Research on the Technology of Small Coal Pillars of Gob-Side Entry Retained in Deep Mines Based on the Roof Cutting for Pressure Unloading in the Lower Key Stratum

Table 2

Rock mechanics parameters.

No.	Lithology	Bulk modulus	Shear modulus	Cohesion	Internal friction angle	Tension strength	Density	Height
		GPa	GPa	MPa	°	MPa	kg·m^-3	m
1	Mudstone	0.3	0.35	0.8	30	0.1	2400	14
2	Aluminous argillite	0.8	1.62	3.8	35	0.4	2450	2
3	4# coal seam	0.3	0.39	3.64	31	0.9	1390	8
4	Mudstone	0.3	0.35	0.8	30	0.1	2400	4
5	Fine sandstone	4.84	3.26	7.8	32	6.5	2650	10
6	Mudstone	0.3	0.35	0.8	30	0.1	2400	17
7	Coarse sandstone	6.28	5.09	9.9	34	5.6	2600	17