Study on Reasonable Chain Pillar Size in a Thick Coal Seam

Table 1

Measurement results of rock mechanical parameters.

Lithology	Compressive strength/MPa	Shear strength/MPa	Tensile strength/MPa	Poisson ratio	Cohesion/MPa	Friction/°
Silty mudstone	11.3	29	1.8	0.29	6.8	35
Fine sandstone	50.9	86.7	2.8	0.24	13.2	49
Pelitic siltstone	30.4	50.4	2.2	0.28	11.1	36
Coal	5.8	9.1	1.4	0.32	3.4	29
Mudstone	9.7	21.1	1.59	0.3	5.3	32
Medium fine sandstone	46.4	39.5	2.7	0.26	11.7	46