NON-DESTRUCTIVE TESTING OF BORED PILES USING THE LOW STRAIN PILE INTEGRITY METHOD

摘要

Non-destructive testing of piles has gained increased acceptance for various purposes such as Quality Control and Quality Assurance, verification of existing conditions, and quantification of dimensions. The correct use of this technique can greatly simplify and expedite investigation, and be economical in addressing concerns or questions on pile conditions. Equally, its incorrect use can cause controversies, delays or create adverse reputation for the technology. A defect present in pile will severely reduce the structural load carrying capacity of the pile. Therefore, post construction test to verify the integrity of piles are extremely important. A most commonly used post construction integrity test is a low strain Pile Integrity Test commonly referred as PIT. In this type of integrity test a low strain dynamic impulse is given to the pile top by hand held hammer and the velocity of pile top is monitored using accelerometer. The low strain impulse generates a low strain wave that propagates through the pile and reflected from various places where there is change in properties of concrete, cross-section area of pile or stiffness of soil surrounding the pile. Such defects are recorded based on reflections detected by accelerometer. The present paper covers the interpretation of pile integrity test conducted on different deep bored piles in project executed in Delhi. This paper also presents the signal characteristics and their interpretations from low strain pile integrity test performed on mainly bored piles varying in length, size, construction method and founded soil strata. In this paper, the locations of accelerometer on the pile head which has a major influence on the test signals also has been discussed.