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ENGINEERING-GEOLOGICAL AND GEOECOLOGICAL SUBSTANTIATION OF MINING SAFETY AT A UNIQUE DEPOSIT OF HIGH-GRADE IRON ORES (KURSK MAGNETIC ANOMALY, RUSSIA)

R. E. Dashko, Ivan Alekseev

Abstract

Among unique deposits of high-grade iron ores (HGIO) of the Kursk Magnetic Anomaly those that are referred to the Belgorod group are ranked as outstanding. One of them, located in the Central European part of Russia, is known as the YakovlevпїЅs underground mine. Its singularity is resulting from following circumstances: 1) high quality of ores, in which iron content exceeds 65%; 2) genesis of HGIO that are originating from ancient crust of jaspilites chemical weathering and appear to be an extremely fine-grained water-saturated deposits; 3) depth of mineral product occurrence more than 600 m; 4) complexity of structural-tectonic conditions, predefining high disintegration degree of the iron ore body and enclosing rocks, and thereto related problem of underground workings stability; 5) specifics of hydrogeological conditions associated with the presence of several high-pressure aquifers above the iron ore body, and with their particular hydrochemical composition; 6) features of mine development, which is carried out under conditions of draining only the iron ore body (Ore-crystalline aquifer), whereas remaining overlying aquifers are keeping their high heads. In the context of pressure gradient formation we observe a constant downward flow of groundwater, mainly from an adjacent stratum of the Lower Carboniferous aquifer, that leads to secondary moistening of iron ores and transfers the weakest fine-grained types of ores into a quick-sand state. While area of mining works is continuously extending, developing gravity processes are dictating probability of local water breakdowns from the undrained Lower Carboniferous aquifer through the protective aquiclude, which is presented by a structurally complex stratum. The paper contains systematization of endogenous and exogenous engineering-geological processes occurring at the mine levels -370 m and -425 m with due consideration of their hazard level in relation to stability of underground workings and safety of mining operations in circumstances of growing ore extraction volumes. Particular attention is given to microbial activity of different genesis in the iron ore body. Main sources of its income into the rock massif are established. Its negative effect on decreasing strength of friable HGIO in the process of their watering is analysed. Special focus is made on the problem of structural materials corrosion damage, most notably lightweight concrete used for backfilling operations. Based on full-scale field and laboratory microbiological studies microbially-induced corrosion of metal arch supports is characterized.

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DOI resolver: doi.org/10.5593/sgem2017/13/s03.040

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