Page 301 - Trenchless Technology Piping Installation and Inspection

Pr oject Considerations for Pipe Replacement Methods 265

that include planned corrective actions if certain events take place.
Pipe-bursting projects require specific additions to their standard
contingency plan. Some of these specific events that are unique to
pipe bursting and should be addressed include:
• Excessive ground movement or vibration
• Slow bursting progress or stuck bursting head
• Problems with bypass system and with diverting and recon-
necting the services to the customers
• Damage to existing water, gas, sewer pipes and power cable,
and the like
• Dewatering problem in insertion or pulling shaft or at lateral
connection pit

Specific issues and potential solutions are briefly discussed in
Sec. 6.9.16.

6.9.15 Safety Considerations
Standard safety procedures, as followed in typical open-cut construc-
tion, should also be followed in bursting projects. In addition, the
workers should understand the components of the bursting system
and how they function, with special attention to the moving parts in
the system. The workers should be trained and equipped with the
necessary tools for confined space entry. The winch pushes against a
thrust block that (along with the soil behind it) must withstand the
forces applied by the winch. The stability of the soil behind the thrust
block should not be compromised. During the flow bypass, the
upstream pipe will be plugged; these plugs should be braced and,
preferably, remotely inflated and deflated. Prior to bursting, the con-
tractor must ensure that there is no gas line or power line close to
bursting head.

6.9.16 Potential Problems
The best method for dealing with potential pipe-bursting problems is
avoidance or minimizing probability of occurrence by properly fol-
lowing the design and construction precautions indicated in this
chapter. However, if some of these precautions are not followed or in
the event of unforeseen circumstances, problems may occur. Some
of the causes of such problems include excess (existing) pipe sag,
relatively large soil displacement, inadequate protection of nearby
utilities, inappropriate bursting system, unforeseen obstacles, and
unexpected site restrictions.
If, prior to initiating the bursting operation, the existing pipeline is
determined to display excessive sag, this condition may be repaired