Numerical Simulation and Analysis of the Causes and Distribution of Secondary Lining Cracks in Overlapping Railway Tunnels

The construction of new tunnels above existing has become increasingly common to optimize underground space utilization. However, such may pose potential engineering hazards due cracking in the secondary lining lower tunnel. This study investigates occurrence and evolutionary characteristics longitudinal cracks tunnel during upper adjacent pre-existing Our findings demonstrate that a significant impact on tunnel, as confirmed by on-site monitoring numerical simulation results. redistribution surrounding rock pressure alters stress distribution which is primary reason for observed cracking. To mitigate risk cracks, two different methods are recommended based density cracks. In areas with less dense method chiseling grouting adopted improve strength lining, while relatively areas, resin anchor rods saddle joints used enhance stability rock. Long-term monitoring, classification, early warning also recommended.