Abstract:

The development height of two zones of overburden was a basic parameter for preventing and controlling mine water hazards and implementing water-preserved coal mining. In order to reveal the movement and failure law of the overburden, which was caused by fully mechanized mining with large mining height in the Ningdong Coal Base in western China, the 1121 fully mechanized mining face of Hongliu Coal Mine was taken as the research object. The development height and failure law of the two zones of overburden were studied by means of drilling, numerical simulation, and comprehensive analysis. The results show that the development height of the two zones of overburden after mining in the 1121 fully mechanized mining face is 81.66 m. The fracture-height ratio is 15.47. In addition, the height of the caving zone is 42.76 m, and the caving-height ratio is 8.10. In the mining process of the fully mechanized mining face, the overlying strata mainly undergo shear and tensile plastic failure, which correspond to the release of compressive stress and tensile stress, respectively. The compressive stress is mainly concentrated in the cut hole of the working face and the coal wall in front of the mining. The tensile stress is mainly concentrated above the goaf. The development of the two zones of overburden can be divided into five stages: incubation, development, slow increase, sudden increase, and stability. Once the development is stable, a slightly inclined saddle shape is shown. Furthermore, there is a positive exponential correlation between development height and mining distance.

Key words: large mining height, two zones of overburden, developemt height, numerical simulation, flushing fluid consumption