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Abstract In order to explore the mechanism of rockburst in coal seam with rock parting, a combination of on-site and numerical experiment is used to study the failure and instability process, crack propagation mechanism, and influencing factors. The following four points were addressed: (1) the instability is a process that roadway in coal seam with rock parting go through from stable locking in the initial stress unloading stage to slipping unlocking, and then to spatter ejection in slipping dynamic load disturbance stage. (2) The fracture development caused by unloading excavation of coal seam with rock parting will change from shear crack to tensile crack. In this process, coal-rock contact surface slip and coal-rock fracture are coupled with each other. (3) The greater the mining depth is, the greater the lateral pressure coefficient is, and the higher the rockburst risk is. On the contrary, the lower the risk of rockburst. (4) When choosing the support form of roadway in coal seam with rock parting, the two supporting forms of bolting (cable) and supplementary masonry support should be preferred. The results enrich the theory of the dynamics of surrounding rock fracture in coal mine, further clarify the potential dangers to mining-area roadways and working faces, and provide technical information to ensure the safe and efficient mining of bifurcated coal seam.

Unloading excavation can increase the possibility of rock burst, especially for coal seam with rock parting. In order to explore the evolution process of rock burst under lateral unloading, the combination of in situ measures and numerical experiments is used to study. The following four points were addressed: (1) the coal seam with rock parting easily causes the stick-slip and instability along the interface, and the process of stick-slip and instability has hysteresis characteristics; (2) the greater the degree of unloading or the smaller the interface friction angle of the Coal-Rock Parting-Coal Structure (CRCS), the more likely it is for stick-slip and instability to occur; (3) the abnormal increase of shear stress and slip dissipation energy can be used as the precursory information of the stick-slip and instability of CRCS; (4) the damage intensity of rock burst induced by stick-slip and instability of CRCS can be reduced by reducing the unloading speed or increasing the roughness of interface. The research results can be used for early warning and controlling of dynamic disaster induced by stick-slip instability in coal seam with rock parking.

AbstractThe coal seam bifurcation area (CSBA) exists widely in coal measure strata, where the geological weak surface (GWS) slip in overburden structure is easy to induce coal burst. The coal mass of coal face shows overall instability failure and high-speed throwing characteristics during the coal burst, seriously threatening the safe and efficient coal mine production. In order to understand the GWS-induced coal burst caused by the slip in CSBA and find the main controlling factors of GWS slip, the GWS slip criterion in CSBA was established based on the coal burst case analysis of overburden structure in CSBA of 1305 coal face (1305CF) in Zhaolou Coal Mine. The case study showed that the angle and range of CSBA are the main controlling factors affecting GWS slip. The FLAC3D numerical model of CSBA was established to analyze the influence effect of main control factors. The results show that the increase of angle and range of CSBA will increase the influence scope and degree of coal face mining, improving coal face burst risk. However, the peak point region of abutment pressure will not be affected, gradually reaching its peak within 0 m ~10 m from the coal seam merging area. With the increase of the angle of CSBA, the integrity of the triangular wedged rock mass along the GWS slip will be enhanced, aggravating the dynamic disturbance to the coal mass. With the increase of the range of CSBA, the slip of triangular wedged rock mass along GWS gradually changes from integral slip to phased slip, which will intermittently disturb the coal mass of the coal face. The research results have certain theoretical significance and practical value for preventing and controlling coal bursts in CSBA.