Running for more than 1,000 km along picturesque coastline, California's Highway 1 is easy prey for many of the natural hazards plaguing the region, including landslides. The California Department of Transportation (Caltrans) is currently building a 1.2 km-long twin tunnel to bypass one of the most landslide-prone stretches of the highway, the Devil's Slide, to help ensure drivers' safe passage.
Roadworkers tunnelling through the Devil's Slide are using laser scanning software developed by the National Science Foundation (NSF) to safely plan the tunnel route. The technology, named the geotechnical Visualisation Tool (gVT), can be used to analyse the rock formation and convert the data into a 3-D image. The gVT was developed by researchers at Virginia Tech in Blacksburg in one of the NSF's Information Technology Research Initiative (ITR) projects.
The detailed 3-D view of the rock exposed in the excavation adds a new tool for improving both safety and construction progress.
The software 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 five millimetres, provides information that the software programme packages into enormous visualizations incorporating up to 10 metres 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.
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. The software can be used remotely, and at any time. 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. Laser scanning is revolutionary for underground mapping because it allows direct collection of digital data in three dimensions at high resolution.
After a careful analysis of the scanned data, the engineers can take manual follow-up measurements to confirm their results. These 3-D visualizations enhance geological documentation and an engineer's ability to make decisions.
In use as part of a suite of private industry engineering tools and software critical to the tunnelling beneath Devil's Slide, gVT is the product of a two-year collaboration between civil engineers and computer scientists. The Devil's Slide application is the first use of gVT in a true construction environment. http://www.tunnelintelligence.com/casestudies-in-detail-12.html
Visit www.nsf.gov/awardsearch/showAward.do?AwardNumber=0324889 27/08.
