This study investigated the hydraulic and mechanical behaviors of unsaturated coarse-grained railway embankment fill materials (CREFMs) using a novel unsaturated large-scale triaxial apparatus equipped with the axis translation technique (ATT). Comprehensive soil-water retention and constant-suction triaxial compression tests were conducted to evaluate the effects of initial void ratio, matric suction, and confining pressure on the properties of CREFMs. Key findings reveal a primary suction range of 0-100 kPa characterized by hysteresis, which intensifies with decreasing density. Notably, the air entry value and residual suction are influenced by void ratio, with higher void ratios leading to decreased air entry values and residual suctions, underscoring the critical role of void ratio in hydraulic behavior. Additionally, the critical state line (CSL) in the bi-logarithmic space of void ratio and mean effective stress shifts towards higher void ratios with increasing matric suction, significantly affecting dilatancy and critical states. Furthermore, the study demonstrated that the mobilized friction angle and modulus properties depend on confining pressure and matric suction. A novel modified dilatancy equation was proposed, which enhances the predictability of CREFMs' responses under variable loading, particularly at high stress ratios defined by the deviatoric stress over the mean effective stress. This research advances the understanding of CREFMs' performance, especially under fluctuating environmental conditions that alter suction levels. (c) 2025 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).

Slope failure, as a natural disaster, can cause extensive human suffering and financial losses worldwide. This paper introduces a new soil moisture extended cohesive damage element (SMECDE) method to predict railway slope failure under heavy rainfall. A correlation between rainfall intensity and soil moisture content is first established to create an equivalence between the two. Considering slope failure mechanisms dominated by the loss of soil or the cohesion of slope materials due to heavy rainfall infiltration, the soil moisture decohesion model (SMDM) is developed using previous experimental data to express how soil cohesion varies with different soil moistures and depths. The SMDM is incorporated into the extended cohesive damage element (ECDE) method to fundamentally study slope failure mechanisms under varying soil moisture levels and depths. The proposed SMECDE approach is used to predict the failure propagation of a selected railway embankment slope at the critical soil moisture or rainfall intensity. This SMECDE failure prediction is validated using relevant data from previous fieldwork and meteorological reports on the critical rainfall intensity at the site. Additionally, the corresponding slope damage scale prediction is validated with a large plastic deformation analysis using the commercial FEM package ABAQUS.

In this study, the anisotropic nature of the medium is used to simulate the stratigraphic conditions. Taking the embankment of a high-speed railway as the object of study, the wave function expansion method is used to obtain the level solution for inverse plane shear wave scattering of the anisotropic half-space medium-waisted ladder form of the embankment. Then, by changing the anisotropy parameter of the soil medium, the effects of different incidence angles, dimensionless frequencies, embankment slopes, and anisotropic parameters on the isosceles trapezoidal form of the embankment structure are investigated. The results show that the anisotropy of the medium not only has a significant effect on the surface displacement of the embankment site but also makes other parameters more sensitive to the site effect, as manifested by the larger amplitude of the surface displacement caused by the incident wave along a certain angle at a certain dimensionless frequency compared to that of the isotropic medium. The embankment structure plays an important role in vibration damping and isolation during the propagation of vibration waves in the horizontal direction, and this phenomenon becomes less obvious with larger dimensionless frequency.

Railway infrastructure holds a crucial role in a nation's economic development as an affordable mode of transportation and promotes social integration. Mud pumping is one of the major challenges the railway network has faced recently in the soft and mountainous terrain within the ballast layer due to high-speed rail loads. Many researchers found that reinforcement of the ballast and sub-ballast interfaces with geosynthetics is a feasible solution to reduce mud pumping. Still, the demand for sustainable geotechnic solutions is continuously increasing, particularly in countries with abundant natural plant resources. However, studies on the natural soil reinforcement in rail embankment are scarce. In this current study, a numerical investigation was conducted to study the effectiveness of geotextiles and geogrids made from natural plants (Geo-Naturals) in railway embankments. The results showed vertical settlements drastically decreased when Geo-Naturals were included in the poor subgrade. Further, the estimated axial forces, in the lateral direction to the rail length, in single-layer geogrids were found to be the maximum in poor subgrade due to higher compressibility. Geogrids placed close to ballast and sub-ballast were effective in the reinforcement function. Geotextile placed at the subgrade and sub-ballast interface accelerated in-plane drainage and reduced excess pore water pressure, thus preventing mud pumping potential. The outcome of the current study showed the effectiveness of geo-naturals in sustainability, eco-friendliness, and cost-effectiveness in railway embankments.

Railway embankments in seismically active areas are prone to earthquake-induced damage. In many instances globally, such damage has led to substantial economic losses. Serviceability assessment of these embankments is pivotal in ascertaining better performance during earthquakes. This work presents a physics-based approach to assess the serviceability of railway embankments subjected to strong ground motions. A series of nonlinear dynamic analyses are performed to evaluate the failure mechanism, progression of the failure plane, accumulation of plastic strain, and deformations of a railway embankment using the framework of smoothed particle hydrodynamics (SPH). The embankment and its underlying foundation are treated as a layered domain, and peak acceleration within each layer is determined through the site-specific nonlinear ground response analysis. The vulnerability assessment of the embankment is carried out considering the vertical displacement of the crest, accumulation of plastic strain, and post-failure scenario under site-specific ground motion characteristics. The vulnerability of the embankment is further quantified through fragility analysis by considering various damage levels. Fragility analysis is carried out using incremental dynamic analysis (IDA) against peak ground acceleration (PGA) of input ground motions as the key hazard indicator. The robustness of the developed vulnerability evaluation framework is also scrutinized through a sequence of stochastic analyses, considering the variability in ground conditions to enhance engineering assessment. The embankment is seen to experience a maximum vertical deformation of 0.05 m at the crest when initial signs of plastic strain development are observed, with deformation increasing to around 0.1 m for moderate damage levels and reaching up to 0.2 m at the point of slope failure. Fragility curves reveal that the right edge of the embankment reaches the first damage level at a PGA of approximately 0.12 g, followed by higher damage levels at PGA's as high as 0.8 g, for a 100% probability of extensive damage. Stochastic analysis shows that the probability of maximum vertical displacement exceeding deterministic values is about 78.47%, with maximum deviations of 2.599 m. For plastic strain, the probability of exceeding deterministic values is 78.49%, with maximum deviations of 13.08. These findings underscore the importance of considering site-specific conditions and the variability of soil properties in seismic assessments to ensure accurate and reliable serviceability evaluations of railway embankments.

In this study, a series of shake table tests were conducted on saturated sand soil foundations to investigate the seismic response of pile-supported railway embankments under equal and unequal thickness heterogeneous liquefiable soil conditions. The model's failure process, the variations of excess pore water pressure, the bending moments of the pile, and the acceleration response under different seismic intensities were analyzed in detail. Test results showed that the pore pressure increased with the increase of seismic intensity, and the liquefaction phenomenon occurred in the loose sand layer under 0.2 g dynamic excitation. The growth rate and peak value of excess pore water pressure in unequal thickness liquefiable soil terrain were greater than that in equal thickness soil conditions. The maximum bending moment of the pile body exhibits an inverted S-shaped distribution. In unequal thickness soil conditions, the edge piles experience higher bending moments compared to those in terrains with the same thickness. Additionally, the position of the maximum negative bending moment distribution for the central pile underwent a noticeable downward shift. During the loading process, the amplification effect of acceleration was greater in the loose sand layer than in the gravel soil layer, and more significant at the center of the foundation or the subgrade in unequal thickness liquefiable soil conditions. Therefore, the influence of terrain factors on the rise of pore pressure and the distribution of pile bending moments was nonnegligible in the seismic design of pile-supported embankment.

In this article, we consider the problem of thermal response of the near-surface ice-rich permafrost to the effects of linear infrastructure and current climate change. First, we emphasize the scientific and practical significance of the study and briefly describe permafrost conditions and related hazards in the study area. Then we present a mathematical model which accounts for the actual process of soil thawing and freezing and consists of two nonlinear equations: heat conduction and moisture transfer. Numerical calculations were made to predict temperature and moisture conditions in the railroad embankment, taking into account solar radiation, snow cover, rainfall infiltration, and evaporation from the surface. The numerical results indicate that moisture migration and infiltration play the primary role in the development of frost heaving and thaw settlement. During winter, the frost-heave extent is monotonously increased due to pore moisture migration to the freezing front. Strong volume expansion (dilatation) is observed near the surface of the active layer with the onset of the warm season and meltwater infiltration. Settlement of the upper layers of the soil occurs in the summer months (June-August) when there is intense evaporation due to drying. Autumn rains stop the process of thaw settlement by increasing the soil moisture. The above processes are repeated cyclically every year. A frozen core shifts to the shaded side of the embankment under the influence of variations in the solar radiation. Over time, the total moisture content of the frozen core is increased which increases differential heaving and negatively affects the stress-strain state in the embankment. The quantitative and qualitative characteristics of the processes of frost heaving and thaw settlement are obtained in the annual and long-term cycles.