Clay Pipe Failure

[MikeKostiz]

I am looking for information on sewer clay pipe failure. I am working on a sewer rehabilitation project that will involve removing and replacing 50-60 year old clay pipe that has been described as having longitudinal and circumferential cracking. I suspect that the cracking is caused by tree roots. I am looking for testing that has been done to determine what kind of pressure tree roots can exert to crack and displace 6"-8" clay pipe and cause the cracking noted above. I would be also interested in the type of cracking that results from soil and traffic loading. Thanks!

 

[saxon]

Mike, Check with the National Clay Pipe Institute at:

http://www.ncpi.org

Check into the "Clay Pipe Engineering Manual".

Hope this helps.
saxon

 

[dicksewerrat]

Longitudinal crcking is ussually caused by the live loads. this is the first fault to appear. If the pipe pressurizes or is suject to ground water, piping of solids back into the pipe can occur. then the cracks will appear at 9:00, 12:00 amd 3:00. Pnce that happens you will start to get ovalized pipe and complete failure. The pipes can be rehabbed with CIPP and stop the failure process.
Roots start out getting throught he joint. thyey increase in size over time and can break out the joint. They can crush a pipe but this doesn't happen as often in the streets, ussually in ayard nearer to the tree.

 

[SanEnr1]

I agree with dicksewerrat in that longitudinal cracking is typical of load issues. The majority of non-root cracking that I have seen in clay pipe is the result of the original installation practices. In many cases, particulary 50+ years ago, pipe bedding practices were non-existent. If your natural soils are clay or rock, the pipe could have been cracked during the initial backfilling operation and the defects you see now may have been in existence for the entire life of the pipe. I usually suspect that initial installation is to blame when I find the same types of cracks throughout several runs of sewer installed in the same timeframe.
When you have a root problem, it is ususally visible via CCTV.
Depending upon the total footage of pipe in question, some type of trenchless technology may be a cost effective rehabilitation option.