FOR TUNNELS DURING CONSTRUCTION
LRRT uses digital photogrammetry to create three-dimensional models of the exposed ground, of the shotcrete surface, and of the final lining surface. To illustrate, the figures below show a 3-D model of an entire tunnel round: face, walls, and crown back 9 m, 30 ft from the face.
This is a series of detailed pictures of the model of the left wall.
LRRT synchronizes with the contractor, and data acquisition never affects the construction schedule. The data acquisition at the tunnel heading takes about 15 minutes (if a 3-D model of the entire round must be made: face, walls, and crown back 9 m, 30 ft from the face), or 2 minutes (if a 3-D model only of the face must be made). These three-dimensional models textured with high resolution pictures may be used to (click on each item for details):
- Carry out a detailed fracture mapping and analysis on the tunnel face, walls, and crown at each round.
- Reconstruct the entire rock mass exposed at the tunnel walls and crown, even if covered with shotcrete.
- Calculate the shotcrete thickness at each point of the sprayed tunnel surface.
- Determine the waviness of the primary lining onto which a waterproofing membrane is to be applied.
- Determine the over- and under-excavation along the tunnel profile at any stationing, and over- and under-excavation volume over any stationing interval.
- Obtain a three-dimensional model of the primary lining surface to be used as a reference for the determination (at any point) of the final lining thickness.
- Obtain the three-dimensional geo-referenced as-built model of the final lining textured with high resolution pictures; a baseline for future inspections (new tunnels).
- Determine the intrados profile of shotcrete or cast-in-place concrete at discrete stationing (e.g., 100, 200 m spacing).