Investigating the variation of the fields of elastic stresses in the rock mass when developing the Peschanskoye deposit

Abstract

Research aim is to study parameter variations in the stress state of the rock mass to ensure safe and efficient mining of the Peschanskoye magnetite deposit (Northern Ural) to the full depth, which has been carried out by Severopeschanskaya mine since 1958 in a complex of hard rock at a depth of 200 to 700 m. Blind, thick, and steep ore bodies are developed by a block-caving method with ore breaking to a clamped medium. From a depth of 400 m, the field is classified as rock burst hazardous. The first rock burst was recorded in 1981 at a depth of 450 m. Research methodology includes full-scale experimental measurements of the rock and ore mass stress state at accessible depths and horizons of the deposit, establishing patterns of stress growth with depth, as well as long-term (since 1990) geo-deformational monitoring of an untouched rock mass stress level in time. Research results analysis has allowed to establish the patterns in stress-strain state changes during mining. Gradients of gravitational and tectonic stresses growth with depth are determined. Alternating (astrophysical) stresses are highlighted in a special line, the extreme values of which are linked chronologically with various information factors. Conclusions. The determined values of rock mass natural stress state variation parameters in combination with the established stresses around the workings and goafs (technogenic impact) make it possible to take into account the main tempo-spatial factors of the impact made by the mentioned loads when selecting rockburst-safe and effective mining parameters for underground geotechnology both at the top horizons when applying controlled collapse of overlying blind deposits and in the prevention of rockburst hazard in the lower horizons of the developed field