Study on Surrounding Rock Stability Mechanism of Gob-Side Entry Retaining with Prefabricated Fracture

Table 1

Physical and mechanical properties of rock mass.

Coal seam and strata	Bulk modulus (GPa)	Shear modulus (GPa)	Tensile strength (MPa)	Cohesion (MPa)	Internal friction angle (°)	Density (kg·m^−3)
Sandy mudstone	8.85	5.93	0.1	2.71	32	2600
Four coals	3.8	4.21	4.38	4.21	32	1400
Fine sandstone	2.0	1.3	0.6	1.6	34	2700