DEM Analysis of the Effect of Lamination Properties on the Stability of an Underground Coal Mine Entry with Laminated Shale Roof

The effect of discontinuities on the fracturing and mechanical behavior of shale has been extensively investigated on a laboratory scale in previous works. It is well agreed that the lamination properties, including discontinuity and lamina properties, affect the behavior of shale. However, it is still unclear how the lamination properties are affecting the stability of the shale roof in an underground coal mine entry. This paper investigated the effect of lamination properties using discrete element method on a mine-scale entry model as an extension to the previous work conducted on laboratory scale models (Q. Shi and B. Mishra, Discrete Element Modeling of Delamination in Laboratory Scale Laminated Rock, Mining, Metallurgy & Exploration, vol. 37, no. 5, pp. 1–14, Sep. 2020). The microparameters for both the laminas and discontinuities were calibrated with laboratory data. In the calibration, a numerical laminated Brazilian disc was created and tested for comparison with laboratory results. The effects of lamina thickness, discontinuity strength, and supporting pressure on the model’s roof strength and the stress distribution were also investigated. Numerical results showed that the lamination properties and supporting pressure contribute significantly to the stress distribution in the roof and its stability. The horizontal stress at a fixed depth in the roof increased with the lamina thickness, discontinuity strength, and supporting pressure. The laminated roof strength was found to increase with the increase of lamina thickness but never exceeds the strength of an intact roof comprising the only matrix.