Stress on Buried HDPE Pipe

[kmccabe1990]

Hi all,

I've encountered a new problem, calculating the stresses on buried HDPE pipe. I have previously done similar calculations on steel pipe and was able to find some standards and guides that pertained directly to that material (e.g. API RP 1102, American Lifelines Alliance "Guidelines for the Design of Buried Steel Pipe", etc.), however my search for similar standards for HDPE pipe have come up empty.

Does anyone have experience with this particular situation? I'm wondering if there is a "procedure"-like calculation similar to the RP 1102 where you come up with a bunch of parameters and end up with an effective stress (see API RP 1102, Sec. 4.8.1.3) to compare against a minimum yield stress.

Thank you very much!

 

[cvg]

http://www.plasticpipe.org/publications/pe_handbook.html

 

[kmccabe1990]

Thanks cvg, I came across this myself and it does seem to be a pretty comprehensive guide. One question though, is this publication considered to be a de facto standard of sorts? While I don't have a lot of options, it would be better if I was able to reference an American standard in my calculations. The PPI guide seems to be a commonly used resource however, so any input on the matter would help.

Thanks!

 

[LittleInch]

Try Chapter VII of ASME B 31.3

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[XL83NL]

Nopt sure what the application is, and I can see how B31.3 may apply to buried pipe (interp. 21-07), but couldnt this also be covered perhaps in B31.4(/31.8)?

 

[KLee777]

Years ago, I designed an underground potable water/firewater dual spec HDPE piping system for a facility that fabricated railcars. We used NFPA 24 for guidance on our hydrants. The pipe was ideal because the fabrication facility was MASSIVE (the total area under roof was 800,000 ft^2...yes you read that right). We dug a trench all the way around the property, heat fused the pipe together, and rolled it into the trench. No thrust blocking required. Winning!

It's been so long ago now that I cannot remember the exact standards I used. However, I do recall that we used Philips Driscopipe. I'm sure it's not called that anymore. In fact, I think it might be called "CP Chem" now. They did have a design guide I used extensively.

Anyway, B31.3 does have guidance as LittleInch stated, but for soil pressure loads you will have to go elsewhere. The handbook CVG posted is a good start to educate yourself on the pipe embedment zone and the types of backfill required. With HDPE, be careful that the backfill specified is graded per the manufacturer's recommendations to avoid large particles that may damage the pipe (i.e., NOT limestone or rocky soils - see ASTM D-2321 for soil classification).

Check this link out: HDPE Pipe Embedment

You must also specify the level of compaction ("Standard Proctor Density") to be used, both in the embedment zone and above it. In my case I remember specifically using AASHTO standards to calculate soil pressures due to 18-wheelers and railcars (of course) rolling over the buried piping. In some areas, these calcs proved that we needed to embed the HDPE in steel pipe conduit to protect it from crushing.

I learned a lot more civil engineering than I ever wanted to with that job. Good luck with yours. Hope I was of some help.

 

[KLee777]

API 1102 may also be helpful, but having not personally used it, can't say for sure. Just wanted to mention it.

 

[dicksewerrat]

What will the pipe carry? potable water? high pressure oil? Sewage?

Richard A. Cornelius, P.E.

http://WWW.amlinereast.com

 

[kmccabe1990]

Thank you all for the input, it really helps when there are so many different resources to use for something like this.

KLee777 - Thanks for the info, fortunately we have some pretty comprehensive specs on the type of soil, backfill, etc. And using AASHTO standards certainly helps things as well, I have referred to some of their standards on things such as truck loads. I've also used API 1102 in the past but it is for buried steel pipe specifically, they make no mention of HDPE in the code.

dicksewerrat - The pipe will be for fire water service, design pressure of 150 psig.

 

[zdas04]

You didn't say where you are. For HDPE it matters a lot. In Australia the APIA design documents have been incorporated into the regulations of a couple of states (but not all). In the U.S. and most of the EU the document that CVG linked is treated as a guideline and any disagreements between it and ASME B31.4 are resolved in favor of ASME or its ISO equivalent (but where ASME/ISO is silent, the document linked is considered "good Engineering Practice"). Mostly the standards organizations are keeping their collective heads firmly in the sand hoping this stuff just goes away.

If I was building HDPE in the States I'd look first to ASME B31.4 (or ASME B31.8 for gas) and I'd fill any gaps with the document CVG linked.

David Simpson, PE
MuleShoe Engineering

"Belief" is the acceptance of an hypotheses in the absence of data.
"Prejudice" is having an opinion not supported by the preponderance of the data.
"Knowledge" is only found through the accumulation and analysis of data.
The plural of anecdote is not "data"

 

[dicksewerrat]

To carry water, I'd look in AWWA in the US.

Richard A. Cornelius, P.E.

http://WWW.amlinereast.com

 

[stanier]

You could try Australian standard AS 2566.1 Design of Buried Flexible Pipelines.

Also texts Buried Pipelines by Moser or Structural Design of Pipelines by Watkins

“The beautiful thing about learning is that no one can take it away from you.”
---B.B. King

http://waterhammer.hopout.com.au/

 

[dicksewerrat]

Ask the pipe supplier which standard they used to supply the pipe.

Richard A. Cornelius, P.E.

http://WWW.amlinereast.com

 

[stanier]

dicksewerrat ,

This is not the way to go. The reason is a buried flexible pipe is a combined structure of soil, pipe and fluid. When a load is applied to the soil the pipe deflects and the soil carries the load. The pipe supplier knows little about your native soil, the trench width and depth, the embedment design, external live and dead loading, water table, pressure, temperature, soil movements in reactive clay etc etc.

The approach taken in AS 2566 considered the European and USA methods of such analysis. This included the work at Iowa State using soil box tests. It is comprehensive and a thoroughly good text on the subject.

It has been in use in Australia for 15 years or so. Although considered a relatively conservative approach is does consider the equations needed to determine deflection, stress, combined loading, strain, buckling criteria etc. The Standard and accompanying Commentary do contain many references that you may wish to draw upon.

You may also like to consider the relevant AWWA standard on the matter as that is quite comprehensive.

“The beautiful thing about learning is that no one can take it away from you.”
---B.B. King

http://waterhammer.hopout.com.au/

 

[vladimir79]

Hi kmccab1990,

dicksewerrat and stanier are pointing in the right direction.

The most helpfull standard for the US is the M45 from AWWA. There is also a company which makes software for the structural calculation of burried pipes:

http://ingsoft.de/easypipe_en.ingsoft

 

[desha]

The KWH Pipe has online calculator for buried pipe analysis based on a PPI Handbook....

http://www.kwhpipe.ca....