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Quarry batter stability in Victoria

Background

Quarry stability is linked to understanding and managing geotechnical risks at quarries. Geotechnical risk refers to how likely the ground is to move. High geotechnical risk suggests there is a high probability of quarry batter failure. Low geotechnical risk suggests there is very little potential for a rock wall to fail.

In other words, if the ground in a quarry is likely to move there is a good chance a quarry wall will fail.

Working near quarry walls can be hazardous due to rock falls and slope failures. As quarries develop over time, they usually get deeper and the overall slope angle becomes steeper. These changes can increase the risk of rock falls or slope failures.

Incidents at Victorian quarries

Large-scale geotechnical failures can occur at Victorian quarries. In March 2016 a haul truck driver was fatally injured when the truck she was operating overturned down a quarry embankment. In May 2016 a fatal incident occurred at another quarry when a male haul truck driver was killed while dumping material from a stockpile dump. 

Earth Resources Regulation (ERR) seeks to improve quarry stability in Victoria

ERR regulates Victoria's quarry industry under the following Acts and Regulations: 

  • Mineral Resources (Sustainable Development) Act 1990 (MRSDA)
  • Mineral Resources (Sustainable Development) (Extractive Industries) Regulations 2010
  • Mineral Resources (Sustainable Development) (Extractive Industries) Amendment Regulations 2014
  • Extractive Industries (Lysterfield) Act 1986.

ERR has Memoranda of Understanding and agreements with other Victorian Government agencies – including the Environment Protection Authority (EPA), the Department of Environment, Land, Water and Planning (DEWLP) and WorkSafe Victoria – to ensure whole-of-government regulation of Victoria's quarry industry. 

The risk-based work plan approach which came into effect in December 2015 means that all new quarries must have work plans. Those work plans have to include information about geotechnical risks on the site if those risks affect public safety, the environment or public infrastructure. The work plans also need to demonstrate how the applicant is keeping those risks as low as reasonably possible. 

ERR expects quarry operators to foster a culture of risk prevention on their sites. To help operators prevent risk, ERR provides advice, publishes guidelines and helps quarry operators find appropriate and applicable standards to guide their risk management decisions.  

ERR inspectors regularly inspect quarry sites, auditing and reviewing quarries' compliance with their work plans. In 2016 ERR started auditing batter stability. Slope stability audits will form an ongoing subject area of ERR compliance audits going forward and findings from these audits will be communicated to industry. 

ERR has strengthened its expertise by appointing experienced and qualified people to geotechnical and hydrogeological positions. These people are helping investigate quarry stability, incidents and work plan assessments.

ERR has also established a panel of experts to provide advice on quarry and mine stability where required.

Minimising quarry instability in Victoria

Most slope failures in quarries can be predicted by diligent geotechnical practices. This includes daily visual inspections, slope monitoring and mapping of geological structures such as joints, bedding planes, faults and shears, and having relevant procedures in place for all quarrying activities. 

It is also important to ensure that pit wall steepness (or 'batter angle') is within design limits, so that rock material is not undercut and increase its likelihood to fail. 

Blasting against walls and groundwater 'trapped' in a wall can both increase geotechnical risk. Importantly, all workers need to be able to recognise potential hazards and act accordingly.

Useful guidelines for reference in relation to quarry stability

The Construction Material Processors Association (CMPA) launched a guideline in February 2016 entitled Working Safely with Geotechnical Risk in Quarries, which aims to support CMPA members in meeting the requirements of the Victorian Occupational Health and Safety Act 2004

The guidelines have been prepared in consultation with ERR and are in addition to ERR's Guidance Material for the Assessment of Geotechnical Risks in Open Pit Mines and Quarries

Other guidelines that may assist quarry operators in managing slope stability within their quarries are: 

Other materials that may be useful include: