Study on the instability law of the coal-rock interbedded roof and its influence on supports in large mining height stope with steeply dipping coal seam

In order to study the instability law of the coal-rock interbedded roof and its influence on supports in large mining height stope with steeply dipping coal seam, the 25213-working face of Xinjiang Coking Coal Group 2130 coal mine is taken as the research object, the instability law of the roof and the interaction between the roof and supports under different layers and thickness coal-rock interbedded roof of steeply dipping coal seam are analyzed by means of physical similarity simulation experiments, numerical analysis combined with Rhino, Kubrix and FLAC3D, and field monitoring. The results show that the failure of coal-rock interbedded roof is caused by the partial compression shear failure of interbedded coal first, and then spread to the adjacent soft coal interbedded and gangue, which leads to the unbalanced roof failure and induces roof caving and rib spalling. The working support resistance, roof maximum principal stress and the roof deformation have obvious asymmetry characteristics in steeply dipping coal seam under coal-rock interbedded roof. With the increase of the number of gangue layers, the range of concentrated stress, surrounding rock deformation and plastic failure of coal-rock interbedded roof above the supports are increased. There are three interaction characteristics between supports and surrounding rock, namely, positive contact between roof and supports, broken roof acting on support shield beam, and the interaction between supports. Compared with the general roof in steeply dipping coal seam, the acting force of coal-rock interbedded roof on the support is significantly reduced. The support working resistance under coal-rock interbedded roof is asymmetrical, generally, the inclined middle and lower part is larger than the upper part of working face. The supports are asymmetrically loaded, and the lateral load of the supports' front leg are greater than the back leg. However, with the increase of the coal gangue roof thickness, the loading degree of the top beam tended to be uniformly distributed. Based on the research results, in order to ensure safe and efficient production of working face, a series of control principles for the stability of the steeply dipping coal seam under coal-rock interbedded roof are put forward, such as shortening the time of the empty-support, regional control, advance blasting and real-time dynamic monitoring of working face rock pressure.