Nondestructive length estimation of an embedded pile through combined analysis of transverse and longitudinal waves

Abstract

This paper presents an important modification of the recently developed nondestructive testing method for estimating embedded depth of pile foundations – EDAR – effective dispersion analysis of reflections. The original EDAR method is based on processing dispersive bending wave signals in the frequency-effective wavenumber domain, thus eliminating the need to perform time-domain peak picking that is difficult due to over-distortion of reflected signals. While EDAR was successful in laboratory settings, preliminary field validation resulted in significant errors. After careful examination of the wave physics, it is discovered that both longitudinal and transverse waves need to be carefully included in EDAR analysis. Specifically, it is shown that the initial arrival is dominated by transverse waves, while the reflections are dominated by longitudinal waves, owing to significant attenuation of transverse waves due to compacted soil around the pile. This observation led to a refined EDAR methodology and accurate estimation of embedded pile depth in field settings.