Abstract:

 A typical mining face of the Huainan mining area was taken for example, and the puking of the nether roof was simulated by UDEC(universal distinct element code). The stress field and the development of overlying coal fissure were monitored and analyzed by  the numerical model. The fissure evolution law was obtained through numerical simulation. The results showed that, after stoping, the caving zone, fractured zone and separation zone appeared in overlying coal, and the O-ring fracture zone developed on the upper side of the acting surface, of which the maximum height was 45 meters. The strike model study showed that the first presses pace was 50 meters, and the period presses pace was 20 meters. The fissures of overlying coal expanded at a 45degree angle above goaf, which developed from down to up and moved forward continuously with  the  advancing mining. This conclusion will give some help for determining borehole location of gas extraction.

Key words:  overlying strata, mining fissure field, mining stress field; , universal distinct element code(UDEC), numerical simulation