14 April 2015

Yeager Airport landslide: on the move again

Posted by Dave Petley

Yeager airport landslide

News reports yesterday indicated that the Yeager Airport landslide had another significant movement event at the end of the weekend (for reference my original post is here this is my post with videos of the site, this post looks like the landslide history of the site, and this one examines reports that the fill slope was moving two years before the landslide occurred)  .  In many ways I don’t think that this should be considered to be a major surprise – the back scarp of the landslide was (and still is) composed of fill that has inadequate support.  The Charleston Gazette has some nice images of the landslide taken yesterday, including this one of the main slide mass and the back scarp:-

Yeager Airport landslide

Courtesy of the Charleston Gazette

.

This is an image from (a similar though not identical) perspective taken at the time of the main failure:

Yeager Airport

via Twitter: https://pbs.twimg.com/media/CAOYonVWoAAbrr4.jpg

.

And this is the two side by side for comparison:

Yeager Airport landslide.

On first inspection it appears that a large block has detached from the left side of the landslide scar (as viewed from the foot of the slope), as indicated above.  The darker material on the more recent image appears to indicate the location of this block prior to collapse.  Bob Aaron has this view on his Twitter feed, taken from a different perspective, which gives a clear view of the detached block:

 

It appears that the weight of this new material on the debris pile caused further movement on the debris pile below, as shown by these two images, also from the Charleston Gazette:

Yeager Airport landslide

Courtesy of the Charleston Gazette

.

Yeager Airport landslide

Courtesy of the Charleston Gazette

.

This rolling up of the asphalt road is consistent with deeper movement in the landslide mass, which in turn is consistent with loading from a failed block at the crown of the landslide.  It appears to me that these is still a steep slope at the rear of the landslide formed from very weak materials, so further failures seem likely.  These failures will probably load the debris pile further, so further movement of the toe of the Yeager Airport landslide slide seems possible.

Further rain is forecast for the next few days in this area.