Wave-based depth evaluation of pile bents in a rail viaduct

In this paper, an improved ultra-seismic inspection was introduced to evaluate the length of a pile bent in a rail viaduct in central Taiwan. The concept of improved ultra-seismic inspection is based on the reciprocal theorem and frequency analysis. Using the reciprocity concept provides investigators with significant operational feasibility in the field. The constant velocity one-dimensional wave theory is used to analyze the frequency spectrum. The frequency-based analysis indicates a good length prediction on the pile bent, i.e., a -3.6% error to the nominal length. The resonance characteristics of waves are independent upon impact positions, but instead, are highly dependent on the mechanical properties and geometric characterization of the concrete pile bent. When using the improved ultra-seismic inspection on integrity testing of deep foundations, one can flexibly collaborate the advantages in operation and analysis approach on length inspection.