Shulou(Shulou.com)11/24 Report--

When you walk on the streets of the city, the ground is full of tall buildings, heavy traffic, a bustling scene.

Looking up at the sky and looking down at the road, few people think about what is underground in the city? What secrets lie beneath the surface that we cannot see?

Today, let Xiaobian lead everyone to "dig three feet into the ground" to dig deep into the underground structures and buildings of those cities!

What is underground in the city? Urban underground facilities are an important part of the city, including various pipelines, sewers, underground passages, underground parking lots, underground shopping malls, etc. Some big cities also have subways. The existence of these facilities is crucial to the functioning and development of cities.

Open the excavator and let's dig and dig together on the ground of the city ~(pure imagination, please do not practice)

Award-free Q & A: Which excavator technology is strong? Picture source pixabay slides up and starts digging ↑

2. What is good about building underground? There are so many underground buildings in cities, so why do people go to so much trouble to build them underground? This is because underground facilities have the following advantages:

1. Land conservation

With the expansion of urban scale, the contradiction between the shortage of building land and urban development is becoming more and more acute, especially in the prosperous commercial area, the development of underground space saves land resources and can alleviate the tension of urban land. Moreover, the houses are built underground, which can reduce the density of ground buildings, expand the green area and improve the ecological environment on the ground.

2. alleviate traffic congestion

Underground vertical space is very large, subway and other traffic lines are built three-dimensionally underground, with less intersection between each other and no interference, which can greatly save commuting time.

3. Anti-noise, anti-interference

Thick layers of soil insulate against noise and other influences, making it quieter and more comfortable to build houses underground. In addition, some precision scientific research devices, because of their sensitivity to external noise signals such as cosmic rays, are built deep underground to prevent interference.

4. Special period for protection

Compared with the above-ground buildings, the underground space is relatively closed, its defense capability is much higher than that of the above-ground buildings, and its post-disaster repair capability is strong, which can be built into the urban disaster prevention and air defense space, greatly improving the urban air defense support force.

5. Warm in winter and cool in summer, energy saving and environmental protection

Compared with the above-ground buildings, the underground space is less ventilated, the temperature difference is small, and it is warm in winter and cool in summer. This advantage saves the consumption of power resources and to some extent alleviates the situation of power shortage during peak periods.

Why not build underground buildings? The core reason was that digging underground was expensive. Ordinary basement within 7 meters deep cost about 2000 yuan, while ordinary 100 meters of high-rise buildings, single civil construction cost only 1000 to 1500 yuan.

Architecturally, it is difficult to build deeper underground structures. The lateral earth pressure and groundwater pressure of the exterior wall of underground building will increase with the depth, and the greater pressure is a great challenge to the pressure of building materials and the design of building structure. Moreover, excessive underground development will also reduce the ground load, which may bring the risk of collapse to the buildings on the surface.

From the use of functional terms, underground buildings waterproof moisture, ventilation, lighting regardless of construction or maintenance is also the focus and difficulty. Even if these problems are solved, problems such as drainage, sewage and fire prevention must be considered to meet the living requirements. It is difficult to achieve good living conditions underground.

Therefore, if it is a residential building excavated several hundred meters underground, it is basically science fiction in terms of existing technology.

4. Future Underground City? There is a saying circulating in the international architecture circle: "The 19th century is the century of bridges, the 20th century is the century of high-rise buildings, and the 21st century is the century of underground space."

With the rapid increase in the number of underground space, the total amount of underground space used in large and medium-sized cities in China has reached the forefront of other similar cities in the world. China has developed into a powerful country in the use of underground space in the world. As for the existing underground facilities construction, underground parking, underground traffic and civil air defense evacuation are the basis for the use of underground space in China, and underground drainage pipelines, subways and underground commercial centers are the focus. At present, underground urban rail transit, underground commerce, underground parking lot construction into the development period.

In the domestic hard science fiction blockbuster Wandering Earth, the "underground city" built by human beings for survival is impressive. With the development of city, underground space is becoming more and more important in the process of modern city development. What kind of underground structures can we build?

Generally, the development depth of underground space in cities is only 100 meters. Regardless of the actual cost, construction at a depth of 1000 meters is possible in a sense.

Looking up, the tallest building in the world is Dubai's Burj Khalifa, which has a standard height of 828 meters. Looking down, heading deeper, the deepest well on Earth today is Russia's Odoptu OP-11 well at 12,345 meters. The average thickness of the crust is 17,000 meters, and there may already be lava below it. This depth is almost the limit of people's imagination. In contrast, the underground space is broader, there is more room for development, but also brings us endless imagination. But apart from the architectural problems discussed above, we don't know what else lies ahead...

As we continue to encroach on the sky, we are slowly shifting our attention to the exploration of underground space. With the continuous progress of science and technology, perhaps in the near future, underground cities will no longer be fantasy, and even magic "Modi" buildings will appear one by one.

resources

[1]Zhang Zhi, Wu Menghan. Review of urban underground space research in China based on CiteSpace [J]. Safety and Environmental Engineering, 2023, 30 (01):25-34.

[2]Du Yulu, Wang Zhichao. Discussion on the Necessity of Urban Underground Space Development and Utilization [J]. Sichuan Building Materials, 2016, 42 (01):100-101+109.

[3]Guiding Opinions of the Ministry of Housing and Urban-Rural Development on Strengthening Urban Underground Municipal Infrastructure Construction, December 30,2020

[4]Design Standard for Pedestrian Underpass in Shenzhen SJG 68, 2019 Edition

[5]Code for Design and Construction of Vehicle Refueling Stations GB50156-2012, 2014 Edition

[6]How deep underground is the subway? What determines its depth? Zhihu

[7]Official website of Qin Shihuang Mausoleum Museum, www.bmy.com.cn/

Cover image generated by BingAI, not real

This article comes from Weixin Official Accounts: Institute of Physics, Chinese Academy of Sciences (ID: cas-iop), author: Childe

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