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SETTING   SLOPE   STAKES.
Figure 14-38.-Setting slope stakes

Engineering Aid 3 - Beginning Structural engineering guide book
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Refer  back  to  figure  14-31  and  take  a  close look  at  the  position  of  the  slope  stakes.  The horizontal  distance  of  a  slope  stake  from  the center line varies, and to determine what it is, you must know three things. 1. The width of the roadbed, including widths of  shoulders  and  ditches,  if  any 2. The side-slope ratio (expressed in units of horizontal run in feet per foot of vertical rise or fall) 3.  The  difference  in  elevation  between  the grade for the road and the point on the natural ground line where the slope stake will be set In  figure  14-37,  view  A,  d  is  the  horizontal distance from the center line to the slope stake, W/2  is  the  horizontal  distance  from  the  center  line to  the  top  of  the  slope,  h  is  the  difference  in elevation  between  the  finished  grade  and  the ground at the slope stake, ands is the slope ratio. The product of h x s gives the run of the slope; that is, the horizontal distance the slope covers. The  horizontal  distance  (d)  of  the  slope  stake  from the center line, then, equals the sum of W/2 plus hs. For example, suppose that W/2 is 20 ft, h is 10  ft,  and  the  bank  is  a  4:1  slope.  Then and In  practice,  you  may  have  to  take  other factors into account, such as transverse slope or the  crossfall  of  the  pavement  (sometimes  called the  crown),  ditches,  and  so  on.  In  figure  14-37, view B, for example, there is a crossfall (h=) across W/2 so that the run (horizontal distance covered) of the bank  (hbs) is the product of s x hb  instead of  hs,  as  in  figure  14-31,  view  A.  The  crossfall is usually constant and may be obtained from the typical design sect ion shown on the plans. Figure 14-37, view C, shows a cut section in which W/2 varies with crossfall, side slope, ditch depth, and back slope. For example, assume that the distance from the center line to the beginning of the side slope is 20 ft, that the cross fall totals 1 ft, that ditch depth is 1.5 ft, and that both the side  slope  and  back  slope  ratios  are  2:1.  The distance   W/2,   then, comprises  horizontal segments  as  follows: 1. From the center line to the top of the slope which is 20 ft Figure 14-37.-Determining slope stake location (distance from center line) for a proposed roadway. 2.  Then  to  the  ditch  flow  line,  which  equals the  product  of  slope  ratio  (2)  times  ditch  depth (1.5),  or  3  ft 3.  Then  to  the  point  on  the  back  slope  that is level with the finished center line, which equals slope ratio (2) times difference in elevation; that is,  crossfall  plus  ditch  depth, The  total  distance,  W/2,  then,  is  the  sum  of SLOPE-STAKE  PARTY  PROCEDURE.— Slope  stakes  are  usually  set  with  an  engineer’s  or automatic  level,  a  level  rod,  and  a  metallic  or nonmetallic tape. In rough terrain, a hand level is generally used instead of an engineer’s level. 14-38







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