Cross Hole Sonic Log Testing of Drilled Shafts 1

[STrctPono]

Do other firms/agencies perform cross hole sonic log testing of drilled shafts for bridges?

If so, do you perform the test on every shaft or a percentage of the shafts?

The way that I am used to writing the drilled shaft specs is typically in a collaborative effort with the geotechnical engineer. The state standard specs is ok but there are some additional requirements we like to incorporate via special provisions.

Normally, the Geotechnical Engineer is the one that actually performs the testing, not the SE. What is your guys' standard of practice in your state?

 

[BridgeSmith]

As far as I know, we've only done it on one bridge so far, and it was specified to be completed for all the shafts. The contract made the contractor responsible for the installation of the tubes, etc., and the testing; presumably the contractor hired a consultant to perform the testing.

Rod Smith, P.E., The artist formerly known as HotRod10

 

[bridgebuster]

ON NYSDOT projects, typically each shaft is tested.

 

[STrctPono]

Thanks for the input. Our firm also specifies CSL testing for every shaft on every bridge.

 

[BridgeEI]

Our DOT does every sixth shaft, but has a minimum they will do per bridge. Same with retaining walls.

I thought the feds were requiring it on each bridge, especially when I was first introduced to it.

 

[minorchord2000]

All shafts...of all the bridges I have designed here in Tucson, each and every shaft has cross sonic logging and gamma-gamma required testing. However, in the local design community there is continued heated discussion about where the testing tubes (PVC) are to be located. I prefer that they are INSIDE the rebar cage of the drilled shafts rather than outside. If outside, the simple act of lifting and maneuvering the rebar cage for insertion into the drilled excavation may cause the PVC tubes to get bumped and break. Since the tubes are required to be filled with water during the integrity testing, breaking the tubes may not be always visible during construction. The ensuing testing would be useless.

 

[STrctPono]

minorchord2000,

Thank you for adding this bit! I actually was not familiar with gamma-gamma testing until you mentioned it. From what I read, it sounds like it can provide improved results over CSL testing as it has the ability to measure density even on a portion of the cover concrete...... but one thing that worries me is the fact that they are using radioactive material to perform the test. I can only imagine that this would be a no-go on many of my jobs as we would be dealing near a stream or the ocean. My first and only steel bridge that I had designed was a plate girder bridge 100 ft above a stream that flowed right into the ocean. We had the Contractor doing some field welding on the girders after they were set on the piers. I called around to some local testing labs to get some radiographic testing done on the welds. The guy made me feel like an idiot when he told me "There was no way in hell he was going to be putting a radioactive device over the stream and risk dropping it and contaminating the whole area!" I had never thought of that before. We ended up going with phased array ultrasonic testing instead.

Leaking CSL tubes is a good point. I've seen several jobs where they break the tubes when lifting the cage. Guys having to scramble to weld the tube back together before the concrete truck comes. We also require that they fill the access tubes with water completely prior to concreting to ensure that they hold water and are not leaking. I have been told that the presence of the water in the tubes can help with the heat generated from hydration and minimizes/eliminates the debonding that can occur between the concrete and access tube. Not sure how much merit that argument has....

 

[Milliontown]

The California Department of Transportation performs GGL or CSL on all piles that are poured in the wet (slurry displacement method).

In their case, State geotechs are the ones who do the testing and analysis, through the foundation testing branch.

Chapters six and nine of the foundation manual may be beneficial to you. Foundation Manual