Engineers Australia

On the need to consider kinematics when seeking to prevent the sudden collapse of the sides of coal mine roadways

Ross Seedsman

Abstract

In 2014 a portion of the side of an underground roadway at Austar Mine collapsed and crushed two coal mine workers. The investigation report prepared by the NSW Mine Safety Investigation Unit concluded that the collapse was a pressure burst. After reviewing the available evidence, this paper suggests that an alternative explanation is possible based on rock slope kinematics. The Austar event possibly can be explained as the collapse of a wedge in association with a very low intensity seismic event. Kinematics using either toppling or planar slide models can provide explanations for the collapse of unsupported ribs where joints or mining-induced fractures are vertical. Behaviour models based on kinematics can provide the basis for the specification of ground support. There is a need for geotechnical engineers in the underground coal industry to collect and analyse orientation data and to better characterise the shear strengths of joints, shears and fractured coal. There is also a need to consider mine seismicity in the context of accelerations as well as velocities.