TAILINGS: BHP Billiton, Vale release Samarco dam report

BRAZIL – A panel of four geotechnical experts has released its findings into the tailings dam failure at the Samarco iron ore mine on Nov. 5, 2015. The panel was commissioned by BHP Billiton and Vale SA, co-owners of the project. The panel found design engineering flaws that led to the eventual collapse. The dam was filled with tailings sand and slimes, delivered through separate pipes. The dam was raised periodically using sand, but he original starter dam had been damaged and that resulted in increased saturation. And during operation, the deposition of slimes occurred in areas where they should not have been. The failure occurred at the dam’s left abutment due to flow liquefaction of the tails. This transformation from solid to liquid was abrupt, turning the dam into a fluid that behaved like water. The panel said the root cause of the failure was lateral extrusion, loading the slimes-rich zone vertically and forcing them to spread laterally. The entire report may be accessed at http://FundaoInvestigation.com/.