Page 272 - Trenchless Technology Piping Installation and Inspection

236 Cha pte r S i x

Direction of insertion

Lubricant system Power unit
Tenbusch
Surface improvements
Work pit
9' × 9' New pipe
Back Cracker Ex.
stop MH
Front jack Lead

Pipe Cone Existing
adapter expander pipe
FIGURE 6.6 The Tenbusch Insertion Method™.

introduction of a lubricant allows for the efficient replacement of
existing pipelines even in soft sticky clays or wet sands.
Dual flexible hose sections, which transport lubricant and hydrau-
lic fluid to the front train, are fed through each new pipe section.
Each new hose section is connected to previous sections and to the
operator’s control panel with quick-disconnect couplings. Using the
new pipe as a support column, the front jack advances the lead train
into the existing pipe independent of the advance of the new pipe
column. The new pipe is jacked behind the lead train piece by
piece by the jacking frame (in the jacking pit). The primary jacking
frame applies the required thrust to advance the new pipe column
(as the front jack is retracted). Instrumentation and controls at the
operator’s control panel (at the jacking frame) allow the operator to
“feel” his or her way through the existing pipe as the new pipe col-
umn and front train are “inch-wormed” into the existing pipe. On
completion of the pipe replacement, the lead train is disassembled
inside a typical 4-ft diameter-receiving manhole and the new pipe is
jacked into its final position. Figure 6.6 illustrates pipe insertion
using the Tenbusch Insertion Method™.

6.3.4 Pipe Eating
The pipe removal process can potentially be executed by horizontal
auger boring, a process that excavates the existing pipe and surround-
ing soil by using a rotating cutting head attached to an auger that
continuously removes the excavated soil. Other potential methods of
pipe eating are using a modified version of the MTBM or using pipe
ramming equipment.

6.4 Existing Pipe Materials
In most bursting applications, the existing pipe is composed of a
rigid material such as vitrified clay pipe (VCP), cast iron, plain con-
crete, asbestos, or some plastics. Reinforced concrete pipe (RCP) can
be replaced when it is not heavily reinforced or if it is substantially