Risk assessment of water inrush from coal seam floors based on multiple methods

Five factors including the thickness of the aquifer, the complexity of the fault, the water pressure of the aquifer, the unit water inflow of the aquifer, and mining height of 51 boreholes in No.2, No.10 and No.12 Coal Mines of Pingdingshan Coalfield are selected as the index factors. On the basis of the constant weight calculated by the analytic hierarchy process and grey relational analysis, the variable weights of each index factor are determined by applying the variable weight theory. By using the matter-element extension method, fuzzy variable set theory, catastrophe theory, and fuzzy comprehensive evaluation method, the water inrush risk of coal seam floors is evaluated and the water inrush risk grade is determined. The comparative analysis of the actual mining situation shows that the fuzzy variable set theory is the most suitable method for risk evaluation of floor water inrush in the study area, and its evaluation results are more consistent with the actual situation. The evaluation based on the fuzzy variable set theory shows that the proportions of safety zones in the pressure zones of No.2, No.10 and No.12 Coal Mine are 4.08%, 14.30% and 0 respectively; the proportions of low threat zones are 76.91%, 83.14% and 85.78% respectively; and the proportions of high threat zones are 19.01%, 2.56% and 14.22% respectively. There is no danger zones in the study area temporarily.