Abstract
Sakai Koro Tunnel is a shield tunnel constructed under Osaka bay. This tunnel is used for transportation of natural gas. The length of the tunnel is 2130m and the deepest level of the tunnel is 45m below the ground level. The two driving shafts were constructed by the method of pneumatic caisson employing ground freezing. One of the shafts is 52m in depth and one of the deepest shafts in Japan. Sandy layer with gravel under high water pressure of 4.5kgf/cm2 was excavated from the both shafts by slurry shield method. These tunnels were connected under the sea by employing ground freezing method. Since a part of the tunnel is subjected to consolidation settlement of the ground in future, elastic washers and flexible segments were installed into the tunnel at the appropriate places to release the influence.
