Mesh-free methods, such as the Smooth Particle Hydrodynamics (SPH) method, have recently been successfully developed to model the entire wetting-induced slope collapse process, such as rainfall-induced landslides, from the onset to complete failure. However, the latest SPH developments still lack an advanced unsaturated constitutive model capable of capturing complex soil behaviour responses to wetting. This limitation reduces their ability to provide detailed insights into the failure processes and to correctly capture the complex behaviours of unsaturated soils. This paper addresses this research gap by incorporating an advanced unsaturated constitutive model for clay and sand (CASM-X) into a recently proposed fully coupled seepage flow-deformation SPH framework to simulate a field-scale wetting-induced slope collapse test. The CASM-X model is based on the unified critical state constitutive model for clay and sand (CASM) and incorporates a void-dependent water retention curve and a modified suction-dependent compression index law, enabling the accurate prediction various unsaturated soil behaviours. The integration of the proposed CASM-X model in the fully coupled flow deformation SPH framework enables the successful prediction of a field-scale wetting-induced slope collapse test, providing insights into slope failure mechanisms from initiation to post-failure responses.

In view of the pollution of unpaved road dust in the current mines, this study demonstrated the excellent dust suppression performance of the dust suppressant by testing the dynamic viscosity, penetration depth and mechanical properties of the dust suppressant, and apply molecular dynamics simulations to reveal the interactions between substances. The results showed that the maximum dust suppression rate was 97.75 % with a dust suppressant formulation of 0.1 wt% SPI + 0.03 wt% Paas + NaOH. The addition of NaOH disrupts the hydrogen bonds between SPI molecules, which allows the SPN to better penetrate the soil particles and form effective bonding networks. The SPI molecules rapidly absorb onto the surface of soil particles through electrostatic interactions and hydrogen bonds. The crosslinking between SPI molecules connects multiple soil particles, forming larger agglomerates. The polar side chain groups in the SPN interact with soil particles through dipole-dipole interactions, further stabilizing the agglomerates and resulting in an enhanced dust suppression effect. Soil samples treated with SPN exhibited higher compressive strength values. This is primarily attributed to the stable network structure formed by the SPN dust suppressant within the soil. Additionally, the SPI molecules and sodium polyacrylate (Paas) molecules in SPN contain multiple active groups, which interact under the influence of NaOH, restricting the rotation and movement of molecular chains. From a microscopic perspective, the SPN dust suppressant further strengthens the interactions between soil particles through mechanisms such as liquid bridge forces, which contribute to the superior dust suppression effect at the macroscopic level.

To study the degree of strength parameter deterioration (DSPD) of Lushi swelling rock in the high slope area under wetting-drying cycles, 114 samples are remodeled. Wetting-drying cycle and triaxial tests are conducted to comprehensively analyze the influence of dry density, wetting-drying cycle path, and number of wetting-drying cycles on the strength deterioration characteristics of Lushi swelling rock. Using the fitting analysis and function superposition methods, the DSPD model of Lushi swelling rock under wetting-drying cycles is established, which considers the previous four influencing factors. The influence of the DSPD of Lushi swelling rock on the stability of high slopes under rainfall seepage and circulation conditions is studied. Lushi swelling rock exhibits significant strength deterioration characteristics under wetting-drying cycles. The overall DSPD for cohesion is higher than that of the internal friction angle. Under rainstorm conditions, strength deterioration leads to a shallower depth of the critical slip surface of the slope and a smaller safety factor. After eight rounds of rainfall seepage and circulation, the safety factor gradually decreases by approximately 14%-28%. This study provides and verifies the DSPD model of Lushi swelling rock under wetting-drying cycles, and the results could provide a basis for disaster prediction and the optimization design of swelling rock slopes.

Granite residual soils (GRS) are often encountered in geotechnical projects in the Guangdong-Hong Kong-Macao Greater Bay Area (briefly written as the Greater Bay Area, or abbreviated as GBA). The rea experiences frequent rainfall, leading to wetting-drying cycles that progressively diminish the shear strength of GRS. This weakening effect is not only significant but also accumulates, exhibiting a direct positive correlation with the number of cycles. Current studies on the soil strength attenuation due to wetting-drying cycles are typically limited to no more than 10 cycles, which is rather insufficient to uncover the long-term water-weakening behaviors and their accumulative impacts on GRS. To address this gap, typical GRS samples were first taken from the GBA and then prepared by making them go through a certain number of wetting-drying cycles (maximum of up to 100). Next, a total of 552 small- and large-scale direct shear tests were conducted to investigate the mechanisms of water-weakening effects on soil internal friction angle, cohesion, and shear strength. The degree of saturation and number of cycles were also examined to see their effects on the cumulation of water weakening. Based on results from the small-scale direct shear tests, a model was developed for assessing the weakening impact of water on soil strength. The accuracy of the model prediction was statistically evaluated. Last, the effectiveness and efficiency of the proposed model were demonstrated by validating against the results from the large-scale direct shear tests.

Extreme rainfall causes the collapse of rammed earth city walls. Understanding the depth of rainwater infiltration and the distribution of internal moisture content is crucial for analyzing the impact of rainfall on the safety and stability of these walls. This study focuses on the rammed earth city wall at the Mall site in Zhengzhou. Based on Richards' equation, the water motion equation of rammed earth wall is deduced and established. The change of moisture content of rammed earth wall and the development of wetting front under rainfall condition are studied. The stability of the rammed earth city wall under rainfall infiltration is analyzed by finite element methods. The results show that the water motion equation can effectively describe the moisture distribution inside the rammed earth city wall during rainfall. As the rainfall continues, the wetting front deepens, and the depth of the saturated zone increases. Just below the wetting front, the moisture content decreases rapidly and eventually returns to its initial value. the water motion equation provides a theoretical basis for analyzing water-related damage in rammed earth walls. Factors such as the initial soil moisture content, rainfall duration, and rainfall intensity significantly influence the distribution of the wetting front and moisture content. The saturation of the upper soil layers reduces the shear strength of the shallow soil, leading to a decrease in the safety factor, which can result in shallow landslides and collapse of the rammed earth wall. The research results can provide theoretical support for the analysis of water infiltration law of rammed earth city walls under rainfall conditions, and provide reference for revealing the instability mechanism of rammed earth city walls induced by rainfall. (c) 2025 Elsevier Masson SAS. All rights are reserved, including those for text and data mining, AI training, and similar technologies.

Modifying lateritic soils, which are widely distributed in humid and rainy regions around the world, for embankment construction is a practical necessity for highway and railway projects. These embankments are susceptible to infiltration of rainfall, wetting and vibration from earthquakes and traffic. Further study is required to investigate the dynamic response characteristics of these embankments under combined action of wetting and vibration. Two scaled-down physical models of embankments were built: one with unmodified lateritic soils, which are typical soils with high liquid limit in central-southern China, and the other with lateritic soils modified with lime at a content of 8%. A self-designed model test system was used to conduct model tests of both embankments under combined action of wetting and vibration. White noise excitation was employed to quantitatively compare the two types of embankments in terms of variations of dynamic properties, such as natural frequency and damping ratio, with wetting degrees. Three types of seismic waves-Chi_Chi, NCALIF and SFERN-were used to quantitatively compare the two types of embankments in terms of variations of dynamic response parameters, including PGA amplification effect, pore water pressure and earth pressure, with wetting degrees and acceleration amplitudes. The test results reveal significant differences in dynamic properties and responses of the two types of embankments. Compared to the unmodified embankment, the damping ratio and PGA amplification factor of the modified embankment are reduced by up to 53.5% and 37.5%, respectively, resulting in an effective mitigation of the combined action of wetting and vibration. Test values of natural frequency, damping ratio, PGA amplification factor, dynamic pore water pressure and dynamic earth pressure of both types of embankments are presented. The research findings provide a theoretical basis for highway and railway construction and for revision of technical specifications in regions with widespread lateritic soils.

Improper anti-drainage treatment of weakly expansive soil subgrades can lead to significant post-construction deformation and uneven settlement, which severely affect the operational safety and service life of engineering projects. To comprehensively analyze the evolution of soil volume and strength under different hydraulic coupling paths during wetting-drying (W-D) cycles, a loaded W-D cycle testing device was developed. Soil volume was measured during the W-D cycles, and the shear strength and soil-water characteristic curves were analyzed after different cycles. The results indicate that during the W-D cycles, changes in soil volume and strength exhibited distinct stages with similar evolution characteristics. Under the investigated loading conditions, the soil demonstrated significant collapsibility during the wetting process, which gradually diminished as the number of cycles increased. Eventually, the W-D cycles caused the soil to reach an equilibrium state, where its swelling and shrinkage behavior became nearly elastic. At equilibrium state, there is a corresponding void ratio for any moisture content, which is the elastic void ratio (e0el). The e0el is irrespective of the number of cycles and initial dry density. Conversely, higher load and larger amplitude in W-D cycles tend to decrease the e0el. Furthermore, by correlating the unsaturated soil matric suction, secant modulus, and stress path, the volume evolution mechanism of the soil was analyzed based on the soil effective stress theory and pore evolution. The results of this study can serve as a crucial reference point for revealing the deformation mechanism of weakly expansive soil subgrades and selecting appropriate road settlement control methods.

The application of novel materials that enhance soil engineering properties while maintaining vegetation growth represents an innovative strategy for ecological protection engineering of expansive soil slopes. Laboratory tests, including wetting and drying cycle tests, direct shear tests, unconfined swelling ratio tests, and vegetation growth tests, were conducted to analyze the effects of xanthan gum on both engineering and vegetation-related properties of expansive soil. The feasibility of xanthan gum for soil improvement was systematically evaluated. The interaction mechanism between xanthan gum and expansive soil was elucidated through scanning electron microscopy (SEM) and X-ray diffraction (XRD) analyses. Results demonstrated that xanthan gum effectively inhibited crack development and strength loss. With increasing xanthan gum content, the crack area ratio decreased logarithmically by up to 58.62%, while cohesion increased by 82.96%. The unconfined swelling ratio exhibited a linear reduction, with a maximum decrease of 43.58%. Notably, xanthan gum accelerated seed germination rate but did not significantly affect long-term vegetation growth. Mechanistically, xanthan gum improved soil properties via two pathways: (1) forming bridging structures between soil particles to enhance cohesion and tensile strength; (2) filling soil voids and generating a polymer film to inhibit water-clay mineral interactions, thereby reducing hydration membrane thickness. These findings offer both theoretical insights and practical guidelines for applying xanthan gum in ecological protection engineering of expansive soil slopes.

Slope deformation due to drying-wetting cycles is a great concern in both the risk warning of slopes and the design of various slope structures on the slope. A new full-process slope deformation analysis method was derived based on slice methods, with innovations in terms of the constitutive equation, displacement compatibility equation, and stress equilibrium equation. A constitutive model of the soil was proposed with defined parameters, and it was reported to perform well in the prediction of the deformation increment and strength reduction due to drying-wetting cycles. The potential slip surface was shown to be a key component of characterizing the full-process deformation of a slope and to exhibit the displacement compatibility trend in which the relative horizontal displacement along the potential slip surface was equal at various locations. A slope deformation analysis algorithm was derived to analyze the shear deformation characteristics of potential slip surfaces and the volumetric deformation characteristics of sliding bodies subjected to drying-wetting cycles. The proposed method was validated by comparing the predicted slope deformation characteristics with centrifuge model test and field observation results under drying-wetting cycles. The method was confirmed to predict the full-process deformation of soil slopes during drying-wetting cycles, including the small deformation stage, prefailure stage, failure process and postfailure stage.

Slip zone soil, a crucial factor in landslide stability, is essential for understanding the initiation mechanisms and stability assessment of reservoir bank landslides. This study investigates the strength characteristics of slop zone soil under drying-wetting (D-W) cycles to inform research on reservoir bank landslides. As an illustration of this phenomenon, the Shilongmen landslide in the Three Gorges Reservoir serves as a case study. Taking into account the impact of both D-W cycles and the overlying load on the soil. the strength characteristics of the slip zone soil are investigated. Experimental results show that slip zone soil exhibits strain softening during D-W cycles, becoming more pronounced with more cycles. D-W cycles cause deterioration in shear strength and cohesion of slip zone soil, especially in the first four cycles, while the internal friction angle remains largely unchanged. The compaction effect of the overlying load mitigates the deterioration caused by D-W cycles. The findings reveal the weakening pattern of mechanical strength in slip zone soil under combined effects of overlying load and D-W cycles, offering valuable insights for studying mechanical properties of slip zone soil in reservoir bank landslides.