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Laser-aided software for tunnel construction

If you ever have cruised on California's Highway 1, you know it offers spectacular views of the Pacific ocean. But several areas of this road are potentially dangerous because they can be affected by landslides. This is why the U.S. National Science Foundation (NSF) is helping the California Department of Transportation (Caltrans) to build a kilometer-long tunnel under Devil's Slide located South of San Francisco. The project engineers will be helped by a software dubbed gVT (for 'geotechnical Visualization Tool') developed at Virginia Tech. This tool, based on ultra-precise laser scans, will improve both safety and construction progress. But read more...
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Written by Roland Piquepaille, Inactive on

If you ever have cruised on California's Highway 1, you know it offers spectacular views of the Pacific ocean. But several areas of this road are potentially dangerous because they can be affected by landslides. This is why the U.S. National Science Foundation (NSF) is helping the California Department of Transportation (Caltrans) to build a kilometer-long tunnel under Devil's Slide located South of San Francisco. The project engineers will be helped by a software dubbed gVT (for 'geotechnical Visualization Tool') developed at Virginia Tech. This tool, based on ultra-precise laser scans, will improve both safety and construction progress. But read more...

Devil's Slide projected tunnel

Before going further, you can see above a map of the Caltrans's Devil's Slide Project. "The project calls for construction of two tunnels beneath San Pedro Mountain, each 30-feet wide and 4,200-feet long. At the northern end, a 1,000-feet bridge will span the valley at Shamrock Ranch. A re-alignment of Route 1 at the southern end will provide safe transition into and out of the tunnel. [...] The bypassed section of Route 1, together with 70 acres of State right of way, will be available for public access and recreational use following the planned tunnel opening in 2011." (Credit: Caltrans) From the above link, you'll have access to many photos and videos.

Devil's Slide tunnel roof

Now, let's go back to the NSF news release about the gVT software. You can see on the left a "close-up image of the tunnel roof showing a gVT measurement location. The arrow is a vector perpendicular to a surface that marks a discontinuity between rock layers. The orientation of the arrow in space gives the azimuth and slope of the surface." Credit: Jeramy Decker, Kiewit Corp.) Here is a link to a slightly larger version.

Here are some additional details from NSF. "Developed as part of a National Science Foundation Information Technology Research Initiative (ITR) project, the software, called "geotechnical Visualization Tool" (gVT), converts imagery of millions of rock-surface points--collected at a safe distance by a laser scanner--into an easily manipulated web of information. The data become a permanent digital record of the newly exposed material. The scan data, at a resolution of 5 millimeters, provides information that the software program packages into enormous visualizations incorporating up to 10 meters of excavated tunnel. Engineers then use gVT to spot potential hazards to both the tunnel and the construction crews before weaknesses in the rock have a chance to trigger a collapse."

Even the engineers were surprised by the precision offered by the software. "The information is so detailed that researchers can observe where rock layers are separating and how fractures are oriented. Researchers can even recreate sections of rock after they have fallen, providing a critical asset for determining where and how to safely drill. Because the data is portable, engineers can conduct all of the analyses from their home base at any time, far from the danger of the tunnel. 'Geologic maps have traditionally been made using manual measurements taken by geologists directly on the rock,' said Joseph Dove, the lead developer of gVT at Virginia Tech."

Now, let's move to the NSF-funded AMADEUS project (Adaptive and Real-Time Geologic Mapping, Analysis and Design of Underground Space). Here is a short introduction. "Underground excavations are used for a wide variety of civilian and military purposes, including mining, road & railway tunnels, and caverns. Permanent storage of the current U.S. stockpile of nuclear wastes will utilize large underground excavations. With increasing world population, demand for underground construction is expected to accelerate in the future. From an Information Technology (IT) viewpoint, design and construction of underground facilities are just emerging from the dark ages. Rock failure in underground mines and tunnel construction continue to claim lives, and the tunneling industry is still beset by frequent failures." Please check the above link for more details.

Finally, if you're really interested by this technology, you can read "Building, Updating and Verifying Fracture Models in Real Time for Hard Rock Tunneling," the dissertation submitted by one of the researchers, Jeramy Bruyn Decker, to obtain his degree of Doctor of Philosophy in Civil Engineering (Blacksburg, Virginia, April 20, 2007, PDF format, 161 pages, 3.39 MB). Decker now works for Kiewit Pacific Co., a subsidiary of Kiewit Corporation which is the contractor 'building' the Devil's Slide tunnel.

Sources: National Science Foundation news release, June 30, 2008; and various websites

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