Pile Integrity Test - Doubts - Can some one clarify them
My most of the questions are related to interpretation of Pile Integrity test results/ reflctogram. I am using PET instrument
1) What is the effect of reinforcement on Pile Integrity Test. Are we required to bend the bars bwfore conducting integrity test?
2) How the results are affected due to different pile construction methods?
3) How the pile top / head shall be prepared? - Shall we grind it to make it flat and smooth?
4) What is the meaning of pile head not clean?
5) What is the pulse width, How to decide pulse width and what does it indicate?
6) How to identify the effects of different soils on pile reflectogram
7) How to identify distinct changes in soil layer?
8) What is FFT – frequency domain analysis of time domain signal?
9) What is the meaning in sharp reflections in FFT curve - does it give rise to 'zigzag' Reflectogram?
10) Which soil has High / low friction?
11) What is case drilling?
12) What is indicated by the width ( wide or sharp reflection ) of the first reflection
Your list of questions is such that you appear to never have used this device before. That can lead to significant trouble down the road.. My advice is hire someone who is experienced with the device and learn from them as the job goes along. I liken this to driving a car. No way should you get behind the wheel and drive without first taking lessons under an experienced person. Before going too far now make sure your professional liability insurance is paid up.
Agree with OG.
PIT is specialized testing and its interpretation should only be done by someone who is experienced in interpreting the data.
The manufacturers of some of the PET equipment state that you need no experience, special education or expertise. Yes, anyone can operate the test equipment....it is simple and consists of a hammer to induce a low frequency wave into the pile and a receiving transducer to capture the reflected wave. It's purpose is to check the integrity of the pile. It does not give you any information on the soil. Interpretation of the wave form is done by proprietary software (black box!)(FFT stands for Fast Fourier Transform, which is a mathematical method of analyzing the spectrum of the vibrations produced when the pile is struck with a hammer for the test). Interpretation of the software data is where the experience of the interpreter comes in.
Yes, I too agree with you, But every new person requires to learn from scratch and can learn only if the technical experts clarify the doubts and give a specific technical answers. As there is on one nearby to my location who is using either PET or any other pile integrity testing instrument, I have no option but to depend upon the outside experts.
In case your search didn't come up with an ASTM test method (USA), search for this since it gives some hints as well as standards to follow. Following accepted standard methods is always a good way to do testing no matter your location.
It has been a long time since I dealt with PIT, but I'll try to answer what I can recall....
1) What is the effect of reinforcement on Pile Integrity Test. Are we required to bend the bars bwfore conducting integrity test? The test is done on the concrete, not the rebar. Rebar has no effect on the test.
2) How the results are affected due to different pile construction methods?The higher the concrete strength, the faster the wave will travel through it; however, the wave gets reflected from a discontinuity without regard to the strength of the concrete
3) How the pile top / head shall be prepared? - Shall we grind it to make it flat and smooth?Make it as smooth as practicable; however, the transducer is coupled to the top of the pile with a highly viscous liquid
4) What is the meaning of pile head not clean?The head of the pile has laitance or other material on it that prevents proper coupling of the transducer
5) What is the pulse width, How to decide pulse width and what does it indicate?Don't recall
6) How to identify the effects of different soils on pile reflectogramThe soil has no effect on the reflection
7) How to identify distinct changes in soil layer? Not done with this test method
8) What is FFT – frequency domain analysis of time domain signal?FFT is Fast Fourier Transform, a mathematical process for analyzing a vibration spectrum
9) What is the meaning in sharp reflections in FFT curve - does it give rise to 'zigzag' Reflectogram? Typically higher strength concrete will exhibit sharper reflections
10) Which soil has High / low friction? PIT will not tell you this.
11) What is case drilling? Drilling and using a casing to keep the hole open
12) What is indicated by the width ( wide or sharp reflection ) of the first reflection Possible influence of top of pile surface effect
OK now that Ron as nicely answered your questions, let's then ask what you are going to do about some questions that may come up, such as "what should I do about a good sized peak reflection say half way to pile tip?", "what criteria is needed to reject acceptance of the pile?", "How do I evaluate pile suitability by some other method". Much depends on the job, such as are there many piles so a few can be ignored, or do I install another one, etc. You still need experienced help, such as at least having them comment on a print out of the display. How about load testing? Are you equipped if necessary?
