Pile Load Test Requirements 2

[Lion06]

I'm working on a relatively small project that is going to require micropiles for no other reason than there is a real lack of real estate to place spread footings.

We are trying to minimize the cost associated with this, and my boss believes that there is a pile load capacity threshold in the code, below which load tests do not need to be performed.

I've read thoroughly through chapter 17, but can't find anything that gives a pile capacity that will eliminate the need for load testing.

Does anyone know if this exists and where it is located?

 

[Ron]

Nope...it is what it is....if you want to know the capacity, no matter how small or large, load test it.

On another note...SEIT...I know you're in PA...I have a friend who is a partner in a firm in Pittsburgh. You seem to be a talented guy....if he can't use you, I'm sure he knows someone who can.

 

[Lion06]

Ron-
Thanks for the compliment, it is much appreciated. Unfortunately, I'm clear on the other side of the state. Our office is in a suburb of Philadelphia, and I live pretty far south (very close to Delaware).

I have a clarification question on the pile load testing requirements. When I read through chapter 17 before, it was really looking for an out to not have to do testing by using some low, threshold capacity. I re-read the pile part of chapter 17 this morning with fresh eyes (and not looking for one specific item), and it's not clear to me if all piles need to be tested. In Table 1704.8, task 2 says, "Determine capacities of test piles and conduct additional load tests, as required". What constitutes a test pile? It's not listed in the definitions. Is a test pile a single (or multiple) pile(s) of the bunch to be load tested? Is it a pile that is cast simply for testing and is not intended to be used?

I was told that ALL piles need to be load tested, but that's not clear to me from reading through the text of chapter 17.

Additionally, (I know it's not in the special inspections' chapter, but..) 1808.2.8.1 says that "The allowable axial and lateral loads on piers or piles shall be determined by an approved formula, load tests or method of analysis". That seems to muddy the water even more. That makes it seem like you can use formulas OR load tests.

 

[Ron]

A test pile is just that. Usually the first or first several piles driven or placed on a project. Generally the test pile is load tested and compared to driving criteria, soil stratification and other parameters. From that, assuming no significant change in placement parameters, the test pile serves as the exemplar or indicator for the other piles. No need to load test every pile.

 

[Lion06]

Thanks a bunch!

 

[PEinc]

StructuralEIT, call me on Monday to discuss this stuff.

http://www.PeirceEngineering.com

 

[Qshake]

SEIT - Are the mirco pile suggested as part of the geotech recommendation? Are other solutions available?

Having worked with micropile (with rock anchors) I know the testing can be tedious not to mention costly.

What about pre-boring and setting H-pile followed by grouting to a specified level?

Regards,
Qshake

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

 

[DRC1]

Many local codes have limits on pile tests. We do not need to load testunless loads exceed 40 tons. If you do need to tes, you could put 3 prouction piles in lie at least 4 ft on center. That way the conctractor could install the three piles, anchor off a beam to the outside piles and load test the center pile.

 

[Lion06]

Qshake=
It's not a geotech recommendation at this point. We're in schematics only and there is no geotech on board yet. Spread footings are possible, but they would need to be so large in plan that it would require the capping and re-routing of several underground utilities. I'll look into the H-pile idea. I'm assuming that pre-boring and grouting means driving won't be necessary. Can this type of pile take uplift? It's not a large value, but we will need the piles to take 6k of uplift each (service loads).

DRC1-
That's kind of what I was looking for at the start of this thread. Do you have a local code or does your jurisdiction reference the IBC?

 

[Zambo]

I realise this isn'texactly what you're looking for, but interesting reading all the same.

http://www.fps.org.uk/fps/piletesting/loadtestinghandbook.pdf

 

[Qshake]

Correct, on the zero driving with prebore and grouting.

I was under the impression you have restraints that don't allow driving - hence the drilled in micro-pile.

You can definitely resist uplift with the H-pile so long as grouting is used.

It's just an alternate. Micro pile are expensive and so is testing.

Regards,
Qshake

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

 

[BAretired]

What about drilled concrete piles, either straight shaft or belled? They are very common in my area. The soil here is predominantly glacial till.

BA

 

[PEinc]

Micropile testing is not always expensive. Frequently, a tension test is performed for a fraction of the cost of a compression test. Also, why would a tension H-Pile need to be bored and grouted (unless rock is too shallow)?

http://www.PeirceEngineering.com

 

[Qshake]

PEinc - when the OP noted micro-pile I figured there was a reason that driving was out of the question. As you know there are several reasons including spatial relation to existing structures, vibration effects on existing structures during driving, lack of head room preventing leads but not yet requiring micro-pile and so on.

I wasn't sure why the OP mentioned micropile rather than some other method....typically for us to use micropile there is a specific reason such as noted above or a high load situation where nesting pile is undertaken.

Perhaps your experience shows micropile to be more economical including the testing. My experience does not.

Regards,
Qshake

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

 

[PEinc]

Qshake,
Someone else mentioned drilling and grouting an H-Pile for tension capacity. My thought was, if rock is not shallow, a driven H-Pile may be sufficient to resist the tension. If someone wants to drill and grout H-Piles, micropiles would probably be cheaper. Micropiles would not be cheaper than driven H-Piles if the H-piles can be driven deep enough. Also, not all micropiles are compression tested. Often, micropiles are tension tested similar to tieback or tiedown anchors. A tension test is cheaper than a compression test.

http://www.PeirceEngineering.com

 

[Teguci]

The FHWA has several manuals on piles and drilled piers. In particular, they have two volumes dedicated to the design of driven piles. As I recall, with driven piles you can perform several types of calculations based on field data due to the driving of the piles. Associated with this field data was an assigned safety factor. For static load testing, the safety factor was 2 and everything else was 3 or higher. This may be what your boss is thinking about. However, I don't think it applies for IBC.

Check out FHWA website. They have quite a few free downloads. Unfortunately, the driven pile manuals have been removed from the download since they updated them in 06

 

[Lion06]

PE-

Thanks a ton for the info and the conversation. It is very much appreciated.

 

[BigH]

Can I question as to what the soil conditions are? Are you interested in compression or tension loadings?
I used to work in the Philly area for a short time. The company did a lot of work in Atlantic City. Certainly, in my view, if the project is "small", you could install some additional piles to reduce the needed capacity to a "small" number for the cost of a pile load test. We didn't do a lot of load testing on piling jobs when I was in Canada either; perhaps it was just that we had very good handle on many previous projects in the areas. Bigger jobs - like my bridge jobs in India required a test pile (pre construction) and then confirmation on 1 or 2 in 50 piles installed.
I like the idea of the bored pile - if the sides will remain open without caving. If I remember correctly, expanded base (Franki) piles were quite popular in the Philly area.

 

[VAD]

StructuralEIT

Not sure of your soil conditions. helical piles can be used as well. The helical screw pile contractor will carryout a load test as well and provide the factored geotechnical resistance at the Ultimate Limit State as well as the bearing pressure at the Serviceability Limit State. The presumption here is that you are dealing with a building structure. terminology may be different in your jurisdiction. The load settlement relationship will allow you to determine the requisite ULS and SLS values for the tolerable settlement in the case of the SLS.

Not sure that I would bother with a load test unless alarge amount of piles are contemplated. Try using the conventional static analysis. This more than often provides suitable answers.

 

[slickdeals]

FHWA Information on Driven Piles is available for download here.

http://www.fhwa.dot.gov/engineering/geotech/library_arc.cfm?pub_number=42