30 January 2019
Planet Labs image of the Brumadinho tailings dam failure
Planet Labs have captured a high resolution image of the aftermath of the Brumadinho tailings dam failure at the Córrego do Feijão Mine in Brazil. This image, which is copyright Planet Labs and used with permission, shows the tailings pond and failed dam:-
It is worth comparing that image with the Google Earth image of the same site:-
There are a few points to note here. First, the central portion of the dam has failed catastrophically, creating a high mobility flow. In fact, very little of the dam itself is intact. Second, the compromised smaller dam to the west of the main failure can also be seen. The toe has scoured out; clearly this needs careful monitoring but the retained volume is not very large. Third, there is a substantial volume of tailings left within the pond that now has not retention in place. These tailings can mobilise in heavy rainfall, so careful management is needed.
Meanwhile the number of fatalities from the Brumadinho tailings dam failure has now reached 84 confirmed losses, of whom 42 have been identified, with a further 276 people reported missing. This would mean that the minimum final total will be 318 fatalities, making this one of the worst mining landslides in recent history. No-one was rescued alive yesterday.
Five people from Vale and from a contractor, TÜV SÜD, were arrested yesterday in relation to the accident.
Finally, a comment by Caner Zanbak from my earlier post on the Brumadinho tailings dam failure noted that there is an article online about the behaviour of the tailings at Dam 1 of the Córrego do Feijão Mine. This presents a detailed analysis of the liquefaction potential of the tailings. It concludes:
“Considering a rapid rise of the phreatic line through the tailings deposit reaching the toes of the intermediate rising dykes, with complete saturation of tailings layers susceptible to liquefied, a post-triggering analysis indicated that the flow failure susceptibility of the Dam I is low even under a such critical loading event”
“The conclusions of these analyses, in addition to laboratory testing program results and based on rigid management procedures adopted in field, demonstrate that Dam I constitutes a safety structure against mechanisms from liquefaction-induced failures”.
Clearly these analyses did not properly characterise the behaviour of the tailings (which is not necessarily a criticism of the authors). I wonder if we know why?