Abstract：
Causes of secondary lining cracking in tunnels are complex and it is important to identify them so that reasonable treatment measures can be proposed to ensure safety during tunnel construction and operation. Using a tunnel that passes through carbon-based phylite as an example, and in light of the cracking characteristics of the secondary lining at the exit section, the measured data at the site and the geological conditions, it is determined that the main reasons for cracking in the secondary lining are poor quality of the surrounding rock, low levels of surrounding rock and early implementation of the secondary lining. Early installation of the secondary lining will result in large tensile stress at the inner side of the secondary lining near the sidewall and haunch, and the earlier the installa? tion of the secondary lining, the larger the tensile stress, which will result in cracking of the secondary lining. It is appropriate to install the secondary lining when the deformation of the primary support is 65%~70% of the final convergence. It is recommended to put more effort into monitoring and measuring and to strictly control the installation schedule of the secondary lining.
2017, Vol. 54 