Stability of Gate Roads Next to an Irregular Yield Pillar: A Case Study

This paper presents results for using an irregular yield pillar for gate road stability in a split-level panel layout (SPL) at a coal mine. The mine extracts 8# and 9# coal seams with a mudstone interlayer. SPL is being used to improve caveability for top coal. The tailgate is driven along the floor of 9# coal seam while the headgate is driven along the roof of 8# coal seam producing a gradually elevated (or curved) section on one end of the panel. Therefore, the gate pillar is of irregular shape and consists of two coal seams and a sandwiched mudstone interlayer. The stability of the tailgate next to this type of irregular yield pillar was investigated using numerical modelling and validated through field measurements and observations. The results show that tailgate with a 6-m-wide pillar has the minimum deformation. The sandwiched mudstone interlayer increases overall stability of tailgate and the yield pillar. The yield zone is smaller especially for the roof of the tailgate which provides a better support condition for the tailgate. Roof-to-floor convergence is smaller than rib-to-rib convergence. The intact zone in the curved section contributes to the overall stability of the gate pillar. Field observations show that stability of the tailgate next to the 6-m SPL yield pillar was maintained along with reduction of other ground control problems.

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