Half spherical Surface Diffusion Model of Shield Tunnel Back filled Grouts

Abstract:

On the assumption that the back filled grouts should be viscosity degeneration fluids, and the grouts diffuse with half spherical surface, the grouts diffusion area and the pressure to shield tunnel segments were derived with Darcy’s law. As a result, the formula to calculate the radius and the pressure were acquired. The diffusion radius and the pressures to shield tunnel segments with different grouting pressures, grouting time, grouts initial viscosities, and soil permeability coefficients were compared between the grouts viscosity degeneration condition being taken into consideration or not. The diffusion model of grouts pressure is also acquired. The result shows that the grouts viscosity degeneration has a significant influence on the diffusion radius and the pressure to shield tunnel segments on the condition of high grouting pressure, long grouting time, and big soil permeability coefficient. The grouting effect can be improved by adjusting grouting pressure, grouting time and grouts properties.

Key words:shield tunnel; back filled grouting; viscosity degeneration; half spherical surface diffusion