29 July 2013

The China landslide car video – how did the occupants survive?

Posted by dr-dave

Many news outlets have been running the dramatic footage, shot on 13th July in Shaanxi Province, of a car being buried by a landslide.  If you haven’t seen it, you can view it here or below:

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The central theme of the coverage appears to be a sense of amazement that the landslide was survivable.  So how did they survive?  Well, there is certainly an element of serendipity here for two reasons.  First, there is a critical issue of timing.  By what is probably a matter of a single second, the landslide impacted on the road just ahead of the car, which had time to brake before being buried.  As the screenshot below shows, if the car had been traveling just a little quicker the landslide would have buried it directly:

13_07 china car 1..

The driver managed to bring the car to a stop on the edge of the impact zone.  The second fortunate element is that the landslide debris then pushed the car away from the main impact zone.  This is a screenshot from the site at the point after the car stopped moving forward and had started to be pushed laterally – note the location of the brake lights:

13_07 china car 2

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Towards the end of the incident the car had been pushed laterally away from the main impact area.  This is the video as the first two passengers escaped:

13_07 china car 3

And finally, the landslide appears to be mostly formed from soil (and a small tree or two).  So, although the video shows some large blocks falling, there are no lumps of large rock on the road, suggesting that these soil blocks shattered on impact.  The strength of the car was sufficiently high that it wasn’t crushed, and so the passengers were protected.  If this had been a rockfall the outcome would have been quite different:

13_07 china car 4

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All of which serves to illustrate two key elements of landslide mitigation.  These are first that timing is everything, such that the easiest way to stop people from being killed in landslides is to ensure that no-one is in their path.  And second that mechanism and material are crucial – the hazard posed by a rockfall is very different from that of a soil fall.  Determining the mechanism of a likely landslide is essential if its possible impact is to be reduced effectively.