Coffer Dam Design / Sheet Pile Design Resources

[jamestkirk]

I need to design a small coffer dam in relatively shallow water to allow the removal and replacement of a badly deteriorated bridge pier.

I'm looking for available design resources for the design of the sheet pile coffer dam. (Total water depth is probably about 2 feet, soil is muck, existing pier is built on piles.)

Anyone know of any good resources out there?

Design Programs?

Text books with lots of good examples?

Also, need sheet piles that when drive will be water tight. I am aware that there were or are sheet piles from Belgium I believe that are water tight.

 

[DWHA]

Sheet piles are not water tight. Contractors set pumps in the dam to keep the water down. The sheeting is tight enough that the pumps keep the water down.

I use pilebuck sheet pile program. You can enter the soil data as it is. Enter the active and passive water data. Select you sheet type. And add walers if necessary. It checks the stress in the sheeting, and give you a FS for the soil failure. However, you do need to check basil heave if the soil is "muck" as you say it is. My foundations book by Das has a section on basil heave, I belive most good soils books will have this.

 

[DMcGrath]

There are other options besides sheet piling. One may be a portable coffer dam (

http://www.portadam.com).

I haven't seen it in practice myself, but the concept looks good. A good resource book is "Handbook of Temporary Structures in Construction" by Robert T. Ratay.

 

[SlideRuleEra]

See the documents on this page of my website:

http://www.slideruleera.net/Steel-Piling.html

Don't let the 2 foot depth of water water lull you into thinking that the pressure to be resisted will be minimal. Since you describe the soil as "muck" you will have the combined pressure of water and saturated soil to resist. If the muck has considerable depth (which it probably does), cofferdams under these conditions have to be more robust than in water alone.

http://www.SlideRuleEra.net

http://www.VacuumTubeEra.net

 

[PEinc]

I would not install a PortaDam on muck. It nees to sit of a stable soil or rock base or else the frames will sink in and overturn.

SlideRuleEra is correct. Also, if the new bridge footing has battered piles, the sheet piling may need to be installed farther away from the footing so that the battered piles can be driven without hitting the sheets.

Also consider any fluctuation in the depth of the water during the time the cofferdam will be in service. Will a rain storm cause the cofferdam to be overtopped? You may need to design the cofferdam for a couple extra feet of water.

 

[Prepakt1]

Sheet piles are like any other structure. I am sure that
you can seal them with certain cement products, and several acrylic compounds, not to forget asphalt coatings. Making them totally waterprooof would be very expensive but you can probably reduce the flow to a minimum. There are products that will plug flowing water.

Intrusion Prepakt /marineconcrete.com

 

[chicopee]

Joints between sheet piles can be made water tight by pouring in coal cinder but for 2' of water it may not be worth the extra effort. Just pump the water out.
We also use pilebuck sheet program.

 

[BigH]

Sheet piles, as indicated, are not watertight. There are a number of papers out there that will explain how to compute the interlock seepage - and you will find that they vary a great deal. I discussed this with someone before and they used to use horse manure in the interlocks! I'll find the references and correspondence later and post them. There is the Waterloo sheets - not used them before.

 

[PEinc]

Special measures to seal the interlocks of sheet pipes are expensive and not used very often. Hot-rolled sheets leak less than cold-formed sheets. For normal excavation support projects, such as bridge cofferdams, it is rare to seal the interlocks with anything other than cinders or some other cheap granular material that can be dumped down the outside face of the sheet interlocks. Open pumping is usually sufficient for dewatering the inside of the cofferdam. Special interlock sealing measures, such as Waterloo and Adeka, are sometimes used for soil remediation projects where treatment of any water infiltration is very expensive and must be minimized.

 

[SlideRuleEra]

In water, with muck, just a day or two of routine pumping should draw in enough fine material thru the interlock to cut water flow significantly.

Be warned... the more that foreign matter that either flows into or is put in the interlock to seal it can make extraction of (temporary) sheeting very difficult. Sometimes it is just better to let the interlock leak and endure a lot of pumping if you want to make sure you can recover the sheeting.

http://www.SlideRuleEra.net

http://www.VacuumTubeEra.net

 

[jamestkirk]

Thanks for all the advice. I remember a job back in 94 or 95 that the City of Toronto did down by the lakeshore installing a new truck sewer. They used a hot rolled sheet pile from Belgium (if I remember correctly, I wasn't on the job, but was aware of it) because the joints provided a very good seal against water infiltration.

The old bridge pier is built on timber piles. We know this as we have excavated down beside the old pier and could see the timber piles. (Did this during low tide).

I did not think of the issue of battered piles. That is an excellent point. Thanks very much.

I have NO EXISTING DRAWINGS for this bridge (substructure at least) I is a second generation bridge and was probably built around 1915 or so.

Here is a link to a photo of the existing pier....

http://i24.photobucket.com/albums/c50/jamestiberiuskirk64/P3100013_rs_rs.jpg

http://i24.photobucket.com/albums/c50/jamestiberiuskirk64/DCP_8675.jpg

 

[boo1]

check free guide at:

http://www.nasspa.com/technical.php

 

[Mannyou]

I have a similar requirement for a relatively shallow (6' deep)cofferdam on muck I want to lay shore to shore across a slow flowing creek. (summer time flow will be non-existant). I was considering building an earth embankment lined with geotextile. Another option I am considering is a portable cofferdam called Aqua-Dam. Has anyone used the aqua-dam or earth embankment?

 

[kslee1000]

Since you don't have information on the existing foundation, proceed with cautious. The existing piles could be in such bad shape, then what is your plan to deal with it? You may wound up needing a huge deep hole either filled with water, or under high head and mucky material.

 

[DRC1]

The US steel Manual in Sliderule Era's website is the best reference. The pile just above the eight is significantly battered. Looking at the picture, I wonder if you could just excavate and pump if all you are going down 2 feet. If pumping the soils are a concern, you could drive upbraced perimeter sheeting outside the excavation to reduce inflow. Anothe option is to exvavate an additional 3-4 feet in the wet, pour it up with a tremie seal, then pump the excavation.
Just a few thoughts.

 

[StephenA]

Adeka supplies a bentonite seal for sheetpile clutches

http://www.adeka.com/Sheet_Pile.html

I have not used it but I would expect it to keep the clutches unclogged for easy extraction.

Stephen Argles
Land & Marine

http://www.landandmarine.com

 

[jamestkirk]

We took cores of the existing concrete pier. The concrete is very poor. It was cast in 1930 and it's done. End of story there. The existing pier has failed simply because the existing concrete has suffered freeze thaw damage and most likely, the existing concrete was low quality at best - even for 1930.

I do not suspect that the existing timber piles have failed in any way

We have also done 2 boreholes around the pier to determine soil characteristics for coffer dam design.

We are in the process of coring through the pier to determine if there is a timber matt under the existing concrete pier.

The plan right now is to:

1. Temporarily join the two spans together

2. Shore the bridge superstrucutre for dead load

3. Drive sheet piles to form a coffer dam

4. Remove the existing pier completely

5. Install steel pony bents to allow the train to pass

6. Form and pour new pile cap and new pier

7. Unbolt spans.

 

[kslee1000]

Have you tried USCOE website? It have quite a few manuals for free download. Also, they are highly experienced in water way works.

 

[dik]

The 1961, National Building Code, "Handbook of Pressure Coefficients for Wind Loads", indicates that for tall square buildings, there is an increase in Cpe of -1.5 from about halfway up the building to the roof. for the lower half it is -0.8. I don't know if this was applicable in Montreal. It was common that various provinces had their own building codes.

 

[Qshake]

USACorps of Engineers has an engineering manual on cofferdams that is well worth the read. So does the AISC or AISI which, I believe, is what slideruleera has on his site.

Other information can be gained from Robert Ratay's Handbook of Temporary Construction and some years ago, Hartman Engineering did a seminar on Cofferdam design and so there may be several publications out there from that. Hartman is a respected Cofferdam design firm.

Regards,
Qshake

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