Aberfan disaster

Morgan, L., Scourfield, J., Williams, D., Jasper, A. Lewis, G. 2003. The Aberfan disaster 33-year follow-up of survivors. British Journal of Psychiatry, 182, 532-536. 

The instability line is not a property of the soil, but depends directly on the state parameter. The slope of the instability line becomes smaller as the state parameter becomes more positive. There is a literature on this functional behaviour, but that literature is of no practical consequence. If the situation in the slope is 0, then the questions becomes this would slope failure be a hazard or otherwise unacceptable If a rapid slope failure, developing without warning, is unacceptable then remedial work is needed an observational approach will not provide safety (for example, the slope in the Aberfan disaster was inspected, and deemed safe, shortly before it failed killing 144 people). 

McLean, I. Johnes, M. 2000. Aberfan. Government and Disasters. Welsh Academic Press, Cardiff, 250 pp. 

This accident had a defining influence on UK legislation and led ultimately to the Health and Safety at Work Etc Act of 1974 (after the Flixborough disaster (Health and Safety Executive, 1975)). The fundamental effect of this legislation was to require companies to demonstrate that their works were safe and that workers were adequately trained. This was the start of the Safety Case concept (McLean (1997) and http // www.nuff.ox.ac.uk/politics/aberfan/eoafinal.htm). ... 

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