In the history of tunnelling, the methods of constructing tunnels and the usage of it have changed. Tunnels can serve a variety of purposes, from simply ferrying people and goods to flood control, and even showcasing such incredible beauty as to become a tourist attraction in its own right. We take a look at some of the most interesting examples of tunnels from around the world.
The Channel Tunnel, England and France
The construction of the 50-kilometre Channel Tunnel in the late 80s came to define the newly coined term, “megaproject”, an international engineering marvel that still contains the world’s longest undersea tunnel section at 37.9 kilometres, with its lowest point 115 metres below sea level. Connecting England to France, the tunnel is the only fixed link between the island of Great Britain and the European mainland, and was the most expensive construction project ever proposed at the time.
The Channel Tunnel carries high-speed Eurostar passenger trains, the Eurotunnel Shuttle for road vehicles as well as international freight trains, responsible for transporting millions of tonnes of freight and millions of passengers every year. The tunnel allows passengers to travel between central London and downtown Paris in just 2 hours and 16 minutes, while a flight between the city’s airports, which are in the outskirts, takes 1 hour and 17 minutes. In practical terms, this means that the train journey is actually faster between city centres.
"This tunnel fundamentally changed the geography of Europe and helped to reinforce high speed rail as a viable alternative to short-haul flights," Matt Sykes, tunnel expert and director at engineering company Arup, said to CNN.
SMART Tunnel, Kuala Lumpur, Malaysia
The Stormwater Management And Road Tunnel, or SMART Tunnel, was built not only to reduce traffic jams in downtown Kuala Lumpur, but also to deal effectively with flash flooding, a problem that plagues the Malaysian capital. The 13.2m diameter tunnel consists of a 9.7km stormwater bypass tunnel, with a 4km dual-deck motorway within the stormwater tunnel. The project also includes a storage reservoir and twin box culvert as well as a holding basin with a diversion and dedicated tunnel intake structures, in order to more effectively handle floodwater volumes.
The world’s first dual-purpose tunnel and Malaysia’s longest, it operates in three ways: ordinarily it functions as a run of the mill vehicular road tunnel, then when rainwater begins to accumulate, it diverts the water to a lower channel, keeping the upper level open to traffic. Finally, when flash flooding is exceptionally heavy, the tunnel is closed to traffic and watertight gates open to channel the overflow safely away from busy areas. In fact, the tunnel can get completely flooded and still manage to get rid of storm water and turn back into a vehicular road in a few hours.
In December last year, the SMART Tunnel faced its most severe test when KL was hit by record-breaking, once-in-a-generation rainfall. Over 22 hours, the SMART Tunnel diverted nearly twice its capacity of water.
“The five million cubic metres of water that we managed is a record high and beyond the tunnel’s actual capacity of three million cubic metres,” said SMART Chief Operating Officer, Mohd Noor Mohd Ali.
To date, the SMART Tunnel has managed to divert floodwaters countless times, averting billions of dollars’ worth of damage.
Guoliang Tunnel, Henan, China
Although most of the world’s most impressive tunnels are modern megaprojects, Guoliang Tunnel beats them all for sheer audacity and roughhewn beauty. This 1.2km tunnel was dug by hand into the side of the Taihang Mountains in China by villagers who wanted to improve access to their hard-to-reach village, nestled within mountain terrain so unforgiving, it allowed the rebel village to resist imperial forces during the Han Dynasty.
The tunnel is a mere 5 metres high and 4 metres wide, which means it can only accommodate one-way traffic. The jagged and steep tunnel also has around 30 openings along the way, making for dramatic views but terrifying drops, earning the tunnel the nickname of "the road that does not tolerate any mistakes."
The villagers took five years to complete the tunnel, using mainly hammers and chisels, and no modern equipment at all. The result was so awe-inspiring that today, the tunnel is a famous tourist attraction that brings welcome revenue to the once remote village.
"This tunnel is beautiful and a tribute to the tenacity of the villagers who built it," Alun Thomas, head of tunnels at engineering consultancy at Ramboll, commented to CNN. "For me it emphasizes how tunnel construction can enhance the environment as well as bringing huge benefits for society.”
Tokyo Bay Aqua-Line, Japan
As you would expect from a nation of islands famous for its high-speed shinkansen trains, Japan is filled with tunnels, so its hard to choose the most spectacular one. However, the Trans-Tokyo Bay Highway, also known as the Tokyo Bay Aqua-Line, consistently makes the list for one of the best tunnels in the world.
The 15.1km crossing consists of both a 4.4km bridge as well as a 9.6-km subsea conduit, which spans Tokyo Bay, connecting the cities of Kawasaki and Kisarazu. Upon completion, it reduced the journey time between from 90 to 15 minutes, and spurred the integration of these two prime areas of industry as well as bypassing the need to travel through central Tokyo, thus also reducing traffic congestion.
The project required the world's largest undersea tunnel boring machines and set the precedent for constructing two-lane road tunnels. A man-made island, Umi-Hotaru, was also constructed atop the Aqua-Line, offering rest areas, a mall and a popular observation deck with fantastic views of Tokyo Bay.
Bund Sightseeing Tunnel, Shanghai, China
Short and sweet, but also spectacular and surreal, the 646.7m Bund Sightseeing Tunnel is fully underwater and spans the Huangpu River, connecting Shanghai's old CBD in the historic Bund to its latest financial centre in Pudong.
Passengers are ferried across in automated cars and can enjoy the psychedelic lights, trippy audio-visual shows and air-dancers along the way, meant to represent a journey from space to the core of the Earth. The three to five-minute tunnel ride is consistently listed in the Top 5 tourist attractions in Shanghai since its unveiling.
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