Monitoring and reinforcement of landslide induced by tunnel excavation: A case study from Xiamaixi tunnel

Deformations of tunnels and slopes are often induced by tunneling in landslide areas. However, the reinforcement measures for controlling slope deformation may be ineffective for preventing slope sliding, owing to the lack of a clear understanding regarding the slope failure and tunnel deformation modes. This study aimed to monitor the entire construction process of the Xiamaixi tunnel, to analyze the deformation characteristics of the lining and failure mode of the slope, and to evaluate the effectiveness of reinforcement measures. The deformation characteristics of the Xiamaixi tunnel and slope were studied in four stages (normal excavation, suspended excavation, continued excavation, and reinforcement and excavation) with reference to field investigations, geological boreholes, measurements, and numerical simulations. The maximum cumulative monitored deformations of the vault settlement and slope were 39.2 mm and 170.9 mm, respectively. The range of the landslide was 60 m along the tunnel axial direction, and 46 m along the tunnel transverse direction. It was found that a tunnel whose vault is located in a potential landslide area may be forced to extrude, but not slip, and that the extrusion deformation of the lining is only caused by the increasing external forces. Reinforcement measures (and other temporary supporting measures) were presented for the slope and auxiliary construction, and their effectiveness was assessed. Finally, the lessons learned were summarized, providing insights for preventing future similar incidents from reoccurring.