Rock fracturing related to strain burst in quartzite rock mass

The paper presents observations of strain bursts and rock fracturing in three cut-and-fill mine stopes in a deep metal mine. The stopes were located in depths from 925 m to 1000 m in a quartzite rock mass. Every stope was excavated in 5 slices with each slice having a height of 5 m. The excavation started in the bottom slice and continued the next slice upward after the previous one had been backfilled. In the bottom slice, no stress-induced fractures were visible on the excavation face, the roof and the walls, but serious strain bursts occurred on the roof and also low frequent but powerful rock fracturing sounds were emitted from the surrounding rock mass. Strain burst gradually disappeared in the second and subsequent slices, but the surrounding rock became more fractured in extension.