A Method Based on Elastic Mechanics for Judging Compound Hard Roof and Its Application

Table 1

Rock stratum occurrence of 8101 working face.

No.	Lithology	Thickness (m)
1	Coarse sandstone	23.27	6# hard rock
2	Medium sandstone	10.42	5# hard rock
3	Medium sandstone	8.58
4	Fine sandstone	6.41
5	Medium sandstone	10.1	4# hard rock
6	Coarse sandstone	9.57	3# hard rock
7	Coarse sandstone	2.45
8	Medium sandstone	16.08	2# hard rock
9	Mudstone	5.24
10	Medium sandstone	12.12	1# hard rock
11	Sandy mudstone	9
12	Coal seam	3.3
13	Sandy mudstone	1.6
14	Coal seam	21.02
15	Fine sandstone	30
16	Medium sandstone	15