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Pr oject Considerations for Pipe Replacement Methods 247

experienced project engineers or construction managers identify these
risks and develop risk management plans to address them. These plans
include quantification of the likelihood of the identified events and
their associated impact or degree of damage. It also includes measures
to eliminate, mitigate or transfer these risks. One of the general mea-
sures to mitigate the project risks is building and maintaining partner-
ships among owners, engineers, contractors, equipment manufactur-
ers, and pipe suppliers. The identification and development of a
realistic plan to manage and share risks appropriately and setting a
contingency plan, is an important part of effectively communicating
responsibilities, defining roles, and building a partnering team.

6.8.7 Ground Movements
The pipe-bursting process creates a cavity in the soil around the pipe
through which the new pipe is pulled. This cavity creates a compres-
sion plastic zone around the new pipe outlined by an elastic zone, as
shown in Fig. 6.8. The magnitude of the compression and the dimen-
sions of these zones correlate with the amount of upsizing, the
diameter of the existing pipe, and the type of soil (Atalah, 1998).
Based on investigations of the ground movements and vibrations
associated with bursting small-diameter pipes in soft soils (Atalah,
1998) and with large-diameter pipes in rock conditions (Atalah, 2004), ∗
guidelines have been developed for safe separation distances from
existing nearby utilities, structures, and pavement.
There is a strong correlation between the distance from the pipe-
bursting tool and the level of vibration. The vibrations due to bursting
are seen to rapidly decline to levels that do not cause damage to build-
ings. For structurally sound residential buildings, minimum separa-
tions of 11 ft in hard soil and large-diameter bursting conditions and 8 ft
in soft soils and small-diameter conditions are recommended. Corre-
sponding minimum separations of 8 ft and 4 ft are recommended from
structurally sound commercial structures. Considering pipes as “buried
structures,” studies by Atalah (2004) suggest that 7½ ft represents a safe
separation distance for pipe-bursting operations for either small- or
large-diameter structurally sound pipes, in various soils, with reduced
spacing possible for small sizes. While below-ground pipelines where
pipe bursting required may include pipes installed in the right of way,
which are usually far from the residential or commercial buildings,
possibility of damage to nearby buildings and adjacent pipelines must
be thoroughly investigated during the planning and design phase of
the project. It is also recommended to document the existing state of
these structures documented (with photos and videos/DVDs) to
protect the pipe-bursting project owner from unfounded claims.

∗The investigation of the large-diameter bursting in rock conditions included
upsizing 24-in.-diameter reinforced RCP pipes by 50 percent. The studies of the
small-diameter bursting in soft soils included upsizing 8- and 10-in.-diameter VCP
by 30 percent.