Load & Haul

Researchers study open-cut mine stability

The Victorian Minister for Energy and Resources Lily D’Ambrosio last week launched a $2.2 million batter stability project at the Yallourn open-cut brown coal mine in Gippsland.

Batters – the sloping walls of a mine pit – can become unstable due to interactions between surface and groundwater levels, excavation work and the structure and strength of soils and rock.

“In worst case scenarios, a slope could collapse or create a sinkhole putting the safety of workers, the community, public infrastructure – such as roads – and the environment at risk,” a state government media statement explained.

The Latrobe Valley region has already experienced such scenarios on more than one occasion. According to Latrobe City Council records, in February 2011, heavy rain led to movement in the northern wall of the Hazelwood open-cut coal mine, which led to cracks in the Princes Freeway. This resulted in the closure of the freeway for more than seven months.

In June 2012, the Yallourn mine’s operations were also disrupted for several months when an embankment constructed to divert the Morwell River across the mine failed during a flood.

Another major collapse occurred at the Yallourn mine well before the 2012 incident. In November 2007, the mine’s northeast batter failed, causing a large, six million m3 block of coal to slide across the mine floor. The collapse led to a complete diversion of the Latrobe River into the mine.

Taking action

An inquiry was held to investigate the 2007 batter failure, which resulted in a recommendation that the Victorian Government establish a Technical Review Board. The advisory panel was subsequently established in 2008 to provide the state government with independent advice on managing risks associated with mine and quarry instability and rehabilitation.

The Technical Review Board recommended that a research project be undertaken to study the risk factors that affect batter stability in mines, which received approval and funding from the Victorian Government in August 2014.

Researchers from the Federation University will be conducting geotechnical and hydrogeological studies of mine batters in the Yallourn Mine as part of the project, with technical support from Earth Resources Regulation, Victoria’s mining and quarry regulator.

“The findings from this research project will be used to make open-cut mining in Victoria safer for workers and the community,” D’Ambrosio stated.

Member for Eastern Victoria Harriet Shing added that the research would also help make open-cut mines more sustainable.

The batter stability project is due to end in June 2020 with the findings to eventually be applied across all of Victoria’s open-pit coal mines.

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