30 January 2013
An unusual quarry landslide in Canada yesterday
Posted by Dave Petley
A somewhat unusual quarry landslide occurred yesterday at the Maskimo Quarry in L’Epiphanie in Quebec, Canada. Montreal CTV News has a good aerial image of the site and the landslide:
http://montreal.ctvnews.ca/search-suspended-for-workers-missing-in-collapsed-quarry-1.1134230
On initial inspection the slip appears to have originated in the materials in the slope above the main quarry face, and then to have cascaded over the edge into the main excavation. Sadly, there were two trucks and excavator on the slope at the time, all of which ended up in the 100 m deep pit. One of the three people operating this equipment was recovered with only reasonably minor injuries; the other two remain missing. The image below, from the Montreal Gazette, shows just what a difficult task the rescuers face:
http://www.montrealgazette.com/news/montreal/Workers+missing+after+quarry+land+slide+%C3%89piphanie/7887851/story.html
It appears to me that the access road for the main excavation has also been buried, which will hamper the recovery operation.
Dave Petley is the Vice-Chancellor of the University of Hull in the United Kingdom. His blog provides commentary and analysis of landslide events occurring worldwide, including the landslides themselves, latest research, and conferences and meetings.
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Hello Dave
I’ve been following this tragedy since just after it happened. Hopefully with the heavier equipment going in the rescuers will be able to make better progress at finding the two missing personnel.
Having a bit of a background with leda clay, I think that it was the culprit in this case. The Montreal area has a great deal of leda clay and have experienced more than their share of landslides as a result. In reading the newpaper articles I have come to the conclusion that the company may have been looking to expand the quarry operation or were simply accessing the gravel deposit above the bedrock. The area of the slide would appear to have been composed of topsoil, gravel, leda clay and bedrock. One of the aerial photos shows a number of stockpiles. Some of these could be topsoil. The heavy equipment was in the process of removing gravel from the site. We just went through an extended January thaw that lasted longer than normal. Snow melted and rain fell. Without the topsoil layer, I think the melting snow and rainwater went through the gravel layer and saturated the leda clay. We then went into a week long deep freeze that may have solidified the gravel to some extent. The leda clay would have been protected from freezing by the gravel layer. When the loader and trucks started to work on the site, the weight and vibration may have been sufficient to liquify the leda clay. The easiest outlet for the flow was the quarry. The leda clay flowed into the quarry, carrying the gravel and equipment with it. This is my own conjecture on what might have happened. Quebec has some excellent experts on leda clay. If it was in fact the culprit, they will find the evidence and produce a report on their findings.
Here’s hoping that the rescuers are successful today.
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