| 摘要 |
The tunnel (20) has three drill holes (23-25) towards the sides and downwardly directed to adjacent crush zones (K) in the rock. These holes serve as water inputs and have check valves so that water may flow into the tunnel but not in the opposite direction. The tunnel can be sepd. from remaining original shafting tunnel (21) by means of a tight, pref. openable intermediary wall (22). |
