An expert panel hired by Vale determined the probable reason for the burst of the company’s Feijão Brumadinho dam, which killed hundreds in January this year, was the result of “flow liquefaction within the tailings in the dam.”
The dam’s design resulted in a “steep upstream constructed slope,” that along with other factors, including weaker fine tailings and loss of suction due to wet season rainfalls, contributed to the disaster.
“The history described above created a dam that was composed of mostly loose, saturated, heavy, and brittle tailings that had high shear stresses within the downstream slope, resulting in a marginally stable dam,” the export report said.
The report was signed by PhD experts Peter Robertson, Lucas de Melo, David Williams, and Ward Wilson.
“The panel concluded that the sudden strength loss and resulting failure of the marginally stable dam were due to a critical combination of ongoing internal strains due to creep, and a strength reduction due to loss of suction in the unsaturated zone caused by the intense rainfall towards the end of 2018,” the experts said.