1 February 2015
New landslide video: a spectacular retaining wall failure
Posted by Dave Petley
Retaining wall failure
I don’t know the background to this spectacular retaining wall failure, which was posted on Youtube on 28th January:
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If you watch closely you can see the acceleration of the landslide in the period leading up to the collapse – right down to individual grains of soil. An additional interesting aspect is the mobility of the landslide – the large object (the truck) was much more mobile than most of the retaining wall.
I wonder what the retaining wall was founded upon? (Other than the obvious “not enough” of course).
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.
I do not think the problem was geological but one of engineering. It looks like the entire road at that point was on fill – though it is difficult to say without a good view of the entire road. I suspect that the wall was meant to be less than a retaining wall but one which would divert rainwater away from the fill towards more ‘solid ground’ – whatever made up the existing slopes. The problem may have been that the wall retained water on the fill and saturated it which exacerbated the somewhat inevitable slide.
Looks like a narrow gabion wall built at or near grade. Probably adding fill because “the road was sinking”. So fortunate they had a spotter and didn’t lose anyone.
In the late 1990’s in northern Calif., a debris flow initiated by poor road drainage onto marginal sidecast fill near the head of a steep swale took out a parked dump truck mid-slope on industrial timberland. Carried it a similar distance downhill, where it remained entombed for several years until the fuel tanks started leaking. The place is still known as The Dump Truck Slide, and shows up on informal maps of the local road network occasionally.
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