Research on diffusion mechanism of power-law grout infiltration grouting in water-rich sand layer under multi-factor coupling

Objective In order to clarify the spherical diffusion law and influencing factors of penetration grouting in water-rich sand layer, the experimental research of penetration grouting was carried out to understand the quantitative influence of different grouting parameters on slurry diffusion. Methods Firstly, the spherical diffusion model test of penetration grouting is carried out, and the macro-diffusion form, micro-filling effect and the changing trend of pore water pressure and earth pressure during grouting are analyzed. Then, based on the spherical diffusion equation of penetration grouting considering multi-effect coupling, the influencing factors of slurry penetration diffusion are qualitatively analyzed, and the error of theoretical prediction of slurry diffusion is quantitatively analyzed. Finally, the significance of water-cement ratio, sand physical parameters and grouting pressure on slurry penetration and diffusion is evaluated by range analysis. Results and Conclusions The results show that the diffusion range of slurry is positively correlated with slurry water-cement ratio and sand porosity, and negatively correlated with sand tortuosity. During the grouting process, the seepage pressure and earth pressure decrease nonlinearly with the increase of the distance from the grouting pipe, while the seepage pressure and earth pressure at the same measuring point increase nonlinearly with the change of time. The time interval of pressure sudden increase is defined. The closer to the grouting pipe, the earlier the region appears and the more significant the pressure change is. The theoretical model considering the time-varying effect, tortuosity effect and uniform infiltration effect of slurry viscosity predicts the slurry diffusion range and the experimental error is -13.26% ~ 11.01%. The significant influence of grouting parameters on the slurry diffusion range is: water-cement ratio, sand porosity, grouting pressure. As the main influencing factor, the water-cement ratio also affects the actual porosity and tortuosity of the sand in the grouting process, which in turn affects the diffusion range of the slurry. The research results can provide some reference for the grouting parameter design of water-rich sand layer in the future.