Proceedings of DFI-India 2019: 9th Conference on Deep Foundation Technologies for Infrastructure Development in India, (DFI)
Low-Strain Pile Integrity Testing and Analysis
Mahesh Hingorani, P.E.
Non-destructive testing of piles has gained fair acceptance for various purposes e.g., quality control/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 question on pile conditions. Equally, its incorrect use can cause controversies, delays, and/or create adverse reputation for the technology. Integrity issues for cast-in-situ piles have resulted in a serious need for non-destructive test inspection methods to detect the extent and location of serious flaws and prevent failures under service conditions. Integrity inspection performed after installation is often the most reasonable alternative available to assess the pile quality. A most commonly used post construction integrity test is the low-strain pile integrity test. In this type of integrity testing, a low strain dynamic impulse is given to the pile top by a hand held hammer and the velocity of the pile top is monitored using an accelerometer. The low strain impulse will generate a low stress wave that propagates through the pile and reflect at places where there are changes in the properties of concrete, cross-sectional area of the pile or stiffness of the soil surrounding the pile. Such reflections are detected by the accelerometer at the pile top and the Time vs. Velocity plot recorded by the accelerometer is used to identify any defects in the pile shaft. There are two main methods of data analysis associated with the pile integrity test viz. the Pulse Echo Method (PEM) and the Transient Dynamic Response (TDR) method. This paper presents the testing, analysis and interpretation of pile integrity test data by Pulse Echo Method from various project sites relating the different construction methods in Indian soil conditions.
|article #3289; publication #1059 (India2019)|