Inference from Pile Integrity Test

[1967pradyot]

In one of our projects we have 1000mm dia bore cast-in-situ pile having a length of around 28.0m, resting in general on silty sand stratum. We have conducted some pile integrity tests and observed that some results are not usual. Following are our observations:

1) In some cases toe reflection is not distinct or not visible at all.
a) What are the possible reasons for such case?
b) What is the acceptance criterion in this case?
c) Any remedial measures, if this is due to some defects?

2) In some piles necking is noticed. The maximum necking is in the range of 15% at 9.0m depth below pile top.
a) In general practice, % of necking is in term of diameter or c/s?
b) What is the acceptance criterion in case of necking?
c) Any codal provision is followed elsewhere in US and European countries?
d) Any remedial measures can be undertaken?

 

[VAD]

1967praydot:

What testing did you do - small strain integrity tests. I presume. I had some tests done in 1987 on 1.2 m diamenter bored piles 20 m deep. Tests were okay, toe indicated.

There is an FHWA publication that discusses necking etc in bored piles and integrity etc. I can't remember the date off hand but withinh the last 6 years. This should give yo some answers as these necked piles were tested. I will make a search and let you know later if you cannot find same.

For the 1987 tests I was concerned about pile integrity wrt to method of installation which was done by a French system -Ben... system. Forgot the name. However, bentonite slurry and a chopping bit was used to advance the hole. The slurry was displeced by the concrete. I was concerned about loss in skin frictional resistance and inclusion of slurry in concrete.

Regards

 

[1967pradyot]

The test was low strain integrity test.
I am not getting any standard reliable literatures/ references. Do you have any?