Currently we are driving a 5" x 2" x 3/8" wall tubing in the ground, standard tubing does not have the wall strength we need. Is there a material that is closer to a T-1 spec (ASTM A572) or something comparable?
My customer keeps bending the tubing as they drive in the ground. They started welding together T-1 plate to give them a tube, however it keeps bending and splitting at the welds. My customer asked me if there was an alternative tubing material to give them a higher yield and tensile. So far I have not found anything. I personally have not watched them driving the tubing into the ground so I can only give you what they have told me. Thanks for any help.
CSA G40.21 hollow sections have a yield strength of 50 ksi, similar to ASTM A572. They are the standard grade of HSS in Canada. I don't think increasing the yield is going to help very much. Perhaps increasing thickness and sharpening the end would help.
Are they driving the tubes open-ended into the ground? If so, the soil is rising inside the tube. Maybe a sharp steel tip is needed to prevent the soil from entering the tube.
After the tubing is driven into the ground at the desired depth, which can be up to 125', it is extracted leaving a "wick" material in the ground. Basically the process brings moisture to the surface so they can develop the area.
Wow! That's pretty deep (125'). I assumed it was much shallower than that. I would have thought that an HSS 5x2x3/8 would drift off plumb as it is being driven to such a depth.
It seems like a very specialized process. I can imagine all kinds of potential problems. You really ought to make a point of watching the driving of a couple of these tubes.
Do they drive a short length until it is just above grade, then weld another length above that and continue, welding a new length each time the previous section is at grade level? And when they pull the tube, how do they prevent the wick material from being extracted?
Is it possible to re-use the HSS after it has been extracted? Or would it be possible if the wall did not buckle?
It would help to know how and where the tubes are failing. Photographs of the failed tubes could be helpful. If they are buckling about the weak axis above grade during driving, the tube is too slender in one direction. A better choice may be HSS4x4x3/8.
Depending on the depth they typically weld the tube together and it is left vertically in the air from hole to hole contained within the mast and/or lead section.
The wick material has a "shoe" at the end that is left in the hole and prevents the wick from being drawn up with the mandrell (tubing).
We have explored in the past changing the mandrell size but many of the jobs are spec'd out and they cannot exceed a certain surface inch. The wick itself is 4" wide.
In a perfect soil condition they use the mandrell until it is either worn out or the mandrell bends so that they can no longer pull it through the drive mechanism.
This may be a stupid question, but, here goes...................... Why do you not use the strongest steel available, and it can be used over and over.
bb
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Take it easy, bb. >"HEAR & you FORGET<>SEE & you REMEMBER<>DO & you UNDERSTAND"<=$=|O|=$=>"Common Sense is Genius dressed in its Working Clothes"<>[Ralph Waldo Emerson]
I have called several mills in the states and unless they purchase 150,000 lbs they won't pour for them. However I realize there may be something I am missing altogether. Any suggestions?
Could not the use of something like coredrilling be used ? The core is withdrawn, the wick is then inserted and the drill rod can be taken away to be reused ? At least you could reuse the difficult part, by drilling rather than hammering ?
Tubing
Re: tubing
