Investigation into the pregelatinized starch additive alleviated the deterioration in rheological properties of slurries induced by high-temperature environment and seawater intrusion during submarine slurry shield tunneling

Abstract

An eco-friendly and effective slurry additive is needed to prepare an appropriate slurry for submarine slurry shield tunneling to control favorable rheological behavior and infiltration characteristics under high temperature and seawater intrusion. In this study, the corn PGS was selected as an additive to alleviate the deterioration in the physical properties of slurries caused by high temperature and seawater intrusion. The effects of different high-temperature environments and seawater intrusion rates on the deterioration of the slurry rheological properties and the variations in slurry flow patterns after adding different proportions of PGS were investigated via a series of experiments on slurry mixing proportions. In addition, the rheological improvement mechanism of PGS under a high-temperature environment and seawater intrusion was revealed respectively, and the morphology of the seawater slurry with PGS was observed via SEM tests. The results indicated that there is a remarkable rising-temperature thinning characteristics of Na-bentonite slurry when the temperature increases from 25 ℃ (room temperature) to 75 ℃, but the variation in temperature hardly changes the flow pattern of the seawater slurries. Compared to the seawater slurry with CMC, more than 0.2% PGS additive can alleviate the thinning phenomenon of seawater slurry caused by high temperatures rise and improve the viscosity of Na-bentonite slurries under seawater intrusion more effectively, which has superior resistance to high temperatures and seawater intrusion during the seabed slurry shield tunneling. The findings of this study could provide references for the preparation and selection of slurries used in submarine slurry shields in the future.