To study the impact of mining of the lower protective layer on the deformation and failure characteristics of the upper roadway, these characteristics of an 879 gas drainage roadway were studied and analyzed during the mining of the II 1051 working face of the Zhuxianzhuang coal mine using similar simulation experiments and numerical simulation methods. The results indicate that with the continuous excavation of the working face, the range of impact of the mining stress gradually spreads and exceeds the level of the roadway. At the present time, the roadway is in a mining stress-rising area. The two sides of the roadway are sheared, and the roof and floor are under tension–shear composite failure. The floor is the most gravely damaged—the depth of its damage is 2.5 m, and the depths of damage on either side and of the roof are approximately 1–2 m. During the advancing process of the working face, the deformation of the roadway increases slowly at first, then increases sharply, and tends to be stable thereafter. The deformation of the floor is the largest, followed by those of the two sides and the roof; the values are 800, 400, and 300 mm, respectively.
In this study, the movement and failure law of working face overburden and the distribution characteristics of mining stress are analyzed using laboratory test and numerical calculation methods to address the problems of large deformation, failure instability, and difficult maintenance of the soft rock roof roadways of deep stope influenced by strong disturbance, the roof gas comprehensive treatment roadway of 17191 (1) working face of Pansan mine of China Huainan Mining Group was considered as the engineering background. The deformation and failure mechanisms of the surrounding rock in soft rock roof roadway are revealed, the surrounding rock control technology of presplitting and roof cutting pressure relief is proposed, and the key parameters of presplitting and roof cutting are systematically studied. According to the results, after mining, the overburden presents the distribution of “upper three zones,” in which the heights of the caving and fracture zones are 7 m and 38 m, respectively, the influence range of lateral mining abutment pressure is 80 m, and the influence height exceeds 42 m. The roadway is located in the same layer as the fracture zone and within the influence range of mining. Under the influence of overburden migration of the working face, the stress field around the roadway, and the mining stress field, the surrounding rock of the roof roadway is significantly damaged, and the floor heave is violent. Based on the stress distribution characteristics of the stope and the deformation mechanism of the roadway, the pressure relief control technology of surrounding rock presplitting roof cutting is proposed. The optimal values of key parameters are determined as the roof cutting height of 49.9 m, the roof cutting angle of 10°, and the blast hole spacing of 10 m. The results of this study have been successfully applied in 17191 (1) working face.
In order to investigate the mechanical characteristics of rocks under saturated water conditions, uniaxial loading experiments were conducted on rock specimens using the RMT-150B Rock Mechanics Experiment System based on theoretical analysis of the damage evolution mechanism of rock specimens considering saturation factors. And the damage of the specimens was monitored using the Soft Island DS5-16B acoustic emission system. During the test, the specimens were taken from six rock samples in different directions at the same roadway section location in a coal mine. The combined findings suggest that: The dispersion rate is positively correlated with the bearing capacity of rock specimens taken from different directions, AE ringing counts, amplitude, and energy appear to have a time-limited steady increase influenced by direction. For rock specimens in the same plane, the rock damage instantaneous energy lag amplitude and AE activity is proportional to the direction angle. The AE localization points in different directions are randomly distributed and scattered in various areas, and fracture beams and surface cracks are produced inside the rock corresponding to the AE acoustic emission.
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