Practices on gas control based on CO2 blasting and permeability improvement technology

In order to solve the difficult falling of the hard roof in No.09114 fully- mechanized coal mining face of Limin Mine and to solve the gas and harmful gas C oncentration over limit at the top corner of the coal mining face, with the study determination, a CO2 blasting fracturing technology with the water injection pressurized f racturing and the bolt withdrawn auxiliary measures of the roof strata above the goaf was applied to the pre- fracturing blasting to the roof strata above the roof in order to eliminate the personal casualties coursed by the sudden roof falling down. With the continued optimizations of the borehole designed parameters and water injection pressure size and practices on the top corner of No. 09114 fully- mechanized coal mining face in Limin Mine conducted, the results showed that before the CO2pre- frac turing blasting conducted, the gas fractional volume during the coal production was 1. 5% ~ 2. 0% and the gas fractional volume during the equipment maintenance was 1. 0% ~ 1. 5%. After the CO2pre- fracturing blasting conducted, the gas fractional volume during the coal production could be controlled at0. 3% ~ 0. 4% and the gas fr actional volume during the equipment maintenance could be controlled at 0. 2% ~ 0. 3%. The gas concentration decreased by 80%, affter used the CO2 blasting fracturi ng technology, the permeability of the seam improved by 53%, and it could be favorable to pre- drainage gas.