Effects Of Pipe Bursting On Nearby Utilities: Prediction, Prevention And Management

5th In A Series From The IPBA
By Matt Timberlake, President, Ted Berry Trenchless Technologies LLC, International Pipe Bursting Association Marketing Committee | September 2011, Vol. 66 No. 9

Editor’s Note: The International Pipe Bursting Association (IPBA), a division of NASSCO, is presenting a series of articles in Underground Construction that will provide the reader with a better understanding of the technology. Many myths and misconceptions exist regarding this proven rehabilitation method for replacing existing underground utilities.

This article will discuss the potential impact on adjacent utilities as a pipe is replaced using pipe bursting technology. From concept through design and construction a true understanding of the effects pipe bursting has by your entire team is essential in preventing utility damage and ensuring a successful project.

First and foremost it is important to understand how pipe bursting works and this article will be written with the assumption that the reader has a basic level of understanding for the pipe bursting method and its common applications. (See previous articles beginning with the May edition of Underground Construction.)

As with any construction project, having a management model in regards to risk assessment and reduction is critical. Although many aspects of utility construction, including pipe bursting, cannot predict an exact scope of impact, tools to manage such an occurrence are available through proper design and risk management.

Pipe bursting, whether static or pneumatic, will pull a hardened steel burst head through an existing pipe and expanding the soil which allows a new pipe to follow in its path. The amount of influence a pipe burst will have on the surrounding soils and adjacent utilities is driven by the amount of expansion required and type of soil surrounding the “potential impact area.”

Rule of thumb
To calculate the potential effects, there are a few general rule of thumb calculations. However, these must be modified to account for varying geotechnical conditions. The potential impact zone is calculated by subtracting the inner diameter (ID) of the existing pipe from the outside diameter (OD) of the expander head that is doing the pipe bursting and then multiplying by 10. This will give you in inches an approximate “potential impact zone” where the possibility of damaging another utility exists if previsions are not made.

An example would be an existing 8-inch vitrified clay pipe sewer main being replaced with a new 10-inch high density polyethylene (HDPE) pipe.

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A common rule of thumb for determining the size of the expander is that it will be 20-25 percent larger than the OD of the newly installed pipe.

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