Influence of water content on seismic activity of rocks mass in apatite mining in Khibiny

The authors analyze connection between the rock mass water content due to surface water (precipitation, snow melting and water bodies) and rock bursts in mines. The seismological monitoring performed from 2001 at the surroundings of the Apatite Circus and Rasvumchorr Plateau apatite deposits identified fluctuation of the general seismic background from year to year and seasonably. For these deposits, increased water content of rocks is seen as a natural trigger for rock mass seismicity during intensive rains and snow melting. The 15 year-long seismic monitoring of the apatite deposits under study has revealed regularity in a seasonal growth of seismicity during snow melting and precipitations, mainly in spring months. Particularities of geodynamical event occurrence allow a conclusion on the ultimately stress state of the upper earth’s crust in whole in the deposits’ vicinities. Reactivation of tectonic disturbances and weakened rock mass zones occurring due to relief of normal compression during infiltration can be a potential principal mechanism of seismic activation of the rock mass during the increased water content periods. The origin of the events observed is linked with the dynamic release of ultimate rock mass stresses when geomechanical conditions change under the action of hydrostatic pressure on tectonically disturbed zones. The authors make a conclusion on necessity to apply the revealed regularities of impact of natural factors on rockburst hazard when planning mining operations and performing geomechanical monitoring.