Mechanical Response and Stability Assessment of Deteriorated Tunnel Linings Under Prescribed Cyclic Stress Changes

Abstract

This study investigates how initial material deterioration and repeated stress changes affect the response of lining–rock systems during tunnel reconstruction and expansion. Monotonic uniaxial compression tests on limestone specimens with gypsum linings were monitored using digital image correlation. A corresponding numerical model was compared with the monotonic test response and used for incremental–static cyclic loading simulations. The numerical series examined cyclic stress amplitude, initial lining deterioration and initial surrounding-rock deterioration separately. Higher cyclic stress amplitudes produced greater convergence and more extensive plastic-zone development. The lining plastic-zone fraction increased more markedly between surrounding-rock deterioration levels of 20% and 30% than across the lower sampled levels, indicating a possible transition within the investigated range. Axial work-density changes depended on the parameter series and were not uniformly monotonic. A weighted five-indicator framework with prescribed engineering weights combines convergence, plastic-zone fractions and lining cohesion loss for relative comparison of the simulated cases. The findings identify regions and material conditions that warrant attention when assessing deteriorated linings and planning tunnel reconstruction and expansion.