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CHAPTER 3 HORIZONTAL CONSTRUCTION - 14070_63
ROAD PLAN - 14070_65

Engineering Aid 1 - Advanced Structural engineering guide book
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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. 3-2







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