Study on the stability of coal pillar under the method of gangue fluidized filling

The overlying rock structure and stress process are systematically analyzed to solve the coal pillar instability caused by the gangue fluidized filling process. The stability model of the key block above the coal pillar and the stability model of the coal pillar were respectively established. The key block instability criterion was obtained through a theoretical analysis of the key block balance equation. In combination with the theory of the plastic zone, the criterion of unstable coal pillars is proposed. The above calculation demonstrates that the pressure of the overburden, the width of the coal pillar, the elastic foundation coefficient of the gangue, and the grouting pressure are the main factors affecting the stability of the coal pillar. Based on the specific geological conditions of Pingmei No. 12 Mine, more calculations are derived: the width of a side of the plastic zone of the coal pillar is only 0.80 m, and the coal pillar will not be damaged during the filling process, and the stability is good.