Abstract: The roof failure accidents in large mined-out area have frequently occurred in domestic gypsum mines in recent years. Up to now, little study has been made on the mechanism of the large roof failure occurrence in gypsum mines. Based on the site investigation on the gypsum mines and in combination with the related rock mechanism theory and numerical simulation technology, it is concluded that the roof failure in the stope and in the large-scale mined-out area in gypsum mines is mainly induced by the decrease of the strength of the gypsum pillars due to its rheology and by the increase of the stress of the pillar due to the expansion of the mining area.

Key words: Roof failure, Numerical simulation, Rheological property