Abstract
The affected area of water inflow into tunnel is due to the average permeability of rockmass which depends on valley area, valley shape ratio and inclination of slop.
The permeability in the a times larger area with the same shape ratio and inclination becomes √a times larger. The permeability with the b times loger valley length in the same becomes 1/bb2 times larger.
The experimental fact shows that pyroclastic rock has the largest permeability, gravel and sand layer has fairly larger, plutonic rock has intermediate and mudstone has smaller one.
Flowing ratio in drought season is the conception to be discussed reffering the amount of rainfall and the decreasing curve of water inflow.
