We conducted a one-dimensional vertical infiltration test on a loess soil column considering the effects of vibration to examine how combinations of vibration frequency and amplitude affect the temporal variation of volumetric water content and the evolution of the wetting front. Scanning electron microscopy (SEM) and mercury intrusion porosimetry (MIP) tests were used to reveal microscopic evolution. Using the experimental data

we determine the unsaturated permeability coefficient of loess with three methods—the VG-M model

the wetting-front advancement method

and the instantaneous-profile method—and perform a comparative analysis. The results indicate that vibration accelerates the water infiltration rate. Under vibration

the depth of the wetting front increases with higher vibration frequencies

and the time required to transition from unsaturated to stable infiltration decreases as the vibration frequency increases. All three methods effectively capture the enhancement of the permeability coefficient due to vibration. The results from the instantaneous profile method and the VG-M model are relatively close

while the unsaturated permeability coefficient calculated using the wetting front advancement method is slightly lower. In the initial stage of the loess soil column’s microstructure evolution

medium pores dominate the soil's internal structure. During the intermediate stage

under the coupled effects of vibration and seepage

the proportion of large pores increases

forming seepage channels. In the later stage

the soil’s microstructure stabilizes

with a significant reduction in large pores and an increase in small and micro pores.