A New Evaluation Method for Water Blocking Performance of Coal Seam Floor: Model Construction, Case Application, and Water-Preserved Strategy

Table 2

Single-factor toughness rating.

Index factor		Toughness evaluation level criteria
		Very bad	Worse	Better	Excellent
	U11
	U12			m
	U13	/s•m	L/s•m	L/s•m	L/s•m
	U14			0.2<ρ<0.5
	U21	Serious damage to the key rock formation	Poor matching of construction technology	Good match of construction technology	Less damage to the key rock formation
	U22	Widespread pollution	Local pollution	No obvious pollution	Green and ecofriendly
	U23	Basic geophysical prospecting	Multi-mode combined detection	Whole process detection	Real-time dynamic detection
	U31	Poor governance	General governance	Ecological restoration is in progress	Green ecology
	U32	High pollution index	Average pollution index	Limited water carrying capacity	High water carrying capacity