Re-Use of Wood Piles

[JedClampett]

I'm doing some work at a Wastewater Treatment Plant. The portion of the structure I need to replace is supported by 50 year old wood piles. Groundwater seems be either at the top of the wood piles or a few feet below. Questions:
[ol 1.]
[li][/li]
[/ol]Is there any chance the piles can be reused?
[ol 2.]
[li][/li]
[/ol]If yes, how should I have them tested? I looked at the Davisson Method, mostly because he was my professor, but is that the best for testing in place piles?
[ol 3.]
[li][/li]
[/ol]Due to all of the uncertainties involved, I'd probably have them bid new piles and have a deduct if they the existing piles test adequately. Is that dangerous? Am I giving the contractor too much room to play games?

 

[SlideRuleEra]

Jed - Even if the piles are treated (if so, probably with CCA or creosote), I would not trust them to support new construction. Just about the worst service for a timber piling is to be partially submerged. Totally dry or completely and continuously submerged is much better - even though totally submerged has been questioned recently. Also, assuming the existing structure has not been demolished yet, the existing piles (where embedded in existing concrete) are subject to damage during demolition.

If the existing piles are spaced far enough apart, perhaps they can be abandoned in place. Replacements driven between the existing piles.

You could do load tests, but the cost could easily exceed the value of replacements. Another possibility would be to have a pile hammer strike a few blows on each existing pile (if they are accessible). Again, the cost issue comes into play. I would write them off.

http://www.SlideRuleEra.net

http://www.VacuumTubeEra.net

 

[msquared48]

Only ran into that sitiation once about 33 years ago. We were using 8: diameter pipe pile and ran into interference from an 18" diameter DF pile from the turn of the last century. Rather than removing or redesigning the foundation, we decided to load test it. This was in an area of Seattle filled during the Denny Regrade of the early 20th century. High water table...

Nevertheless, the wood pile did not budge, but the short 8" Pipe pile test section did at the head of the pile. Classic wavy failure mode that I had the contractor cut off the hard of the pile. I still have it today...

Needless to say, that pile was better than those we were intsalling...

Mike McCann, PE, SE (WA)

 

[dicksewerrat]

Is the old structure settling? is it heavier or lighter than the new one. Are the footprints similar? If not settling, heavier and similar footprint consider your pile deduct process. You need a pile hammer to set new ones, cut a few old ones and hit them a few times.

Richard A. Cornelius, P.E.

http://WWW.amlinereast.com

 

[JedClampett]

No settling, the new structure weighs about the same as the new.
Thanks for the information.

 

[Panars]

You can do PDA testing on timber piles. I've done something similar when reusing existing steel piles. We have the contractor remove the footing, test a representative number of piles, and then make the decision as to how many new piles to add. It definitely makes construction sequencing more challenging, but it can be done.

 

[BigH]

The parliament buildings in Sweden were built, if I remember correctly, over a thousand years ago on wood piles. If you are not going to subject the pile to "environmental disturbance" it should be okay to reuse - but judgment is needed. I know of a location in British Columbia where a wood pile was "exposed" to see how it behaved over a 20 year (or so) period and it was in great shape - then they backfilled the pile and came back a year later and it had severely deteriorated (what I meant by environmental disturbance.)