An Underappreciated Mechanism for Failure of Tailings Dams

Abstract

In at least two out of the three recent major failures of tailings dams, two in Brazil and one in Australia, where incipient failure due to other causes has been evident, the occurrence of small earthquakes or mine blasts immediately prior to the failure has been essentially ruled out as the principal trigger. This is in accord with the widespread belief that very short period / higher frequency motions are not “seen” by large earth structures. That may be true in many cases, but if there is an incipient failure due, for instance, to uncontrolled seepage, piping and erosion, the characteristic dimension of that feature will be much smaller and it is possible, even likely, that high frequency motions can impact the potentially unstable local structure and trigger a larger progressive failure. This phenomenon is illustrated with a simple example. The importance of correctly modeling progressive failure is also addressed.