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Sewer  Stakeout - 14070_217
Laser Method of Laying Pipe - 14070_219

Engineering Aid 1 - Advanced Structural engineering guide book
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station   where   you   will   set   a   hub.   Consider   fig- ure 10-19, for example. This is a plan showing a line running from a curb inlet through two manholes to an outfall.   The   dotted   lines   are   offsets   (greatly exaggerated for clearness) to points where you will set the hubs. Note that at stations 5 + 75 and 1 + 70.21, you set two hubs, one for the invert in and the other for the invert out. The invert elevations at the manhole (MH) are given on the profile. Suppose that the invert out at CI “A” #2 is 122.87 feet. The gradient for this pipe is 2.18 percent. Station 8 + 50 lies 0.50 station from CI “A” #2; therefore, the invert elevation at station 8 + 50 is 122.87 feet minus (0.50 x 2.18), or 122.87 feet minus 1.09,   or   121.78   feet.   You   compute   the   invert elevations at the other intermediate stations in the same  manner. Suppose now that you are starting the stakeout at CI “A” #2. The final-location party left a center-line stake at this station. You occupy this point, turn 90 degrees left from the line to MH “A” #1, and measure off the offset; for example, 8 feet. This is presuming that, if the ground slopes across the line, the high side is  the  side  on  which  the  hubs  are  placed  in  figure 10-19. Hubs are always placed on the high side to prevent them from being covered by earth dozed off to form a bench for the trench-digging rig. You drive a hub 8 feet offset from station 9 + 00 and determine the elevation of the top of the hub. The vertical distance from the top of the hub to the invert at station 9 + 00 is the difference between the invert elevation and the elevation of the top of the hub. The invert  elevation  at  station  9  +  00  is  122.87  feet. Suppose the elevation of the top of the hub is 126.94 feet. Then you would mark the guard stake for this hub, CI “A” #2 inv. C 4.07´. Suppose the elevation of the top of the hub driven at station 8 + 50 is 127.33. The invert elevation at this station is 121.78; therefore, you would mark the guard stake for this station, 8 + 50, C 5.55´. The manner in which the construction crew will use these hubs to dig the trench to grade will vary according to the preference of the supervisor for one of  several  methods.  One  method  involves  the  erection of a batter board across the trench at each hub. The top of each board is placed on the posts at a set distance above  invert  elevation;  for  example,  10  feet.  Fig- ure 10-20 illustrates this method. Take station 9 + 00 in figure 10-19, for example. The elevation of the top of the hub is 126.94 feet and the invert elevation is 122.87 feet. To be 10 feet above invert elevation, the top of the batter board must be placed on the post 5.93 feet above the top of the hub. To  get  this  distance,  the  field  constructor  would  simply Figure 10-19.—Sewer stakeout plan. 10-20







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