EVALUATION OF NATURAL STRESSES IN ROCK MASS AT LOWER HORIZONS OF KHOLBINSKY MINE

Abstract

The paper presents the results of natural stress measurements at the lower horizons of the Kholbinsky mine in 2017. 4 observation stations have been laid down at the horizons 1290 – 1190 m. Maximum measurement depth is 940 m. Natural stresses were determined by the slot unloading method based on the method of the Institute of Mining of Ural Branch of RAS. 7 samples of rocks and ores were taken at the measuring sites to carry out the laboratory tests of physical, strength and deformation properties. It is established that the average rock density was 2.75 g/cm3, the Poisson's coefficient was 0.18 and the elastic modulus was 50.1 GPa. The measured stresses at a depth of 860 - 940 m are as follows: vertical -23,6..25,8 MPa, horizontal longitudinal -12,4..38,8 MPa, horizontal transverse - 13,7..55,1 MPa. It is established that the values of measured stresses are significantly influenced by the tectonic structure of the deposit: the maximum values of horizontal stresses are fixed in the center of the deposit between large tectonic faults, and the minimum values are fixed on locally destroyed areas. Based on the measurement results, the forecasting dependences have been proposed to evaluate the initial stresses: to
calculate vertical stresses from the weight of superimposed rocks, to estimate horizontal longitudinal stresses as 80 % of vertical ones and horizontal transverse as 170 % of vertical ones. The obtained regularities have been used as boundary conditions to evaluate the stress-deformed state of mine workings and pillars. The "Conclusion on Bump Hazard and Gas-Dynamic Aspects at Zun-Kholbinskoye Gold Ore Deposit" has been developed for practical application.