“Underground” Japan

Japan is an island country with many mountains and forests and little arable land. Most of the population is concentrated in the narrow coastal plains. Therefore, the situation of “more people and less land” has prompted Japan to always strive to actively use underground space.

From natural space to artificial creation

Speaking of the underground space naturally generated in Japan, we have to mention the national special natural monument designated by the Japanese government, the largest stalactite cave-Qiufang Cave. Akiyoshi Cave is located 100-200 meters below the “Akiyoshidai National Park” in the eastern part of Mine City, Yamaguchi Prefecture. In ancient times, it was a beautiful seabed with coral reefs. After submarine volcanic eruption and ocean plate movement, it became the largest in Japan 350 million years later. The plateau of the karst landform. Qiufangdong is said to be formed 300,000 years ago, with a total length of about 9 kilometers, but currently only about 1 kilometer is open for sightseeing. The height difference in the cave is about 40 meters, and you can see many stalactites, stalagmites, waterfalls and abysses. The temperature in the cave is maintained at about 16 degrees Celsius throughout the year, warm in winter and cool in summer. In 1926, when Emperor Showa, who was the crown prince at the time, visited this place, he gave it the name “Akiyoshi-dong”. In 1975, when the Sanyo Shinkansen was opened, the number of tourists visiting Qiufangdong reached a record high of about 2 million. Since then, although the number of tourists has decreased, it has remained at 600,000-700,000 per year in recent years.

Speaking of artificially created underground spaces, there are various functions and uses, including residential and living facilities such as basements, underground streets, underground parking lots, production facilities such as mines, tunnels, and underground power stations, air-raid shelters, underground reservoirs and other air-raid and disaster-prevention facilities. Infrastructure such as subways, integrated pipe corridors, and underground research facilities, etc. Representative examples of these underground spaces with different functions and uses can be found in Japan.

On April 1, 1930, a 500-meter-long “underground street” with shops on both sides of the underground pedestrian passage of Tokyo Metro Ueno Station officially opened. It is the “originator” of Japanese underground street. The underground mall is very popular because it is free from the interference of bad weather such as rain, snow, wind, and cars, so you can shop and walk comfortably and comfortably. Today, Japan’s underground malls are spread across major cities across the country, and they have evolved from a purely commercial nature to a multi-functional urban complex composed of transportation, commerce and other facilities. After 1973, due to fire factors, the Japanese government once imposed strict restrictions on the construction of underground streets, resulting in a decrease in the number of new urban underground streets. However, the scale of individual underground streets has become larger and larger, the design quality has become higher and higher, and the disaster resistance capacity has increased. It has become stronger, and Japan has formed a relatively sound system for the development and utilization of underground shopping malls in terms of legislation, planning, design, and management. Take the Yaesu Underground Street in Chuo-ku, Tokyo as an example. It is located under the city roads and Tokyo Station Plaza, with a total area of ​​more than 70,000 square meters. The first phase opened in 1965 and the second phase opened in 1969. It is now the second largest single underground street in Japan. At the beginning of its construction, an expressway passed through this underground street. At that time, it was the first very successful case in the world where an expressway passed through the city center and organically integrated with the underground street.

As we all know, Japan is a country with relatively scarce mineral resources. After years of mining, the original mineral resources are gradually depleted. In addition, due to high mining costs and increased imports, Japan’s domestic mining sites have been closed one after another. On the other hand, some of these abandoned mining sites have been re-used for scientific experimentation, research, sightseeing and other fields, and even some abandoned mining sites have brought economic benefits to the local area due to the large number of visitors. “Field Site” is one of them. The site of the Otani Stone Underground Excavation Site is located in Otani Town, Utsunomiya City, Tochigi Prefecture. The surrounding area is covered with tuff layers called Otani Stone. Because tuff is resistant to weathering and fire, and is soft and easy to mine, it has been used as a raw material for building stone walls and foundations since ancient times. Nowadays, there are many excavation relics left in the underground of that area. In order to let later generations understand the mining history of Otani stone, the “Otani Museum” established on the site of the Otani stone underground excavation site was officially opened in 1979. The origin of Otani stone, changes in mining methods and transportation methods are displayed in the museum. material. On the other hand, the Otani Stone Underground Excavation Site at a depth of 30 meters under the Otani Archives is a huge underground space formed after 70 years of excavation. Its area is 20,000 square meters, equivalent to the size of a baseball field. During World War II, it became an underground military supply factory of the Japanese military. After the war, it was once again used by the Japanese government as a warehouse for storing rice. Now, this mysterious underground space has become an attraction that attracts a large number of tourists. In addition to receiving tourists, it is also popular for art exhibitions, concerts, theater performances, film and television drama shooting, wedding ceremonies and other activities.

Library on the 8th floor

When Japan uses underground space, it also pays great attention to the characteristics of underground space. For example, unlike the ground, the stratum up to about 15 meters underground has a very small range of temperature changes with climate, with constant temperature and humidity. This feature allows the underground space to be used for items such as precision instruments and books that require special preservation. The National Diet Library of Japan is the largest library in Japan and the only national library. It currently has about 45 million copies of various collections including various books, magazines, newspapers, video materials, and music records. According to Japan’s publication deposit system, the National Diet Library of Japan stores all publications in Japan. As a result, about 750,000 pieces of various materials enter the National Diet Library of Japan each year. About half of the huge amount of various materials in the museum are collected in the Tokyo Main Building, which was built in 1961, and a new building was built in the Tokyo Main Building in 1986.

The Tokyo Main Building of the National Diet Library of Japan is located in Nagata-cho, Chiyoda District, Tokyo, the political center of Japan. It is surrounded by important buildings such as the National Diet Building, the Prime Minister’s Residence, and the office buildings of various central government departments. The new Tokyo Main Building has a high height Restrictions, can only choose to dig down the space. The new building of the Tokyo Main Building of the National Diet Library of Japan was finally completed. The length from east to west is about 148 meters, and the length from north to south is about 43 meters. There are 4 floors above ground, 8 floors underground, and the deepest part is 30 meters underground. The 8th floor underground is actually a bookstore, which can store about 7.5 million pieces of various materials, and the total length of the bookshelves is about 240 kilometers. A temperature of 22 degrees Celsius and a humidity of 55% are maintained in the library, and the entire environment is designed on the premise that it is suitable for the preservation of books and materials. At the same time, in order to prevent the library from being flooded and to suppress the temperature rise, there is no toilet on the basement floor of the entire new building, but only one hand washing place. In addition, since the surrounding area of ​​the underground space is rock and soil, the seismic wave after an earthquake has a relatively small impact on the rock and soil. Therefore, the seismic resistance of the underground space is relatively good. When the “March 11” earthquake occurred in Japan in 2011, about 1.8 million pieces of materials from the old library of the Tokyo Main Building of the National Diet Library of Japan on the ground were shaken down from the bookshelves, and 80 staff members took 10 days to do so. Finishing is complete. In contrast, the library on the 8th floor of the basement of the new library was almost unaffected, and only 20 collections of materials were shaken down from the shelves. As a result, the seismic resistance of the underground library in the new library has also attracted widespread attention.

As the library’s collection of materials is semi-permanently preserved, and the collection of materials continues to increase, in recent years, the National Diet Library of Japan is gradually transitioning to the direction of microcopying and e-books. The underground library of the Tokyo Main Building of the National Diet Library of Japan It will be the first and last large-scale underground library in Japan.

In terms of disaster prevention facilities, Japan has also given full play to the role of underground space. Japan has a maritime monsoon climate, the main characteristics of which are mild and humid throughout the year and four distinct seasons. Especially in the rainy season and typhoon season, the water volume of the river increases sharply, which is prone to flooding. To this end, Japan has built a large number of flood control projects to effectively reduce flood disasters. The most famous of these is the “Outer Capital Circle Waterway”. Located in Kasugabe City, Saitama Prefecture, the outer Guofangshui Road of the Capital Circle is a large flood discharge tunnel built about 50 meters underground on National Road 16. composition. The project started in 1992 and was completed in 2006. It is the most advanced sewer drainage system in the world, which integrates Japanese civil engineering technology. Anyone who has seen the Guofang Waterway outside the capital area will be shocked by its magnificent design. There are five cylindrical shafts with a depth of about 70 meters and a diameter of about 30 meters, each of which is large enough to accommodate a space shuttle or a statue of Liberty. The surge tank is a huge reservoir with a length of 177 meters, a width of 78 meters, and a height of 18 meters, in which 59 cement columns with a diameter of about 2 meters and a height of 18 meters, weighing 500 tons, stand side by side. When people enter this huge space, they feel that they are very small, and they also feel that it is very solemn and sacred, as if they are in an ancient Greek temple. Therefore, it is also known as the “underground temple” in Japan. This huge reservoir is only used in the rainy season and is open for visits on weekdays. It has also become a popular attraction for many tourists.

The library above the cloud provides unlimited play space for children. In the library, children can take off their shoes and feel the warmth of the wooden floor, and they can read books anywhere.