determine
a route for it to follow. This mute may be chosen by the
use of maps, aerial photographs, aerial reconnaissance,
ground vehicle reconnaissance, walk-through
reconnaissance, or by any combination of these. Once
the route is chosen, a surveying crew makes the
preliminary survey. This survey consists of a series of
traverse lines connecting a series of traverse stations.
A survey party will stake in each of the traverse
stations and determine the bearing and distance of the
connecting traverse lines. From this information, an
Engineering Aid will draw the points of intersection
(PI) and the connecting lines. Then an engineer will
compute the horizontal curves at each point of
intersection, and an Engineering Aid will draw the
curves and mark the stationing. This drawing is the
proposed center line.
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