Key roof cutting parameters of self-formed roadway with dense boreholes and roof cutting
Blasting-free dense borehole roof cutting technology is increasingly used in gob-side roof cutting self-forming road-way.Taking the 203 working face of Ruineng Coal Mine as the research background,the key parameters of the dense bore-hole roof cutting and pressure relief gob-side entry retaining process,such as the height of the dense borehole roof cutting,the angle of the directional slit drilling,the borehole aperture and the borehole spacing,were studied.The results show that the increase of the aperture has a larger effect on the plastic zone connecting between dense boreholes;the increase of top-cutting angle can in a certain extent weaken the horizontal restriction of goaf roof,ensuring the timely collapse of goaf roof;the reasonable increase of top cutting height can reduce support resistance of roadway side while ensuring the success of top cutting;and the smaller spacing of borehole is conducive to the connecting of plastic zones.The roof cutting parameters with a roof cutting height of 8 m,a hole inclination angle of 15°,a hole diameter of 48 mm,and a hole spacing of 200 mm were determined.The roof of the goaf can fall in time and form the roadway side with stable bearing capacity.After mining of the working face,the maximum displacement of the roof and floor in the middle of the roadway is 250 mm,and the maximum displacement of the roof and floor on the roof cutting side is 170 mm.The pressure behavior of the retention section is sta-ble.The effect of roof cutting and pressure relief and roadway formation meets the needs of mine.The method of determining the key parameters of gob-side entry retaining with dense borehole roof cutting and pressure relief is verified,which provides engineering reference for the same type of mines.
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