Abstract: Tests for time-dependent characteristics of cement grout are carried out, which find that cement grout of commonly used water-cement ratio conforms to Bingham fluid. Viscosities of grouts with different water-cement ratios increase greatly as grouting time increasing. According to the experimental results, considering the time-dependent characteristics of viscosity of cement grout, the diffusion law and model of pressure on segments of shield tunnel of backfilled cement grouting are found and derived respectively. A case is given. The results from theoretical calculation show that diffusion radius and pressure on the segments increase with the increase of grouting pressure when grouting time is constant on one hand. After considering viscosity variation of cement grout, diffusion radius and pressure on segment are smaller than the results obtained under fixed viscosity; and as the grouting pressure increases, the disturbance on pressure from viscosity of grout gets more obviously. On the other hand: when grouting pressure is constant, diffusion radius and pressure on the segments increase with the increase of grouting time. However, the values increase rapidly in the beginning and slow down later. The results can provide a guide to selecting appropriate techniques and parameters of cement grouting.

Key words: shield, cement grout, grouting, viscosity, diffusion law, segment pressure