Evaluation of Bridge Abutments and Bounded Wall Type Structures with Ultraseismic Waveform Tomography

Abstract

A new ultraseismic waveform tomography technique for a bounded medium is presented for evaluation of concrete bridge abutments, or wall piers, and the supporting soil and rock underneath them. Ultraseismic wave fields are measured on top of abutments and inverted by a full waveform inversion (FWI) technique. The technique includes forward modeling to simulate wave propagation for estimated waveform data and a cross-adjoint inversion to match estimated to measured data for the extraction of material properties (S- and P-wave velocities, or VS and VP) of the tested medium. For the forward modeling, because wavelengths of the intended ultraseismic waves (200–1,200 Hz) in concrete are several times that of the thickness of a bridge abutment, the abutment is considered a thin plate. A finite-difference solution of two-dimensional (2D) elastic wave equations in a thin plate was used for the forward simulation. The presented FWI technique was applied to two synthetic data sets generated from realistic bridge abutments supported directly by soil-and-rock or pile foundations. The results revealed that the waveform analysis was able to characterize accurately both the VS and VP profiles of abutments and the supporting soil-and-rock or piles underneath them. Abutment depths, embedded low-velocity anomalies, and individual pile tops were clearly identified.