Page 360 - Trenchless Technology Piping Installation and Inspection

310 Cha pte r Ei g h t

Equipment
1. Jacking frame: A jacking frame must be constructed of guide
timbers, backstop, and pushing or jacking head. Guide tim-
bers or rails must be constructed to the exact line and grade
of the pipeline and must be anchored in such a manner as to
be capable of maintaining the alignment and gradient
throughout the jacking operations.
2. Backstop: The backstop must be constructed as to provide a
bearing area capable of supporting no less than 200 percent of
the estimated maximum jacking pressure and must be per-
pendicular to the alignment of the pipe. It must be anchored
and braced in a manner to ensure that this position will be
maintained throughout the jacking operation.
3. Jacking head: The pushing or jacking head must be constructed
to fit the pipe to be jacked and to ensure that the pressure
developed by the jacks will be evenly distributed on the
periphery of the pipe. An opening large enough to permit the
entrance of men and materials must be left and maintained in
the jacking head.

Method Description
1. The contractor must excavate the boring and receiving pits at
the approved locations. Any required sheeting, shoring, or
bracing that is required to provide for safe working condi-
tions must be provided by the contractor.
2. After the excavation is completed, the placing and jacking of
the pipe must follow immediately to avoid unnecessarily dis-
turbing the stability of the embankment and roadbed.
3. The contractor must dewater the pit excavation in a manner
appropriate for the conditions.
4. The leading section of the pipe must be equipped with a jacking
head securely anchored thereto to prevent any wobble or vari-
ation in alignment during the boring and jacking operation.
5. The driving end of the pipe must be properly protected
against damage, and the intermediate joints must be similarly
protected by the use of sufficient bearing shims to properly
distribute the jacking stresses. Any section of pipe showing
sign of damage must be removed and replaced, or repaired.
6. Efforts must be made to avoid loss of earth near the cutting
head.
7. If jacking pressures are high, the contractor is to be
allowed to work uninterrupted, (24 hours a day/7 days