Use of Automated Geotechnical Instrumentation to Monitor Post-disaster Stability of a Highway Embankment Failure

When highway embankment failures occur, the owner must assess site conditions to determine whether the highway may remain operational in the time leading up to permanent repairs. The topic of this study pertains to a significant embankment failure that occurred in June 2023 in Edmundston NB; this failure occurred at the Two-Mile Brook crossing, where the hydraulic asset consists of a 3.5 m by 2.9 m concrete arch culvert beneath 15.2 m of fill. After heavy rains in June 2023, restrictions on the culvert flow capacity led to rising headwaters causing a significant embankment failure. The failure destroyed municipal infrastructure and impacted a neighboring residential property. The highway was closed immediately for public safety, and design of a replacement structure was initiated immediately. To provide continued operation of the highway in the time leading up to permanent repairs, a 60 m-long single-lane temporary modular bridge was installed near-grade on timber abutments, and an automated monitoring system was installed for public safety. A 25 m-long ShapeArray was installed horizontally beneath the modular bridge and near the critical abutment to monitor vertical deformation; should deformations in excess of the threshold value be recorded, interested parties would be notified immediately by “push-notification” sent automatically using a cloud-based data-hosting service. During the 56-day monitoring period described herein, no alerts were triggered; the data suggests that the instrumented bridge abutment settled by approximately 20 mm and that the embankment settled by approximately 2–4 mm. The innovative risk-informed decision-making process pursued in this disaster response was shown to yield an acceptable outcome.