It is of great importance to study the behavior of loess moisture infiltration based on the loess permeability velocity to prevent geological disasters by loess collapsibility and get effective solutions for the problems of practical engineering. In this study, a custom-made permeation device was used to measure the permeation velocity of collapsible loess before and after water immersion and consolidation. The infiltration characteristics of the undisturbed collapsible loess under different consolidation pressures were discussed, and the influence of the pore characteristics on the permeability velocity was analyzed by the mercury injection test. Meanwhile, the correlations of various types of pores on the permeability velocity were studied by the gray relational entropy method to further reveal the water infiltration mechanism in loess. The results showed that the soil is compressed after consolidation and immersion tests, and the pore volume and pore diameter decreases. However, permeability velocity increases rather than decreases, and the self-weight collapsible state has the most significant permeability velocity. To the collapsible loess, the permeability velocity decreases with the increase of soil pore area. Additionally, small pores show the strongest correlation with permeability velocity. The conclusions of this study have a positive role in guiding foundation treatments and slope stability in collapsible loess areas.

It is practical to carry out sponge cities to manage rain and floods in collapsible loess areas where water resources and water disasters are prominent. The infiltration laws of the partial anti-seepage bioretention in collapsible loess fields are helpful to ensure the effectiveness and safety of sponge city, which were learned from the field test and numerical model. The seepage field and displacement field of loess sites with different collapsibility grades were compared during rainwater infiltration of the bioretention with the numerical model; the suitability and optimization suggestions for foundation treatment of this structure in various sites were proposed. It is found that the infiltration characteristics can be divided into three stages, and the infiltration range of bioretention increases with increasing infiltration time under the same site type, and the higher the collapsibility level of the site is, the more significant the rise in infiltration range. The settlement of adjacent roads in class II and III collapsible fields is far greater than that in class I and is greater than the settlement standard. The facilities’ bottom part foundation can be replaced to ensure the functionality of the facilities and the safety of the surrounding roads in the actual project.