Application of Roof Pre-fracturing and Blasting Technology to Prevent Hydraulic Powered Support Jamming Accident

Due to the load transmission role of the high water pressurized loose aquifer, the key stratum in the overburden strata would be completely broken and t hus the hydraulic powered supports jammed accident occurred during the mining operation period of No.7121 coal mining face in Qidong Mine. The prevention and contr ol of the hydraulic powered supports jammed accident should prevent the roof completely broken and the roof pilot pre-fracturing blasting would be a suitable method to prevent and control the hydraulic powered support jammed.According to the geological mining conditions and the overburden strata structure features of No.7121 coal mining face, the roof pre-fracturing blasting plan and the related technical parameters was set up.The practice results showed that based on the good support quality pr otected in the coal mining face, the roof pre-blasting measures applied could reduce the average resistance of the powered support at the central and down parts of the coal mining face by 246 kN, the periodical pressurized distance could be reduced from 34.1 m to 23.0 m and the pressurized sustained length would be reduced from 2 0.2 m to 5.0 m.Therefore, the possibility of the overburden stratum completely broken could be reduced and the active role would be played to prevent the powered sup port jammed accident.