Page 38 - Trenchless Technology Piping Installation and Inspection

New Pipeline Installations 13

FIGURE 1.9 (a) Open shield wheel TBM. (b) Excavator TBM. (Source: Pipe
Jacking Association.)

1.6.2 Utility Tunneling
In the utility-tunneling (UT) technique, the same process as conven-
tional pipe jacking is used, except that in the utility-tunneling method,
a temporary support structure (called a liner) is simultaneously con-
structed as the excavation of tunnel proceeds. Normally, the support
structure or liner is traditional tunnel liner plates (TLP) or steel ribs
(SR) with wooden lagging (WL). After completion of the tunnel, pipe