Help with PIT test intepretation

[jefe2004]

Hi, long time haven't post in here,

Right now i'm having a problem of making a decision whether a CSP pile is acceptable or not.

I had a report of a PIT (Pile Intergrity Test) of 13 driven CSP piles condition, the report contains the PIT Graphs and also the summary of BTA value.

From the BTA value summary, the lowest value is 85%, now i have found several journals about this BTA value which states that :
100 % (BTA Value) = Undamaged
80 ~ 99 % (BTA Value) = Slight damaged
60 ~ 79 % (BTA Value) = Damage
Below 60 % (BTA Value) = Broken

now if the BTA value is below 60% i would easily reject the piles, or even below 80% i could suggest a load test to determine whether the bearing capacity is acceptable or not.

But the slight damaged really confuses me, since there are 9 of the value are 95%, two are 85%, and one 100% (i attached the summary), it seems that this wouldn't be a problem so the piles are acceptable, but does anyone have a suggestion? can this BTA value can be used as a reference to accept the piles or not? since it only states the pile condition without determining what action should be done..

Thanks a lot before,

Sincerely

Jeff

 

[Panars]

The beta value is a measure of the change in impedance of the pile, and the impedance is a combination of the elastic modulus and the cross section area. If there is a reduction in either, it will result in a reduced beta value. Therefore, you need to consider the project specific details before rejecting the pile. A common cause of a decreased beta value is a reduction in diameter. You might get this when drilling from a soft soil into a stiff one. In this situation, the reduced beta value is expected and not a cause for concern. But if I was drilling from a stiff soil into a soft one and saw a reduced beta value, I would be concerned because it probably indicates the hole started to collapse. Also note that the reduced beta value indicates a possible reduction in area, but the PIT test cannot tell you what the actual diameter is. So if the nominal diameter is 40, but the actual diameter is 50 at the top and then sharply reduces to 40 at some depth, the pile would still be acceptable, but the PIT results will show a reduced beta value.

You can find papers explaining the PIT test and interpretation of results on the manufacturer's website (

http://www.pile.com)

One paper you might want to look at is the following:

http://pile.com/Reference/TransportationREsearchRecord/FormalizedProcedureforQualityAssesmetn.pdf