Crosshole Sonic Logging Tubes

[SrVaro]

I am working on a project that is including a deep foundation of drilled caissons. The geotechnical engineer has included a recommendation for cross hole sonic logging tubes to allow for possible non-destructive testing. The only additional information within the report specifies for (4) access pipes within the concrete.

I understand the tubes will be tied to the caisson rebar inside of the cage for the full length of the shaft. The typical diameter is usually 2" (inside). These can be either steel or PVC, and steel is usually recommended for better bonding. The end caps and couplers need to be watertight. The bonding between the concrete and the tube is extremely important.

Has anyone ever used these before and could give any additional insight and/or recommendations?

Thank you.

 

[Ron]

Downhole logging tubes are common. Contact Olson Instruments...they have some good info on the process...

http://www.olsoninstruments.com/

Note...I'm not affiliated in any way with Olson Instruments nor am I recommending its products...just check them for info.

 

[Qshake]

We use these CSL tubes of PVC quite often here in the Midwest and have found no issues with their use in reqards to reduced structural capacity.

I've seen so many CSL reports I'd bust if I read another one!

I will say this, who ever is doing the concrete operations better make sure the drilled shaft is clean, especially at the bottom and that if using a tremie method due to high water table, the seal best be watched closely. We've rejected several shafts on the basis of poor quality concrete at the bottom of the hole, likely due to poor cleaning and also due to poor seal in tremie operations.

One of the biggest problems especially on small diameter shafts is getting the contractor to drill a straight hole down the center of the shaft to pressure grout. This always brings up the question of what to do if the shaft can't be grouted....which the contractor never likes the answer.... And nobody ever likes to go around with the contractor.

Regards,
Qshake

Eng-Tips Forums:Real Solutions for Real Problems Really Quick.

 

[Zambo]

I would use steel tubes 50mm diameter (but check with the instrument supplier). If you use PVC (to save money) check that it will not soften and crush, the concrete inside a pile will get hot.

Crushed PVC tubes (for sonic logging or shaft grouting) are not uncommon.