Study on the Application of Gob-Side Entry Retaining via Roof Cutting under the Condition of a Hard Thick Roof

Table 1

Physical and mechanical parameters of each lithology.

Lithology	Modulus of elasticity (GPa)	Shear modulus (GPa)	Cohesion (MPa)	Friction angle (°)	Density (kg/m^3)
Coal	5	1.9	0.8	30	1350
Sandy mudstone	9.1	6.5	1.3	32	2500
Medium sandstone	13.1	9.02	4.4	35	2400
Fine sandstone	10.6	7.3	2.9	30	2450
Limestone	17.9	11.52	6.2	37	2550