When to conduct pile load test

[ndjiji]

Hi,

After pile driven into soil, when is the appropriate time to conduct the pile load test (maintained load test & pda test)

1. Is the resting period for skin friction and end bearing pile is different? I read that some suggesting straight away, some said 3 days, 2 weeks and even 1 month.

2. Will different type of soil affect the time for testing?

3. What about the bored pile?

Thank you

 

[oldestguy]

I'd do a Google search.

Here is one link. Note the text from which it comes.

http://www.pilebuck.com/foundation-...atic-pile-load-testing-pile-dynamic-analysis/

http://www.pilebuck.com/foundation-manual-caltrans/

 

[ATSE]

General rule: for silts and clays, the longer the wait, the higher the static capacities (full-scale load test). For mostly sandy profiles, 1 to 2 days.
Practically, the sooner the better, so pile production can start.
For auger cast piles, we never waited more than 1 week.
If the contractor is pushing for a shorter wait time between installation and test, the test results will be conservative (everyone wins unless the test results are lower than expected).

 

[geotechguy1]

For PDA tests on large project we usually do some tests at the end of initial drive and some after a week or two to determine the amount of setup (or relaxation).

I have seen piles with fairly substantial relaxation so you should be cautious about assuming that the longer you wait the higher the capacity will be as this is not always true.

 

[L0k]

My experience was minimum one week to allow the soil thixotropy, releasing the excess pore water pressure and soil dilatation.
The bored pile will be depending on the concrete strength to hold the maximum load.

 

[ATSE]

geotechguy1:
In what soil profiles do you see substantial relaxation beyond 7 days?
Is this demonstrated by full scale pile load tests, or just PDA, or both?

 

[geotechguy1]

Driving piles in very dense silty sand. The mechanism is supposedly negative pore water pressure generated during driving. Demonstrated by PDA tests in some cases, in others simple observation - the pile reaches practical refusal at the maximum allowable energy, but is able to be re-driven a day later.