Geotechnical Bureau LLC, Saint-Petersburg, Russia:

V. Yu. Sinegubov, Associate Professor, Candidate of Engineering Sciences, vs.geotechburo@gmail.com

Heading and stoping in mines change the stress–strain behavior of adjacent rock mass, which can lead to adverse consequences, including the limiting state of rocks and formation of damaged zones. The damaged zones appear not instantly but are associated with mining operations. The parameters of the damaged rock zones depend on geotechnical conditions of stoping, on mechanical properties of rocks and on the stoping impact. Natural structural discontinuities in rock mass even more complicate calculations. Traditionally, the size of the damaged zones is controlled via mine support installation. However, in hard rocks, efficiency of mine support systems is not so high. This article presents an analytical solution on the support design and conditions to ensure that no damaged zones arise in adjacent rock mass. The analysis of the physical, mechanical and structural properties of rock mass, typical of mines of Apatit’s Kirovsk Branch of allowed reliable numerical modeling and comparison of sizes of damaged rock zones in various stopes without support and with rock bolting and shotcrete lining. The damaged zone pattern in adjacent rock mass around an arched stope is analyzed as a case-study of mines of Apatit’s Kirovsk Branch, and the effect of the rock bolt support and shotcrete lining on the size of this zone is determined. The calculations show that in the discussed geological conditions, the use of mine support reduces the size of the damaged zone by 7–20 %, which helps optimize the support design and expands its application field but fails to totally eliminate damaged zone formation. The mechanical properties and structural discontinuities in rock mass have a serious effect and should be in spotlight of the analysis.

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