Analysis of the Occurrence Mechanism for Coal and Gas Outburst Based on Multiple Discriminant Indices

Table 2

Mechanical parameters of coal and rock.

Coal and rock	Density (kg·m^−3)	Bulk modulus (GPa)	Shear modulus (GPa)	Internal friction angle (°)	Cohesion (MPa)	Tensile strength (MPa)
Fine sandstone	2600	37.4	26.9	45	15.4	7.8
Limestone	2650	30.4	16.5	38	14.6	7.3
Coal	1410	14.8	6.06	25	2.1	1.8
Mudstone	2400	23.3	10.8	28	3.7	2.8
Sandy mudstone	2400	24.2	12.5	46	6.8	4.1
Medium grain sandstone	2400	34	21.4	36	13.4	6.5