Abstract: This study examines an existing metro tunnel adjacent to a deep excavation in Guangzhou’s granite strata, using field-measured data to characterize tunnel deformation during excavation. Results show that the retaining system could not effectively cut off hydraulic connectivity, causing substantial tunnel settlement, with a maximum value of 42 mm. Ensuring tunnel safety therefore requires strict control of groundwater cutoff performance to avoid large external water-level fluctuations. Because the station structure is stiffer than the running tunnel, stiffness mismatch produced notable differential deformation near their connection, warranting intensified monitoring. Additionally, grouting near metro tunnels in granite areas can induce uplift deformation and must be rigorously controlled. These findings provide guidance for safe excavation and tunnel protection in granite regions.

Key words: Deep Excavation, Metro Tunnels, Settlement, Granite Strata