Failure mechanism and stiffness degradation of double lining with inner R/FRC lining subjected to internal water pressure

摘要

? 2022In this study, optimal fibre reinforced concrete (FRC) with a conventional reinforcing bar lining (R/FRC) is proposed as the inner lining to withstand internal water pressure. A full-scale test for a shield tunnel with a double lining of the external segmental lining and inner R/FRC lining was performed under internal water pressure to investigate the mechanical behaviour and failure mechanism of the structure. Cracking in the inner R/FRC lining initially appears at the segmental joints and then evenly progressed along the lining circumferential direction. Based on test observations and analysis, the failure process of the double lining can be divided into four stages, and the main damage in each stage is presented as follows: (1) stage I: initial cracking in the R/FRC lining near the segmental joints; (2) stage II: debonding of most fibres across cracks; (3) stage III: damage to segmental joints; (4) stage IV: yield of reinforcing bar of R/FRC lining and destruction of concrete at damaged segmental joints. Cracking of the R/FRC lining significantly decreases the stiffness and accelerates the deformation of the double lining. The evolution of the stiffness degradation of the cracked R/FRC lining was then calculated to assess the structural bearing status. An analytical model for the stiffness degradation of the R/FRC lining was then proposed and verified using the test results. Moreover, the effects of the fibre volume fraction and fibre aspect ratio were analysed. The test results and proposed model can be used to design a double lining with an inner R/FRC lining subjected to internal water pressure.