Abstract: In recent years, the phenomenon of clogging of drainage board and sharp reduction of drainage performance due to clumping of fine soil particles around the drainage board has been found in vacuum pre-pressing projects, which is called “soil column effect”. Currently this phenomenon mostly occurs in soft foundation treatment projects dealing with newly dredged and blow-filled silt, and it is not common to see it in naturally deposited soft soils. Based on the slow consolidation of deep soft soils encountered in a soft foundation treatment project in the Songnen Plain, in this study, a numerical analysis is carried out considering the “soil column effect” and the attenuation coefficient is obtained through the inverse analysis of the permeability coefficient in the soil column area. It is concluded that the “soil column effect” can also occur in naturally deposited soft soils when specific conditions are met, which is due to the influence of comprehensive factors such as the high water content of soft soils, strong mobility, and the unsuitability of the particle size gradation and the aperture of the drainage board.