A new look at the statistics of tailings dam failures

Abstract

Tailings dams are commonly built incrementally to increase the storage capacity of the Tailings Storage Facility (TSF), usually without interrupting the mining activities. Dam management practices, lack of knowledge on tailings behaviour and the poor performance of monitoring and management processes have resulted in disastrous tailings dam failures with human and economic losses, as well as huge environmental consequences to ecosystems and local communities. In the literature, correlation analyses have been carried out considering different variables: stored volume, released volume, runout distance, dam height, peak discharge. Several databases of tailings dam failure are available online, each with different levels of detail. This paper computes the statistics of tailings dam failures using an up-to-date database on failures and a catalogue of existing TSF. The existing correlations between stored and released volumes have been verified using a larger database. The new proposed regression analysis considers the functional relationship between released volume and characteristics of the dam such as height and stored volume (i.e., dam factor). The effect of construction type, fill material and failure mode on the released volume has also been evaluated as well as the frequency of tailings dam failure as function of the construction method. Tailing dams built using the upstream construction method turn out to be more prone to failure, and more susceptible to static and dynamic liquefaction. The new correlation provides more reliable estimates of the expected released volume as a function of dam height and stored volume and should prove useful for runout analyses and risk assessment of tailings dam failure. Finally, the analyses carried out show that there is no correlation between the water pond extension and the released volume.