ABSTRACT
For highway tunnel, the research on tunnel second lining structure cracking mechanism and the influence of cracks on the structural safety is of great significance. A finite element model is established to analyze the second lining cracking propagation. Based on stress intensity factor of fracture mechanics theory, the numerical calculation results under different conditions are obtained. The results indicated that stress intensity factor of type I (KI) at crack tip has weak relation with crack width, so as the propagation of the cracks. However, the values of KI increase with crack depth, the effect of bias is in favor of crack expansion. When the crack tip is within the depth of 3.0 and 12.0 cm, KI is less than the fracture toughness of type I (KIC) of crack tip. When the depth of the crack reaches 15 cm, KI is greater than the fracture toughness (KIC). Thereby, 12 cm is taken as the threshold of unstable failure of second lining crack. According to research achievements and the experience of the second crack treatment, the suggestion on the second lining of the tunnel cracking prevention and treatment is put forward.
