Page 383 - Trenchless Technology Piping Installation and Inspection

Inspection and QA/QC for Trenchless Installation and Replacement Methods 333

imposed by the operation. The specified allowable jacking
capacity of the casing pipe must be 3 times greater than the
maximum jacking forces imposed by jacking operations as
identified by theoretical calculations.
• Steel casing pipe must have minimum yield strength of
35,000 psi.

Casing Pipe
Steel casing pipe, also known as encasement pipe is most commonly
used in horizontal auger boring.

1. Steel casing pipe must have a minimum wall thickness of
0.25 in. or as specified in the specifications for construction,
whichever is larger.
2. Casing pipe must be round. Steel casing pipe must have a
roundness tolerance, so that the difference between the major
and minor outside diameters must not exceed 1 percent of the
specified nominal outside diameter, or 0.25 in., whichever is
less.
3. Casing pipe must have square and machine-beveled ends.
The pipe end maximum out-of-square tolerance must be 0.04 in.
(measured across the diameter).
4. Casing pipe must be straight. The maximum allowable
straightness deviation over any 10-ft length of steel casing
pipe is 0.125 in.
5. Pipe must be without any significant dimensional or surface
deformities. All pipes must be free of visible cracks, holes,
foreign material, foreign inclusions, blisters, or other deleteri-
ous or injurious faults or defects. Any section of the pipe with
a gash, blister, abrasion, nick, scar, or other deleterious fault
greater in depth than 10 percent of the wall thickness must
not be used and must be immediately removed from the
site.
6. Casing pipe must be used within the entire roadbed influence
area. The roadbed influence area is defined as the subsurface
area located under the road and shoulder surface, between
each shoulder point or back of curb, and continues trans-
versely outward and downward from each shoulder point or
back of curb on a 1-on-1 slope.
7. Only new casing pipe must be used, unless otherwise
approved by the engineer/inspector.
8. Casing pipe must have smooth interior and exterior walls to
reduce jacking force and prevent casing rotation.