Experimental study and engineering application of slurry permeability mechanism of slurry shield in circular-gravel stratum

Abstract

The key to maintain the stability of the excavation face of slurry shield in the construction of high-permeability circular-gravel stratum is the film-forming quality of slurry. Taking the use of slurry shield in the construction of Nanning Metro in circular-gravel stratum as a case, and with the help of self-designed slurry permeation device, this paper carries out the permeation film-forming experiments of different ratios of slurry in circular-gravel stratum to study the effects of slurry specific gravity, viscosity, and grouting pressure on amount of infiltrated water, film-forming time, and slurry film shape and carries out a verification at the construction site. The conclusions are as follows: slurry specific gravity increases linearly with the content of clay, and the viscosity increases linearly with the content of CMC. The higher the slurry specific gravity is, the better the film quality is. The higher the slurry viscosity is, the earlier the slurry film is formed and the smaller the amount of water infiltrated from slurry is. The effect of slurry specific gravity on the amount of infiltrated water is greater than that of viscosity. The field verification results show that when the slurry density is 1.07 g/cm3, the slurry film has been basically formed, and when the mud density is 1.15 g/cm3, the slurry film has been formed completely. When the slurry viscosity increases from 24 to 33 s, the liquid level of the air cushion chamber and the number of air compressors change slightly. When the water loss of the slurry is 14 s, the slurry level of the sedimentation tank changes slightly, and slurry loss is effectively controlled; when the viscosity of the slurry increases and cause water loss to reaches 12 s, the viscosity of the slurry achieves the optimal effect. This study can provide reference for studies of similar projects in the future.