The paper considers the problem of refining the critical depth of rock burst hazard for the Nyorkpakhk apatite-nepheline ore deposit in the context of transition to underground mining. The relevance of the study results from the discrepancy between the value of 400 m (according to regulatory documentation) and the actual mining and geological conditions, especially considering the significant impact of the existing open pit on the stress-strain state of the rock mass and other natural factors of the region. The aim of the study is the development and testing of a comprehensive methodology for assessing the critical depth of rock burst hazard, including core discing analysis, seismicity monitoring, spatial numerical modeling of the stress-strain state using the CAE Simulia Abaqus software, assessment of the rock burst hazard potential of rocks based on the Kaiser criterion, and comparison with a geomechanically similar analogue Oleniy Ruchey deposit. Core discing analysis revealed only local stress zones associated with tectonic faults, without characteristics pointing to rock burst hazard down to the +100 m level. The results of numerical modeling confirmed the absence of stress concentrations down to the +35 m level both before the start and after the completion of open pit mining. Comparison using the similarity method showed expected manifestation of rock burst hazard below the +50 m level. The studies, according to the described methodology, enabled scientific justification of increasing the critical depth of rock burst hazard relative to the regulatory value, down to the +100 m level. It has also been determined that for the Khibiny deposits there is no direct correlation between the brittleness criterion and the propensity for rock burst hazard. The proposed methodology is recommended for testing at rock burst hazardous deposits with complex mining and geological conditions.

The paper justifies a design of reinforcing mine support of the protective roof at the priority high-grade ore mining site of the Yakovlevskiy deposit. Experience of mine roadway support with the KMP-A3 standing support has been analyzed. A reinforcing support is offered consisting of rock bolts back bracing the ore exposure, which best fits with continuous miner roadheading and consolidating stowing (concrete).

The article presents the consistent patterns of the changes in stress-strain state of the massive by the minings of the first stage of protective overlapping in the Yakovlevsky deposit. The change of the stress-strain condition of the rock massive, which is weaked by the mining was determined by the method of finite elements. The stresses distribution in the massive, the displacement of the contour of the minings, the size of conditional zones of non-linear deformations has been obtained. For stoping passes at the first stage the cutting with combine and application of fastening with the anchors has been suggested.