Abstract: The intrusion deformation in the tunnel induced by the poor geological conditions and other reasons after the installation of the primary lining was observed and the thickness of the secondary lining did not meet the original design requirements. The evaluation of the construction monitoring data of the intrusion deformation during the primary lining stage indicated that the deformation in the lining system had stabilized. To minimize the disturbance in the primary lining system caused by the removal of the steel supporting system, the design change approach was implemented by reducing the thickness of the secondary lining and strengthening of the steel reinforcement bars in the secondary lining system. The new design approach in the secondary lining system was validated by using MIDAS-GTS NX finite element numerical analysis software. It is concluded that the factor of safety in the strengthening segment met the design requirements. The construction monitoring indicate that the new approach was safe, and no cracking was observed.

Key words: Tunnel, Primary Lining, Deformation Intrusion Limit, Secondary Lining, Validation