Underwater Concrete (creating a crib for building a dock) 1

[akek1155]

We are planning to construct a crib for the foundation of a dock in water that is approximately 6' deep. The crib will be approximately 10'(L) x 8'(W) x 6.5' (D). Can anyone provide me with suggestions on the best way to pour concrete underwater once the form has been constructed?
The lake bottom is rock and sand. There is no current to this lake. Is there a specific type of concrete that should be used? Would it be best to reinforce this structure? The lake does freeze and average ice thickness is approx. 8-12" annually.

 

[bimr]

In many areas, you may only repair existing crib dock structures. Due to the environmental impact that cribs have on submerged wetlands and the crushing effect on the ground structure, some regulatory agencies do not allow for the construction of new cribs. The crib dock's main nemesis is ice. This is especially true when this type of dock is left unbubbled during the winter season.

http://www.fhwa.dot.gov/environment/fspubs/02232812/page05.htm

Do you have plans and a permit?

 

[SlideRuleEra]

Can anyone provide me with suggestions on the best way to pour concrete underwater once the form has been constructed?

Here is a somewhat dated article (1962) that describes the traditional way for placing concrete underwater with a what is called a tremie:
ftp://imgs.ebuild.com/woc/C620261.pdf

http://www.SlideRuleEra.net

http://www.VacuumTubeEra.net

 

[chicopee]

One of our CTDOT jobs, we had Tremie pours. The proper concrete mix was important since we were pouring in salt water. We had to clean the river bottom of all sediment and years of industrial accumulated waste and we did this with an excavator and air lift pumps. The tremi pour, once started could not be stopped as the pour had to be completed. The tremie pipe head had to be submerged in the poured concrete all the time and had to be slowly raises to keep up with the pour increasing height.

 

[graybeach]

You can check DOT websites for a tremie concrete spec. One I found on NYSDOT's site was a good starting point for a specification I prepared recently.

You could still have some scour under your crib due to wave action from boat wakes, and the ice could shift things about.