Analysis of developmental features and causes of the ground cracks induced by oversized working face mining in an aeolian sand area

In order to satisfy the energy demand of China, it is an effective way to exploit coal resources efficiently in western China. When a coal seam with a shallow burial depth is mined on a large working face with width of 300 m in a semi-desert aeolian sand area of western China, the induced subsidence and damage of ground surface are remarkably different from those induced by a traditional mining condition. By taking Working Face 12,406 of Bulianta Coalmine in Shendong Mining Area as an example, this paper, based on actual measurement data, analysed the developmental features and causes of ground surface racks. Research results showed that the shape of the static crack in the peripheral area on the working face was very similar to that contained in the actual measurement results of other areas; specifically, such static crack was arc-shaped and the actually measured static crack angle was 84.5°. However, the dynamic crack above the working face took on uniqueness in two developmental cycles (expansion to restoration). This phenomenon is not available in other research areas. Starting from the structure of rock strata, this paper analysed the two developmental cycles of dynamic cracks according to the periodic fracture theory of key stratum and verified the results of theoretical analysis by employing the similar material model.