Diffusion mechanisms of power-law grouts in water-rich sand layers during permeation grouting

ObjectiveThis study aims to clarify the spherical diffusion patterns of power-law grouts in water-rich sand layers during permeation grouting and their influential factors. To this end, permeation grouting experiments were conducted to gain insights into the quantitative impacts of varying grouting parameters on grout diffusion.MethodsUsing model experiments on spherical diffusion during permeation grouting, this study analyzed the macroscopic diffusion morphologies and microscopic infilling effects of grouts, as well as the trends of permeation and soil pressures during grouting. Then, based on the spherical diffusion equations for permeation grouting that consider multi-effect coupling, this study analyzed the factors influencing the permeation and diffusion of grouts qualitatively and the theoretical prediction errors of grout diffusion quantitatively. Finally, through range analysis, this study assessed the significance of the impacts of the water-to-cement ratio, physical parameters of sandy soils, and grouting pressure on grout permeation and diffusion.Results and ConclusionsThe results indicate that the diffusion range of grouts was positively correlated with the water-to-cement ratio of the grouts and the porosity of sandy soils but negatively correlated with the tortuosity of sandy soil. During grouting, the permeation and soil pressures decreased nonlinearly with an increase in the distance from the grouting pipe. Nevertheless, the permeation and soil pressures at the same measurement point increased nonlinearly over time. The time interval of sudden pressure increase was defined. A closer distance from the grouting pipe corresponded to an earlier sudden pressure increase and more significant pressure changes. The theoretical model that considered the multiple effects of grouts, including the time-varying effect of viscosity, tortuosity effect, and uniform infiltration effect, yielded prediction errors of grout diffusion ranges varying from −13.26% to 11.01% compared to the experimental results. The significance of the impacts of grouting parameters on the grout diffusion range decreased in the order of the water-to-cement ratio, sandy soil porosity, and grouting pressure. As a dominant influential factor, the water-to-cement ratio affected the grout diffusion range during grouting by influencing the actual porosity and tortuosity of the sandy soils. The results of this study can serve as a reference for the design of grouting parameters for water-rich sand layers.