The surface crack of ballastless track slab can seriously reduce the serviceability and durability of high-speed railway (HSR). Aiming at accurately and efficiently detecting the slab cracks, this research proposes an infrared thermography (IRT)-based method for the surface crack, which is the most serious and common crack type in track slab. A three dimensional finite element (FE) model of IRT detection of concrete slab with surface cracks is established. The relation between the width of detectable cracks and the ambient temperature can be thereby obtained by inputting the measured thermodynamic parameters in the model. Parametric study shows that with ambient temperature higher than 15 °C, cracks with a width of no less than 0.2 mm can be well detected. Scale model test and field test are conducted, IRT method can effectively locate the slab surface cracks with width as small as 0.14 mm when ambient temperature is no less than 20 °C.

This study develops a quantitative framework to assess performance degradation and damage evolution in CRTS I ballastless track slabs. Based on the impact-echo method, the internal void distribution characteristics of the new and old track slabs were obtained. The track slabs were sampled separately by drilling cores to verify the distribution of voids, and uniaxial compression tests were conducted simultaneously to quantify the attenuation of bearing capacity. The on-site wheel–rail force and temperature field data were monitored, based on the established three-dimensional finite element model of CRTS I ballastless track, and the damage distribution characteristics of the track slab under different load combinations after performance degradation were studied. The results show the following: (1) As the performance of the track slabs gradually deteriorated, it was reflected in the increasing internal void distribution area from 0.5% to 3.6%, corresponding to a 22.4% decrease in core strength. (2) The on-site monitoring results showed that the average wheel–rail force was 84.5 kN. The temperature gradient range varied from −50.4 °C/m to 100.0 °C/m, exceeding the allowable value of the design specifications. (3) The actual damage distribution of the track slab after performance degradation under different load combinations significantly increased at key stress locations such as near fasteners, convex abutments, and anchor holes of prestressed steel bars, which required special attention in actual maintenance and repair.

Aiming at the juncture defects of CRTSⅡslab ballastless track in China high speed railway, an on-line monitoring system for temperature field and deformation of track slab was set up.The temperature variation and the relative displacement between slabs and junctures were obtained in real time. Experiments showed that the relative displacement of wide and narrow juncture could reach 0.11mm and 0.70mm caused by the temperature change of the track slab,which was the main reason for junctures'destruction. The linear correlation coefficients between the relative displacement and the temperature of the junctureswere 0.870 and 0.946,which could provide references for maintenance and repair of ballastless track.

With China’s high-speed rail network undergoing rapid expansion, turnouts constitute critical elements whose safety and stability are essential to railway operation. At present, the efficiency of wheel–rail force safety monitoring conducted in the small hours reserved for the construction and maintenance of operating lines without marking train operation lines is relatively low. To enhance the efficiency of turnout safety monitoring, in this study, a three-dimensional BIM model of the No. 42 turnout was established and a corresponding wheel–rail force monitoring scheme was devised. Collision detection for monitoring equipment placement and construction process simulation was conducted using Navisworks, such that the rationality of cable routing and the precision of construction sequence alignment were improved. A train wheel–rail force analysis program was developed in MATLAB R2022b to perform signal filtering, and static calibration was applied to calculate key safety evaluation indices—namely, the coefficient of derailment and the rate of wheel load reduction—which were subsequently analyzed. The safety of the No. 42 turnout and the effectiveness of the proposed monitoring scheme were validated, theoretical support was provided for train operational safety and turnout maintenance, and technical guidance was offered for whole-life-cycle management and green, sustainable development of railway infrastructure.

Steel-spring floating-slab tracks (SSFSTs) are widely used as efficient vibration-damping beds, and in China, they are mainly used in subways and municipal railroads. The shear hinge is an important component that improves the stability of the line, and field research has found that the top-mounted shear hinge (TMSH) undergoes varying degrees of damage, which indirectly affects the safety and stability of line operation. In this work, we studied the causes of damage to TMSHs, designed a new TMSH structure with a rubber-pad layer installed based on modal theory and rubber-pad vibration-damping theory, and proved that the new structure can reduce the occurrence of damage by comparing it with the original TMSH structure. The main aspects of this study are as follows: Firstly, the ultimate load capacity of the existing and new TMSH structures was checked by establishing a refined finite-element model. Then, modal analysis and frequency-response function analysis were carried out based on modal theory and frequency-response function theory to reveal the causes of TMSH damage and prove that the new structure can effectively delay damage. Finally, the modal and vibration patterns of the two structures were obtained via indoor hammering tests and compared with the simulation results. The results show that the two TMSH structures are in line with the strength requirements, and the existing TMSH damage mainly results from the resonance between its natural frequency and the high-excitation frequency of the floating slab under long-term cyclic train loading, causing high-frequency vibration fatigue damage. It is also demonstrated that the new structure can effectively reduce the natural frequency of the TMSH so that its value is located in the region of low vibration on the floating slab. The excitation vibration levels of the TMSH mounted on the curved section of the 4.8 m floating slab and the 3.6 m floating slab were reduced by 9 dB and at least 3 dB, respectively. After adding rubber pads located in the 400–3000 Hz floating-slab high-vibration-level region of the TMSH damage-prone parts, the amplitude reduction, including lateral excitation of damage-prone parts, resulted in a vibration amplitude reduction of more than 30 dB. However, the vertical excitation of the mid-end and rear-end bolts slightly increased their amplitudes, whereas the shear-rod amplitude was reduced by 48 dB, and the front-bolt amplitude was reduced by 5.28 dB. The natural frequency and vibration pattern obtained from the hammering test were consistent with the simulation results, and the reliability of our conclusions was verified from both experimental and simulation perspectives.

Slab-replacement operations are crucial for restoring deteriorated CRTS I slab ballastless tracks to operational standards. This study investigates the structural implications of the operation by evaluating the strength characteristics and material properties of track components both prior to and following replacement. Apparent strength was measured using rebound hammer tests on three categories of slabs: retained, deteriorated, and newly installed track slabs. In addition, samples of old and new filling resins were collected and tested to determine their elastic moduli. These empirical data were subsequently used to develop a refined finite-element model that captures both pre- and post-replacement conditions. Under varying temperature loads, disparities in component performance were found to significantly affect stress distribution. Specifically, before replacement, deteriorated track slabs exhibited 10.74% lower strength compared to adjacent retained slabs, whereas, after replacement, new slabs showed a 25.26% increase in strength over retained ones. The elastic modulus of old filling resin was measured at 5.19 kN/mm, 35.13% below the minimum design requirement, while the new resin reached 10.48 kN/mm, exceeding the minimum by 31.00%. Although the slab-replacement operation enhances safety by addressing structural deficiencies, it may also create new weak points in adjacent areas, where insufficient stiffness results in stress concentrations and potential damage. This study offers critical insights for optimizing maintenance strategies and improving the long-term performance of ballastless track systems.