Influence of Perturbation Grouting of Shield Tunnel on Soil Strength and Transverse Convergence of Tunnel Linings

Abstract:

The transverse deformation of shield tunnels in soft soils may ultimately threaten the safety of tunnel structure and is often controlled by using the perturbation grouting method. To study the effect of perturbation grouting around a tunnel， cone penetration tests were conducted to analyze the influence of grouting on the soil around two sides of a tunnel and reinforced through grouting. K0 consolidated undrained extensive shearing triaxial tests were performed on standard samples made from the soil obtained from field， and， as a result， the undrained extensive shear strength and the secant modulus were computed. A linear model was used to fit the data of grouting volume and horizontal convergence of the tunnel， and thus， an equation was built to describe the relationship between the normalized convergence value and the relative grouting volume. The effect of grouting on reducing horizontal convergence was analyzed using the built equation. The results show that perturbation grouting improves the ps by 110.8% of the soil at the grouting center and 97.6% of the soil at the edge of the grouting region， and the grouting reinforcement effect is non-uniform. In addition， the su of the soil after grouting is increased by about 112% and the E50 by about 132%. The cumulative horizontal convergence of the tunnel is reduced by about 24% after grouting measures are adopted. Using the obtained results， the recovery extent of the transverse deformation of a tunnel can be estimated according to the amount of grout， which can provide reference for subsequent design of perturbation grouting schemes to treat the transverse deformation of the soft soil shield tunnels.