Determination of ratio of fractured zone height to mining height in full-mechanized caving mining

In order to calculate the fractured zone height of roof of coal seam No. 3 under aquifer after full-mechanized caving mining,the analogy method,numerical simulation and working face measured method were introduced. The calculation shows that the ratio and the fractured zone height given by the analogy method are 18 and 163. 08 m,respectively; that the ratio and the fractured zone height given by the numerical simulation method are 14. 57 and 132 m,respectively; that the ratio and the fractured zone height given by the measured method are 13. 47 and 122 m,respectively. Through the comprehensive analysis,the followings are concluded: the ratio of the full-mechanized caving mining is less than that of the fully-mechanized slicing. When there is hard rock roof,the range of the ratio—the height of the fractured zone to the mining height — is from 12. 71 to 18.The ratio of the coal seam is 14. 57. The result determines the ratio of fractured zone height to mining height in full-mechanized caving mining of coal seam No. 3 accurately and provides theoretical basis for preventing the conducting from aquifer to working face.