Tunnel excavation through ground surface water - using shield and bentonite suspension to support workface and allow stepwise advance

摘要

A pit is first excavated to the depth of the tunnel floor and a caisson is sunk into the pit. A working face shield (1) is then constructed to form the caisson end wall and is supported by hydraulic jacks (7). Soil is then excavated from the space (5) outside the shield. As the excavation proceeds this space is filled with bentonite suspension which supports the working face during the excavation. When the space has been excavated to the full depth the shield is advanced with a stepwise motion. USE - For digging tunnel through ground surface water or under a water basin.