Iwate-Ichinohe Tunnel
Encyclopedia
The is a 25.810 km terrestrial railway tunnel in Japan — part of the Tōhoku Shinkansen
, linking Tokyo
with Aomori
. When opened in 2002 it was the longest in-use terrestrial (land based) tunnel in world, but the title was overtaken by the Lötschberg Base Tunnel
in June 2007.
The tunnel is located 545 km away from Tokyo Station on the Tōhoku Shinkansen line, midway between Morioka
and Hachinohe
. Surveying commenced in 1988. In 1991 construction began, and the tunnel holed through in 2000. The tunnel became operational when the railway line opened in 2002. Maximum depth is about 200 m.
Geology along the tunnel route can be divided into three sections:
Faults cross the path of the tunnel.
The tunnel is a single bore twin track design. A horseshoe shape, the cross-sectional dimensions are: 9.8 (width) x 7.7 m (height) (an excavated area of approximately 70 to 85 m²). It rises at a gradient of 0.5% from the Tokyo portal for approximately 22 km, then drops at a gradient of 1% down to the Aomori portal. The New Austrian Tunnelling method
(NATM) was adopted to cope with the geology. NATM techniques deployed included rock bolts, shotcrete and steel supports. Excavation methods were dependent on the geology, drill and blast
or mechanical excavation and full face or bench cut methods were used. To speed up and reduce the costs of construction the tunnel was divided into seven sections, with intermediate access ramps or inclined shafts.
Tohoku Shinkansen
The is a Japanese high-speed Shinkansen rail line, connecting Tokyo with Aomori in Aomori Prefecture for a total length of 674 km, Japan's longest Shinkansen line. It runs through the more sparsely populated Tōhoku region of Japan's main island Honshu. It has two spur lines, Yamagata...
, linking Tokyo
Tokyo
, ; officially , is one of the 47 prefectures of Japan. Tokyo is the capital of Japan, the center of the Greater Tokyo Area, and the largest metropolitan area of Japan. It is the seat of the Japanese government and the Imperial Palace, and the home of the Japanese Imperial Family...
with Aomori
Aomori Prefecture
is a prefecture of Japan located in the Tōhoku Region. The capital is the city of Aomori.- History :Until the Meiji Restoration, the area of Aomori prefecture was known as Mutsu Province....
. When opened in 2002 it was the longest in-use terrestrial (land based) tunnel in world, but the title was overtaken by the Lötschberg Base Tunnel
Lötschberg Base Tunnel
The Lötschberg Base Tunnel is a railway tunnel on the BLS Lötschbergbahn's Lötschberg Line cutting through the Alps of Switzerland some below the existing Lötschberg Tunnel. It is currently the world's longest land tunnel and accommodates passenger and freight trains. It runs between Frutigen,...
in June 2007.
| Timeline | |
|---|---|
| 1988 | Surveying commenced |
| August 1991 | Construction commenced |
| September 2000 | Holed through |
| 1 December 2002 | Line opened |
The tunnel is located 545 km away from Tokyo Station on the Tōhoku Shinkansen line, midway between Morioka
Morioka, Iwate
is the capital city of Iwate Prefecture, Japan.As of 2005, the city has an estimated population of 300,740 and a population density of 588.11 persons per km². The total area is 489.15 km²....
and Hachinohe
Hachinohe, Aomori
- Neighbouring municipalities :Aomori Prefecture*Sannohe District**Hashikami**Gonohe**Nanbu*Kamikita District**OiraseIwate Prefecture*Karumai-History:...
. Surveying commenced in 1988. In 1991 construction began, and the tunnel holed through in 2000. The tunnel became operational when the railway line opened in 2002. Maximum depth is about 200 m.
Geography and geology
The tunnel passes through hilly terrain near the Kitakami and Ou mountains. The Mabuchi and Kitakami rivers run near the tunnel's Tokyo portal.Geology along the tunnel route can be divided into three sections:
- 17 km from the Tokyo end: MesozoicMesozoicThe Mesozoic era is an interval of geological time from about 250 million years ago to about 65 million years ago. It is often referred to as the age of reptiles because reptiles, namely dinosaurs, were the dominant terrestrial and marine vertebrates of the time...
and PaleozoicPaleozoicThe Paleozoic era is the earliest of three geologic eras of the Phanerozoic eon, spanning from roughly...
strata (argilliteArgilliteAn argillite is a fine-grained sedimentary rock composed predominantly of indurated clay particles. Argillaceous rocks are basically lithified muds and oozes. They contain variable amounts of silt-sized particles. The argillites grade into shale when the fissile layering typical of shale is...
, granodioriteGranodioriteGranodiorite is an intrusive igneous rock similar to granite, but containing more plagioclase than orthoclase-type feldspar. Officially, it is defined as a phaneritic igneous rock with greater than 20% quartz by volume where at least 65% of the feldspar is plagioclase. It usually contains abundant...
, hornfelsHornfelsHornfels is the group designation for a series of contact metamorphic rocks that have been baked and indurated by the heat of intrusive igneous masses and have been rendered...
and chertChertChert is a fine-grained silica-rich microcrystalline, cryptocrystalline or microfibrous sedimentary rock that may contain small fossils. It varies greatly in color , but most often manifests as gray, brown, grayish brown and light green to rusty red; its color is an expression of trace elements...
) - 5 km central section: NeogeneNeogeneThe Neogene is a geologic period and system in the International Commission on Stratigraphy Geologic Timescale starting 23.03 ± 0.05 million years ago and ending 2.588 million years ago...
volcanic tuffTuffTuff is a type of rock consisting of consolidated volcanic ash ejected from vents during a volcanic eruption. Tuff is sometimes called tufa, particularly when used as construction material, although tufa also refers to a quite different rock. Rock that contains greater than 50% tuff is considered...
, which was susceptible to swelling and caused engineering difficulties. - 4 km from the Aomori end: a combination of the previous two sections, as well as mudstoneMudstoneMudstone is a fine grained sedimentary rock whose original constituents were clays or muds. Grain size is up to 0.0625 mm with individual grains too small to be distinguished without a microscope. With increased pressure over time the platey clay minerals may become aligned, with the...
and andesiteAndesiteAndesite is an extrusive igneous, volcanic rock, of intermediate composition, with aphanitic to porphyritic texture. In a general sense, it is the intermediate type between basalt and dacite. The mineral assemblage is typically dominated by plagioclase plus pyroxene and/or hornblende. Magnetite,...
of the Neogene period.
Faults cross the path of the tunnel.
Engineering
New Austrian Tunnelling method
The New Austrian Tunnelling method was developed between 1957 and 1965 in Austria. It was given its name in Salzburg in 1962 to distinguish it from old Austrian tunnelling approach. The main contributors to the development of NATM were Ladislaus von Rabcewicz, Leopold Müller and Franz Pacher...
(NATM) was adopted to cope with the geology. NATM techniques deployed included rock bolts, shotcrete and steel supports. Excavation methods were dependent on the geology, drill and blast
Drilling and blasting
Before the advent of tunnel boring machines, drilling and blasting was the only economical way of excavating long tunnels through hard rock, where digging is not possible. Even today, the method is still used in the construction of tunnels, such as in the construction of the Lötschberg Base Tunnel...
or mechanical excavation and full face or bench cut methods were used. To speed up and reduce the costs of construction the tunnel was divided into seven sections, with intermediate access ramps or inclined shafts.