Comprehensive safety factor of roof in goaf underdeep high stress

Abstract

The safety factor of roof under deep high stress is a quantitative index for evaluating roof stability. Based on the failure mode of surrounding rock of stope roof, the mechanics model of goaf roof is constructed, and the internal force of roof is deduced by the theory of hingeless arch. The calculation method of roof safety factor (K) under the environment of deep mining is proposed in view of compression failure and shear failure of roof. The calculation formulas of shear safety factor (K₁), compression safety factor (K₂) and comprehensive safety factor (K) of roof are given. The influence of stope span and roof thickness on roof stability is considered in this paper. The results show that when the roof thickness remains constant, the roof safety factor decreases with the increasing of the stope span; when the stope span remains constant, the roof safety factor increases with the increasing of the roof thickness. The deep mining example shows that when the stope span is 30 m and the roof thickness is 10 m, the roof comprehensive safety factor is 1.12, which indicates the roof is in a stable state.

Keywords

deep mining / high stress / hingeless arch / comprehensive safety factor / stope span

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