The Breaking Span of Thick and Hard Roof Based on the Thick Plate Theory and Strain Energy Distribution Characteristics of Coal Seam and Its Application

Table 3

Mechanic parameters of interface of coal seam and strata.

Strata	Normal stiffness/GPa	Shear stiffness/GPa	Cohesion/MPa	Internal friction angle/°
Sandstone	4.2	2.2	0.49	15
Sandy mudstone	2	1.1	0.26	12
Mudstone	1.52	0.83	0.2	12
Siltstone	4.2	4	0.39	9
Mudstone	1.5	0.8	0.19	10
4# coal seam	0.33	0.12	0.14	10
Siltstone	3.9	3.9	0.37	7
Lamprophyre	4.2	4.2	0.67	17
2# coal seam	0.31	0.11	0.135	9
Lamprophyre	4	4	0.63	15
3–5# coal seam	0.3	0.1	0.11	9
Sandstone	4	2	0.47	14