Evaluation of Unknown Foundations Using Surface-Based Full Waveform Tomography

Abstract

An application of two-dimensional (2D) time-domain full waveform tomography is presented to evaluate existing foundations using surface-based seismic wave fields. The full waveform inversion (FWI) technique is based on a finite-difference solution of 2D elastic wave equations and the Gauss–Newton inversion method. Both compression-wave (P-wave) and shear-wave (S-wave) velocities are inverted independently and simultaneously to increase the credibility of characterized profiles. The FWI technique was applied on both synthetic and real experimental data sets. Inverted results of synthetic data revealed that individual embedded foundation elements (piles) and soil between piles were distinguished. For real experimental data, seismic surface wave fields were measured next to two drilled shafts with a 1.2-m diameter and a 15-m length and then inverted by the FWI technique. The waveform analysis successfully profiled embedded shaft elements and subsurface soil stratigraphy, and shaft lengths of 15 m were also predicted.