Assessment of the Rock Burst Hazard of the Rock Mass of the Strezhan Deposit

The article considers the aspects of assessment of the rock burst hazard of the rocks of the Strezhan deposit using various methods: visual inspection, fracturing of the massif, core disking, and lab tests for extreme deformation. In 2023, ore samples and host rocks were selected at the Strezhan deposit to determine their deformation and strength properties. The studies revealed their high strength. In the same year, the components of the stress tensor were measured at the mine using the well hydraulic fracturing method at two measuring stations at a horizon of +750 m (at a depth of approximately 240 m from the daytime surface). It has been established that the natural field of the Strezhan deposit is characterized by a tectonic regime with horizontal tectonic stresses as maximum stresses, whereas vertical stresses are minimal. The azimuth of the maximum horizontal stress was 140 ± 10° in the northwest-southeast direction. As a result of field measurements of the natural stress field at the horizon +750 m at the Strezhan deposit, the values of the highest horizontal stresses in the rock mass (ore) were established as equal to 15.2 MPa. This means that the level of stress of the rock mass at the horizon +750 m (mining horizon) is insufficient to destroy mine workings. Calculations established the critical depth of mining operations as 500 m for the rock burst condition. In addition, ores prone to rock bursts have been detected in the deposit: solid copper-zinc and sulfur-pyrite. The assessment of the structural disturbance of the deposit rocks via the rock quality index RQD = 60.26 % enabled the classification of the deposit rock mass mainly as moderately fractured, where dynamic manifestations of rock pressure are not registered and not forecasted within the designed mining depths. As a result of the studies, it has been established that the rock mass of the Strezhan deposit located at a depth of 500 m from the daytime surface can be classified as non-hazardous in terms of rock bursts on the condition of observation of the mining technology adopted in the design.