Numerical Simulation on the Distribution Evolution of Overburden Fractured Zone in Coal Mining and Its Visual Detection

Based on the mining conditions of Muchengjian Coal Mine in Beijing, the evolution process of the overburden fractured zone was simulated by the distinct element software UDEC. The simulation results show that with the increase of the mining area, fractured expansion space continues to increase upward and is arched distribution. The fracture changes significantly during primary mining and develops slowly latterly. It reaches steadily 8 times thickness of mining coal eventually. The author uses drilling camera detection technology for detecting destruction of overburden and the development situation of the fracture. Based on the results of detection, overburden fracture can be divided into mild fracture zone, moderate fracture zone, and severe fracture zone according to the fracture degree. The fracture develops unevenly in boreholes and shows that the fractured zone and complete zone appeared alternately. The simulation results have a good agreement with the measured data. And the height of stress arch is suit for the upper limit of fracture development, which can be provided guidance for coal mining in the similar conditions.