Extraction of drilled pile casings without a hammer.

[malaycobra]

I have a client who has asked us to write a procedure for "dry" pulling casings with a crane (i.e. no extraction hammer will be used)

His client and the crane manufacturer have their doubts, but I believe it's possible to proceduralize the process and perform the maneuver safely.

Do anyone have any experience of this process or developed any way to quantify the force needed to pull the casing?

The casing is 84" diameter and 60'-0" long.

http://www.hliconsulting.com

Specialists in Heavy-Lift and Transport Planning

 

[BigHarvey]

Your client is very funny but he should concentrate on being a client if he is not a piling expert !

Is there any particular reason why he doesn't want a hammer to be used ( Railway company ?) or is it just because he says so ?

If the pile has been installed with a vibrohammer then it is likely to be pulled out with a vibratory hammer or a casing oscillator. If it has been installed with a drop hammer, it will be very hard ( = impossible in my mind ) to pull it out.

As a heavy lift specialist, I guess you know what will happen to the boom of your crane if something fails on the line during this "dry" pull !

 

[Zambo]

84" is about 2.1m diameter so not a small pile. The force is the friction between the pile concrete internally and the soil externally. I can't give you figures for this but for an 18m long casing the force wil be considerable - and that is why a vibro extractor would normally be used.

I suppose you could try fitting a pvc sleave liner to the inside of the casing, but still I think the force required would be large and if the pile casing did start to move could be difficult to control.

Could you jack instead using large steel plates on the ground to jack against and then take the load by the crane when it becomes free. You would need jacks with a long stroke, but even then I think the operation would just take too long.

 

[malaycobra]

Thanks for your replies.

We suggested the jacking idea to our client, and he will do that if he cannot get permission to "dry pull" This is merely a contingency in case they lose their hammer. It is not meant to be a common practice.

He says they routinely pull casings like this, and the only issue is getting started. Actually pulling the casing against un-compacted earth and wet concrete is simply a function of the crane, and can be monitored through the load indicator in the crane. The procedure calls for the LMI to be verified prior to lifting.

I wrote him a procedure that requires the weight of the casing to be doubled, and that the crane shall not exceed 85% of its rated capacity.

If the damn thing still won't move, they are required to stop, fix the hammer and use it or go and get jacks.

http://www.hliconsulting.com

Specialists in Heavy-Lift and Transport Planning

 

[Zambo]

We don't know the soil conditions, but it seems unlikely that the soil at -18m can be considered "uncompacted". I also think that just doubling the weight of the casing will not adequately assess the force needed to extract.

I think your casing will weigh around 9T, perhaps if you have a breakdown you will end up leaving the casing in.

 

[malaycobra]

The casing weighs 40,000 Lbs

The 275t crane is actually rated for 165,000 Lbs

I certainly will not allow them to pull that much, as a sudden release would have unpredictable consequences.

I really just trying to put a conservative, safe procedure together for something that appears to happen in the field quite frequently.

It seems I'm not going to get any professional support, so I may decline to give my opinion.

http://www.hliconsulting.com

Specialists in Heavy-Lift and Transport Planning

 

[BigHarvey]

Three years ago we have successfully extracted 2m and 2.2m diameter dolphins which had been driven with a D55 Delmag diesel hammer in sands, using a PTC 200 HD vibrohammer ( after emptying the materials inside the pile with an air lift )

 

[Zambo]

malaycobra,

that is a much bigger crane than I typically see on a piling site. So I had a look on the internet to see if I could find anything useful. I think I did including a sample calculation, but still they don't recommend a straight pull without rotation or vibration.

http://www.fps.org.uk/fps/safety/FPSExtractionFinalJun2010.pdf

 

[malaycobra]

Zambo, you are hereby awarded a black-belt in Google-Fu!

I pride myself on my search abilities, but I missed that one.

Thanks a lot!

http://www.hliconsulting.com

Specialists in Heavy-Lift and Transport Planning

 

[aeoliantexan]

I have heard about pulling piles with a extractor, a frame or stiff leg that sits on the ground and has a multipart block and tackle to multiply the pull of the crane. Properly guyed, this should be safer than a heavy direct pull with the crane.

 

[BigHarvey]

aeoliantaxan, this is called an oscillator ( louvoyeuse in french ) it twists and jack up or down a steel tube.