Understanding the environment:

The client had a major collapse at a fault crossing a 1940’s headrace tunnel. This tunnel supplied water to a hydroelectric power station and the collapse restricted the flow of water and power generation capacity. Rocks, clay material and wooden bracing had flowed downstream for over 100m from the failure. Understanding the depth and height of the failure was important for designing a by-pass tunnel and understanding the failure mechanism for potential interaction with the surface. Access to the failure area was only available via a surge shaft into the tunnel as directly above the failure area is in a National Park.

Going for a hand-held LiDAR walk:

MineLiDAR completed a hand-held scan of the existing 1940’s development up to the failure. We then customised a skid with a pole to be able to safely get the unit inside of the failure void as the opening was too small to obtain drone access.

What we captured:

  • Tunnel profile from the surge shaft to debris flow clearly showing the blasting profile from the original 1940’s development along the debris flow showing block sizes and allow estimation of the volume of failure into the failure where the use of LiDAR intensity clearly identified a dyke within the fault zone and fault offsets through the dyke
  • Scan shows the failure surface and rill of failed material allowing failure dimensions to be measured and failure volume calculated to for bypass tunnel design engineers
  • Size of the failure was measured approximately 18m high by 17m wide by 12m across
  • Scan could have not been performed but other techniques without removal of a significant volume of debris flow material. This enabled the by-pass design to be completed with confidence by understanding the shape and volume of the void

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