English：

Soft soil layer has low strength, large deformation and high compressibility, and it is easy tocause subgrade settlement and deformation when super-large diameter shield tunnel undercrossing,whichaffects the normal operation of existing high-speed railway. Based on the project of the Suzhou EastTunnel of the Tongyong High-speed Railway underpasses the existing Shanghai-Nanjing Intercity High-speed Railway, before the super-large diameter shield tunnel undercrossing, the surface directionalcontrol area deep hole grouting reinforcement technologywas adopted to improve the weak soil above thetunnel. Before construction, pre-tests were conducted to determine parameters such as the slurry mix ratioand grouting pressure. Numerical simulation analysis was adopted to verify the effectiveness of thegrouting reinforcement technology. The grouting reinforcement effect was evaluated by the core drillingmethod and the elastic wave CT method. The research results show that the appropriate groutingreinforcement range is the 10m× 40m× 100m area 2m away from the top of the tunnel. After groutingreinforcement, the density of the soil beneath the roadbed is improved, the bearing capacity is enhanced,the settlement is reduced, and the strength and deformation meet the requirements.