| Abstrakt: |
Abstract: Coal measure strata are composed of multiple interbedding strata with different hardnesses. A sudden release of energy that was stored in surrounding rocks of tunnels may induce a rock burst; however, the specific strata in which the energy is accumulated cannot be accurately determined, thereby leading to ineffective prevention and management techniques for rock bursts. To address this problem, this study conducted axial loading tests on three different types of rock specimens (coal, gritstone and fine sandstone) and their composite specimens, and ascertained the energy accumulation rules of various components of the composites prior to a buckling failure. According to the results: for the coal-bearing binary composite specimens, the energy accumulated in coal occupied 88.5 %, 79.0 %, 71.4% and 79.6 % of the total energy accumulated in the specimens respectively; for the binary composite specimens composed of gritstone and fine sandstone, the energy accumulated in gritstone took up 61.2 % and 76.5 % of the total energy accumulated in the specimens respectively; and for the ternary composites, the energy accumulated in the coal occupied 79.8 %, 74.0 % and 76.3 % of the total energy accumulated in the specimens respectively, followed by the energy accumulated in the gritstone (12.1 %, 22.0 % and 18.8 %), and finally by the energy accumulated in the fine sandstone (only 8.1 %, 4.0 % and 4.9 %). Accordingly, in the composite rock strata, a small amount of energy was stored, and energy accumulation was more difficult in competent rock with large elastic moduli, while non-competent strata with small elastic moduli were preferable with regard to energy storage and accumulation. It can thus be concluded that the energy in coal-rock composites was accumulated mainly in non-competent strata, i.e., non-competent strata were key energy strata; additionally, the greater the difference in the hardness of the various components. |
