ERT Feasibility Study to Assess Unknown Bridge Foundation Depth

Abstract

There are many historical bridges around the world whose crucial information regarding their foundations is unknown. Such information is essential for an accurate safety assessment regarding scour hazard. Current methods for identification of bridge foundation characteristics are typically expensive, potentially disruptive, and limited in their applications. Thus, the numerical feasibility study described in this paper assessed whether a nondestructive geophysical technique such as electrical resistivity tomography (ERT) could be used for this purpose. Synthetic scenarios were created accounting for different combinations of material resistivity. Two standard measurement sequences (dipole–dipole and Schlumberger) and an optimized one (“Compare R” method) were tested. Results showed that the depth of the bridge foundation was roughly well represented in all cases. However, the optimized sequence revealed slightly better results. Although this small improvement observed did not significantly affect the results of the simplified scenarios assessed by this study, it could be decisive for more complex scenarios. These findings demonstrated that ERT can be used to identify the depth of bridge foundations in an inexpensive, rapid, and nonintrusive way, allowing for more accurate assessment of bridge safety and scour risk ratings.