Open Cut » Highwall Mining
Slope stability is a critical safety and production issue for coal mines. For safety reasons, Mine Managers are required under statute law to regularly examine rock faces in active pits and assess the risk of slope failure. However, it is difficult to predict the progression to slope instability from signs such as visible cracking, audible creaking and increased rilling of spoil. Hence, Mine Managers take a conservative approach when deciding whether to expose personnel and equipment near a potentially unstable slope. Over-cautious decisions impact on the mine's productivity, while the reverse emphasis places lives at risk.
This report describes the operation and field results of a radar system specifically designed to monitor slope stability in coal mines. Termed the "Slope Stability Radar", it has been successfully trialed at Drayton and Moura mines. These trials demonstrated that outward deformation movements of a rock face can be detected with an accuracy around 1 mm, a factor of ten better than the original aim. The value of the radar is that it provides full area coverage of the rock slope from a stand-off position, without the need for reflectors attached to the rock face. It overcomes the shortcomings of conventional monitoring systems by providing greater coverage of the rock face, hence giving a better understanding of the geodynamics, which should in turn lead to extra warning time. This translates to greater productivity in the sense of lower risk associated with recovery of coal. It would enable direct recovery, where under conventional monitoring conditions the area would be quarantined on grounds of excessive risk.
The project was originally targeted at highwall mining, but it soon became apparent that this remote monitoring technique has broad application in other areas of coal mines, such as lowwall (spoil pile), in-pit bench and general highwall stability. Twelve months of further development and trials are necessary towards making the Slope Stability Radar practical and easy-to-operate in coal mining operations. After this, we envisage that geotechnical contractors will operate the system for mines on a short-term "needs" basis. For longer-term monitoring, the mines may choose to purchase a system and operate the system themselves.
This final report is published as a CD containing the final report as both an MS Word document and a pdf file. It also contains a well produced brief movie that highlights the project outcomes and some of the mine site field work.