Analysis of the displacement increment induced by removing temporary linings and corresponding countermeasures

Temporary shotcrete lining plays an important role in stabilizing tunnel structures. However, demolition of the temporary lining has negative impacts on the preliminary lining. Based on a case study of using pre-tensioned anchor cables to minimize the risk caused by removing temporary linings, a comprehensive study has been carried out on the displacement caused by removing temporary linings as well as countermeasures. A calculation model was established based on a bedded-beam model recommended by the International Tunneling Association (ITA). Using this model, the influences of three factors, the axial force in the temporary lining, the thickness of the preliminary lining and the deformation modulus of the ground, were studied in detail. Countermeasures were proposed corresponding to each of the influence factors and a countermeasure grading system was constructed. The research results presented in this paper can be valuable references for design and construction of tunnels involving use of temporary linings.