A study into the seismic settings and rock-bump hazard at the Kukisvumchorr apatite-nepheline deposit at the deep +10 m level

This article presents the results of studying seismic activity with increasing mining depth using the Kukisvumchorr apatite-nepheline deposit (the Khibiny Mountain Range) as a case study. The study is based on a statistical assessment of the seismic settings of the deposit as a whole and a predictive assessment of the state of Block 9/12 at the deep +10 m level. The following main seismicity levels were used to describe the dynamics of the seismic settings: extremely high, high, elevated background, average background, and reduced background. Geomechanical situation in adjacent Blocks 12/15 and 15/18, where mining operations are underway, was analyzed to forecast the condition of Block 9/12. Zones with higher seismic activity and a high level of stress-and-strain state in the boundary part of the mass at deep mining levels (+25 m; +50 m; +75 m; +10 m) were identified using the methods of regional rock-burst hazard forecasting, i.e. analytical (numerical) stress state modeling, visual inspection of the mine workings, and the results of continuous seismic monitoring. A visual inspection of the mine workings confirmed the development of localized areas showing signs of rock pressure. A spatiotemporal assessment of the seismic anomalies has shown that seismicity moves along with the advance of the mining front, including the depth changes. Significant geodynamic phenomena have been observed in the lower mining levels over the past 9 years, as mining operations have progressed to the deeper mine levels. Preventive measures have been proposed to reduce the risk of rock bumps.