2 May 2014
Baltimore Retaining Wall Collapse
The extraordinary collapse of a retaining wall between an urban street and a railway line within a cutting in Charles Town Baltimore has attracted a fair amount of attention this week. The collapse of the wall, and the consequent landslide, dropped several cars into the cutting. Remarkably, the collapse was caught on video, available on youtube:
As someone noted on Twitter, the discussion between the people at the scene is quite interesting. I suspect that they might have been less close to the event if they had been aware of what was about to occur.
The debris field created by the collapse in Baltimore is complex:
Judging by the deposit, the retaining wall was a comparatively thin masonry structure with weak sediments (possibly, in part, fill) behind. The collapse occurred during heavy rainfall, which suggests that excess pore water pressures may have been a factor. It would be interesting to hear about the inspection regime on this structure and about the nature of the drainage system that was in place.
Two interesting aspects to highlight. First, if you watch the video the progressive development of the failure is evident. The car on the left develops an increasing tilt through time, which that on the right slowly subsides. This is a screenshot of the two cars at about 12 seconds from the start of the video:
And these is the same two cars just before the collapse:
Second, the Google Street view image for the section of road that collapsed shows a very poorly maintained road surface with an interesting set of linear cracks running parallel to the retaining wall:
These linear cracks are not present to the east on the same street, even though the road surface is also poorly maintained. This section of course is not above the railway cutting: