Construction of immersed tunnel in Osaka Port

The Sakishima Tunnel constructed under a main fairway in Osaka Port is the first combined roadway and railway immersed tunnel in Japan. This project required the solution of various engineering problems posed by the severe conditions for design and construction. In designing the tunnel, many engineering reviews including model experiments were carried out to overcome the problems by utilizing tunnel elements with steel-concrete composite structure, V-block construction for a terminal joint, floating caisson construction, and other methods. Construction was performed by tunnel element manufacturing, construction control for settlement and navigational safety control, etc. The ventilation system utilizes fuzzy logic to ensure a comfortable and safe undersea tunnel environment.