perched water table on a pipeline 1

[kasansa]

Hi


How would you treat a perched water at cosntruction stage?

We layed and backfilled the pipeline as normal with selected fill however the ground is seeping into the trench and sogging up the line.

 

[BigInch]

If there's too much water where you can't excavate a normal section, you have to use a dragline in a wide low angle sloped side "V" trench and then float the (weighted, if you need it) pipe pipe in, cut the buoyancy tanks one at a time and let it settle into position. Then backfill with the same dredged material, if its not soup and still suitable, or provide alternate sand backfill around the pipe, perhaps with a rock dump, gabbion or concrete mat, concrete filled bags, etc., over the top. If you did a preconstruction survey, you would have been able to go to the party prepared for that with weights and buoyancy tanks, draglines and tow winches. At least now, if you have the buoyancy issue solved all you have to do is see if its lifting the line as it backfills naturally, or if you have to put saddle weights on top and fill it yourself.

"We have a leadership style that is too directive and doesn't listen sufficiently well. The top of the organisation doesn't listen sufficiently to what the bottom is saying." Tony Hayward CEO BP
"Being GREEN isn't easy." Kermit

http://www.youtube.com/watch?v=hpiIWMWWVco

http://virtualpipeline.spaces.liv

 

[zdas04]

kasansa,
You are not going to find better advice than BigInch gave you. If you can bury the pipe and your total bouyancy is right then the perched water is no problem. Think about it--how much water surrounds the pipe running from an offshore platform?

David

 

[bimr]

It is common to start construction at the end of the pipeline that has the the lowest elevation. The water will then drain down the pipeline within the bedding towards the end with the low elevation.

 

[BigInch]

Might turn into a river though, if you hit the source.

"We have a leadership style that is too directive and doesn't listen sufficiently well. The top of the organisation doesn't listen sufficiently to what the bottom is saying." Tony Hayward CEO BP
"Being GREEN isn't easy." Kermit

http://www.youtube.com/watch?v=hpiIWMWWVco

http://virtualpipeline.spaces.liv