Battered Pile Load Test

[dmoler]

If a load test is performed on a battered pile, should it be performed with the loading along the pile axis, applied on the top vertically, or other? Would a fixed head condition load test be different from a free head condition load test? I might actually have to do this in the next few months, and am having trouble finding info on it.

 

[GeoPaveTraffic]

To me it would depend on what the purpose of the load test is as to how the pile should be loaded. If the purpose is to satisfy the requirement that all piles over 40 tons be tested, then I would load it along the axis.

If you load along the axis then fixed/free head should not make a difference.

If you loaded the pile vertically, the head condition would have a lot of impact on the performance of the pile since the load transfer down the pile would be different. Also, I'm not sure how you would set up the test to ensure safety. You would have to have something setting opposite of the pile to take the unbalanced portion of the applied load. The safetest might be to install three battered piles like tripod legs. If the fixed head condition was most interested, then you could pour a cap and load all three at once. Of course the amount of load required could be quite high.

 

[dmoler]

I appreciate the response. Right now, looks like a structural eng. not from here is treading on my turf. He took the phrase "test every pile type" and ran with it.

The vertical pile recommendation I gave is a 150 ton pile installed to 50 feet in sand and then 10 feet into cemented sand.

The three pile head with a pile cap would require a very high load, but it can be done. Load distribution along three piles (using strain gauges) loaded at the same pile cap might be difficult to evaluate.

Your three battered pile idea gave me another idea. That is, install a heavy duty pile as the central pile to apply the load on, and install the reaction piles battered. Then load the central "dummy" pile and monitor the battered piles. If they are ok in tension, then they will be ok in compression. That way several piles could be tested at once. A problem is the connecting frame, but that is the pile contractor responsibility. That has to be modified from the standard.

Well, hopefully next week at the meeting I will convince those present to drop this requirement. Maybe once the price from those bidding comes in it will.

 

[VAD]

I would go with your suggestion in your last paragraph. Just my curiosity, what is the SE concern about testing all pile types apart from your feeling that he ran with your idea.

Looking at it another way this may be good research which is often not a bad idea if it can be afforded. I would discuss further with SE. Maybe he has this in mind.

Regards

 

[dmoler]

I was not very clear earlier, but the state's building code requires pile load tests for each type and size of pile. This is interperted locally to mean augercast type versus driven type, concrete vs. steel H, ect. The SE is from another state, read the florida building code to comply with his structural elements, and seems to think that a battered pile is a different 'type'. I think the SE is in Wisconsin, and the buildings there are not designed to withstand hurricane force winds, so he may not do this that often.

A battered pile load test would be fun to do, really.

 

[DRC1]

Tension tests on battered piles are okay and are fequently done for minipiles. Compression tests really should not be done on batter piles for a number of reasons, but to answer your question, I would think the test should be prefomed axially.I have been asked to do this and have gotten the engineer to agree to testing a plumb pile instead. Problems with compression batter pile testing are: assume you are testing to 50 tons, the reaction frame should be approximately 125 tons. Very hard to provide that reaction at a batter. Now you have the jack. In a plumb load test, the weight vector is concentric with the test load vector. Now it is at an angle, trying to move the jack out of line. Once the jack slips, the data from the test is ruined. (not to mention that I would not want to be too close at that moment) Then there is the problem of bearing plates and load plates - how do you hold everything while you pu a seating load?, instumentation, etc. You will end up spending at least 25% more for this test and the data may not tell you anything in the end.
Tell the SE that auger cast vs pipe is the pile type, and that plumb vs.battered is not a different pile type, but a different orientation. Doing a plumb test will give you all the data you need to evaluate the battered piles.
I would tell him if he stays out of your piles, you won't offer your comments on his connection details.

 

[SlideRuleEra]

I concur with the others that a load test on a battered pile is not needed. If necessary, another "trick" you could use to convince the SE to forget about this is to have the contractor give you two prices - one for a load test on a plumb pile, the other for a similar (axial) test on a battered pile. If the price differential what I expect, the SE should "come to his senses" quickly.

http://www.SlideRuleEra.net

 

[dmoler]

Ok, I convinced the structural people that this is not needed and standard compression, tension, and lateral load tests will be sufficient. Since it is a 40 story building, in the end I suggested an o-cell test would be the only real way to do this safely, and to spend that type of money on this the developer 'saw the light'. Many thanks for the responses.