Kanmon Tunnel outbound line, inbound line of Kanmon Tunnel inbound line
The Kanmon Railway Tunnel connects Hikoshima Enoura-cho, Shimonoseki City on Honshu and Umenoki-cho, Moji District in the City of Kitakyushu in Kyushu. The outbound line was opened in 1942, and the inbound line in 1944. Constructed by Japan in wartime, Iit was the world’s first seabed tunnel that was constructed by Japan in wartime. Until the tunnel was complete, the Kanmon Route was used for transportation by ship to connect Bakan (present-day Shimonoseki) on the Sanyo Railway (present-day Sanyo Line) and the Kyushu Railway. In 1911, to improve the transshipment of cargo on freight cars that had become laborious, a railroad connection ferryboat was operated that carried the freight cars on barges laid on railroad tracks. They came and went on the Kanmon Route. However, the tidal currents of the Kanmon Straits would suddenly and intensely change direction, and since there were many boats sailing there operating the connecting ferryboat was difficult and dangerous. The idea of directly connecting Honshu and Kyushu by railway existed at that time, and the president of Japan Railway Bureau, Shinpei Goto raised the issue of strengthening the Kanmon connection and set about formulating a specific proposal in 1901. Three proposals were presented to improve the connection in the Kanmon Straits. They were the construction of a seabed tunnel, the construction of a bridge, and the strengthening of the train-car carrying vessels in current operation. The proposal for the carrying vessels was immediately dismissed because it would impact the navigation of other ships. This whittled down the proposals to 2. After repeated review, it was determined that a bridge could possibly be a military target and required a great height to allowso that ships, which had become large, could to freely sail underneath. Given these particularslimitations, the proposal for a tunnel was adopted in 1919. Thereafter, construction on the tunnel was delayed due to circumstances such as the Great Kanto Earthquake and the Showa Depression, but the groundbreaking ceremony was held in 1936. In a time when military capabilities had increased, the tunnel excavation work was given the top priority. The shaft for the tunnel was moved forward using submarine drilling through Japan’s first genuine air shielding method. In the shielding method, the tunnel wall of the rear working face is temporarily supported by pipes called shields, and the shields are moved forward while drilling the working face, thereby creating rear walls. ItThis prevents tunnel collapse due tofrom spring water and ground pressure. The outbound line was opened in 1942, and freight car transport began in June of that year. In 1944, the inbound line was also opened. The amount Approximately 68,000 tons of cement was used over the 8 years starting from the groundbreaking ceremony was approximately 68,000 tons. More than 3.4 million workers were employed, and the work cost approximately 39.28 million yen. It was a huge project undertaken by the nation. The opening of the tunnel considerably improved the transportation time for goods. During the war, it was used to ship soldiers and military supplies, and even today is still usedutilized to transport freight and passengers today.