Study and Application of Roof Cutting Pressure Releasing Technology in Retracement Channel Roof of Halagou 12201 Working Face

Table 1

Parameters of each rock layer.

Lithology	Density/kN/m3	Tensile Strength/MPa	Internal Friction Angle/°	Cohesion/MPa	Bulk Modulus/GPa	Shear Modulus/GPa
Siltstone	22	4.3	28	0.8	2.11	1.86
Fine sandstone	23	7.3	30	1.0	3.81	3.05
Mudstone	20	3.2	28	0.2	0.20	0.15
Coal	13	3.3	29	0.2	0.35	0.18