This study aims to investigate the sliding mechanism of slopes along railways in loess regions under the coupling effect of extreme rainfall and train vibration. Using the Baotou-Xi'an railway as a case study, a physical model of slopes along railways was developed to account for the impacts of dry-wet cycles, extreme rainfall, and train vibration. The experiments revealed that during the dry-wet cycle phase, the pore fractal dimension of the slope soil decreases from 2.95 to 2.81, indicating an increase in macropores, which enhances water transport efficiency in the soil. Following extreme rainfall, the pore water pressure and moisture content data of the soil approach peak levels, suggesting increased soil saturation and weakened stability. Subsequent vibration loading results in highly saturated soil, as evidenced by fluctuations in volumetric moisture content (from 48 % to 50.7 %) and pore water pressure (from 1.6 to 1.8 Kpa). Train vibration contributes to crack formation and expansion, while water infiltration establishes a pore-crack-seepage network. This network, combined with rainfall and train vibrations, destabilizes the soil structure and triggers landslides in loess regions along railways. The continuous application of vibration load further expands the sliding range. Meanwhile, an equation was derived to determine the sliding distance in relation to the number of vibratory loads applied. The sliding mechanism of slopes along railways under the combined influence of rainfall and train vibration has been preliminarily verified through micro, meso, and macroscopic perspectives.

The formation layers of railway embankments are often unsaturated and subjected to coupled cyclic traffic-induced and hydraulic loading. Understanding this coupled response requires the development of a testing protocol capable of subjecting soil samples to cyclic loading while continuously monitoring water retention response of the soil. An accurate measurement of the suction variation for the case of repeated cyclic loading is crucial for interpreting the response of the soil considering the principles of unsaturated soil mechanics that are commonly neglected during the design of this infrastructure. In this paper, we present the use of a high-capacity tensiometer of capacity 2MPa and resolution 0.5 kPa developed at Durham University, capable of measuring suction on the body of soil samples. The setup allowed continuous monitoring of suction at the mid-height of the unsaturated soil sample during cyclic triaxial testing while continuously measuring the volumetric deformations with the help of local displacement transducers. The obtained results indicated that the volumetric compression during cyclic loading reduced the voids ratio leading to an increase in the degree of saturation under constant water content conditions that reduced the soil suction. The obtained results were then interpreted by using mean Bishop's stress where the permanent strain was consistently found to increase with an increase in the Bishop's stress ratio. The resilient modulus was also found to be correlated to Bishop's stress ratio.

Due to factors such as groundwater seepage and soil stress coupling effect, significant deformation and instability problems often occur during the construction process of super large deep excavation groups involving iron, seriously affecting the safety and stability of the project. This article aims to explore the coupling effect of super large deep excavation groups involving railways during the construction process, and how to effectively control construction deformation. This article combines theoretical analysis and numerical simulation to study the coupled effects of seepage and stress during the construction process of super deep excavation groups involving iron. With the help of finite element software, a numerical model of a large and deep excavation group involving iron was established, and the deformation and stress distribution at different construction stages were simulated. The research results indicate that the coupling effect of groundwater seepage and soil stress has a significant impact on the deformation and stability of the super deep excavation group involving iron. Therefore, reasonable construction measures and deformation control methods should be taken during the construction process.

Pile-supported embankments are typically composed of soil-rock mixtures. within these structures, while the soil arching effect is crucial for effective load transfer, it remains incompletely understood, particularly when the impact of various loading conditions needs to be considered. This study investigates this problem using a 1 g physical experimental modeling approach. Subsequently, a DEM model for a full-scale pile-supported embankment of high-speed railways, accounting for multiple pile interactions, is established with proper model calibration. Numerical simulations are conducted to explore the load transfer mechanism and soil arching processes under self-weight, embankment preloading, and train-induced dynamics influences. The findings indicate that under self-weight, fully developed soil arching structures can be achieved with a sufficiently high embankment height, although they can diminish as the soil-pile relative displacement increases. However, during embankment preloading processes, represented by static loading, pressure can be transferred from pile caps to subsoil regions, potentially compromising the integrity of soil arching structures. Train-induced dynamics effects are modeled as cyclic loading inputs, revealing that an increase in loading frequency leads to weakened dynamic pressure fluctuation for both pile caps and subsoil regions, with a limited impact on the valley values of the pressures. Additionally, a higher loading frequency corresponds to smaller accumulated loading plate settlements.

A self -sensing cementitious geocomposite was developed based on laboratory data, and it demonstrated good physical and mechanical properties, durability, and piezoresistivity performance. It consisted of stabilized cemented sand containing multiwalled carbon nanotubes (MWCNTs) with graphene nanoplatelets (GNPs) as conductive fillers. This geocomposite could be used to detect damage based on the relationship between electrical impedance and mechanical performance, making it suitable for use as structural layers in railway lines. In this study, the effects of MWCNTs and GNPs, as well as of degree of saturation, were evaluated on the compaction, secant modulus, resilient modulus, electrical resistance, and piezoresistivity of the geocomposite. Scanning electron microscopy (SEM) and microscopic imaging were used to analyse microstructural alterations induced by varying concentrations of MWCNTs and GNPs. This innovative geocomposite, intended for installation in Portuguese railway lines as part of the EU project IN2TRACK3, is aimed at capturing performance data, identifying structural damage levels, and estimating load intensity, axle numbers, and train speed. The feasibility of its use is discussed based on literature studies and research conducted under the IN2TRACK2 and IN2TRACK3 projects, and its potential advantages over traditional methods for monitoring rail track health are highlighted.

This article presents the results of field study near a Northern Railway embankment (Hanovey station) in a field work area of the Geocryology Department (Moscow State University), where we performed cone penetration tests, measured the thickness of the active layer and soil temperatures, monitored settlement of the embankment, and performed laboratory tests. A mathematical model was compiled in the Qfrost program based on these data taking the unevenness of the snow cover in the study area into account. Calculations of the temperature regime of the embankment until 2050 taking climate change into account (according to the RCP 4.5 scenario), showed that the thickness of the talik at the embankment will increase by 40% in 30 years and without taking this factor into account, by 17%. This article also discusses the features of the position and structure of the embankment, as well as the composition and properties of frozen soils, which significantly affect the stability of the embankment.