Settlement control of slurry shield tunnelling crossing adjacent buildings in mixed ground of round gravel and mudstone

The micro-disturbed construction in mixed ground is a major challenge in the shield tunnelling construction. The Nanning metro line 1 crossing You'ai buildings is confronted with the challenge of mixed ground of round gravel and mudstone. The sleeve-valve-pipe grouting technology is applied in the round gravel with strong permeability by using the field tests to determine the mixture ratio of composite grout. The deformation monitoring of adjacent buildings and structures of shield-driven tunnels together with feedback-control during construction is the core part of the micro-disturbed construction control. The mixed ratio $\lambda$ of round gravel and mudstone is defined and the variation of tunnelling parameters is analyzed with different$\lambda$. The measured results show that the sleeve-valve-pipe grouting is quite useful to reduce settlement. The automatic monitoring can reflect the influence of the shield tunnelling construction on the surroundings. The average values of slurry pressure, torque and total thrust significantly increase, while the penetration rate decreases when $0.15\le \lambda 0.6$, which is quite bad for settlement control. When $\lambda \ge 0.6$, the torque and total thrust continue to increase while the fluctuation of slurry pressure diminishes and the penetration rate is very low. The priority is to control the slurry pressure in excavation chamber and the grouting is crucial to control settlement. Moreover, it is beneficial to modify the slurry properties, to reduce the advance speed and to increase the cycle time when tunnelling in mudstone.