Interview with Academician Sun Jun: Tunnels are being built frequently – what are the key factors?

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This post was last edited by hesonchang214 on 2017-1-13 at 10:03 ----Interview with Academician Sun Jun at the International Conference on Bridge and Tunnel Technology. In recent years, the number of large-diameter, long-distance tunnels constructed in China has been increasing gradually. With the advancement of construction technologies, the challenges encountered during construction have been overcome one by one. However, issues such as tunnel operation safety, energy conservation and consumption reduction, and environmental pollution caused by vehicle exhaust emissions are receiving increasing attention from ** and all sectors of society, and have become major challenges in today’s tunnel operation management. How to develop and utilize this increasingly large \"new market\" of urban underground space in a more rational and efficient manner is crucial for the healthy development of cities in our country, and it has become an issue that needs to be addressed urgently. In response to these issues, Mr. Sun Jun, a senior academician of the Chinese Academy of Sciences, a first-class honorary professor at Tongji University, and a renowned expert in tunneling and underground engineering, offered his own **. 1. Reporter: What are the large-scale tunnel projects that are currently planned and under construction in China? Academician Sun: As an example from Shanghai, the large-scale tunnels currently under construction include the Beiheng underground road passage, the Yanjiang Tunnel that crosses the river, and the Zhoujiazui Road Tunnel that also crosses the river. In other provinces and cities, there are several large-diameter shield tunnels, such as the Sanyang Road Tunnel in Wuhan, the Maolizhou Tunnel in Hengqin, Zhuhai, the Suei Passage in Shantou, the Yangtze River Tunnel in Wuhu, and the Dalian Bay Undersea Tunnel. Additionally, the much-anticipated Shenzhen-Zhongshan Passage in Guangdong has had its design finalized. Due to various environmental constraints in the surrounding area, this passage will adopt a design that combines a bridge on the west side with a tunnel on the east side, using an artificial island as a transition point. It will be China’s second bridge-tunnel structure of this type after the Hong Kong-Zhuhai-Macao Bridge, and it is worth looking forward to. Currently, a tender for the design plan of this channel is underway. Preparatory research is also being actively carried out in China for the construction of several cross-sea strait tunnels. Ma Liu Chau Tunnel, Sanyang Road Tunnel 2: Reporter: For soft-soil tunnels in subway sections, circular shield tunneling with separate upstream and downstream lanes is currently the common approach used in China. Given different requirements, are there any other new types of special-shaped shield machines? What are the application prospects of a recently developed large-section rectangular-shaped shield machine? Academician Sun: Building on the use of double-circle shield machines for constructing subway tunnels in earlier years, Shanghai Tunnel Engineering Co., Ltd. has achieved success in recent years by using large-section rectangular jumbo shields and rectangular-shaped shield machines for tunneling under main roads in Zhengzhou City and for the Ningbo Metro Line 3. The use of a rectangular, double-row large-span shield (about 11m wide) in place of the traditional separate circular shields for the upper and lower tracks not only saves underground space and improves the utilization rate of the cross-section, but also generally avoids the need to occupy land on either side of the street (with traditional separate circular shields, the depth of the subway tunnel built using this method may increase due to the pile foundations of buildings along the street, or difficult procedures such as pile cutting and replacement may be required). Its main advantages are also reflected in the fact that it introduces another type of underground station; namely, in addition to the island-type underground stations commonly used in China today, side-type stations can be adopted when conditions permit, which is more suitable for stations with lower passenger traffic. The quasi-rectangular shield machine used in Ningbo 3. Reporter: Apart from tunnel construction, the development of various types of urban underground spaces in China is in full swing. What is Academician Sun’s opinion on this? Academician Sun: In terms of the construction of urban underground transportation systems, we have achieved remarkable results that are truly worthy of pride for the world and the entire nation. However, in terms of various aspects such as underground leisure, health care, entertainment for urban residents, and major underground municipal facilities, these are already common practices abroad, but they have not yet been introduced in China; there is still a long way to go. 　　The underground environment is quiet and peaceful, free from the hustle and bustle of the city. If proper ventilation and dehumidification can be ensured (through careful design and installation of appropriate facilities), the temperature and humidity in such an underground space will remain very pleasant throughout both winter and summer. It is also protected from harmful environmental factors such as vehicle exhaust, extreme cold and heat, typhoons, thunderstorms, and fog. Moreover, if it’s possible to introduce natural sunlight into the underground space, it truly becomes an underground \"paradise\". And this has already become an undeniable reality in some developed countries; today is the time for our country to start making efforts in this area as well! As the core element of urban underground spaces, the subway can connect various such spaces together, creating a comprehensive network that covers all underground areas. Areas surrounding several major underground subway stations have been selected for the planned development of various distinctive underground commercial streets, shopping malls and supermarkets, as well as shopping centers. There are also various underground leisure walkways, underground gardens, playgrounds, underground libraries, and underground green spaces as well as entertainment and cultural activity centers that offer opportunities for people to exercise and maintain their health underground. All these will greatly improve the quality of life and standards of urban residents. There are many successful examples abroad in this area that are worth our reference and emulation. 4. Reporter: With the introduction of various policies, there is an increasing number of underground ducts being built for municipal uses, and Guangzhou is constructing deep-level water storage and drainage tunnels to prevent flooding and manage water levels. What are the prospects for development in this area? Academician Sun: Utilizing deep underground spaces to create channels for water storage, flood drainage, and also for extracting water during dry seasons should be tried first in large cities where there is a need for such facilities and where the financial and material resources are available. This is another new channel that should be developed as soon as possible to utilize underground space. Every year, at the turn of spring and summer, continuous heavy rains in southern China pose a severe burden on many cities; the resulting waterlogging poses serious challenges to urban management as well as to municipal and disaster prevention agencies. The so-called underground water storage, flood drainage, flood control, and drought resistance systems referred to here are large-scale underground networks for water storage and drainage built in deep underground spaces. These include large underground pumping stations, deep drainage tunnels (artificial underground rivers), large underground reservoirs, as well as large underground sewage treatment facilities. As a powerful supplement to the existing urban drainage and flood control systems, it, together with the existing shallow underground drainage networks, forms an efficient and comprehensive urban drainage network. I see very promising prospects for development! These were the excellent answers given by Academician Sun Jun during a Q&A session with journalists at the 2016 International Conference on Bridge and Tunnel Technology held in Shanghai this year. It is also reported that Academician Sun Jun will continue to participate in the 2017 International Conference on Bridge and Tunnel Technology to be held next year.