Abstract��
Insufficient thickness of the tunnel lining will significantly change its mechanical state and threaten the safety of the tunnel structure. A numerical simulation is conducted to analyze the safety state of tunnel linings under the conditions of integral or local insufficient lining thickness based on a two-lane highway tunnel in surrounding rock of class IV. The results show that insufficient lining thickness leads to a decrease of the axial force and bending moment on the defective section of the tunnel and an obvious reduction of the ultimate bearing capacity of the tunnel structure, which significantly reduces the safety factor of the tunnel structure at the defective section. Additionally,the internal force, bearing capacity and safety factors of the defective section are strongly influenced by a local insuf? ficient lining thickness, while sections far away from the defect are relatively less affected by this. The relationship is linear between the lining thickness and the safety factor of the tunnel structure under the condition of an integral or local insufficient lining thickness, and the critical thickness of the tunnel lining for meeting structural safety requirements is determined by a regression analysis.
2017, Vol. 54 