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Abstract Water outbursts from coalmine floor and hydraulic fracturing have the homologous mechanical mechanisms，which are all to determine the critical water pressure during failure process(water outburst coefficient is defined as critical water pressure per unit thickness of floor). The effect of effective stress coefficient is remarkable through hydraulic fracturing theoretical analysis. The influence of different effective stress coefficients during the process of water outburst in coal mine floor is discussed from static and transient aspects by in-situ case simulation，respectively. The formula of modified critical water outburst coefficient under different seepage conditions in coal mine floor is derived according to the theory of effective stress. Finally，calculation and field test methods of modifying water outburst coefficient are proposed according to different seepage conditions in coal mine floor，which have significant theoretical and practical senses for understanding the essences of water outburst induced by rock failure，the connotation of water outburst coefficient，and the guidance of seepage control design by grouting.
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Received: 20 May 2011
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2011, Vol. 30 
