MINE WATER
Tailings management aims to progress despite headwinds Tailings storage facilities (TSFs) are great achievements of civil engineering and have tested some of the best brains in the mining sector. Now, despite current headwinds related to the Covid-19 pandemic, the industry is planning to raise the bar even further by advancing its best practice in a concerted fashion over the next decade.
T
he impetus for this, according to Adriaan Meintjes, partner and principal civil geotechnical engineer at SRK Consulting, has been a series of TSF accidents in the past few years. The most recent – and dramatic – was the failure of the TSF at Vale’s Córrego do Feijão iron ore mine in Minas Gerais, Brazil. The event, which took place on 25 January 2019, killed over 250 people. “This led to an industry-wide response from a range of organisations – which could be compared in some ways to the response of the security community to the New York terror attacks in 2001,” says Meintjes. “Needless to say, consultancies like SRK have been kept very busy, as mining companies assess their fiduciary risk connected with TSFs.” He highlighted the difficulties in TSF engineering, stemming mainly from the dynamic nature of the infrastructure
Vibrating wire with transmitter installation on a TSF
– which is subject to the facility’s growing capacity. The contents of the TSF shift constantly, with chemical and structural changes in the tailings themselves as the orebody and mineral processing parameters alter. “The changes in and interactions of all these factors – often over a lifespan of decades – complicate the planning, construction, operations, decommissioning and closure of these facilities,” he said. “If errors occur during any of these stages, failure can result.”
New lessons
The Feijão accident surprised experts for various reasons. An important one was how quickly and completely the integrity of the TSF failed. The front wall was inspected in the days before the failure and deemed to be stable, but it collapsed completely in less than one minute. This mode of rapid failure is a brittle failure,
Adriaan Meintjes, principal civil geotechnical engineer, SRK Consulting
similar to glass breaking. It is normally expected that early signs of failure are ductile and gradual, and can be picked up and addressed long before a total collapse. It was also troubling that the facility was in a mature stage of its life, and was in fact in the process of decommissioning;
