Key Takeaways & Executive Findings
- •• Combined subgrade settlement and earthquake excitation significantly amplify dynamic responses of train-slab track systems compared to individual effects. • Short settlement wavelengths (10 m) are particularly critical, causing base-subgrade separation and heightened sensitivity of safety indexes. • Wheel unloading rate and derailment coefficient increase with earthquake intensity, with specific thresholds (0.17g and 0.29g) for a 10 m wavelength and 20 mm amplitude. • The refined numerical model provides a tool for assessing running safety under complex service conditions, aiding in design and maintenance of high-speed railways.
Abstract
Subgrade settlement is a common issue in soil ground within earthquake-prone regions, posing a threat to the safe operation of train-slab track coupled system (TSCS) in high-speed railways (HSRs). This study aims to analyze the mechanical behavior evolution of TSCS under subgrade settlement and earthquake excitation. The refined numerical model of slab track under subgrade differential settlement is established. The short settlement wavelength of 10 m causes the separation between the base and subgrade. The dynamic model of TSCS under subgrade settlement and earthquake excitation is developed. The dynamic response of TSCS exhibits more pronounced fluctuations under the combined effects of subgrade settlement and earthquake excitation than under the effects of settlement or earthquake alone. The evaluation indexes for the running safety of train on slab track under different settlement wavelengths exhibit varying degrees of increase with settlement amplitude and are particularly sensitive to the short settlement wavelength of 10 m. The wheel unloading rate and derailment coefficient of TSCS increase with earthquake intensity. Under the settlement wavelength of 10 m and amplitude of 20 mm, the wheel unloading rate of TSCS exceeds the allowable limit when the earthquake intensity exceeds 0.17g, and the derailment coefficient exceeds the allowable limit when the earthquake intensity surpasses 0.29g.
1. Introduction
Over the past decade, high-speed railways (HSRs) have seen a significant surge in construction worldwide. CRTS II slab track is the preferred ballastless track type laying on the HSRs, due to its fine integrity and superior stability [1−3]. The increasing demand for traffic volume and operation speed for train-slab track coupled system (TSCS) in HSRs leads to fresh challenges in the running safety of train considering complex service conditions [4−6]. Subgrade settlement is a prevalent issue in soft soil ground, widely distributed in earthquake-prone Southwest China, such as the Southwest Plateau Railway [7−10]. Subgrade settlement and earthquake excitation often occur simultaneously in TSCS, leading to the deterioration of the mechanical characteristic of TSCS in HSRs. Therefore, it is important to analyze the mechanical characteristic of TSCS subject to subgrade settlement and earthquake.
Many pieces of research focused on the mechanical behavior of TSCS either subgrade settlement or earthquake excitation separately. Firstly, the impact of subgrade settlement on the static and vibration behavior of TSCS has attracted many researchers. The mechanical property of ballastless track subject to subgrade settlement has been investigated, based on the numerical simulation [11, 12]. GUO and ZHAI [13], and CUI and LING [14] investigated the deformation characteristic of ballastless track subject to various settlement amplitudes and wavelengths. CUI et al [15] analyzed the size of separation between the base and subgrade for slab track subject to subgrade settlement, with the aid of the finite element model (FEM) using the cohesive zone model (CZM). With the aid of the mechanical analysis of ballastless track under subgrade settlement, the vibration characteristic of TSCS considering the settlement-induced track deformation has been explored [16, 17]. CAI et al [18], and ZHANG et al [19] explored the dynamic characteristic of train-track system subject to subgrade settlement, using the three-dimensional coupling dynamic model. JIANG et al [20], CUI et al [21], and WANG et al [22] evaluated the operation safety of train on ballastless track under different settlement wavelengths and amplitudes. The impact of subgrade settlement on the mechanical behavior of TSCS is noticeable. Among these, a few scholars analyzed the deformation characteristic of slab track induced by subgrade settlement, considering the cohesive constitution between the slab and CA motor and the concrete plastic damage. The influences of settlement-induced track deformation on the dynamic behavior of TSCS considering the contact condition between the track and subgrade are also examined.
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LOU Ping, SHI Tao, YANG T. Y. (2025). Mechanical behavior of train-slab track coupled system under subgrade settlement and earthquake excitation. Journal of Central South University. https://doi.org/10.1007/s11771-025-6109-x
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Frequently Asked Questions
What is the main focus of this study?
The study analyzes the mechanical behavior evolution of train-slab track coupled systems (TSCS) under combined subgrade settlement and earthquake excitation, using refined numerical models to assess dynamic responses and running safety.
How does subgrade settlement affect the train-slab track system?
Subgrade settlement, especially with short wavelengths like 10 m, can cause separation between the base and subgrade, leading to increased dynamic responses and reduced running safety.
What are the key safety indexes evaluated?
The study evaluates wheel unloading rate and derailment coefficient as key safety indexes, which increase with earthquake intensity and settlement amplitude.
What are the critical thresholds for safety under combined effects?
For a settlement wavelength of 10 m and amplitude of 20 mm, the wheel unloading rate exceeds the allowable limit when earthquake intensity exceeds 0.17g, and the derailment coefficient exceeds the limit when intensity surpasses 0.29g.
Why is this research important for high-speed railways?
This research provides insights into the combined effects of settlement and earthquakes, which are common in earthquake-prone regions, helping to improve design and maintenance strategies for safe operation.
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