Analysis of impact of demolition and reconstruction of old residential buildings above existing metro tunnels on vertical ground displacement

The demolition and reconstruction of old residential buildings above existing metro tunnels can cause unloading and reloading, resulting in deformation of the overlying soil. Simplified numerical simulation analysis is conducted to investigate this engineering problem. Seven types of working conditions are established to study the influence of metro tunnel quantity and spatial arrangement on vertical ground displacement. The research reveals that: tunnels create a stiffness enhancement effect that effectively reduces vertical surface displacement. The reinforcement effectiveness ranked from strongest to weakest: double tunnels horizontally parallel > double tunnels vertically stacked > single tunnel > no tunnel. The horizontally parallel configuration of double tunnels also exhibits smaller differential settlement. When the burial depth of the uppermost tunnel exceeds 24.8m, its impact on surface vertical displacement becomes negligible. For vertically stacked double tunnels, the reduction in vertical surface displacement is primarily attributed to the upper tunnel, while the lower tunnel shows very limited influence.