In 2010 a massive rockslide closed Interstate I-70 in Glenwood Canyon, 160 miles West of Denver. In many places the canyon is too narrow for a standard road to be built so the road was built above the Colorado River with the east and westbound lanes serving as the road boundaries.
The problem with the road is one specific area just west of Hanging Lake Tunnel; this area is more prone to rockslides more than other areas. The area has been a problem for Colorado Department of Transportation (CDOT) and the Federal Highway Department, so they contacted me during the last road closure roughly a year ago.
The Federal Government proposed monitoring this section of road using a radar system, due to the very small amounts of movement the IBIS-M radar system was used. The radar system was looking for less than 1mm movements and alarms would be set off if it detected more than 2mm to 5mm movements. This would hopefully allow time to close the highway and scale the rocks in question to remove them without any damage to cars on the road. Laser scanners can’t compete with these types of movements but we can provide assistance in this application.
On March 2nd 2011 we conducted a test to prove the concept. For this exercise a test spot on the rim of the adjacent canyon wall was used. Accessing the rim was a difficult task by foot, so a helicopter transported us to the top of the canyon. Using our I-Site scanner, we provided a 3-D model of the slide area. The IBIS-M radar system was setup to map the slide area for movements and also show the coverage area the radar was capable of.
The radar system is great for detecting movements, but detecting exact locations of the movement is difficult with the system. I used the I-Site scanner to provide a DTM (Digital Terrain Model) of the slope area. The DTM data was combined with the radar data and allowed us to identify slide features and problems.
The radar system has problems once the movements get beyond a certain threshold, so CDOT will use the I-Site system to detect displaced rock and identify where the movements come from. We’ll work with them to determine the volume of slide rock and provide a new base line for the radar system.
I-Site Technical Services Manager
April 20, 2011
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