The existence of multiple layers of red paleosol within loess strata presents a unique challenge due to its high hardness, which resists settlement deformation upon exposure to water. This attribute significantly influences the subsidence measurements of the loess strata. Despite this, the current literature lacks reports on the control effect of paleosol on collapsibility, leading to a deficiency in the theoretical basis for scientifically selecting collapsibility in these strata. This paper seeks to bridge this gap by examining the differences in self-weight collapsibility under various conditions, both indoor and outdoor, across different paleosol layers and strata. The analysis is grounded on statistical results derived from immersion tests conducted in the Loess Plateau. Moreover, the research zeroes in on two test sites in Xi’an, conducting extensive immersion tests and considering measurements such as water diffusion, changes in water content, soil pressure, and cumulative collapsibility under different test conditions. The study probes into the influence of paleosol layers on water infiltration and their role in controlling total weight collapse. The final results suggest that the presence of a paleosol layer inhibits collapsibility transfer to the lower layer and restricts water infiltration, thereby reducing total collapsibility. Discrepancies between measured and calculated collapsibility values showed a positive correlation with the number of paleosol layers. This research offers valuable insights into the collapsibility mechanism of paleosol-loess strata.

Physical model experiments are increasingly applied in the study of the water infiltration law in loess with roots. In the past, due to differences in study objects and the limitations of measuring techniques, the infiltration law in loess with roots is rarely evaluated by using appropriate indoor physical model experimental data. In order to investigate the law of water infiltration in loess with roots, we designed a new soil column experimental device that can automatically collect data and images. By comparing the soil column experiment data of loess, we analyzed variables in root contents (the ratio of root mass to dry soil mass) and root types. Roots with diameters of 0–2 mm, 2–5 mm, and 5–10 mm are defined as type I, type II, and type III, respectively. It was found that the water infiltration rate, water-holding capacity, and saturated permeability coefficient increase with the increase in root content. In loess containing different root types, the root types were found to improve the rate of water infiltration, water-holding capacity, and saturated permeability coefficient in the soil. The root types were ranked in descending order in terms of their impact: root type II had the highest improvement, followed by root type III, and then root type I. The phenomenon of circumferential flow existed when water infiltrated loess with roots. Root content and root type would affect the radius of circumferential flow, infiltration path, and cross-section. When calculating the saturated permeability coefficient of loess with roots, ignoring the effect of circumferential flow would lead to a higher result.