State of Technology Report for Force Main Rehabilitation, Final ...

Since the original pipe is destroyed in the bursting process, the new pipe must be designed to carry all of
the operational loads, including internal pressure, external soil pressure, and traffic loads. After insertion
of the new pipe behind the bursting head, the soil will tend to close back on the pipe providing support.
The design of the pipe is similar to direct burial pipe based on soil-pipe interaction. Actually, some of the
most demanding loads may be exerted on the new pipe during the installation. The new pipe will see
flexural loads as it enters the launch pit, axial tensile loads due to friction and pipe weight, external
buckling pressure due to soil fill and groundwater, and possible surface damage from contact with shards
of the old pipe.
Static Pipe Bursting
Static bursting was originally developed by British Gas to replace CI
gas mains. It works well with CI and asbestos cement pipes. Pipe
diameters from 2 to 60 inches (50 to 1,500 mm) can be burst using the
static method, which relies upon brute force to shatter the existing
pipe. Lengths up to 400 feet (122 meters) typically can be burst using
the static approach although much longer lengths can be burst under
the right combination of ground conditions and bursting equipment.
TT Technologies Grundoburst ® and Hammerhead Hydroburst ® are
two examples of equipment designed for static bursting, as
illustrated in Figure 3-24.
Figure 3-24. Static Bursting Head
Pneumatic Pipe Bursting
With pneumatic bursting, an air operated hammer shatters the old pipe
with impact as the bursting head is pulled through the line. Pneumatic
bursting works well with the same materials as the static method, plus
PVC. Broken pieces are pushed outward by a rear expander, which
can also upsize the resulting void. Diameters from 4 to 60 inches (100
to 1,500 mm) and lengths up to 500 feet (152 meters) typically are
burst with the pneumatic method. TT Technologies Grundocrack ® is
an example of pneumatic pipe bursting equipment (Figure 3-25).
Figure 3-25. Pneumatic Bursting Head
Hydraulic Pipe Bursting
Hydraulic pressure is used to expand the burster, which breaks the old pipe and pushes the pieces into the
surrounding soil. An expansion cone can also be accommodated for upsizing. The hydraulic method can
be used with the same materials as the static method and in diameters from 6 to 20 inches (150 to 500
mm). Xpandit is an example of equipment designed for hydraulic pipe bursting.
Tenbusch Insertion Method
The Tenbusch Insertion Method (TIM) deviates from the static and dynamic pipe bursting methods.
Instead of using the bursting head to pull a new pipe into the void created by the burst, Tenbusch jacks the
new pipe in place of the existing deteriorated pipe. The leading element is a heavy steel guide pipe,
which maintains alignment within the center of the old pipe. Behind the lead is the cracker, which
fractures the old pipe, followed by a cone expander that radially expands the fractured pipe into the soil.
This is followed by the front jack which is a hydraulic cylinder that acts like an intermittent jacking
station to provide the axial thrust to the leading equipment. The front jack bears against the pipe (via an
adapter) that is also being jacked into the void. Lubricant is introduced at the adapter to minimize
friction. The lead equipment is designed to be disassembled at a 4 feet (1.2 meters) diameter receiving
manhole and removed. With the Tenbusch method, only rigid pipes that can withstand the high axial
jacking loads are used for the replacement. This is mainly clay and DI pipe.
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