Grouting Pressure Distribution Model for the Simultaneous Grouting of Shield Tunneling While Considering the Diffusion of Slurry

Abstract

According to the field test of urban subway tunnels, the internal force of the lining segment of the shield tunnel during the synchronous grouting stage is 1–1.5 times that in the steady stage. To study the distribution model of grouting pressure on the lining segment produced by synchronous grouting, we investigated Bingham fluid and a synchronous grouting slurry while they penetrate excavation soil and fill shield tail interspace. Then, we deduced the calculation formula for diffusion radius, the amount of grout during grouting behind a segment, the radial displacement of excavation caverns caused by the squeezing effect of penetration pressure, and the effective stress of soil in the diffusion zone. The amount of grout that can fill a shield tail interspace during synchronous grouting was identified. Considering the time-varying of slurry viscosity, the limit equilibrium equation and the fluid mechanics method were used for the deduction of the distribution model of grouting pressure on a lining segment produced by synchronous grouting. The calculated results indicated that the diffusion radius and the amount of grout that can fill a shield tail interspace increase as the grouting pressure increases and that grouting slurry diffusion reduces the grouting pressure on a lining segment. The actual measured grouting pressure value is consistent with the theoretical calculation results in this paper by combining the engineering example of the Changsha Metro Line 4. The theory proposed by this paper provides a theoretical basis for fine analysis of the distribution of grouting pressure during shield tunneling construction.