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The revelation of the distribution characteristics of stress and fractures in the floor strata is of great significance to improve the regional gas drainage efficiency and to eliminate or reduce the risk of coal and gas outburst in adjacent coal seams during multi‐seam mining. In this paper, the stress distribution in the floor under mining condition was derived, and the characteristics of stress zones in the floor were elaborated while mining the 22201 working face in Shaqu coal mine in Shanxi province, China. Besides, the propagation laws of fractures in different stress zones were theoretically analyzed, and the distribution law of fracture angles in the floor strata under different mining‐induced stresses was obtained. The research results demonstrate that the compression and transition zones show high vertical stress and less developed fractures and are dominated by fractures with a large angle (>60°), which is unfavorable for gas drainage. The expansion zone in the floor within 2‐40 m in the rear of the working face is characterized by high unloading degree of vertical stress and developed fractures. Moreover, fractures with a small angle (<60°) dominate the spatial distribution of the fractures, which is favorable for gas drainage. The research results can not only be a beneficial supplement to the theory of coal and gas co‐exploitation in multi‐seam mining but also provide theoretical support for optimizing the design parameters of cross‐measure boreholes under similar conditions. [ABSTRACT FROM AUTHOR]

Extraction of a protective coal seam (PVCS)-below or above a coal seam to bemined with the potential of coal and gas outburst risk-plays an important role not only in decreasing the stress field in the surrounding rockmass but also in increasing the gas desorption capacity and gas flow permeability in the protected coal seam (PTCS). The PVCS is mined to guarantee the safe mining of the PTCS. This study has numerically evaluated the stress redistribution effects using FLAC3Dmodel for a longwall face in Shanxi Province. The effects ofmining depth, mining height and inter-burden rock mass properties were evaluated using the stress relief angle and stress relief coefficient. Vertical stress distribution, stress relief angle and stress relief coefficient in the PTCS were analyzed as the face advanced in the PVCS. The results showed that the stress relief achieved in different locations of the PTCS varied as the face advanced. Sensitivity analyses on the pertinent variables indicate that the stress relief in the PTCS is affected most by themining depth followed by the inter-burden lithology and themining height. Furthermore, the elastic moduli of different layers within the inter-burden rock mass are more important than their uniaxial compressive strength (UCS) and Poisson's ratio. These observations can guide gas drainage borehole design to minimize the accidents of coal and gas outbursts. [ABSTRACT FROM AUTHOR]