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?
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?