Depth Evaluation of Submerged Pile Bents

Developing an appropriate and efficient inspection pattern for an unknown bridge substructure is a critical issue for bridge engineers, contractors, and bridge agencies. This paper introduces a two-phase near-surface inspection strategy to determine the foundation depth of fully submerged pile bents of an existing bridge. Electrical resistivity tomography inspection provided the overall interface between bridge substructure and surrounding soft soils. Ultraseismic inspection provided more information to determine the depth of the substructure. Time-lapse waveform image analysis and frequency analysis of ultraseismic inspection results also displayed varying degrees of reliability for estimating the pile bent length, which was positively confirmed with the bridge design charts. The entire set of investigations demonstrated strong conclusiveness in determining the foundation depths when the results from these two testing methods were corroborated with appropriate analysis modes.