Safety Comparison of Coal Seam Floor Water-inrush Criteria Based on Two Yield Criterion

To predict the water-inrush from coal seam floor,a thick single rock stratum with higher strength(or compound body of two-layer thick hard rock stratum with certain weak intercalation and short distance) in remaining complete strata of mining floor was simplified as a clamped rectangular thick plate,and a mechanical model for water-resisting key stratum of coal seam floor was built.Two mechanical criteria for predicting water-inrush from floor were derived,one based on yield criterion of Tresca and other based on that of Mohr-Coulomb(M-C).According to field prediction results of water-inrush from floor,two criteria were analyzed.The results indicate that M-C yield criterion tends to be preferable to Tresca yield criterion in reflecting the practical engineering properties of mine rock mass,and that water-inrush critera based on M-C yield criterion is more safe and reliable for predicting water-inrush from coal seam floor.