Pile integrity test
A pile integrity test (also known as low strain dynamic test, sonic echo test, and low strain integrity test) is one of the methods for assessing the condition of piles or shafts. It is cost effective and not very time consuming.
The test is based on wave propagation theory. The name "low strain dynamic test" stems from the fact that when a light impact is applied to a pile it produces a low strain. The impact produces a compression wave that travels down the pile at a constant wave speed (similarly to what happens in high strain dynamic testing). Changes in cross sectional area - such as a reduction in diameter - or material - such as a void in concrete - produce wave reflections.
This procedure is performed with a hand held hammer to generate an impact, an accelerometer or geophone placed on top of the pile to be tested to measure the response to the hammer impact, and a data acquisition and interpretation electronic instrument.
The test works well in concrete or timber foundations that are not excessively slender. Usually the method is applied to recently constructed piles that are not yet connected to a structure. However, this method is also used to test the integrity and to determine the length of piles embedded in structures. Widely used in Australia now on existing structures.
This method is covered under ASTM D5882-00 - Standard Test Method for Low Strain Integrity Testing of Piles.
References
Rausche, F., Likins, G. E., Hussein, M.H., May, 1988. Pile Integrity By Low And High Strain Impacts. Third International Conference on the Application of Stress-Wave Theory to Piles: Ottawa, Canada; 44-55
Hussein, M.H., Garlanger, J., June, 1992. Damage Detection for Concrete Piles Using a Simple Nondestructive Method. Proceedings of the First International Conference on Fracture Mechanics of Concrete Structures: Breckenridge, CO
Likins, G. E., Rausche, F., Miner, R., Hussein, M.H., October, 1993. Verification of Deep Foundations by NDT Methods. ASCE Annual Meeting: Washington, D.C.
Massoudi, N., Teferra, W., April, 2004. Non-Destructive Testing of Piles Using the Low Strain Integrity Method. Proceedings of the Fifth International Conference on Case Histories in Geotechnical Engineering: New York, NY. (CD-ROM)
Ankesh Kumar Gupta (Electronics Engineer),October 2010,Rajasthan, India.
70% failures of structures occur due to foundation failure http://en.wikipedia.org/wiki/Integrity_Testing
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