Stress Distribution and Gas Concentration Evolution during Protective Coal Seam Mining

Table 1

Mechanical properties of various sediment rocks.

Rock	Volume modulus (K/GPa)	Shear modulus (G/GPa)	Tensile strength	Cohesion (C/MPa)	Density	Friction angle
Coal	1.35	0.85	1	1.8	1400	27
Mudstone	5.3	2.4	3.13	2.8	2703	29
Sandy mudstone	8.1	7.9	2	2.4	2619	30
Medium sandstone	10.2	17.7	4.6	7.8	2810	39.9
Medium-fine sandstone	15.8	20.2	6.7	9.6	2710	35.3
Fine sandstone	12.23	15.6	4.41	6.5	2606	35.4