The Challenge
During its operating life, the Brooks Aqueduct has suffered from the effects of a series of design flaws. For example, the poor durability of the shell concrete, due to its high water-cement ratio and lack of air entrainment, has resulted in cracks that have transferred the tensile forces required to support the load to the steel bars used in the superstructure.
To what extent have the effects of time, combined with minimal maintenance and repair, compromised the structural integrity of the Brooks Aqueduct?
How effective have the interventions made by Alberta Culture and Tourism been in stabilizing and restoring the Brooks Aqueduct?
Methods
A multi-scale, multi-sensor campaign began during the summer of 2017 to acquire a baseline three-dimensional (3D) dataset of the Brooks Aqueduct. Two complementary geomatics technologies were used:
- A Leica HDS 6100 Terrestrial laser scanner was used to capture the east and west open ends of the aqueduct. These ends were created when a section of the aqueduct was removed to make way for Range Road 142 during the early 1980’s. Paddle targets were placed at various locations around the structure, as well as mounted to the structure itself. The paddle targets were used for registration of the data sets.
- DJI Phantom 4 and Inspire 1 drones were flown over the entire aqueduct using Pix4D software to capture overlapping images of the structure. These images were processed in batches using Pix4D Desktop software. Once processed, each section was then merged to a single point cloud of the aqueduct.
- A Matrice 600 Unmanned Aerial Vehicle (UAV) with Phoenix Aerial Scout Velodyne VLP-16 Puck Lite Lidar Camera is an airborne lidar system. Controlled by an operator on the ground, the system continuously collects color camera imagery and laser scanner data according to a pre-programmed flight plan. An attempt was made to fly the UAV/Lidar system over the aqueduct during the fall of 2017. Unfortunately, technical problems with the camera prevented any data capture.
- A Riegl ZMX450 mobile mapping system with ladybug 5 panoramic camera (mounted on a truck) was used in place of the UAV/Lidar system to capture three of the aqueduct’s four sides (the north site is largely impassible). APPLANIX POSPac version 8.1 used to process lidar data.
Monitoring
The terrestrial lidar data captured by the HDS 6100 and Riegl ZMX450 will be used as baseline information for identifying and tracking damage to the aqueduct in the years to come. The east and west ends of the aqueduct will be scanned annually and compared with earlier scans to search for new damage, as well a structural changes.
A Building Information Model (BIM) for the Brooks Aqueduct has been created for recording and tracking damage to the structure. The BIM consists of a Cloud Database and Mobile App. An operator using the App can record and georeference any damage they identify to a virtual schematic of the structure. This information is then uploaded to the Cloud Database. The Brooks Aqueduct BIM will allow Alberta Culture operatives to accurately record new damage, as well as search the database for previously reported damage.
