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Existing Pipeline Renewal and Replacement Methods 63

2.3.9 Trenchless Replacement Methods
When capacity of pipelines is found to be inadequate, the pipe can be
replaced with a trenchless replacement method. There are two main
types of trenchless replacement methods: pipe bursting and pipe
removal (also called pipe eating, see Table 2.5). See Chap. 6 for more
information on pipe replacemnt methods.

Pipe Bursting
Pipe bursting, as the name implies, uses a hammer to break the existing
pipe and force broken fragments bursting head into the surrounding
soil while a new pipe is pulled and/or pushed in its place simultane-
ously. There are different variations of pipe bursting method:

• Pneumatic pipe bursting: a pneumatic hammer is used to break
the existing pipe.
• Static pipe bursting: the energy to break the existing pipe is in
the pulling with no percussion action. Compared to pneu-
matic method, this is a quiet operation and action preferable
in clayey soils or when there is need to cut (split) cast iron or
ductile iron pipe.
• Hydraulic pipe bursting: the bursting head articulates to
create the bursting action, without the noise of the pneu-
matic systems but pulled along with a cable like pneumatic
systems.
• Insertion method (also called pipe expansion): this method jacks a
new rigid pipe (such as clay) into the existing pipe. Clay and
ductile iron are the two most widely used segmental pipes.

Figure 2.13 illustrates a schematic of pipe bursting operation. This
method can be used to replace natural gas, water, and sewer pipes.
This technique is useful in size-for-size replacement and up-sizing of
pipeline sections. A pit is excavated to make new insertion possible
based on the required bending radius of the new pipe. Pipe bursting
is applied for pipes ranging from 4 to 48 in. The length of installa-
tion is based on the project and site conditions and can be in the
400 ft range.
The pipe-bursting technique may not be applicable when
replacement occurs in hard soil conditions, such as “expansive”
clays, densely compacted soils and backfills, or soils below the water
table. In addition, pipe bursting projects could be complicated fur-
ther by close proximity to other underground utilities (less than 10
times outside diameter of new pipe), past point repairs that rein-
force the existing pipe with ductile materials, and a collapsed sec-
tion of existing pipe. See Chap. 6 for a complete discussion of pipe
bursting method.