| Waterproof rock tunnels have been constructed in Japan when it was necessary to reduce the impact on the hydrological environment. This study performed case analyses of existing waterproof rock tunnels in Japan and seepage analysis on the hydrological behaviour related to the waterproof rock tunnels to discuss the practicability of design and construction. The results of the case analyses show that the cross sectional shapes were examined considering the aspect ratio as a design parameter to find the most reasonable shape. Waterproof structures of tunnels have been designed taking into consideration the prevention of waterproof sheet damage, the need to constrain the spread of water leakages and the restoration of the waterproof property. The results of the seepage analysis of the waterproof?drainage coexistence tunnels indicate that measures such as a ground improvement, a curtain grouting and installation of the appropriate drainage systems are required to ensure tunnel safety and to preserve the hydrological environment when the excavation disturbed zone has a relatively high permeability. |
