Cracking mechanism of secondary lining for a shallow and asymmetrically-loaded tunnel in loose deposits |
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| Affiliation: | 1. State Key Laboratory of Simulation and Regulation of Water Cycle in River Basin, China Institute of Water Resources and Hydropower Research, Beijing 100048, China;2. College of Architecture and Civil Engineering, Beijing University of Technology, Beijing 100022, China;3. Institute of Rock and Soil Mechanics, Chinese Academy of Sciences, Wuhan 430071, China;4. Key Laboratory of Active Tectonics and Volcano, Institute of Geology, China Earthquake Administration, Beijing 100029, China;5. Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China;1. Key Laboratory of Transportation Tunnel Engineering, Ministry of Education, Southwest Jiaotong University, Chengdu 610031, Sichuan, China;2. Sichuan Highway Planning, Survey, Design and Research Institute Ltd, Chengdu 610041, Sichuan, China;3. Department of Road and Bridge Engineering, Sichuan Vocational and Technical College of Communications, Chengdu 611130, Sichuan, China;1. State Key Laboratory of Mechanical Behavior and System Safety of Traffic Engineering Structures, Shijiazhuang Tiedao University, Shijiazhuang 050043, China;2. Key Laboratory of Large Structure Health Monitoring and Control, Shijiazhuang Tiedao University, Shijiazhuang 050043, China;3. China Railway Eryuan Engineering Group Co., Ltd., Chengdu 610031, China;4. Test and Measure Technology Company of the Fourth Highway Engineering Co., Ltd., Beijing 100025, China |
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| Abstract: | Tunnels constructed in loose deposits with low strength and complex composition are usually subjected to asymmetrical stresses at the entrance and exit. The secondary tunnel lining is prone to excessive deformation, cracking, or even collapse, seriously affecting the safety of tunnel construction and operation. In this paper, a large shallow highway tunnel in loose deposits is used as an example to study the cracking mechanism of secondary lining. Triaxial consolidated-drained shear tests are carried out on large remolded specimens to obtain the mechanical parameters of the surrounding soil. Three-dimensional numerical modeling is conducted based on the field monitoring data to simulate the process of tunnel construction and to analyze the mechanical mechanism of cracking in the secondary lining. It is shown that even with the 30 m advance pipe roof at the tunnel entrance, the apparent difference in stiffness between the retaining wall and the surrounding soil results in an obvious stress concentration at the spring of the secondary lining near the end of the retaining wall, due to the effect of highly asymmetrical stresses. In addition, loose deposits are very sensitive to construction disturbances. Large horizontal deformation towards the lower topography occurs during tunnel construction. With increasing overburden depth, the stress concentration at the spring level and the horizontal deformation in the secondary lining increases, which are the main reasons for cracking in the secondary lining. These findings can be useful for tunnel design and construction in the similar type of loose deposits. |
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| Keywords: | Shallow tunnel Asymmetrical stress Loose deposits Cracking of secondary lining |
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