A joint project between three western universities is designed to keep motorists safer from a problem in the mountain west – rockfalls onto highways.
This old problem now involves Lidar, which uses tens of thousands of data points taken with extreme accuracy using lasers. You've probably see Lidar before, as most of the time it's flown using an airplane to produce a highly accurate 3D picture of the earth below and can be used to screen out trees and vegetation to get a high definition view of the geology below.
Now a project led by the University of Washington partnering with Oregon State University and the University of Alaska Fairbanks is using Lidar a different way to accurately read slopes hanging over highways. How do you tell the difference?
"The areas that are actively failing have a jagged structure to them that allows more water in," said Joseph Wartman, Ph.D., an associate professor of civil and environmental engineering at the University of Washington.
Still being tested increasingly with drones, Wartman says the program does not compare movement of rocks one year from the next, but identifies characteristics like that jaggedness that indicates an area of rock that's more likely to eject rock and boulders down onto the highway below.
"It's particularly acute in the Pacific Northwest because of the combination of topography and the rainfall that occurs," said Wartman. "As water enters the cracks, it imparts a hydraulic jacking pressure against these rock slopes...that's one of the things that can push these rock blocks out as well."
Highway departments have had geotechnical engineers for decades who have a good eye for risky cliffs hanging over roads, but Wartman says their investigations often involve having to carry out examinations by climbing on the rocks themselves, and the analysis can be more subjective. Wartman says the Rockfall Activity Index (RAI) can provide accurate assessments from a safer distance, faster, and is more objective using the same algorithms to survey different slopes. Drones are now being tested.
Findings of the RAI were recently published in Engineering Geology.
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