Application of Terrestrial Laser Scanning in Identifying Deformation in Thin Arch Dams

Dams are relatively simple hydraulic structures that provide vital services to communities in the United States (U.S.). However, many of the dams in the (U.S.) have surpassed their design life. Dams experience changes from external threats that result in deformation of the structure. Traditional surveying techniques provide limited information on deformation in pre-determined areas of a structure, but the collection effort can often be lengthy. In this research, different instruments used for change detection were reviewed and Terrestrial Laser Scanning (TLS), also known as ground-based Light Detection and Ranging (LiDAR), was selected as the most probable method to accurately evaluate deformation in dams. TLS is a remote sensing instrument that uses light to form a pulsed laser to measure ranges to variable targets, and it provides the ability to measure displacement with high accuracy using dense point clouds collected in a short amount of time. Deformation is identified by measuring changes in point clouds generated by TLS. The accuracy of TLS to identify deformation was tested on a thin arch dam at the Big Black Test site in Vicksburg, Mississippi, using the TLS system, Terrestrial Laser Scanner RIEGL VZ-400, for data collection and for registering scan positons between a pre-test condition and a post-test condition. Final data analysis was performed using Microstation TopoDOTTM Wall Monitoring Tool