An experiment to determine the width of coal pillar when mining seams under hard-to-cave main roof conditions

Abstract

Ensuring roadway stability is one of the keys to determining production efficiency and labor safety in Vietnam's underground coal mines. However, it is difficult to determine the reasonable width of coal pillars to protect the roadway and roadway deformation therefore usually occurs. Especially when exploiting coal seams in the deep and hard main roof conditions, the deformation of the roadway becomes even more serious, affecting labor safety. Using the mining data of Seam #10 at Ha Long Coal Company as the reference case of this research, a scale model of equivalent materials has been conducted. The stability of the roadway has been simulated and analyzed in different widths of coal pillars. The results show that, when exploiting coal seams under a hard-to-cave roof, very thick and long roof consoles are formed in the gob. The stability of the coal pillar and roadway is influenced by the sagging, rotation, and fracturing of the main roof in the gob. Under the impact of static and dynamic loads of the main roof, a coal pillar of less than 40 m width is not stable enough to protect the roadway. As the width of the coal pillar decreases, more apparent cracks in the roadway roof appear, and the coal blocks on the walls of the roadway are broken and wider. Visual monitoring results show that a coal pillar of more than 40 m in width can ensure the stability of the roadway. However, it causes a much more loss of coal in the pillars, a challenge for further research.