Stability analysis and failure control of a longwall panel with a large mining height considering fracture distribution

With the increasing coal cutting height of a longwall panel with a large mining height, joints and fractures have a more obvious influence on coal wall stability, which intensifies rib spalling. To investigate the influence of the fracture distribution on the stability of a coal wall with a large mining height, this paper utilizes a large panel in the Zhaogu No. 2 coal mine as the research object. The coal strength and fracture occurrences are measured to obtain the probability distribution function of the fracture spacing and density. A 3D numerical model of the panel with a non-through fracture is established by using 3DEC software based on the Poisson's disk model and Monte Carlo principle, and numerical experiments of rib spalling and the optimization of flexible reinforcement control technology are conducted. The method of prefabricating non-through fractures and physical experiments are proposed to analyze the stability and damage degree of the coal wall under different fracture tendencies. The results show that the existence of fractures changes the direction and magnitude of the stress field, thus making the stress and displacement of the coal wall show anisotropy, revealing a high correlation between the densities and sizes of joints and the coal strength. When the joints are parallel to the coal wall with a 45 degrees dip angle, the coal wall stability is the most unfavorable with the largest damage range. The optimal grouting position and flexible material diameter are determined; i.e., a grouting position at 60-70% of the coal wall height and a material diameter of 20 mm exhibit the best control effect. The research results provide a new approach for the control of rib spalling in fractured coal.