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Tremie concrete to steel pile bonding strength

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Guest090822

Structural
Jan 18, 2017
260
thread255-380420

In designing a concrete tremie slab for a cofferdam I am coming up with a really thick slab. One of the geotechnical engineers I work with said that I can reduce the thickness by taking advantage of the bond between the tremie concrete and the new piles. He also indicated that some engineers account for the bond acting on the perimeter of the sheet pile wall as well.

I'm comfortable taking advantage of the tremie concrete bonding to the new piles, but have concerns that using the bond of the tremie concrete where it meets the sheet pile since I don't think the sheets are "clean" and a good bond may not develop.

The state of Indiana has guidance for determining the resistance of the bond with the piles. They base it off of a 36 psi bonding strength and if the depth of the tremie is greater than the pile depth "d" (From AISC manual - not the embedment) then only allow you to use "d" times the perimeter of the pile times the 36 psi bond strength. I just don't think it is a good idea to apply the 36 psi bond to the perimeter of the cofferdam sheets as I think that is somewhat unreliable, but at the same time if it seals out the water then a bond must be developed. Maybe use 25% of the strength or something like that?

I should note that the soil has some boulders and there is a dense layer of material not too deep. The boring logs indicate that the H-piles can be driven, but the sheets can't be driven deep enough to prevent seepage/piping.

Any suggestions?
 
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Based on the guidance from "Construction Dewatering" attached file on 01/22/17 I understand it now. If taking advantage of conrete to pile bond I'll use the Indiana DOT guidance. They limit the amount of bond contribution so it adds in a factor of safety. The resulting tremie slab is reasonable. Definitely don't want to go too thin but trying to avoid excessive/overdesign like I've seen in so many areas of engineering over the years.
 
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