Someone has experience, calculation

[Metalero]

Someone has experience, calculation memories, handbooks, blueprints, etc. about the design and construction of caissons for the repair of pipes under shallow water?

 

[racookpe1978]

Er, what depth?
What diameter pipeline?
What operating fluid, pressure, temperature?
What operation do you intend doing on the pipeline?
How long a section must be exposed?
Do you "know exactly" where the repair ??? is to be made, or must you expose the pipeline and begin measuring thickness/inspecting metal?
Do you require crane access, or from a barge or a pier or a the shore?
How long will it be exposed?
When a problem happens - What do you plan on doing?
What weather (lake rises? Tide moves? Hurricane blows through? Spring floods come?) is expected while it is exposed?
What bottom condition? Mud, rock, sand, water lilies, weeds, barnacles and zebra mussels?

 

[Metalero]

Er, what depth? 15ft max depth
What diameter pipeline? Between 6” and 16” diameter.
What operating fluid, pressure, temperature? Oil and gas, variable conditions.
What operation do you intend doing on the pipeline? Mainly non destructive inspection.
How long a section must be exposed? 10ft max.
Do you "know exactly" where the repair ??? is to be made, or must you expose the pipeline and begin measuring thickness/inspecting metal? I know exactly.
Do you require crane access, or from a barge or a pier or a the shore? Crane access and from a barge.
How long will it be exposed? A few hours until 1 or 2 days.
When a problem happens - What do you plan on doing? Mmmm.
What weather (lake rises? Tide moves? Stationary water in lakes, swamp and marsh.
Hurricane blows through? Spring floods come?) is expected while it is exposed? No
What bottom condition? Mud, rock, sand, water lilies, weeds, barnacles and zebra mussels? Mud and sand mainly.

 

[LittleInch]

So what sort of size "caisson" are you looking at?

If you're in the 5-6m x 5-6m mark, you might be best off with a box type arrangement with two U shaped cutouts in two ends, drop it in under self weight, pump it out and then start digging the inside out. Or alternatively a circular design, but that won't like the cut outs.

The issue with any Caisson like this is bracing and re-inforecment to stop the bloody thing collapsing and also blow out of the floor when you have men down there.

Your main alternative is to interlocking sheet pile the thing, taking care not to sever your pipe in the process. This is actually really quite difficult.

Then as you pump out and dig out the centre core you need to stop and fit stongbacks, cross re-inforcement etc and this makes the digging out bit really hard.

Then sealing the gap between the steel and the pipe gets really hard as you try to prevent liquid mud from being forced thought the gap under pressure from the soil above.
Or are you thinking of a pressurized caisson?

It might be easier in the end to drain the swamp ( No Donald Jokes please).

Seems to be a lot of effort and cash and safety issues to repair a pipe.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[Metalero]

So what sort of size "caisson" are you looking at? Yes, I'm in the 5-6m x 5-6m mark.

I was thinking in a rectangular 6x5m clamshell type caisson, to install while it is hanging from a crane buggy. Using wire ropes and pulleys to close it around the pipe, of course the same wires to open after finished the work (ideas?) .

The issue with any Caisson like this is bracing and re-inforecment to stop the bloody thing collapsing and also blow out of the floor when you have men down there. YES, i'm looking for calculation method for de structrue and reinformcement. i think a metal mesh made with aluminum square tubular for the structure and plate for the shell will be ok (i need a durable thing).

Then sealing the gap between the steel and the pipe gets really hard as you try to prevent liquid mud from being forced thought the gap under pressure from the soil above.
Or are you thinking of a pressurized caisson? NO, i'm not thinking in pressurized caisson. just water in the surrounding, and caisson open at the top.

It might be easier in the end to drain the swamp ( No Donald Jokes please). No, ecological issues.

Seems to be a lot of effort and cash and safety issues to repair a pipe. More than one pipe.

 

[SlideRuleEra]

MarriolaV - What you are describing is a "braced cofferdam" in 15' of open water (not soil). It is made from driven steel sheet piling, with internal bracing ("wales" and struts). A depth of 15' is not particularly deep, but is more than enough to kill a few workers if not designed / constructed properly. Hydrostatic pressure on the wall is high, "aluminum tubing and metal mesh" are a waste of time and money. Soil properties are important. Knowing that the soil is "mud and sand" is enough to indicate potentially serious problems, more soil information is needed. Since the pipe runs completely through and out of the cofferdam at both ends, the design / construction of those ends is tricky.

You will find some information on the principles needed, but there are no books, or software, to tell you how to design / construct a "real" cofferdam, each one is different. Consider it to be "specialty" design work, by others.

I found a brief description, with photos, of a project on the web that seems to be similar to what you need to do: Link

http://www.SlideRuleEra.net

 

[Metalero]

SlideRuleEra this is what I want:

 

[LittleInch]

SRE - nice link and good words.

Marions, note the "not been done before" bit of that that link. They sealed the end by adding a second ring of pulled and by the sound of it pumping grout between them.

I forgot to ask how many million dollars you have spare....

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[LittleInch]

So use that contractor.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[Metalero]

littleinch
not useful commentaries about de $ and use that contractor
How much $ do you think i need for construct the caisson, just the caisson?

 

[LittleInch]

Anything with marine works costs a lot more than you might imagine.

My first order estimate is min $500000.

This is serious civil engineering stuff and the calculations depend hugely on soil conditions.

But you've said that is what you want so I don't understand why you don't approach that contractor?

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[SlideRuleEra]

MarriolaV - You asked for calculations, here are two of the most basic:

1) Say that the dewatered structure you want is 18' (5.5m) square and 15' deep.
For fresh water, total hydrostatic force (inward) around the perimeter of the dewatered structure is:
0.5 (15 ft)² (62.4 lb/ft³) (18 ft/side) (4 sides) = 505 kips (2250 kilonewtons)

2) Buoyancy (uplift) force from displaced water = (18 ft)² (15 ft) (62.4 lb/ft³) = 303 kips (1350 kilonewtons)

Now, go design the structure to safely resist those forces... and they are "real" forces acting constantly on the structure, not statistical probabilities that "may" or "may not" happen.

LittleInch - Thank you.

http://www.SlideRuleEra.net

 

[chicopee]

Notice the battered interlocking sheets in the picture of the cofferdam provided by SlideruleEra. Not shown in the picture are the joints of the interlocking sheets being watertight by introducing a coal like granular substance and dewatering pump(s) may be required. Also for cranes on barges, you will need to develop new load charts for cranes mounted on barges as OSHA in their safety regulations has guidelines for such operation. Also must maintain OSHA clearance guidelines for overhead high tension electrical lines if such exposure exist.

 

[FormerAIS]

An out of the box thought: Underwater welding is probably a good bit cheaper, depending on the scope of repair.

Quality is not an act, it is a habit - Aristotle