Abstract: “Mining above aquifer”, as the main method to explore coal seams above confined aquifer, in which the determination of coal seam floor failure depth is the key factor and precondition. Taking the 1066 workface of Taoyuan Coal Mine for example, the high-precision microseismic monitoring technique is used to monitor the continuous and dynamic failure characteristics of an inclined coal seam floor above a confined aquifer, which can overcome the limitation of traditional method in field measurement of floor failure depth, especially for the failure depth of an inclined coal seam floor (the inclined angle of coal seam is between 25°and 45°). The monitoring results show that: (1) compared to the coal seam floor nearby the workface return airway (upper crossheading), the failure depth of coal seam floor nearby the workface conveyance roadway (lower crossheading) is deeper, with wider failure zone. (2) from the whole aspect, the failure zone of the inclined coal seam workface floor presents an asymmetric form. According to the results of microseismic monitoring, the maximum failure depth of the coal seam floor nearby the workface return airway and the workface conveyance roadway as well as the dangerous area of water-inrush from floor are determined. Finally, the floor failure depth determined by microseismic monitoring is compared with the failure depth calculated by the empirical formula; some existing deficiency of the empirical formula for calculating the floor failure depth are pointed out.

Key words: inclined coal seam, microseismic monitoring, failure depth, water-inrush from floor