3. Acquisition and Quantification of Main Controlling Factors of Water Inrush from Coal Seam Floor in Coalfields of North China

The main controlling factors of coal seam floor water inrush in combination with a large number of cases of water bursting in China have been analyzed over many years. We have not only theoretically analyzed the water pathway, water filling source and water filling intensity leading to the coal floor water bursting, but also assessed the influences of water-filled aquifer, coal seam floor, within underlying aquifer floor, geological structure, and coal mining disturbance on coal seam floor water inrush. Based on these above results, a main factor system of floor water bursting is established. To effectively eliminate the influence of data diversity of main factors index on evaluation results, this study has developed a unified quantitative criterion to make the final water bursting evaluating result more consistent and comparable. With the quantitative criterion, a quantitative indicators system is established for these main factors, including water-filled aquifer pressure, water yield property, and impermeability of weathering crust (three factors about aquifer); equivalent thickness of effective water-resisting layer, position and thickness of key layer (two factors about water-resisting layer); distribution of faults and folds, distribution of collapse column; distribution of faults and folds endpoints and intersections, and fault-scale index (four factors about geological structure); development zone of underground pressure, development zone of water head intrusion, and brittle rock thickness under the disturbance of mining engineering (three factors about mining engineering disturbance). We have also applied the dimensionless method to eliminate the impacts of those main factors from inconsistent dimension on water inrush evaluation, which lays a foundation for information integration of multi-factor analysis.