The Jiyoshi Tunnel on National Highway No. 440 is 2,990 m long and passes directly under Shikoku Karst plateau lying across 25 km east-to-west, over the division between the two Prefectures of Ehime and Kochi in the southwest of Shikoku. In the Ehime Prefecture section, the limestone bedrock that appeared along with water inflow of 20 ton/min in the vicinity of 700 m from the portal was aquifer similar to that of the Seikan Tunnel, that is a typical undersea tunnel. The aquifer had groundwater pressure of 2.65 MPa at maximum.
Under these requirements, safe and efficent construction work was realized by introducing new technologies, and by devising better design and construction processes. It can be evaluated that this work was contributed to the development of new technologies for tunnel construction.