Mine pressure law and control technology of main roadway coal pillar working face passing through empty roadway

Due to the adjustment of the layout of the mine working face, the coal pillar working face often faces the situation that the overburden roof is difficult to control when passing through the abandoned roadway. In order to solve this problem, taking the outer coal pillar working face of the second panel of Zhaogu No.2 Coal Mine in Henan Province as the engineering background, theoretical analysis, numerical simulation and field test are used to study the fracture combination structure of the working face and the overlying strata of the empty roadway, simulate the full-cycle evolution law of roof stress-displacement under different support strength, analyze the characteristics of mine pressure in the working face, and put forward the corresponding control technology. The results show that the different fracture forms of the main roof have a significant impact on the characteristics of mine pressure behavior. The fracture positions of the key blocks can be divided into three types : above the coal pillar, above the empty roadway and above the solid coal. By establishing the mechanical model of the working face passing through the empty roadway, the mechanical mechanism of the advanced breaking of the basic roof is studied. The basic roof is supported by the empty roadway-coal pillar-working face support system, forming a stable bearing structure of ' masonry beam '. The critical value of the support strength of the basic roof sliding instability space-time roadway is 4.6 MPa. The numerical simulation shows that the superposition effect caused by the advanced support stress of the working face and the stress concentration of the empty roadway has a significant influence on the coal pillar. When the working face is advanced to 5 m from the empty roadway, the coal pillar is unstable and the basic roof is prone to advanced breaking. In the process of working face passing through empty roadway, the distribution characteristics of advance support stress of coal pillar change from ' bimodal type ' to ' isolated peak type '. There are obvious differences in the distribution characteristics of roof stress under different support strength. It is determined that the support strength of the empty roadway is 4.5 MPa, which can prevent the basic roof from breaking in advance. Finally, the ' anchor net cable ' support method is used to reinforce the roof of the empty roadway in the outer coal pillar working face of the second panel. The working resistance of the hydraulic support during the empty roadway is within the safe range of the study area, and no accidents such as roof collapse and support crushing occur. The technical problems of the empty roadway in the outer coal pillar working face of the second panel are solved, which can provide reference for similar working faces.