29 October 2008

Highway 97 latest update

Posted by Dave Petley

The latest update on the Highway 97 landslide in Canada (see here and here) is as follows:

  1. The slope is still moving. Between 19:00 on Monday and 14:00 on Tuesday the mass moved about 15 millimetres (i.e. about 0.8 mm per hour). This is quite high for a large mass. The rate of movement is described as being constant;
  2. The mobile volume is now estimated to be 200,000 cubic metres;
  3. The road remains closed (unsurprisingly!);
  4. There are provisional plans to remove material from the top of the unstable slope and to move it to the toe. The aim here is to reduce the mass that is driving the movement and to increase the mass that is supporting it.

I am sure in the background there is an enormous amount of work going on. Analysis of the pattern of movement in time and space, especially by looking at vectors of movement and accelerations and decelerations will give a pretty good idea of what is happening in the slope. This gives a potential for providing a short term warning of an impending collapse, but does not really tell us how likely this is in the medium term.