Study on bearing mechanism and stress calculation method of tunnel secondary lining of fiber reinforced concrete
Cui Guangyao1 Zuo Kuixian1 Zhu Changan2,3 Zhang Guoqiang4
1. North China University of Technology, Beijing 100144, China;
2. Key Laboratory of Transportation Tunnel Engineering of the Ministry of Education, Southwest Jiaotong University, Chengdu 610031,China;
3. Highway Planning, Survey, Design and Research Institute, Sichuan Province Transportation Department, Chengdu 610041, China;
4. Sichuan Expressway Construction and Development Corporation, Chengdu 610041, China
Sufficient exploitation of the toughness of fiber reinforced concrete is the hot and difficult topic for the design of tunnel second lining. Based on the laboratory tests on plain concrete, steel fiber reinforced concrete and basalt fiber reinforced concrete, it is found that the addition of fibers has a far better impact on the toughness of concrete than the strength of concrete. In view of the excellent toughness of fiber reinforced concrete, the cracks of secondary lining of fiber reinforced concrete are regarded as plastic hinges, and the bearing mechanism of tunnel secondary lining of fiber reinforced concrete is proposed. Under the confining pressure, the first plastic hinge occurs in the lining, and with the increase of the confining pressure, the plastic hinges may rotate, which further lead to the occurrence of more plastic hinges. When the structure transforms from the statically indeterminate state to a rotating mechanism, the secondary lining structure is damaged. Furthermore, the stress calculation method for the cracked tunnel secondary lining of fiber reinforced concrete is discussed, and then the calculation formula is derived and validated based on model tests. Research results can be referred for popularization and application of fiber reinforced concrete to underground engineering.
