In the loess tableland, gully slope instability induces severe soil erosion and land degradation, yet the synergistic effects of dominant vegetation under varying restoration modes combined with dynamic rainfall regimes and topographic variations on gully slope stabilization mechanisms remain inadequately quantified. Therefore, the dominant vegetation species under natural (NR) and artificial restoration (AR) was chosen as the object. Through field sampling, root-soil complex mechanical experiments, and numerical simulations, the protection effect of dominant vegetation under different restoration modes combination with rainfall and topographic variations was investigated. The result revealed significant differences in basic soil physical properties, root morphological characteristics, root and root-soil complex mechanical properties among five dominant vegetated plots under the different restoration modes (P < 0.05). The soil properties in the Scop plot under AR were slightly better than those in the other plots. The roots in the Spp plot developed better under NR. The shear strength of Lespedeza bicolor Turcz. was the highest under NR. The tensile strength of Digitaria sanguinalis (L.) Scop. was greatest under AR. The tensile force and tensile strength of single roots exhibited a significant positive linear correlation and a significant negative exponential correlation, with root diameter, respectively (P < 0.01). For the unstable gully slopes (F-s < 1.0), maximum displacement occurred at the slope foot, where tensile shear failure dominated, while the interior experienced compressive yielding. The grey relational analysis identified rainfall intensity as the primary destabilizing factor, followed by dominant vegetation species, slope height, and slope gradient. Notably, when rainfall intensity reaches or exceeds 0.06 m/h, or when slope height exceeds 20 m combined with long-duration rainfall, the regulatory impacts of dominant vegetation under different restoration modes on the gully slope stability are substantially diminished and become negligible. This study provides a theoretical basis for gully slope protection and ecological environmental construction in loess tableland.

Flow instability impacts negatively on hydraulic structures. Changes in water pressure or the periodic impact of water flows cause structural damage to channels. The rapid increase in water depth leads to overflows or sprays, which erode soil adjacent to channels. In this study, flow instability was examined through the basis of theories and experiments. The theoretical discriminants for flow instability were inferred by Vedernikov number and the effect of slopes on the Froude number was considered. A rectangular cross- channel was selected for the experiments. The experimental results were compared with theories, it was shown that when the flow conditions were on the margin of instability, the discriminant established by this study is able to accurately determine the occurrence of instability. Through this new discriminant, the discrepancy which appears in traditional method can be avoided. The presented results are ideal for channel design and offer new approaches for flow instability prevention.

This study evaluates dykes stability of bauxite residue storage facility using limit equilibrium (LEM) and finite element methods (FEM), considering diverse construction phases. In LEM, steady state seepage is simulated using piezometric line while factor of safety (FOS) is determined by Morgenstern-Price method using SLOPE/W. In FEM, actual loading rates and time dependent seepage is modelled by coupled stress-pore water pressure analysis in SIGMA/W and dyke stability is assessed by stress analysis in SLOPE/W, referencing SIGMA/W analysis as a baseline model. Both the analysis incorporated suction and volumetric water content functions to determine FOS. FEM predicted pore pressures are validated against in-situ piezometer data. The results highlight that coupled hydro-mechanical analysis offers accurate stability assessment by integrating stress-strain behaviour, pore pressure changes, seepage paths, and dyke displacements with time. It is found that inclusion of unsaturated parameters in Mohr-Coulomb model improved the reliability in FOS predictions.

Calcareous sands provide the foundational support for various marine infrastructures. In the harsh marine environment, earthquake or wave loads apply multidirectional cyclic shear stresses to the foundation soil. To explore the undrained multidirectional cyclic response of sand, a series of simple shear tests were performed on reconstituted sand specimens considering the effect of phase difference (theta). By comparing the results with those of siliceous sand under similar conditions, the behavior of calcareous sand under multidirectional cyclic loading became clear. The results demonstrated that calcareous sand shows a lower degree of cyclic instability compared to siliceous sand, corresponding to the weaker strain-softening observed in calcareous sand during monotonic shear tests. The trend in normalized pore water pressure evolution in siliceous sand exceeds that in calcareous sand. Furthermore, under multidirectional cyclic shear conditions, the liquefaction resistance decreases by 30 % in extreme cases, irrespective of sand type. The liquefaction resistance of calcareous sand surpasses that of siliceous sand. However, as the cyclic stress ratio decreases, the reverse trend is observed, regardless of the impact of theta. Subsequently, the possible causes of the above experimental phenomena are explored from the perspectives of shear modulus and energy dissipation.

In the dynamic response analysis of slopes, the displacement of sliding surfaces is an important indicator for assessing stability. However, due to the uniform dynamic parameters of the Newmark slide block method, it is difficult to accurately analyze the displacements of large-scale slopes. To address this issue, the spatial distribution characteristics of dynamic parameters need to be considered to accurately analyze the stability of slopes. Under the combined action of rainfall and reservoir water level change, the Shiliushubao old landslide in the Three Gorges Reservoir area remains stable. To investigate the seismic stability of slopes, simulated seismic waves were employed. Firstly, the dynamic triaxial test, designed with cyclic loading, was employed to investigate the variation rules of the dynamic parameters of slope soil, and to establish a functional relationship. Then, the stochastic seismic motion model was used to generate artificially seismic waves in the Three Gorges Reservoir Area. Finally, to assess the stability of the old landslide, finite element software, GeoStudio 2018 was used to obtain the spatial distribution characteristics of the dynamic parameters and to calculate the permanent displacements of the reservoir bank slope by inputting random ground motion loads and dynamic characteristic functions. It is demonstrated that under the most unfavorable working conditions of heavy rainfall and the earthquake in the specific region, the permanent displacement of the Shiliushubao old landslide will be less than the critical permanent displacement, the old landslide is not to experience instability again.

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.

Antislide piles are currently applied widely in slope reinforcement engineering, but investigation of the stability of slopes stabilized with this measure under the action of mainshock-aftershock (Ms-As) sequences is very limited. In this study, the probability density evolution method (PDEM) and the Newmark method is adopted to evaluate the reliability of slope reinforced by antislide piles subjected to Ms-As sequences considering the spatial variability of material parameters. Firstly, stochastic Ms-As sequences are generated by combining a physical function model, the Copula function, and the narrowband harmonic group superposition method. In addition, the spectral representation method is taken to generate the random field and the parameters are assigned to the numerical model. Then, the Newmark method is applied to batch-calculate the permanent displacement (Disp) of the slope caused by the Ms-As sequences. The effects of pile position, pile length, and coefficient of variation of cohesion and friction angle (COVC and COVF) on the average value of Disp are discussed. Finally, based on the PDEM, the seismic reliability of the slope strengthened by antislide piles subjected to the Ms-As sequences are obtained. The research results indicate that with the COV increases, the average value of Disp of the slope shows a gradual tendency to increase, and the average value is more sensitive to COVC. Compared with the unreinforced slope, the Disp of the slope strengthened by antislide piles is reduced. The cumulative damage caused by the aftershock and the risk of failure can be significantly reduced by setting a reasonable antislide pile.

The present work introduces an analytical framework based on the limit-equilibrium method for the determination of the local factor of safety (FS) and global factor of safety (FSG), and local displacements along the critical slip surface using the Morgenstern-Price (MP) method of slices. This proposed work computes displacements along the critical slip surface in addition to a single FSG. The unsaturated shear strength models, in conjunction with the soil-water characteristic curve (SWCC), are considered. The MP-based equilibrium equations to determine FSG are utilized as an objective function in the metaheuristic search algorithm of particle swarm optimization to determine the critical center, critical radius, and minimum FSG for unsaturated finite slopes. It is recommended to use a particle size of 75 and conduct 50 iterations for optimal results. The effects of SWCC fitting parameters on the critical slip surface, FSG, point FS, and point displacements are also investigated. Two distinct benchmark slope scenarios with and without negative pore water considerations are utilized in the current study. This approach enables a detailed investigation into the influence of various unsaturated soil parameters, such as af (related to the air-entry value), nf (related to the slope of the SWCC), and mf (related to the residual water content), as well as constitutive model parameters including the linear shear modulus (G) and the fitting parameter (rho). The maximum displacement occurs at the slope's top crest. Under benchmark conditions, the first scenario shows a reduction in point displacement by 3.30%, 1.98%, and 10.23% for SWCC-1, SWCC-2, and SWCC-3, respectively. However, in the second scenario with SWCC-3, the critical slip surface's position changes, affecting local displacements. This results in an increase of 32.72% (i.e., from 21.45 to 28.47 mm) in point displacement at the top when comparing SWCC-3 with no SWCC consideration. The current study advocates that the effect of fitting parameters of the SWCC should be used to better understand the local FS and displacement, because the critical slip surface is contingent on the values of the SWCC. Ignoring SWCC parameters can lead to an underestimation of slope displacement, because they significantly influence the critical slip surface position and displacement magnitude. Their inclusion is essential for accurately assessing slope stability and preventing errors in displacement prediction.

Fibre reinforcement technology has been widely adopted in soil improvement due to its cost-effectiveness, simplicity, and environmental benefits. In many fibre reinforcement projects, the soil is often in an unsaturated state. However, the numerical simulation mechanisms of fibre-reinforced unsaturated soils remain poorly understood. In this study, a Vangenuchten (VG) model considering fibre incorporating fibres was proposed based on the original VG model. This model considering fibre accurately describes the soil water characteristic curve (SWCC) of fibre-reinforced sand (FRS), as verified by water-holding characteristics tests. Then, unsaturated triaxial tests confirmed the applicability of an unsaturated soil elastoplastic constitutive model and a fully coupled soil-water-air finite element-finite difference (FE-FD) method for simulating the mechanical behaviour of unsaturated FRS. Finally, using the SWCC parameters derived from the VG model considering fibres and mechanical parameters from saturated triaxial tests, slope models were established to analyse the stability of both unreinforced and fibre-reinforced slopes. The results show that the interweaving action of fibres within the soil enhances its strength, reduce permeability, and decreases both saturation and pore water pressure, ultimately increasing slope stability. This study provides valuable insights into the SWCC characteristics and the numerical calculation of FRS under unsaturated conditions.

Soil-rock mixtures (S-RM) are prevalent in both nature and practice, and stability of S-RM slopes is one of the focuses for engineers. In addition to soil strength, seepage erosion is one of the main factors affecting the stability of S-RM slopes. As water infiltration complicates the multi-field coupling effects and micro-scale mechanical behaviors of S-RM, it is essential to investigate seepage-induced S-RM landslides from both macro and micro perspectives. This study proposed a CFD-DEM fluid-solid coupling method, and the method was validated with Darcy experiments and lab slope stability experiments. The method was then applied to analyze seepage-induced slope instability, focusing on the impact of rock content and rock shape. The results indicate that slope failure under seepage showed the same characteristics as debris flow, with instability features such as sliding surfaces, damage range, and particle motions varying according to rock content and shape. As rock content increased, the accumulation of slope transitions through three distinct modes. Slope was prone to failure along the soil-rock interface, and low rock content further impaired the stability. The slope deformation was primarily driven by changes in particles contact. Once slope instability occurred, the system tended to adjust particle contacts to achieve new state of equilibrium.