Dip Angle Effect on the Main Roof First Fracture and Instability in a Fully-Mechanized Workface of Steeply Dipping Coal Seams

Table 1

Physical and mechanical parameters of coal and rock.

Lithology	Thickness (m)	Compressive strength (MPa)	Elastic modulus (GPa)	Cohesion (MPa)	Friction angle (deg.)	Poisson’s ratio
Medium sandstone	6	57	15	2.4	35	0.2
Fine sandstone	7.2	70	18	2.6	30	0.18
Sandy mudstone	6.8	35.6	9.5	1.2	38	0.28
Mudstone	2.5	21.5	6.2	0.9	24	0.3
Coal seam	4	13.4	5.8	0.62	20	0.35
Mudstone	3	21.5	6.2	0.9	24	0.3
Sandy mudstone	7.6	35.6	9.5	1.2	30	0.28