Abstract: In this paper, the concept of water inrush risk coefficient was proposed through theoretical analysis, and the theory and method of the evaluation of water inrush danger under the Quaternary loose aquifer, as well as the reasonable design method of waterproof coal pillar were established. The results show that the thickness of effective protective layer is calculated by the distance between the top of mining seam and bottom of Quaternary loose aquifer minus the height of caving and fractured zone which is formed after mining the whole height at one time. If the thickness value is less than zero, the  water in the Quaternary loose aquifer may influx into the working face, which will result in roof water inrush. If the thickness value is larger than zero, the water inrush risk coefficient, which is the ratio of hydraulic pressure in Quaternary loose aquifer to the thickness value of effective protective layer, can be used to evaluate the water inrush danger. On this basis, the thickness of protective layer and the reasonable height of waterproof coal pillar are put forward according to the hydraulic pressure value of loose aquifer. Adopting the method metioned above, the water inrush danger of No. 8 coal seam mining under Quaternary loose aquifer in Donghuantuo minefield, Kailuan mining area, and the reasonable waterproof coal pillar were evaluated. The evaluation results consistent well with the actual conditions.

Key words: Quaternary alluvial water；water inrush risk evaluation；coal mining；waterproof coal pillar