Identifying small defects in cast-in-place piles using low strain integrity testing
- Vol52(2), April
- New York Springer 2022
- 270-279p.
The high requirements for the reliability of pile foundations define the need for robust non-destructive quality control procedures. The low strain test is a widespread, quick, and relatively inexpensive method for pile integrity testing. The method is based on the analysis of elastic waves which are induced and registered on the pile head surface. To study the resolution of the test method, an experimental site of 10 cast-in-place piles with pre-fabricated defects was initiated. The field testing with a low-frequency input force pulse did not permit the identification of the flaws. To explore further, the numerical simulations using the finite element method were performed. Numerical simulation results show that the resolution of the test method increases for shorter input pulses which can be generated by light hammers with a hard head material. However, the input pulses with remarkably high-frequency content can be the reason for the signal anomalies, unrelated to pile integrity. The simulations show that the defect detectability depends on its location. The flaws near the pile top can go undetected or result in unexpected anomalies of low strain test data. To ensure the proper data collection and analysis, a set of few hammers of different weights and head materials should be used during the field testing.