Sealing Pipe Jacking Sleeves

[JFCmech]

Hi
I have a problem with pipe jacking sleeve joints that are letting in ground water. Ground water level is approximately 1m above sleeve invert during very rainy season. The sleeves are "in the wall joint" types - SANS 677. The seals that were fitted must have been damaged during installation, as they are letting ground water into the sleeve area. Inside the sleeve we have a concrete bed to provide a level surface for a steel pipe. The sleeve ID is 1800mm and the steel pipe is 900NB. Space is limited inside for access to seal the leaking joints. The steel pipe coating has been damaged by the water ingress and thus the pipe needs to be protected too. Normal paint repairs are not possible due to limited access.
Does anyone have any ideas to solve the two problems?
It has been proposed to try and use products like Vandex plug, where access permits, to seal the jacking sleeve joints, but this will not be possible in some areas due to access constraints.
Another proposal has been to fill the sleeve with a light concrete mix (8% cement) together with waterproofing product like Krystol Internal Membrane. This would seal and protect the steel pipe from corrosion, but is not without its challenges. Buoyancy of the steel pipe during casting would be one concern.
Any ideas are welcomed.
Thanks

 

[LittleInch]

I've never seen anyone fill the bottom half of a sleeve before to install a pipe in a sleeve of that size - 2.4m+ maybe, but not that small. Anyway, this problem is why pipeline crossings using sleeves / casings have fallen out of fashion and your options are kind of limited. It is a bit alarming that the pipe coating has bee damaged just by water - pipeline coatings are normally much better than that - what is the coating

1) Replace the crossing with a different pipe crossing - I don't know how long or why this crossing uses a casing but this is an option to replace it with a non casing crossing - probably far too expensive
2) Filling the pipe is difficult as you really need to avoid voids and gaps in the filling grout / concrete. foam concrete can go a long way if you get it right.
3) I have seen epoxy high build spray systems mainly used for internal coating of water pipes which use a pipe / lance type injection system to spray high build epoxy onto the internal surfaces of existing pipes. Probably worth looking up internal pipe coating systems

My motto: Learn something new every day

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

 

[JFCmech]

Thanks LittleInch
The design was originally for other pipes and services to be able to use the sleeve. Due to the pipe jacking contractor being roughly 400mm off course, the installation had to be adjusted, thus it is a less than ideal situation. Where access to the pipe originally existed, it is now limited. The pipe coating was supposed to have been in a dry environment, which it is now not, due to an unusually high water table and leaks, not experienced during previous rainy seasons. It is a three coat Enamel coating system, not suited to wet conditions.
1) We will not consider a new crossing at this stage.
2) Thanks for the foam concrete idea, I will investigate that further.
3) Unfortunately a conventional coating will not work, as we cant get in there to do surface prep. I did consider something like bitumen, but it was considered too dangerous due to either heat or solvent required. Tape wrapping was also considered, but once again access is an issue.
Regards

 

[LittleInch]

A lot of the water main repair stuff works on the basis of no or limited access and poor surface prep. moral of the story - Allow for flooded conditions when / if the tunnel leaks...

Is this a gravity sewer?

you could also think about internal lining of your pipe so that you don't really care about the existing steel pipe. Depends on contents and pressure rating etc, but might be the best long term solution

My motto: Learn something new every day

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

 

[JFCmech]

The lesson has been learnt - assume it will leak!
This is a gravity fed raw water steel pipe with Epoxy lining inside.
Design pressure 500kPa.
We are a bit too far down the line to try and change the piping system with a lining although that suggestion is a good one. What lining method did you have in mind?
I was also looking at shotcrete / gunite options, which may or may not work.
The search continues ...

 

[LittleInch]

Kind of depends how long it is, but if its fairly straight and already has a lining, then some sort of PE swage lining is the first port of call. there are many companies offering their wares on this technique. Over a short length shouldn't restrict flow too much or at all but can normally handle a through wall defect of a reasonable size

My thinking was that it would be a fit and forget solution and the sleeve can flood as it does now and if the pipe corrodes then there is no impact. given your pipe isn't leaking now it is something you can plan a shutdown for and do it in good time, rather than in a panic if / when the pipe corrodes and starts leaking.

just an idea maybe as plan B if you can't seal the lining with some sort of spray application.

How long is this thing?

If your pipe is full of water if you do any concrete filling you should be Ok in terms of buoyancy. in any case it hasn't got far to go before it hits the top!

My motto: Learn something new every day

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

 

[JFCmech]

The longest sleeve section is 61m long and is theoretically straight. I'm not sure what lengths can be achieved and what wall thicknesses are used. I will give that option some thought - Thanks.

The buoyancy could likely be sorted out with a few small spacers as you indicated, as the vertical distance is not much.
The force is still quite large even with the pipe filled with water. I get it as about 7.18 kN/m using wet concrete density of 2400kg/m3 and pipe at 187 kg/m.

 

[cvg]

Buoyancy of the steel pipe during casting would be one concern

grouting in "lifts" can solve that problem quite easily without a need for spacers. One or two thin lifts of flowable fill / grout and then fill to the top.

 

[JFCmech]

Thanks cvg
By "lifts" do you mean to cast the infill in layers to just above the centerline of the pipe?

 

[cvg]

yes. the allowable depth of the lift can be calculated so that bouyant force does not exceed the dead weight

 

[JFCmech]

Makes sense - thanks will do the calcs

 

[dicksewerrat]

Have you looked at Hydrophobic grout? It can be pumped a fairly long distance. Call Avanti or DeNeef.

Richard A. Cornelius, P.E.

http://WWW.amlinereast.com

 

[JFCmech]

Thanks, I will look into that.