Study on Gas Occurrence Law in Stress Concentration Zone of Remaining Coal Pillars in Close Protection

Abstract

According to the law of mine pressure appearance of No.9 coal seam 9106 working face passing through No.8 coal seam in Xinjing Mine of Yangmei Group, the combination of theoretical analysis, numerical simulation and field measurement is adopted, firstly, the mechanical model of protective layer is established, the mechanical calculation formula of protective layer is obtained; secondly, through FLAC3D numerical simulation, the stress distribution rule and influence range of coal pillar pressure area are revealed; finally, the field monitoring verification is carried out. The results show that: the vertical stress state at the completion of protective layer mining is centered on the residual coal pillar, spreads to both sides in sequence; the further away from the remaining pillar, the wider its spread; the influence range of the remaining coal pillar is 33 m, the maximum stress value is 38.6 MPa; through actual measurement of the gas drilling cutting index in stress concentration zone and the pressure relief zone, the result shows that cuttings desorption index K1 value, amount of cuttings S value and stress distribution state have good correlation, at the same time, it is concluded that the coal seam gas can be fully released under the condition of close protection seam mining.

Keywords

• protective layer mining
• remaining coal pillar
• numerical simulation
• stress concentration
• scope of influence