Study on Broken Floor Rock Mass by Mining Underground Pressure

As the dangerous level of floor water inrush in Chinese coal field is becoming more and more serious annually, the widely used formulas of broken floor rock mass are belonged to nonlinear type or empirical type. However, they are not well conformed to the practical situation and including mining underground pressure. The biggest depth of broken floor rock mass and the length of gob-floor or mining-floor until the maximum broken floor location are expressed by theoretical formulas on integrity theory. Taking a mining face in Chinese Anhui Province as the object, the relationship between broken floor rock mass and mining underground pressure is studied by numerical simulation, the theoretical analysis, and the DC exploration. The peak and scope of broken floor rock mass will enlarge until reaching limit value with the increasingly advanced distance. The mining gob stress contour is saddle-shaped, and its growing speed is becoming slower, so the 180 m coal mining face has reached the sufficient mining stage. Wave velocity of broken floor rock mass from 0 m to 16 m is greatly decreased by the mining disturbance, and it is basically conformed to theoretical formula and practical situation. The results can be relatively better used in the pressure mining of the Ordovician limestone, because it can provide some safe guarantee for mining deep coal seam.