As part of this work I’m taking a look at the mobility of tailings failures<\/a> in relation to other major landslides.\u00a0 Tailings dam failures inflict a huge impact in terms of loss of life, environmental effects and social damage.\u00a0 It is well established that the impacts can extend for tens or even\u00a0 hundreds of kilometres downstream – the Ok Tedi tailings failure in Papua New Guinea<\/a> for example extended for 1,000 km and disrupted the lives of 50,000 people.\u00a0 Of course much of this damage was caused by remobilisation of the tailings by the river, but the issue of the runout of the landslide itself is very pertinent.<\/p>\n A good way to analyse the runout of landslides is to examine the so-called Fahrb\u00f6schung angle, which is the ratio between the vertical change of the landslide (from crown to toe) to the length of the landslides (again from crown to toe).\u00a0 More mobile landslides have a lower Fahrb\u00f6schung angle.<\/p>\n Using case studies described in the World Mine Tailings Failures (2020) catalogue<\/a>, and going back to original topographic and satellite data, I have been able to calculate the Fahrb\u00f6schung angle for 27 tailings dam failures.\u00a0 I have then compared these with the mobility of large landslides using data presented in a famous paper (Legros 2002<\/a>) a couple of decades ago.\u00a0 I have also included in the graph data for coal waste landslides:-<\/p>\n Graph of the Fahrb\u00f6schung angle against volume for tailings dams and large landslides from Legros (2002)<\/a>.<\/p><\/div>\n .<\/p>\n Taking the large landslides first, it is well-known that the Fahrb\u00f6schung angle decreases as landslide volume gets larger – the reasons for this remain a little unclear.\u00a0 Interestingly the same effect is seen for coal waste landslides and for tailings landslides, both of which are more mobile than large landslides. But, most significantly, the tailings landslides have a far lower Fahrb\u00f6schung angle than that of the large landslides, but with much greater scatter too.\u00a0 Indeed, in many cases the Fahrb\u00f6schung angle is two orders of magnitude lower – in other words, tailings landslides travel far further than other large landslides.<\/p>\n The reason for this high mobility is likely to the nature of the materials that are released in the tailings dam failure.\u00a0 Typically, the failure involves materials that have been crushed and that, at the point of failure, are saturated and have undergone liquefaction.\u00a0 The extreme mobility at the time of failure was of course illustrated rather elegantly by the Brumadinho failure in Brazil<\/a>.\u00a0 Interestingly, many investigations of tailings dam failures tend to focus on the failure mechanism, and to ignore what happens thereafter.\u00a0 This needs attention.<\/p>\n![\"Mobility](\"https:\/\/blogs.agu.org\/landslideblog\/files\/2020\/02\/20_02-tailings-1a.jpg\")
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