3D Imaging Project

Hydro Electric Dam Spillway Inspection

Limestone Baffle block with diver copy

For the first time since they opened the gates, hydro engineers can ‘see’ the condition of their baffle blocks — sitting 60 ft deep, in high flow-water.

Maintenance Objective: Detailed inspection to determine the amount of concrete-loss in the bottom sill (concrete pad) around the baffle blocks — large engineered blocks of concrete that disperse the energy of the water coming out of the dam.

Engineering and Environmental Concerns: Concrete loss, due to erosion, could devastate the whole downstream river basin.

Imaging: Processing and Reporting: An Acoustic Solution

  • Point Cloud data was captured using the Kongsberg 1171 Scanning Sonar.
  • The data points in this project were about an inch (2.54cm) apart (0.5% of range).
  • All 7 baffle blocks showed various signs of damage.
  • Point Cloud data was meshed to create a 3D image of the holes and the sides of the blocks. This mesh was given a ‘skin’ and animated for a turntable view of each block and the surrounding bed.
  • The 90 second animation made it easy for engineers and decision makers without an engineering background to ‘see’ the condition of the asset.
  • The attending linear and volume measurements of the damage are accurate enough for reliable budgeting and planning of remedial action.

The Dive: With a depth of 60’, divers would be limited to 50min at maximum depth per day to complete the inspection.

Low visibility and strong flow made it too difficult for divers using tape measure to get accurate 3D measurements.

Each baffle block with a particular setting took approximately two hours to scan – 2 scans per, 1 hour per scan

The project took a total of 10 days doing trials, 2D scans, and the data processing, image-rendering and measurement-gathering took 3 days.

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