Calculation Method of Overburden Damage Height Based on Fracture Mechanics Analysis of Soft and Hard Rock Layers

Table 3

Key layer parameter calculation result.

Number	Lithology	Rock thickness (m)	Key layer number	Breaking span (m)	Height upper coal seam (m)
1	Medium sandstone	6.03	Key layer 1	36.3	5.12
11	Fine sandstone	10.27	Key layer 2	50.3	41.11
18	Fine sandstone	12.56	Key layer 3	81.4	75.33
20	K8 sandstone	40.61	Key layer 4	158.9	80.54