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Figure 10-19.Sewer stakeout plan.
Construction Sheets

Engineering Aid 1 - Advanced Structural engineering guide book
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Laser Method of Laying Pipe Figure  10-20.—Setting  sewer  line  to  grade. subtract the specified cut from 10 feet. At station 8 + 50, for example, the height of the top of the batter board above  the  top  of  the  hub  would  be  10  –  5.55,  or 4.45 feet. The offset is measured off from a point directly above the hub along the batter board; a mark here is directly over the center of the pipeline. Battens are nailed  on  the  batter  board  to  indicate  sewer  center-line alignment.  A  string  is  stretched  and  tacked  along these battens; this string indicates the horizontal loca- tion of the line and follows the gradient of the line, but at a distance of 10 feet above the invert. The amount of cut required to be taken out at any point along the line can be determined by setting a measuring pole alongside the string. If the string indicates 8.5 feet, for example, another 1.5 feet of cut must be taken out. Corners  of  rectangular  manhole  boxes  are  staked out much as building corners are staked out. For a box located where a line changes direction, it may be desired that the center line of the box bisect the angle between the  lines.  The  box  for  a  curb  inlet  must  be  exactly located with respect to a street curb to be constructed in the  future;  therefore,  curb  inlets  are  usually  staked  out with reference to the street plan, rather than with refer- ence to the sewer plan. Another  useful  device  for  controlling  pipeline excavations  and  laying  pipe  is  the  laser.  So  many applications are being found for the laser that it may eventually be the only tool needed for the layout and control  of  construction  projects.  It  can  be  quickly, accurately, and economically used for purposes such as   distance   measurement,   alignment   for   tunnel borings,  setting  of  pipes  with  desired  grades,  and setting   of   line   and   grade   for   many   types   of construction. The laser is an intense light beam that can be concentrated into a narrow ray, containing only one color  (red)  or  wavelength  of  light.  The  resulting  beam can  be  projected  for  short  or  long  distances  and  is clearly visible as an illuminated spot on a target. It is not disturbed by wind or rain, but it will not penetrate fog. A laser can be set up on a bracket or even attached to a transit telescope. The beam is aligned in the proper direction  at  the  desired  grade  and  can  be  left  relatively unattended. Today, instead of using batter boards and strings, lasers can be used to control the alignment for excavat- ing trench and setting a pipe. The laser can be set so that it shines on the boom of a backhoe so that the equipment operator can clearly see the illuminated spot. By its position,  the  operator  can  closely  control  the  depth  of digging. For laying the pipe, the laser is set in the proper direction at the desired distance above the pipe invert. With the aid of the L-shaped pole or templet, as shown in figure 10-21, the workmen can control the invert elevation. It may also be possible to direct the laser beam from the inside of manholes through the pipes being laid and to control the grade without any interfer- ence from the backill operations. This can be done even if the pipes are too small for human access. Underground Duct System Layout The stakeout for an underground power line is similar to that for a sewer. For the ducts, cuts are Figure 10-21.—Pipe laying with a laser. 10-21







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