Pile Length Estimation by Measurements of Waves from Multiple Sources

Abstract

The length of pre-existing piles is an essential parameter for building renovation or tunneling under a building. Some conventional methods to identify pile lengths are the parallel seismic test, side echo test and sonic echo test. A parallel seismic test requires a borehole to be built parallel to the pile for testing. The side echo test and sonic echo test are performed by knocking on the side or head of a pile to generate elastic waves which travel in the pile’s body and reflect at the pile tip. The accuracy of side echo test may be enhanced by increasing the number of receivers or seismic sources. One of the tests in this category is the Ultra Seismic method (Jalinoos and Olson, 1996). A technique similar to the Ultra Seismic method is investigated in this study by installing a receiver on a pile’s side and using it to detect waves generated from 10 knocking positions on the pile’s body. Based on test results on several driven piles in Bangkok area, the most suitable receiver-sources layout and signal processing method are determined. The differences between estimated and actual pile lengths in this study are between 2.96% and 6.29%.