In order to grasp the impact of the lower coal seam on the disturbed"key layer"of the upper coal seam during close distance coal seam group mining,a model of mining under the coal seam group goaf is established using FLAC3D numerical simulation method.The contact surface unit is used to simulate the fracture surface of the key layer,and the goaf is treated with softening method.The stress failure characteristics of the overlying rock in the disturbed key layer fractured surface of the upper coal seam during downward mining are analyzed,and the reliability of the numerical simulation is qualitatively verified through on-site engineering practice.The experiment results show that the simulation effect can be achieved by prefabricating the disturbed key layer fractured surface and using the stope softening method to treat the goaf,which is more in line with the objective reality situation.Due to the presence of asymmetric stress combination arches above the disturbed key layer,it ensures that the fractured block can form rotary deformation without step sinking when the fractured block is above the working face.At the same time,the stress distribution at the interface of the fractured block is analyzed.
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