Abstract:

The safety and longterm stability of tunnel engineering rely heavily on the lining construction time, primarily determined through insitu monitoring of the stability of the surrounding rock. However, this approach needs a rational theoretical basis. To address this issue, a method that uses displacement back analysis technology is proposed for a new railway tunnel project. This method considers the constraint effect of the lining on the surrounding rock and primary support. It involves fitting a deformation curve based on primary support monitoring data to determine the residual deformation. The corresponding surrounding rock stress field is derived using displacement back analysis. This stress field is then applied to the primary support and lining via the finite element method to obtain the lining stress. Evaluation criteria, such as allowable tensile stress and shear safety factor, comprehensively assess lining safety and determine its earliest construction time. The results show that the residual deformation of the primary support decreases gradually over time, with a substantial deceleration rate within the first 10 days after primary support completion. The earliest lining construction time for a specific tunnel case is 39 days after primary support completion. At the insitu lining construction time (100 days after primary support completion), the monitoring results of the lining internal force align well with the back analysis results, confirming the feasibility of the proposed method.

Key words: tunnel, earliest lining construction time, back analysis, residual deformation, allowable stress, shear safety factor