Bending Moment Characteristics of Hard Roof before First Breaking of Roof Beam Considering Coal Seam Hardening

Table 1

Engineering example of hard roof fracturing ahead of working face.

Hard roof of working face	Advanced fracturing distance
Old roof of coal mine in western of Xuzhou	About 4m [1]
Roof of 741003 working face of Muchengjian mine	5-8 m [24]
Roof of coal seam 2 of Beijing Mining Bureau	About 6m [24]
Old roof of coal seam of Xinqiu mine	6.3m, 8m [23]
Roof of 8320 working face of Dafeng mine	9.98m [25]
Old roof of Sanhejian mine in Xuzhou	About 10m [26]
Roof of east 708 working face of Zhangxiaolou mine	11.56m [25]