Stress Analysis for Pipeline Buried in Peat 1

[mch22112]

Hi all,
Has anyone performed stress analysis for a pipeline buried in peat? I'm attempting a preliminary stress analysis using Caesar II and an American Lifelines Alliance soil model. Actual soil data is not yet available. Does anyone have typical soil properties for peat? Although an imported / engineered backfill may be used I would like to start by analysing pipeline behaviour in the native soil.
Thanks
Mark

 

[BigInch]

If you have an open mind, screw anchors are a great way to cross swamp and peat bogs. Many people don't have any experience with them and shy away, but I've used a lot of them in Minnesota, ("Land of 10,000 Lakes") and they work great. No concrete coating needed.

Independent events are seldomly independent.

 

[brimmer]

Probably stating the obvious but we use saddle weights to cross huge areas of muskeg/swampy areas where I am.

The Floodwood swamp in Minnesota brings back a lot of memories if you have ever been there BigInch...

 

[rconner]

I remembered a lengthy thread getting pretty wild on another forum some time ago at

http://cr4.globalspec.com/thread/80027/Excavating-in-Slime,

that while really not the same subject sort of touched on related issues. If you are working much around such stuff or the like with heavy equipment this might make for at least entertaining read -- one of most amazing posts to me read,

"In 1830 Robert Stephenson (of "Rocket" fame to all of you who know about the history of early railways) was building a rail line between Liverpool and Manchester. The route had go over several miles of of a peat bog known as "Chat Moss". His solution was to put bails of cotton onto the moss, covered by bracken with a top layer of shale. The rail line, without substantial structural modification, is still in use today carrying regular passenger trains and some 6000 ton coal trains."

Anyone who has been around Northern Minnesota much knows that many of the at least older roads are sort of like riding on a roller coaster. I guess this is perhaps some due to differential support of the subgrade, but I've also thought may have had something also to do with sort of ice lenses formed periodically in the near always very high water content native soil (as from personal experience I know it's just so darn cold to boot!))

 

[BigInch]

brimmer, I don't remember Floodwood by name, but I did work on a lot of the Northern Natural Gas system from Owatonna to Hibbing. Actually the thing I remember the most were the mosquitos ... Oh.. and the fresh northern pike filets they sold in a lot of the local restauraunts ... and the northern lights. Took me a while to figure out what those were. Thought they were some kind of flood lights pointed upwards. After driving for some 50 miles, I realized I was never seeming to get any closer to them. Then they started waving around and changing colors.

rc, yes the freezing ice lenses jacks up the roads wherever they form. In near permafrost, after a few thousand years, they eventually build into small hills 20 to 50 feet tall. They freeze, thaw, but not completely, then freeze again.

Independent events are seldomly independent.

 

[brimmer]

I seem to remember a large pipeline failure in a bog here a few years a go that required some larger scale engineering for a solution to continue to allow the company to operate the pipeline through the bog. They used geotextile fabric, brought in fill, used other methods to stablize the pipe in that area. Attached is a breif article on the methods they used.

 

[BigInch]

Check out the screw anchor possibility. Goes in much easier than all of that. As long as you can get to good soil down below somewhere, they'll work.

Independent events are seldomly independent.

 

[dicksewerrat]

Some of those old roller coaster roads were built on top of logs laid across the right of way. Called corduroy. The road floats a little. But this was 70-80 years ago. They probably didn't remove the logs for the newer road. And yes it gets cold there. that's why I moved to south Carolina for the winters. Walleye is better than northern.

Richard A. Cornelius, P.E.

http://WWW.amlinereast.com

 

[mch22112]

Some very good / entertaining ideas there! Thanks! We are still waiting on trial pit test results.

 

[rconner]

"Copy" on the mosquitos and walleyes, in that order (I have also wondered with regard to the former how it is anatomically possible those big coldblooded bloodsuckers manage to emerge from the swamps about the same time "the ice goes out")!!

 

[BigInch]

Don't they migrate in like ducks.

Independent events are seldomly independent.

 

[LittleInch]

I don't know whether its allowed on this site, but me and the company I used to work for have spent years, yes years, designing a pipeline accross a peat bog in Ireland and more recently shetlands up to 5 m deep. if you really have no option then the only real way of doing it is to dig it out and lay a stone road to lay the pipeline in. Trust me, nothing else works as your pipeline will either flex all over the place as the pipe to soil friction is virtually zero and hence as said above will have a virtual anchor length of hundreds of metres or the pipe will float or sink. Apart from any other consideration it is very diffcult to safely construct and peat, once youve worked it a few times turns to liquid mush. Peat only exist where it rains over 250 days a year so it will rain a lot when you're triny to drag your digger / sideboom out of the bog it has just fallen into. Let me know if you want to know more....