Deep filtration effect widely exists and plays an important role in the process of permeation grouting in porous media. Based on the mass conservation equation

linear filtration law and seepage continuity equation as well as Darcy law

a theoretical model is developed for three-dimensional slurry frontal surface. The migration of the slurry frontal surface migration and the variation of the permeability coefficient of the deposition layer are examined based on in-situ grouting test; the measured values are compared with the theoretical ones. It is shown that the permeability coefficient varies as the frontal surface migration. At the constant grouting pressure

the deep filtration effect is more significant

and the slurry diffusion distance is shorter when the water-cement ratio is smaller. At the same diffusion distance

the permeability coefficient of the deposit layer above grouting point source is larger than that below the grouting point source

due to the influence of gravity effect. The grouting diffusion distance and the permeability coefficient of the deposit layer at a specified point are positively correlated with the water cement ratio. The above result has practical bearing

in which it can help construction designs.