Study on Permeation Grouting Rules for Loess and Method for Predicting Migration Radius

Pressure grouting method can significantly enhance the strength of soil, and is widely used in foundation reinforcement. There already have some theoretical studies on pressure grouting, but the actual diffusion process of grouting can not be reflected exactly. Firstly, this paper conducts a field permeation grouting test on undisturbed loess of late pleistocene of quaternary, and acquires the pressure effected relationships of quantity vs. time. The test reveals that the grout quantity approximately increases linearly with the pressure until a certain grouting time point. The time point increases with grouting pressure and we try to define the pressure effected time point as the effective grouting time. After the effective grouting time, the grouting quantity remains constant due to the approaching of max migration radius and the stopping of grout migration. And then, considering the piston-like displacement effect of grout on porous mediums due to pressure, this study introduced the effective grouting time into the theoretical derivation process based on porous mediums’ fluid percolation pore pressure equation and Darcy’s law. The author combined the initial conditions and boundary conditions of pore pressure with the continuity conditions of permeation velocity, and performed the Boltzmann’s transformation and reduced-order processing to derive the equation for the migration velocity of the grout front and the migration radius of grout. Finally, by substituting the effective grouting time and the effective grouting quantity into the equation, we could obtain the grouting reinforcement radius. The equation can accurately predict the actual grouting reinforcement radius, and the applicability of the equation is verified by verification test.