48 / 2023-05-15 19:11:40

Prediction and prevention of rockburst hazard in Nikolayevskoye deposit of deep-seated polymetallic ores with a complex tectonic structure

deposit, underground mining, mathematical modeling, geodynamics, tectonic structure

In the Far Eastern region of Russia, as in many other mining areas, the development of solid mineral deposits takes place in increasingly complex mining, geological and geomechanical conditions. During underground mining operations, dynamic manifestations of rock pressure are a serious problem. The most dangerous forms of which are destructive tectonic impacts, as well as man-made earthquakes, which can have catastrophic consequences. The problem of forecasting and preventing dangerous dynamic phenomena during the underground mining has been one of the most difficult in the world science and mining practice for many years. This is due to the multifactorial nature of the conditions and causes of geodynamic events, the high diversity of the properties of rock massifs exposed to intense man-made impacts during the mining operations, as well as the lack of knowledge of processes and phenomena in extremely stressful complex geo-environments.

The safety and efficiency of mining operations in such conditions depend on the timely forecast of zones of dangerous stress concentrations, as well as on an accurate assessment of the degree of influence of stoppings and the tectonic structure of the deposit which change the stress-strain state of the surrounding massif.

The deposit where the issue of scientific justification of safety measures and reduction of geodynamic risk is particularly acute is the Nikolaevskoe polymetallic deposit, which is classified as rockburst hazardous. In recent years there has been a significant increase in the number and intensity of dynamic manifestations of rock pressure and technogenic seismicity.

Studies of the stress-strain state of massif were carried out using numerical modeling methods by the finite element method, with verification of the results by instrumental methods.

The mining of the Kharkov and Vostok-1 zones located in the zone of influence of the tectonically active fault TN-3 is accompanied by increased seismic disturbances and manifestations of rock pressure. Annually, in the TN-3 fault zone, the geoacoustic rock pressure monitoring system “PrognozADS” registers events of various energies, and the foci of acoustically active zones formed in this case migrate mainly to the mining operation sites.

The developed finite element models, taking into account the geological structure of the ore-rock massif, the configuration of the worked-out spaces, as well as the features of the tectonic structure, will allow us to determine the spatial location and parameters of potentially rockburst prone zones formed during the mining of ore blocks with the greatest reliability.

Analysis of the simulation results showed that the development of reserves within the depths of 660-710 m in the area of the Kharkov resources leads to increased concentration in the inter-chamber pillars, stopes, as well as in the roof of the workings on sublevels. At the same time, the location of the chambers being worked out relative to the TN-3 tectonically active zone has a significant influence on the stress level, the closer the chamber is located, the higher the stress level is.

With the transition of mining operations to deep levels (760-800 m), there is a redistribution of stresses. The growth of stresses is observed both in the pillars of various configurations and in the roof of mine workings on deep horizons, which is due to the significant amount of accumulated worked-out spaces. In addition, unloading areas are observed.

A further increase in the depth of mining to 800 m and below leads to an even greater complication of the geodynamic situation. Thus, the stresses in the mine workings at level -433 m directly under the chamber 3 of the "Lower" Block are 2-3 times higher than the initial level.

Along with the formation of zones of increased stress, the development of reserves in the area of influence of the tectonic zone of TN3 also leads to the appearance of unloading areas up to tensile stresses, in some cases exceeding the shear strength.

The performed research results allowed us to establish important regularities of the formation of natural and man-made stress fields under the influence of the most significant factors: the depth of mining, the position relative to the direction of maximum compressive stresses, the location relative to the tectonically active zone, which in turn allows us to choose the most rational ways to control rock pressure.