Security analysis of dismantling temporary supports of large-span shallow tunnel in upper-soft and lower-hard stratum

For composite lining tunnel, initial liner is the most dangerous when temporary supports are dismantled before construction of second-layer liner. A project example of Qingdao metro is introduced. Using in-situ monitoring and numerical simulation, this paper contrasted deformation of rock and initial liner before and after dismantling temporary supports. Security of dismantling temporary supports is analyzed. Measured data show that volume growth and growth rate of displacement are small. Displacement results of numerical simulation are well consistent with measured data. The results show that the security of initial liner is little influenced by dismantling temporary supports. As a result, this study provides evidence for information-oriented construction of tunnel as well as experience for the future related projects.