Fluctuations in reservoir water levels have a significant impact on the seepage and slope stability of earth dams. The varying rate of the water level and soil–water characteristic curve (SWCC) hysteresis are the main factors affecting the seepage and the stability of dam slopes; however, they are not adequately considered in engineering practices. In this study, the SEEP/W module and the SLOPE/W module of Geo-studio were employed to analyze the seepage features and the stability of downstream slopes, taking into account the water level fluctuation rate and the SWCC hysteresis. The results reveal that the pore water pressure of the representative point forms a hysteresis loop when the water level fluctuates, which becomes smaller as the water level variation rate increases. Within the loop, the pore water pressure with a rising water level is greater than the value when the water level is dropping, and the desorption SWCC derives greater pore water pressures than the adsorption SWCC. Similarly, the safety factor (Fs) curves under the condition of water level fluctuations also form a hysteresis loop, which becomes smaller as the variation rate of the water level increases. When the water level fluctuation rate increases to 4 m/d, the two curves are tangent, meaning that the Fs with a rising water level is always greater than the value when the water level is dropping. The desorption SWCC derives a lower Fs value than the adsorption SWCC as the water level draws up, but this initiates no evident difference in the Fs value when the water level draws down. These findings can be used to inform the design and operation of earth dams under fluctuating water levels.

The rheological behavior of clay in a water–salt environment determines the long-term deformation and structural stability of building materials and geotechnical engineering. In this study, the effects of salinity on the rheological behavior and microstructure stability of the clay mineral illite were investigated through steady-state and dynamic rheological tests. The results reveal that specimens with different salinities exhibit shear thinning behavior during the steady-state rheological test. When the shear rate is higher than 0.5 s⁻¹, the flow curves are described well by the Herschel–Bulkley model. As the salinity increases from 0 to 1.8 mol/L, the yield stress varies from 1500 to 3500 Pa. With the increase in salinity, the consistency factor of the specimens increases, while the flow coefficient decreases. Under dynamic loading, high-salinity specimens exhibit higher modulus and yield stresses, thereby enhancing the stability of the microstructure. The viscoelastic–plastic constitutive model under dynamic loading has been established, which can effectively describe and calculate the long-term deformation of clay minerals. These research results provide reference and guidance for understanding the rheological behavior of clay.

In the construction of permeable roads in collapsible loess regions, a critical technical conflict exists between the water permeability requirement of road surfaces for sponge city development and the collapsibility of loess. Traditional pavement treatments impair permeability or trigger loads worsening loess collapse. Low-density, permeable and high-bearing lightweight soil suits pedestrian and non-motor roads. Based on the mechanism of loess collapsibility, this study proposes a novel foundation treatment approach: lightweight soil replacement is adopted to reduce self-weight stress and overburden pressure, thereby mitigating the collapsibility of subgrades for pedestrian and non-motor vehicle roads. The effectiveness of this treatment method is validated via multi-stratum centrifugal model tests. The research indicates that the regional correction coefficient β₀ value obtained from the field immersion test was 1.56, whereas the corresponding β₀ value obtained from the multi-stratum centrifugal model test was 1.78, with a discrepancy of 0.22 between the two values. It is verified that the multi-stratigraphic centrifugal model test method can be used to obtain consistent results with the field immersion test, while possessing the distinct advantages of low cost and short test duration. Following 1.5 m of soil replacement, the site collapse value under overburden pressure was calculated to decrease by 22.73% based on laboratory tests, whereas the collapse value under overburden pressure measured by the centrifugal model test was reduced by 23.04%. These results demonstrate that lightweight soil replacement method can effectively reduce the site collapsibility. Field immersion test and the multi-stratigraphic centrifugal model test were conducted on self-weight collapsible loess in the Weicheng District of Xianyang City. The regional correction coefficient β₀ was determined, ranging from 1.56 to 1.78. This empirically derived range is more representative of the site conditions in the northern loess tableland of Xianyang than the value of 0.90 specified in the current standard for loess engineering in the Guanzhong region. Therefore, it provides a technically justified basis for selecting β₀ in high-grade loess plains across Guanzhong region in Shaanxi Province, China.