Load and permeability evolution law of lower layering in upper slicing of inclined extra-thick coal seam

In order to obtain the load and permeability evolution law of lower layering in upper slicing of inclined extra-thick coal seam, taking the 9-15 (06) working face of Xinjiang Liuhuanggou Coal Mine as the research object, the stress transfer model of the floor in goaf was constructed. The development of coal load in lower layer were simulated during the advancing process of the upper layering, then taking this as the stress path of lower layering coal samples. The stress loading and unloading experiments of lower layering gas-bearing coal were carried out, and the permeability evolution law of lower layering coal was obtained. The results show that, with the advancement of the upper layering, the vertical stress of the coal in the lower layering has experienced original rock stress, stress increase to the peak value of supporting stress, pressure relief after the peak value of the support stress, stress increases to stability. Along the coal seam inclined direction, after the coal of lower laying enters the goaf, the stress recovery degree of the coal gradually increases tilt from the upper part to the lower part of the goaf. The permeability of lower layering coal has experienced initial permeability, permeability decreases, permeability increases, permeability increases sharply, permeability decreases and restores stability. After the coal at different positions enters the goaf, the maximum recovery degree of permeability increases with the expanded of the maximum recovery degree of stress. The research results lay a foundation for revealing the spatio-temporal evolution law of gas emission of lower laying coal.