Abstract
Water-bearing caves in the Maokou limestone have caused disastrous water inrushes in mines in southern China. A linkage analysis between the hydro-mechanical coupling and the strength reduction method was used to investigate the stability of water-resistant rock pillars. The factor of safety (FOS) of the pillar was established, and a criterion for establishing the required width of the pillar was proposed in engineering practice, i.e., the width of the pillar should be based on the blast hole depth and blast-disturbance depth, along with a FOS of 1.5. The permeability of the water-resistant pillar and the probability of water inrush both increase as the strength reduction factor increases because the effective width of the pillar narrows. A numerical analysis of the Qiyi coal mine “4·16” water inrush accident shows that the cause of the inrush was that the 3.0 m wide barrier left by roadway excavation was too narrow to withhold the karst water pressure of about 4.0 MPa.
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