Stress Analysis of Negative Coal Pillar Gob-Side Entry and Its Principle of Preventing Rock Burst

Table 3

Mechanical parameters for rock masses.

Lithology	Thickness (m)	Density (kg·m^−3)	Bulk modulus (GPa)	Shear modulus (GPa)	Cohesion (MPa)	Tensile strength (MPa)	Friction angle (deg.)
Medium sandstone	50	2500	5.90	4.23	8.82	2.75	28
Mudstone	8	2500	3.2	3.85	8.7	1.50	25
Siltstone	13	2600	4.88	3.45	26.6	2.85	35
Limestone	6	2500	3.88	3.45	9.24	1.38	30
Shale	7	2550	3.85	1.84	8.7	1.5	29
Sandy mudstone	6	2500	3.2	3.5	10.2	1.05	30
Siltstone	10	2600	6.23	4.95	18.8	2.75	32
Mudstone	5	2500	3.2	3.85	8.7	1.50	25
Coal	6	1400	1.2	1.1	1.0	0.45	20
Mudstone	3	2500	3.2	3.85	8.7	1.50	25
Limestone	6	2500	3.88	3.45	9.24	1.38	30
Siltstone	3	2600	4.88	3.45	26.6	2.85	35
Medium sandstone	7	2500	5.90	4.23	8.82	2.75	28
Limestone	20	2500	6.23	5.9	10.8	2.75	32