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CONSTRUCTION  SURVEYS - 14070_212
Figure 10-12.Ditch inlet and pipe culvert - 14070_214

Engineering Aid 1 - Advanced Structural engineering guide book
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For projects such as this, the EA surveyor is often required  to  perform  as-built  surveys  to  determine  the work in place for each of the construction activities. These surveys are usually performed on a periodic basis,  such  as  biweekly  or  monthly.  The  results  of these  surveys  are  then  used  to  determine  the completion percentage of the project. When doing as-built surveys for the purpose of monitoring  and  reporting  progress,  the  techniques,  or methods, that you use are nothing unique. Simply use the method that is best suited for the job at hand. Also, for this type of as-built surveying, extreme accuracy is  usually  not  required;  for  example,  if  you  are determining how much of a total road surface has been paved, measurements to the nearest foot are usually sufficient. Now let’s look at some stakeout surveys. Culverts  and  Bridges As in other types of layout for construction, the stakeout of culverts and bridges generally includes providing  line  and  grade.  The  procedures  and precision required will vary with the magnitude and complexity of the job. DITCHES AND CULVERTS.—  For  minor  open drains  or  outfall  ditches  a  few  feet  deep,  a  single  line of  stakes  will  serve  for  both  alignment  and  grade.  By running   profile   levels,   you   can   determine   the elevations of the tops of the stakes. As a guide to the construction workers, mark the cut on each stake to show  the  depth  of  drain  below  each  station. For drains that are very deep, you must cross- section the line and set slope stakes. The grade for a ditch is measured along the  flow line; that is, along the bottom of the ditch. When pipe culverts without wing walls and aprons are staked, only the alignment and invert grade are required;  however,  when  head  walls,  wing  walls,  and aprons are used to intercept drainage water, to retain earthwork, and to prevent erosion, grade stakes, as well  as  horizontal  alignment  stakes,  will  be  required. Large  bridge  culverts  and  box  culverts  require  stakes and  hubs  for  batter  board  alignment  similar  to  those required  for  a  building  layout. Figure  10-11  illustrates  the  stakeout  of  a  box culvert that crosses below an airfield taxiway. The angle at which the culvert crosses below the taxiway may be written on the plans, or it may be taken from the  plans. Assume that this angle is 84°30´, as shown. To run the center line of the culvert, setup the transit at  A and turn  the  84°30´  angle  from  the  center  line  of  the taxiway. Place reference stakes at  B, C, D, and E along  the culvert center line far enough beyond the limits of the culvert to make sure they are not disturbed by the construction work. In this case, points  B and D are set arbitrarily at 5 feet (measured at right angles) from the location  of  the  outside  face  of  the  culvert  headwalls. Figure 10-11.—Stakeout of a box culvert. 10-15







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