1、附录 Risk identification and risk mitigation During metro station construction by enlarging shield tunnel combined with cut-and-cover method Zhang Xinjin Liu Weining Lu Meili (School of Civil Engineering and Architecture, Beijing Jiao tong University, Beijing100044, China) Abstract: Constructing a met
2、ro station by enlarging shield tunnels combined with a mining /cut-and-cover method provides a new method to solve the contradictions of construction time limits of shield tunnels and stations. As a new-style construction method, there are several specific risks involved in the construction process.
3、 Based on the test section of Sanyuanqiao station on Beijing metro line 10, and combined with the existing methods of risk identification at present including a review of world-wide operational experience of similar projects , the study of generic guidance on hazards associated with the type of work
4、 being under taken ,and discussions with qualified and experienced staff from the project team etc., the specific risks during the construction process of the metro station constructed by enlarging shield tunnels combined with the cut-and-cover method are identified. The results show that the specif
5、ic risks mainly come from three construction processes which include constructing upper enclosure structures, excavating the soil between shield tunnel sand demolishing shield segments. Then relevant risk mitigation measures are put forward. The results can provide references for scheme improvement
6、and a comprehensive risk assessment of the new-style construction method. Key words: shield tunnel； cut-and-cover method； metro station； risk identification； risk mitigation In recent few years, the shield tunneling method has been widely applied in the running tunnel construction of Beijing metro b
7、ecause of its advantages such as quickness, safety and little influence on the surrounding environment etc. But only running tunnel is constructed by the shield tunneling method, and the station is still constructed by the traditional cut-and-cover method or mining method at present. The contradicti
8、on of construction time limit of shield tunnel and the stations has not been well solved. Based on the investigation of domestic and international information, and combined with domestic level of technology and economy, a new solution for the problem is put forward. By the new solution, shield machi
9、ne passes a series of the stations in the line first, then the metro stations are constructed by the cut-and-cover method or the mining method in the proper time, most of the segments are remained, but only a passage is opened at the segments to provide the condition of climbing aboard and getting o
10、ff for passengers. Considering that the construction method has not been used before in China and it would be greatly difficult to enlarge the station by the mining method , authors studied the scheme of constructing metro station by enlarging shield tunnel combined with the cut-and-cover method fir
11、stly based on the test section of Sanyuanqiao station on Beijing metro line10. As a new-style station construction method, there would be several specific risks during the construction process. In this paper, the risks during the construction process of metro station constructed by enlarging shield
12、tunnel combined with the cut-and-cover method are identified and relevant risk mitigation measures are put forward. 1 Project Situation Sanyuanqiao station is a transfer stations between line 10 and the airport line, which locates at the green space between Jinshun road and the airport expressway. I
13、t is an underground double-layer and island-style station. Its length is 160.9m. There are four station passageways, one transfer passage, one secure passage and two air ducts. According to the general project plan of line 10 and the construction environment of Sanyuanqiao station, the station is co
14、nstructed by general cut-and-cover method after the shield passes the tunnel in the scope of the station, and all shield segments are demolished. In order to explore the way of only part of shield segments are demolished, the starting 18.6m of Sanyuanqiao station on Beijing metro line10 is selected
15、as the test section. The structure scheme of metro station constructed by enlarging shield tunnel combined with the cut-and-cover method is studied, and only parts of shield segments are demolished. The technology has not been used before and it is at the development and research stage. There are sp
16、ecific requirements to many aspects including shield segments, construction process, and the treatment of the joints etc. Fig.1 shows the general plan of Sanyuanqiao station and the location of the test section, and Fig.2 shows the arrangement of shield segments. The airport line； Line10； Test secti
17、on Fig. 1 General plan of Sanyuanqiao station 2 Risk Identification and Risk Mitigation 2.1 Survey of risk research Since Einsteinetal introduced risk analysis to tunnel and underground engineering in the 1970s, certain achievements on the research of risk management have been obtained in overseas,
18、mainly in Europe countries and America. Comparing with overseas, the research of risk management in tunnel and underground engineering in China started relatively later, but with large scale development of underground space in recent few years, the researches of risk management have got unprecedented concern.
