Study on key parameters of self-formed roadway without coal pillar by roof cutting and pressure relief in medium and thick coal seam

Currently, the mining technology of self-formed roadway without coal pillars for roof cutting and pressure relief is widely used in the thin coal seam, and most of the related researches are carried out around the application in the thin coal seam, while the research of application in the medium-thick coal seam is less. In order to improve the recovery rate of coal resources and avoid the stress concentration problem caused by the filling body position caused by the traditional filling method to achieve gob-side entry retained, the short-wall beam with the top cut was used as the theoretical basis. Taking the No.62711 working face of the Du′erping Coal of Mine Xishan Coal Electricity Group as the engineering background, the process flow and key technical parameters of the mining technology of self-formed roadway without coal pillars in the middle-thick coal seam were analyzed. The stress distribution of the surrounding rock and the roof displacement of the roadway when the traditional longwall mining method and the top-cutting pre-split blasting heights were 4, 6, and 8 m and the top-cutting angles were 5°, 10°, 15° and 20° were respectively analyzed. The results show that under the conditions of reasonable pre-splitting blasting cutting height and cutting angle, not only can the roof rock layer be forced to collapse in time after the working face is mined and fill the gob, but it can also effectively cut off the stress transmission path between the roadway and the roof rock layer of the gob, so that the stress concentration area is transferred to the depth of the solid coal, and the stress environment of the surrounding rock of the roadway is improved, and it plays the role of roof cutting and pressure relief. Meanwhile, the optimum blasting scheme is obtained through field test. This research has played a theoretical guiding significance for the application of “non-pillar gob side entry retaining formed by roof cutting and pressure release” in medium and thick coal seams.