28 October 2008
Arthon have posted an update on their website of the situation at Highway 97 in Canada:
“Slight movement in Rock Mass overnight. Road likely closed until Thursday at a minimum. Options being considered for removal of rock”
There is also quite a nice news report with footage here. In the report there is a good description of the use of precursor indicators that can be used to warn of a large-scale failure. They are quite right that movement data, sounds, the opening of cracks and the occurrence of small falls can be used to indicate that a large slip might occur. However, they will need to understand the slope quite well before this option is adopted, and they will need to be particularly cautious when it rains or there is snow melt.
Arthon have published some excellent pictures, including a couple of aerial shots, here. The picture below is the best of them to give an oversight of the problem:
Click on the image for a link to the full size version. Note that a few metres below the main crack there appears to be a smaller tension crack running across the slide, perhaps suggesting that it is starting to break up a little.