Abstract: In response to the issue of unclear influence of slurry diffusion and soil pressure around the tunnel during grouting at the bottom of the shield tunnel, grouting unit tests and simulation tests on grouting uplift at the bottom of the shield tunnel were carried out. The analysis of the grouting unit test reveals that the slurry undergoes splitting and diffusion during grouting, leading to “slurry leakage”. Interestingly, the additional soil pressure from grouting does not increase, and in some cases, it decreases post “slurry leakage”. In the tunnel grouting lifting model test, the slurry experiences compaction diffusion and splitting diffusion with a somewhat random direction. As the splitting and diffusion of slurry solidifies in the soil layer, its fluidity decreases gradually until diffusion ceases. Transitioning from squeezing diffusion to splitting diffusion, the soil pressure around the slurry bubbles decreases significantly. After completing the grouting, the additional soil pressure diminishes due to slurry consolidation and contraction. The model shield tunnel exhibits “transverse elliptical” and longitudinal bending deformations under the additional soil pressure, inducing additional loads interacting with the surrounding soil. Hence, in practical construction, in addition to the “small amount multiple times” grouting principle, enhancing slurry consistency is crucial to prevent “slurry leakage”.

Key words: shield tunnel, differential settlement, grouting lifting, grouting diffusion, tunnel deformation