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 2

Mechanic parameters of coal seam and strata.

Strata	Density/(kg/m^3)	Bulk modulus/GPa	Shear modulus/GPa	Internal friction angle/°	Cohesion/MPa
Sandstone	2810	60	54.6	42	1.97
Sandy mudstone	2678	36.3	31.2	38	1.55
Mudstone	2504	2.5	1.21	31	1.38
Siltstone	2740	45.4	39.2	42	1.98
Mudstone	2500	2.78	1.2	30	1.378
4# coal seam	1456	2.71	1.2	31	1.349
Siltstone	2736	44.4	41.2	45	1.88
Lamprophyre	2825	46.1	42.8	49	4.87
2# coal seam	1452	2.7	1.19	30	1.347
Lamprophyre	2812	44.1	41.6	47	4.63
3–5# coal seam	1450	2.68	1.18	30	1.346
Sandstone	2800	58	54.4	41	1.92