Evaluation Method of Water Hazard Control Effect of Coal Seam Floor in Deep Mining: Sequence Verification Evaluation

Table 2

Classification standard for permeability of rock and soil.

Permeability grade	Hydraulic conductivity, (cm/s)	Permeable rate, (Lu)	Rock mass characteristics
Infinitesimal permeability			Complete rock mass or fractured rock mass with equivalent opening less than 0.025 mm
Micropermeability			Rock mass with equivalent opening of 0.025 mm-0.05 mm fractures
Weak permeability			Rock mass with equivalent opening of 0.05 mm-0.01 mm fractures
Medium permeability			Rock mass with equivalent opening of 0.01 mm-0.5 mm fractures
High permeability			Rock mass with equivalent opening of 0.5 mm-2.5 mm fractures
Strong permeability			A fractured rock mass with communicating holes or equivalent openings larger than 2.5 mm