Failure mechanism features and precursor characteristics of coal roadway groups in fault zone under confined conditions

After the stress wave penetrates the fault, it changes the stress direction and destroys the stress balance of the deep underground mining surface and roadway during mining activities, causing the roadway and underground equipment to collapse. To reveal the failure mechanism, we studied the precursor characteristics of unstable failure of rocks in deep roadway groups. With conducting two PFC numerical models based on common roadway layouts, we studied crack development and failure conditions of surrounding rocks near roadway groups by investigating the force chain fracture, coordination number, energy evolution, and acoustic emission moment tensor in the models. The results show that the overall deformation failure of the roadway group first occurs in the upper roadway, and the weak force chain break in the force chain field of the lower roadway is obvious, especially before and after the peak value, accompanied by the coordination number in the direction of 80° with the joint plane significantly reduced. At the same time, obvious force patterns were observed in the roadway group area: irregular gathering (>90°) and swirl (<90°). These findings clarify the mechanism of fault disturbance in roadways surrounding rocks and help to better understand the deformation failure feature and energy evolution process of coal.