Experimental Study on Vacuum Grouting in Silty Sand Stratum

Vacuum grouting is a new grouting method to control the groundwater in geotechnical engineering, which is often used in the strata where penetration grouting is difficult to reach an expected slurry diffusion radius, such as sand and silt strata. There are some theoretical studies about the influence of the vacuum field on the law of the slurry diffusion. However, the research on soil properties is rare. In this paper, through a self-designed grouting device, grouting in the silty sand after vacuum field action is studied. The test results indicate that with the increase in vacuum degree, the grouting capacity has an obvious improvement. When the vacuum degree is −15 kPa, the grouting capacity increased by 45.9% compared with the blank control group (0 kPa). Then, through the thermogravimetric analyzer and zeta potential meter the change of bound water and electric double layer in the silty sand after the effect of the vacuum field through a small device is studied. The results show that the effect of the vacuum field could make an influence on free water and loosely bound water, but the change of firmly bound water is unnoticeable. With the change of the vacuum degree, the variation of the water is increased. When the vacuum degree is −15 kPa, compared with the blank control group, the variable weight of free water is 5.79% and loosely bound water is 2.86%. As the bound water has a relationship with the effective void ratio, it can be inferred that the vacuum field may have an effect on the permeability coefficient of silty sand. These conclusions provide a reference for the theoretical study of vacuum grouting.