The objective of this investigation is to improve worker safety through a better understanding of mine excavation response to rockbursts. The improved understanding should lead to improved mine layout and support design. The project is a continuation of GAP 201 and consists of two main enabling areas namely:
- a comprehensive investigation of rockbursts that have caused damage and posed a hazard to workers
- measurement and analysis of the dynamic response of the rock surrounding excavations following seismic shaking
Twenty-eight accident site investigations were completed in the years 1994 to 1997, inclusive, mainly as part of project GAP 201. Six additional investigations were done in 1998 as part of this project and in combination with the initial findings have served to highlight certain aspects of the rockburst phenomenon. These aspects include the existence of the following problem areas that need to be addressed:
- a lack of knowledge of the stress fields affecting a particular mine
- an underestimation of the extent of the unstable zone surrounding tunnels
- poor condition of tunnel support elements due to corrosion
- siting of tunnels in areas of fault loss and tunnels intersecting faults at oblique angles
- ineffective gully support design and implementation
- shape of remnant pillars
- backfill usage
The source mechanism in the vast majority of cases was diagnosed as a seismic event resulting from slip on either a dyke contact or a fault. In some cases the seismic data coupled with the extent, nature and location of the damage make the degree of certainty, with respect to the source mechanism involved, extremely high.
Other source mechanisms include remnant pillar failure, stabilising pillar foundation failure and face bursts.