Abstract The buoyancy and long setting time of the mortar used for simultaneous grouting in shield tunnel con? struction lead directly to the problems of a staggered segment, damage and tunnel clearance invasion, which affect the acception and operation of metro tunnels. The mechanism of segment uplift is analyzed, and the concepts of generalized buoyancy and buoyancy density of segment are put forward. The conventional bentonite is replaced by xanthan gum for simultaneous grouting, and this greatly increases the pseudoplasticity of the mortar. Experiment calculations and analysis show that after ten minutes the generalized buoyancy of the mortar with the xanthan gum decreases greatly compared with that of conventional mortar due to its special pseudoplasticity, and the buoyancy is close to zero. Practical application in the Chengdu metro shows that the mortar with xanthan gum effectively fills the gap between the segment and the excavation profile, and the problem of uplift of the shield tunnel can basically be solved.
Abstract：
The buoyancy and long setting time of the mortar used for simultaneous grouting in shield tunnel con? struction lead directly to the problems of a staggered segment, damage and tunnel clearance invasion, which affect the acception and operation of metro tunnels. The mechanism of segment uplift is analyzed, and the concepts of generalized buoyancy and buoyancy density of segment are put forward. The conventional bentonite is replaced by xanthan gum for simultaneous grouting, and this greatly increases the pseudoplasticity of the mortar. Experiment calculations and analysis show that after ten minutes the generalized buoyancy of the mortar with the xanthan gum decreases greatly compared with that of conventional mortar due to its special pseudoplasticity, and the buoyancy is close to zero. Practical application in the Chengdu metro shows that the mortar with xanthan gum effectively fills the gap between the segment and the excavation profile, and the problem of uplift of the shield tunnel can basically be solved.
2017, Vol. 54 