pile load test

[chekre]

Hello,

i have a preliminary pile load test where a central pile if being placed between 4 anchor piles. The designer is requesting a maximum load of 2 times the service pile load capacity along with a high strain dynamic test.
Generally, once the pile is subject to the ultimate pile load test, we cant re-use it to make any other test.
However, what about to do the high strain dynamic test on the central pile and once the test is done, then we can begin to do the ultimate load test. i think it is an acceptable approach.

waiting for your comments. thank u

 

[oldestguy]

High strain was never required for the many pile load tests I have run. We applied load through a hydraulic jack. Once the double of service load would not continue to move, we stopped. Not sure how one then puts high strain on without possibly damaging with the extra load needed then.

 

[Ron]

I would not subject a pile to static load testing after a high strain dynamic test.

Use one or the other, but not both.

 

[Okiryu]

Dynamic test may or may not reach ultimate soil failure (plunging failure of the soil), if plunging failure is not reached you may be able to do he static test. I would suggest you contact Garland Likins or somebody at PDI or GRL, they are very responsive and definitively can help you. If you can share with us your findings after your discussions with them, it will be great!!

 

[LRJ]

I agree with Ron that doing a static test after a dynamic test will probably just complicate matters. However, such a situation may be what you consider representative, so it may be worthwhile.

Out of interest, do many practitioners here undertake a number of pile load tests on a frequent basis, i.e. enough to form a database? If so, what normalisation procedures do you adopt?

In my experience normalising by the predicted static capacity provides much clearer trends than normalising by a capacity achieved after a certain period of time, and I've seen other references in the literature to support this approach. I'm interested to know what other people do.

 

[jayrod12]

for us it depends on whether we need an improved geotechnical resistance factor (stupid limit states foundation design). Without load testing the resistance factor is typically 0.4 but can be increased to 0.5 or even 0.6 with proper additional testing.

I miss working stress foundation design.

 

[Okiryu]

I was thinking on this and if you have driven piles, the static test will be conducted after the dynamic test anyway...the OP didn't mention the type of pile and also it will depends on his soil conditions.

I think that a way to make attractive all this type of tests, is for allowing for a reduction in the FOS if you conduct them. At least that is happening in my area. I was talking with PDI and they suggested that 2% of the installed piles is a typical number for dynamic testing. Number of restrike test can be lower depending if you know that your site is prone to set-up or relaxation. While typical FOS may be 3, doing 2% of dynamic testing may allow to decrease it to 2.5.