Page 234 - Moving the Earth_ The Workbook of Excavation

DITCHING AND DEWATERING

5.36 THE WORK

FIGURE 5.25 Loading on pipes. (Reprinted with permission from Elwyne and Seelye’s Design, John Wiley & Sons, Inc.)

If the floor is rock, it should be cut from 6 inches to 3 feet below pipe grade, the depth depending
on the height of fill to be placed, and backfilled with earth or pea gravel. If it is mud, space should
be allowed for enough pea gravel to stabilize the surface. Saplings or wire lath might be laid under
the gravel to provide extra stability.
If one end of the culvert is to rest on fill and the other in a cut, the fill under it should be thor-
oughly tamped to avoid unequal settlement.

Placement. Each section should be placed with the longitudinal seams at the side shoulders. The
cross joints should have the external part of the overlap upstream, so that if the joint is not tight,
seepage will tend to move into the pipe instead of out of it.

Joints. Sections are usually fastened together by a one-piece band. This is placed under the end
of the first piece, and the second is laid so that the band will overlap each by the same number of
corrugations. The coupler is then drawn tight by turning down the nuts with a wrench.
This joint resists any force tending to pull it apart, being about as strong as the pipe itself. If the
pipe will be subject to very severe stress, a two-piece coupler riveted to one or both sections may
be used. The pipes are placed so that the collar lines up, and it is fastened with the bolts and nuts.
If the pipe is large enough to work inside (36-inch or more ordinarily, but less if a small worker
is available), a one-piece band may be installed in the regular way, and holes then drilled through
the band and the pipes, and bolts used to strengthen the joint.
If watertightness is important, an asphalt sealer may be placed inside the band before installing,
or a special coupling may be used.