Study of Rockbursts in the Khibiny Massif
KOLA REGIONAL SEISMOLOGICAL CENTER APATITY (RUSSIA)
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In the last several years there has been a great increase of seismicity in the Khibiny Massif. This began to manifest itself after large volumes of rocks had been extracted from a high-stress environment in connection with the mining activity for the Khibiny apatite deposits. In particular, the increase in the seismicity has been significant after 1980. During this same time period the annual ore excavation at the Khibiny mines has increased from 19.1 to 46.5 million tons. A geometrical correspondence between the configuration of the mines and the coordinates of Khibiny earthquake epicenters has been detected. We have reviewed the mining practice in the Khibiny Massif, and compiled detailed statistics on explosion times and explosive charge sizes. We have demonstrated a correlation between the yields of underground explosions and their magnitudes. The overall correlation using all underground explosions is about 0.72, but it is as high as 0.89 when considering explosions from Mine only. This mine has deeper underground part and well recorded underground explosions. When considering open-pit explosions, we note that other investigators have been unable to find any correspondence between the aggregate yields and the seismic magnitudes. We attribute this difference to the different shot practice for open-pit and underground explosions. Some of the increased seismicity in the Khibiny Massif is possibly connected with the open-pit mining, and could be associated with the removal of large volumes of rock, causing a change in the stress regime. In particular, this manifests itself in a gradual displacement of lines of equal seismic energy release in the direction of Mine. Our results thus support the conclusions in previous studies that the rock extraction from a high-stress environment can cause increase in overall seismicity.
- Mining Engineering