Breakthrough in Japanese Railways 14 A History of Railway Tunnels in Japan Shigeru Onoda Introduction Techniques for mining ore also advanced in the Edo period, and specialist miners performed excavation work Only about 30% of Japan’s land area is flat with the at mines. remaining 70% being mountainous. The cities on the flat land have well-developed subway systems with many railway Introduction of modern tunnelling technologies (1870s to tunnels. As of 2013, 3813 km of Japan’s 27,497 km of railway 1900s) lines (approximately 14%) is in tunnel. Railway tunnels were the starting point for modern tunnelling The three main methods for constructing railway tunnels technologies in Japan. The first railway line built in Japan in are mountain tunnelling, shield tunnelling, and open cut (cut- 1872 between Shimbashi and Yokohama had no tunnels, and-cover) tunnelling. Other methods include immersed- and the first tunnels were built on a section of track between tube tunnelling and caisson tunnelling. Early railway tunnels Osaka and Kobe opened in 1874 passing under a high- in Japan used technologies from abroad, but eventually the bedded river flowing from Mt Rokko. Three short tunnels— nation developed its own technologies. Tunnel construction the 111-m long Ashiyagawa Tunnel, 50-m Sumiyoshigawa in Japan often faced difficulties due to the complex geology, Tunnel, and 61-m Ishiyagawa Tunnel—were constructed but technical improvements were made by using feedback by the cut-and-cover method under the supervision of a from each tunnelling experience. This article looks back at British engineer. All were later changed to aqueduct bridges the advancement in railways and the progress in Japan’s around 1920, so the tunnels are no longer used. tunnel technologies. This was followed by the 665-m Osakayama Tunnel constructed from 1878 to 1880 between Kyoto and Otsu. History of Railway Mountain Tunnelling This tunnel was built by Japanese engineers alone, without using foreign advisors due to the intention of Masaru Inoue Japanese tunnels before railways (prior to 1870s) Director of the Railway Board to promote domestic railway It is unknown when the first tunnels were dug in Japan— technologies. Miners were called from Ikuno silver mine the same is true for tunnel history worldwide. Tunnelling and traditional mining techniques and stonemasons were in earnest as civil engineering started during the Edo period (1603–1868) with a record of a tunnel for the Tatsumi Aqueduct (Ishikawa Prefecture) excavated in 1632. This 3.3-km long, 1.5 to 2.1-m wide, 1.8-m high tunnel was dug through easy geology, so it was completed in just 9 months. Drifts were dug during construction to confirm the tunnel position and secure ventilation, and lighting was by oil lamps. In 1666, the 1.3-km long, 2-m high, and 2-m wide Hakone Aqueduct Tunnel (located between Kanagawa and Shizuoka prefectures) was dug over a span of 4 years. The 180-m long Aonodomon (blue tunnel) at Yabakei Gorge (Oita Prefecture) was completed in 30 years from 1720 to 1750. It was Japan’s first tunnel for transport purposes and was purportedly dug by the monk Zenkai Ishiyagawa Tunnel (1874) (Japan’s first railway tunnel) (Author) (1691-1774). Japan Railway & Transport Review No. 66 • Oct 2015 38 Breakthrough in Japanese Railways 14 Osakayama Tunnel built solely by Japanese engineers (1880) (now preserved as railway memorial) (Author) used. With the completion of Osakayama Tunnel, tunnelling Progress in tunnel construction (1910s to 1920s) in Japan made an early departure from the techniques of Little progress in tunnelling technologies was made for foreign engineers. In 1884, the 1352-m Yanagase Tunnel some period after the Sasago Tunnel, until the age of long on the Hokuriku Line was completed as Japan’s first tunnel tunnels arrived in the 1910s because construction of trunk longer than 1 km. An overview of its construction is reported lines had eased off with construction of mountain routes in the Minutes of Proceedings of the Institution of Civil and improvement to grades. Engineers by Kinsuke Hasegawa. The first Tokaido main line route between Otsu and Early tunnels were built mainly using a construction Kyoto constructed in 1880 bypassed Mt Osaka to the south method called ‘Japanese excavation’ where tunnels were where the Osakayama Tunnel was constructed; the 1865-m advanced at a top heading first. Construction was easy Higashiyama Tunnel and 2325-m Shin-Osakayama Tunnel using this method, so it was employed for most railway were completed subsequently in 1921 to relieve the steep tunnels constructed until around 1920. Attempts to shorten grade and shorten the route. the construction period by using vertical shafts were made The steep grade on the Tokaido main line between at an early stage in works such as the 928-m Kabuto Tunnel Kozu and Numazu going over Mt Hakone led to the 1918 on the Kansei Railway (Kansai Line today) completed in construction of the 7804-m Tanna Tunnel at the ‘neck’ of the 1889, the 1629-m No. 2 Itayatoge Tunnel on the Ou Line Izu Peninsula. Construction also started in 1922 on the 9702- completed in 1894, and the 2656-m Kamuriki Tunnel on the m Shimizu tunnel, passing under the approximately 2000- Shinonoi Line completed in 1896. The Kamuriki Tunnel was m high Mikuni mountain range and shortening the route Japan’s first railway tunnel longer than 2 km. between Takasaki and Niigata. The 4656-m Sasago Tunnel on the Chuo Line completed These long tunnels could be constructed thanks to in 1903 became Japan’s longest tunnel until completion of the advances in construction technologies (such as switching Shimizu Tunnel on the Joetsu Line in 1931. The Sasago Tunnel from the Japanese excavation method where a top heading excavation used electric locomotives to remove spoil and it is advanced first to the New Austrian Method where a was the pinnacle of tunnel construction in the Meiji period bottom heading is advanced first). The spread of electric (1868–1912). A hydroelectric power plant was built near the railways also helped because electric trains eliminated the worksite, providing power for electric locomotives, lighting, need to ventilate smoke from steam locomotives. Building and fans and contributing to more efficient construction and a long tunnels also changed design considerations in better construction site. selecting routes, marking a departure from the old concept 39 Japan Railway & Transport Review No. 66 • Oct 2015 Figure 1 Ikoma Tunnel Excavation Cress Sections (1914) (Tokyo Institute of Technology) of climbing with steep grades and sharp curves and building Electric Railroad (Kintetsu Corporation today). Construction tunnels only when absolutely necessary. on this tunnel between Osaka and Nara started in 1911 and An important controversy arose in tunnelling technology its 3388-m length was second only to the Sasago Tunnel. at this time: the issue of whether to build two parallel single- It is a double-track tunnel using standard gauge and was track tunnels or one double-track tunnel when constructing completed in 1914 despite a collapse and flooding, proving double-track lines. Most railway tunnels up to that time were that long double-track tunnels could be constructed. single-track, and a new adjacent parallel single-track tunnel Meanwhile, the New Austrian Method was being was excavated when doubling track. With more opportunities introduced from Europe as a replacement to the prevalent to construct double-track tunnels in this era, opinion was top-heading (Japanese) method. It enabled efficient split on which design was best. With parallel single-track construction of long tunnels in shorter times. With the switch tunnels, the excavated cross section is smaller so excavation from brick and stone linings to concrete, most tunnels speed is faster and a more stable tunnel face is secured starting from the 1252-m Nokogiriyama Tunnel on the Boso when digging in weak ground. However, this design is not West Line in 1915 embraced cast-in-place concrete and ideal for ventilating smoke from steam locomotives and concrete blocks as lining, and most tunnel linings were overall construction costs tended to be higher. concrete by the 1920s. For this reason, although the Shin-Osakayama and Higashiyama tunnels between Otsu and Kyoto and 2457-m Attempts at difficult construction (1920s to 1930s) Izumigoe Tunnel between Kozu and Atami on the Tokaido Work on the Tanna Tunnel (Fig. 2), a Japanese tunnel main line were constructed as parallel single-track tunnels, project that became world famous, started in 1918 to most of the tunnels between Kozu and Numazu, including improve the steep route over Mt Hakone. The construction the Tanna Tunnel, used a double-track cross section. was hindered by weak geology with spring water, a large The turning point was the Ikoma Tunnel (Fig. 1) on Osaka fault fracture zone, and altered rock exhibiting swelling; Japan Railway & Transport Review No. 66 • Oct 2015 40 Breakthrough in Japanese Railways 14 Figure 2 Tanna Tunnel Excavation Cross Sections (1934) (RTRI) Shimizu Tunnel breakthrough (1929) (celebrated with rice wine and completed in 1931) (RTRI) it required 16 years to complete and took the lives of 67 build and expressed his respect for the bravery of Japan’s workers. Supplementary construction methods such as tunnel workers. He also expressed criticism, saying that drainage boring, drainage and detour drift drilling, shield the difficulty was a result of the engineers failing to conduct tunnelling, and pneumatic tunnelling were adopted and the geological surveys. experience was applied to later tunnel construction. Robert Furthermore, the 1922 construction of the Shimizu Tunnel Ridgway, the Chief Engineer for the New York subway visited on the Joetsu Line experienced rock burst due to the high the Tanna Tunnel construction site when he was in Japan to ground pressure caused by more than 1000 m of overhead attend the World Engineering Congress in Tokyo in 1930, burden and construction was plagued by large volumes of and said that he knew of no other more difficult tunnel to spring water.