Field monitoring and change detection of municipal infrastructure using cost-effective techniques

ABSTRACT: Smaller municipalities in Canada face challenges in proactively monitoring and repairing aging infrastructure despite the increasing costs of repairing and maintaining infrastructure over the past two decades. Water-retaining structures constructed and maintained by Canadian municipalities are directly impacted by the soil-structure interactions under freeze-thaw cycles and seasonal ice pressure at different scales; especially under the direct influence of extreme weather events due to climate change. Soils that experience freezing and thawing may have different properties depending on the thermal state, which can result in frost heave and thaw settlement (or weakening) that damage the retaining structure. In this pilot study, we implemented a novel cost-effective field monitoring program for a water/ice-retaining wall for a critical infrastructure in a small municipality in AB. The wall displacement was monitored with a combination of GPS, routine total-station surveying, and terrestrial laser scanning (TLS). The survey was conducted on benchmarks and target points for two years. The TLS data was used to create a 3D model (point cloud), and change detection was performed using the M3C2 algorithm. Results showed the critical portion of the retaining structure moved about 20 mm/year, with evident seasonal and cyclic deformation behavior due to the interplay between ice-load (winter) and soil-weakening (autumn). The results support the use of routine surveying and remote sensing as cost-effective monitoring techniques for identify temporal and spatial changes as well as failure modes. The techniques used in this study serve as the foundation for the development of an early-warning system and asset management plan for municipal infrastructures with limited resources.