Stability Evaluation of the Goaf Based on Combination Weighting and Cloud Model

Table 2

Grading criteria of quantitative indicators for the evaluation of the stability of the goaf.

Factors	Class
	Class I	Class II	Class III	Class IV
Rock mass quality X3 (%)	<50	(50, 70)	(70, 90)	≥90
Dip angle of ore body X4 (degree)	<3	(3, 30)	(30, 50)	≥50
Goaf volume X5 (10^3, m^3)	≥81	(24, 81)	(6.4, 24)	<6.4
Maximum exposed area X6 (m^2)	≥2,700	(1,200, 2,700)	(800, 1,200)	<800
Height of mined-out area X7 (m)	≥30	(20, 30)	(8, 20)	<8
Span of mined-out area X8 (m)	≥120	(80, 120)	(40, 80)	<40
Embedding depth X9 (m)	≥600	(450, 600)	(300, 450)	<300
Exposure time of goaf X10 (a)	≥20	(10, 20)	(6, 10)	<6