Comprehensive Evaluation and Decision for Goaf Based on Fuzzy Theory in Underground Metal Mine

Table 1

The classification of goaf stability.

Factor index		Assessment ranks
		Stable I	Basically II	Understable III	Unstable IV
Rock mass quality factors U21	Point load strength U11	>10 MPa	4∼10 MPa	2∼4 MPa	0∼2 MPa
	Intactness index U12	>0.75	0.75∼0.55	0.55∼0.35	0.35∼0
	Dominant joint occurrence U13	Very favorable	Favorable	General	Unfavorable
Goaf parameters U22	Hydraulic radius U14	<15 m	15∼30 m	30∼45 m	>45 m
	Buried depth U15	<100 m	100∼200 m	200∼400 m	>400 m
	Goaf height U16	<8 m	8∼20 m	20∼30 m	>30 m
	Engineering layout U17	Very reasonable	Reasonable	General	Unreasonable
	Mine pillar and layout U18	Pillars and layout standard	Pillars and layout not standard	No pillars or layout not standard, start breaking	No pillars or layout not standard, serious breaking
Induced factors U23	Groundwater U19	<35 L•min^−1	35∼55 L•min^−1	55∼70 L•min^−1	>70 L•min^−1
	Protective measures U110	Very reasonable	Reasonable	General	Unreasonable
	Mining disturbance U111	No impact	Weak	Influence	Great influence
	Adjacent goaf U112	No	Small	Some	Many
Quantized range Vr		0.75∼1.00	0.50∼0.75	0.25∼0.50	0.00∼0.25