Surrounding Rock Stability Classification Method of Coal Roadway Based on In Situ Stress

Table 5

Classification results of surrounding rock stability of coal roadway.

Grade	Strength of surrounding rock			In situ stress		N	C0	Displacement convergence prediction
	Roof	Rib	Floor		σh			Roof-to-floor	Rib-to-rib
	(MPa)	(MPa)	(MPa)	(MPa)	(MPa)	(M)	(%)	(%)	(%)
I, very stable	>50.5	>15.3	>38.5	<8.9	<9.6	<0.6	>34	<6.0	<5.6
II, relatively stable	31.8∼50.5	10.4∼15.3	25.4∼38.5	8.9∼15.6	9.6∼20.0	0.6∼; 1.4	27.2∼34.0	6.0∼13.5	5.6∼15.4
III, medium stable	18.3∼31.8	6.8∼10.4	14.6∼25.4	15.6∼27.8	20.0∼32.4	1.4∼; 2.4	21.0∼27.2	13.5∼19.5	15.4∼25
IV, unstable	<18.3	<6.8	<14.6	>27.8	>32.4	>2.4	<21.0	>19.5	>25.0