切顶留巷围岩卸压特性及支护效果OA

To investigate the key technical parameters roof-cutting pressure relief of the cut and the effect of retained roadway,this study conducted in-depth research by taking Dongrong No.2 Coal Mine as the engineering background,and implemented an experimental project of roof-cutting and roadway retaining by using shaped charge blasting in the return air roadway of the 1803 working face.The height of roof cutting for roadway retaining and the depth of blasting boreholes were calculated and determined,the stress and displacement changes of the surrounding rock in the roadway after roof cutting were simulated and analyzed,and the deviation angle of the blasting boreholes for roof cutting was optimized,meanwhile,the effect of retaining roadway was investigated on site.Research results show that the reasonable height of roof cutting for roadway retaining in 1803 working face is 6.0 m,and the reasonable depth of blasting boreholes for roof cutting is 6.5 m.After roof cutting,the vertical stress on the roof of the retained roadway decreases by up to 30%,and the vertical displacement decreases by up to 33%.It is found that the pressure relief effect is best when the roof cutting boreholes are inclined towards the goaf by 15°.The spacing between blasting boreholes on site is 0.6 m,with hole-separating detonation implemented,and a reinforced support system consisting of U-shaped steel retractable pillars-single hydraulic props-fly ash bags was added implemented.The monitoring data of roadway retaining shows that the average approaching displacement of the roof and floor is 385 mm,and the average approaching displacement of the two sides of the roadway is 245 mm.The pressure of the roadway side supports is maintained at 37-40 MPa,and the deformation of the surrounding rock in the roof cutting roadway is stable,indicating favorable roadway retention performance.