In order to find out the influence of subgrade frost heave on the deformation of track structure and track irregularity of high-speed railways, a nonlinear damage finite element model for China Railway Track System III (CRTSIII) slab track subgrade was established based on the constitutive theory of concrete plastic damage. The analysis of track structure deformation under different subgrade frost heave conditions was focused on, and amplitude the limit of subgrade frost heave was put forward according to the characteristics of interlayer seams. This work is expected to provide guidance for design and construction. Subgrade frost heave was found to cause cosine-type irregularities of rails and the interlayer seams in the track structure, and the displacement in lower foundation mapping to rail surfaces increased. When frost heave occured in the middle part of the track slab, it caused the greatest amount of track irregularity, resulting in a longer and higher seam. Along with the increase in frost heave amplitude, the length of the seam increased linearly whilst its height increased nonlinearly. When the frost heave amplitude reached 35 mm, cracks appeared along the transverse direction of the upper concrete surface on the base plate due to plastic damage; consequently, the base plate started to bend, which reduced interlayer seams. Based on the critical value of track structures’ interlayer seams under different frost heave conditions, four control limits of subgrade frost heave at different levels of frost heave amplitude/wavelength were obtained.

Long elastic sleeper track (LEST) is a medium vibration reduction track, which is gradually used in urban rail transit in recent years. In order to analyze the structure of LEST used in subways and to study the dynamic effect of the elastic cushion stiffness and vehicle speed, a dynamic model of the vehicle–track–tunnel–soil coupling system was established based on the finite element method and vehicle–track interaction dynamics theory. The results show the following: (1) LEST is more advantageous in vibration reduction performance compared with the common slab track and the low vibration track under the same track stiffness, and LEST also has better integrity and stability than the low vibration track; (2) The lower the cushion stiffness is, the smaller the accelerations of the tunnel wall are, but the dynamic displacements of the track rise in time domain. Considering the dynamic displacements and accelerations, the cushion stiffness is recommended to be 20–30 kN/mm. (3) High vehicle speed has a detrimental effect on the dynamic response, especially the accelerations of track. It is necessary to pay more attention to vibration when the vehicle speed exceeds 100 km/h in the subway if LEST is used.

While the track irregularity in turnout areas has a significant impact on wheel-rail contact, driving safety, and stability, the impact of track irregularity in front of the incoming turnout on vehicles is often overlooked. This paper fills the gaps in the study. As a result, a rigid-flexible coupled dynamic model of the vehicle and turnout is developed. The effect of various irregularities in front of the turnout on the dynamic performance of a vehicle at high speeds has been investigated based on a random sampling method. The results show that different types of track irregularities in front of the turnout have different effects on the dynamic responses of vehicles. The vehicle dynamic performance is most sensitive to short-wavelength (3 m) irregularities in front of the turnout. The alignment irregularity with long-wavelength (40 m) has a significant effect on the wheelset lateral force and lateral acceleration of the vehicle body, caused by two-point contact between the wheel and rail. The frequency range of the effect of the irregularities on the wheel-rail force, safety indicators, and accelerations of the vehicle is mainly below 200 Hz, 50 Hz, and 20 Hz. In this study, a comprehensive assessment of different irregularities is conducted, as well as a quantitative reflection on the effect of the irregularity on the dynamic indicators, providing a reference for maintenance.

The vulnerability zoning of the urban ground subsidence in Tangshan City was investigated in this study, taking into account factors such as the geological lithology, rainfall, population density, road network density, seismic acceleration, and river network density. The main research of this paper is slow land subsidence affecting large territories. A single-factor analysis was conducted using ArcGIS, followed by a grid-weighted overlay analysis. Values were assigned to each factor to generate a vulnerability zoning map. The analytic hierarchy process (AHP) and information value evaluation model were then employed to assess the ground subsidence risk. An evaluation index system was established, comprising the evaluation objective layer, criterion layer, and indicator layer. An evaluation judgment matrix for the ground subsidence risk was constructed, with the calculation of the weight and information value of each risk evaluation indicator, and the total information value of the study area. Four risk levels were determined: high, moderate, relatively low, and low. The findings demonstrate the scientific validity, rationality, and practical applicability of the vulnerability zoning research and risk assessment method for addressing the ground subsidence in Tangshan City. This study contributes to the understanding and management of the ground subsidence risk, providing a robust framework for urban planning and disaster mitigation.

Rapid urban expansion and the development of urban rail transit networks have led to a deteriorating vibration environment along metro lines. These long-term vibrations pose significant challenges to adjacent buildings, such as opera theatres, and to the well-being of nearby residents. Consequently, there is a critical need for vibration evaluation and the implementation of mitigation solutions. This work provides a numerical investigation into the dynamics of vibrations observed in an opera theatre located above a metro station. A unified coupling method, known as the train-track-station-solum-opera model, is proposed and validated with field experiments. By employing contact theory, deformation coordination criteria, and spring elements, various components are meticulously modeled and coupled. Using this unified coupled approach, metro-induced vibrations at the opera theatre are predicted and evaluated. Additionally, vibration control measures are employed from the perspectives of transfer paths and vibration receivers to mitigate and isolate excessive theatre vibrations. The results, based on a case where the distance between the metro line and the opera theatre is 42 m, demonstrate that metro operations can lead to vibrations exceeding acceptable limits at the opera theatre near the metro station. Therefore, it is imperative that vibrations are assessed before constructing vibration-sensitive buildings along metro lines and that mitigation measures are implemented to meet specifications. In this work, the application of extruded polystyrene (XPS) plates and optimization of building structures effectively reduced excessive theatre vibrations by 1–2.5 dB, offering viable attenuation options without requiring modifications to the existing metro system.

The turnout is a vital railway infrastructure. Setting reasonable reduced values of the switch rail is the key to ensuring high stability and security when a vehicle passes a turnout. Poor reduced value condition leads to a car body swing or even derailment. To improve the turnout performance and reduce maintenance costs, of great importance is studying the reduced value. However, the current research did not consider wear rail profiles, and most optimizations were based on the given reduced values. Therefore, to promote dynamic performances as a vehicle passes through the turnout and to improve the traditional optimization method for the reduced value, the following investigations were carried out in this study. First, the tracking measurement of the rail profiles was conducted, and the variation law of the rail wear and the reduced value were analyzed. Further, based on the vehicle-turnout coupled model, an optimization model for the reduced value of the switch rail by the multi-island genetic algorithm was proposed. This model aims to minimize the dynamic responses. The objective functions of a vehicle passing a turnout in the main and diverging route were determined under the constraint conditions of the monotonicity of the reduced values. Finally, the optimizations were carried out in cases in which a vehicle passes on the main and diverging routes. The optimal results indicate that, after optimization, the objective function for the main and diverging routes decreased by 33.66% and 11.92%, respectively, illustrating the effectiveness of the optimization model.