According to the inner forces distribution of double span tunnel under the surrounding rock loading action during different construction stages
the failure mode of the tunnel lining are made by a series- parallel connection system. Then
the Monte-Carlo random FEM is adopted to calculate the reliability of tunnel lining section
with full consideration of influence of the material characteristics
geometric dimensions
elastic resistance coefficient of surrounding rock
loading
etc.; and by using the breadth border method
a range estimation method
the system reliabilities of tunnel lining during different construction stages are studied. The system reliability index of a typical tunnel case is calculated in the end. The calculated results show that the system reliability index of middle wall is smallest after the single tunnel is excavated; and it can’t be safe when be used in long-term. When the tunnel is in construction
the safety of middle wall must be pay attention; and the double arch should be built as soon as possible.