Page 361 - Trenchless Technology Piping Installation and Inspection

Inspection and QA/QC for Trenchless Installation and Replacement Methods 311

a week), until the pipe has been jacked between the speci-
fied limits.
8. If appreciable loss of soil occurs during the boring and jacking
operation, the voids must be packed promptly to the greatest
extent practicable with flowable fill (see DOT flowable fill
requirements).
9. The contractor must protect the excavation until the opera-
tion is complete and the excavation is backfilled.
Overcut Allowance
When using this method, the allowable overcut is 1 in. greater than
the outside diameter of the pipe.

Soiltight Joints
Soil tight pipe joints are required to ensure the integrity of the road-
bed. Pipe must be constructed to prevent earth infiltration through-
out its entire length. Conventional pipe jacking is normally for use
above the water table or for de-watered ground.
Lubrication Fluids
Lubrication fluids are required for this method of pipe installation to
reduce jacking forces.
Pipe Locating and Tracking

1. During construction, monitoring, and plotting, boring
progress must be undertaken to ensure compliance with
the proposed installation alignment and allow for appropri-
ate course corrections to be undertaken. Longer drives over
500 ft should have intermediate jacking shaft installed.
2. Pipe installed by this method must be located in plan as
shown on the drawings, and must be no shallower than
shown on the drawings unless otherwise approved.

Jacking Force Calculation
1. The estimated jacking force must not exceed one-third of
specified allowable jacking capacity of the pipe to avoid pipe
damage.
2. The estimated jacking force must exceed the resistant force
required to install pipes with the microtunneling method.
3. Influential factors of the estimated jacking force include
• Length of drive
• Weight, grade, and diameter of the pipe
• Height of the overburden
• Soil characteristics