Abstract:The subgrade is an essential structural foundation in high-speed railway engineering, and its long-term stability directly affects railway transportation safety. With continuously increasing train speeds and axle loads, cumulative settlement of subgrades under dynamic loading is becoming increasingly prominent. Consequently, it has emerged as a critical interdisciplinary research hotspot across railway engineering, geotechnical engineering, and engineering mechanics. This paper reviews domestic and international research achievements regarding cumulative settlement of subgrades subjected to high-speed train loading. Specifically, it summarizes recent developments in experimental investigations, theoretical analyses, and influencing factors related to cumulative settlement, highlighting the complexity and key technical challenges associated with long-term subgrade deformation. Moreover, the paper outlines future research directions, including examining the effects of intermittent loading on long-term deformation, as well as investigating the particle breakage mechanism of subgrade fill materials and its impact on deformation behavior. This review aims to provide theoretical support for the design and optimization of high-speed railway infrastructures.

Abstract:Prefabricated pavement technology, as an efficient and environmentally friendly method for road construction, has gained widespread attention globally in recent years. Despite significant research achievements, a comprehensive summary and synthesis were still lacking. This paper systematically reviews the research progress of prefabricated pavement technology from three key perspectives: pavement structural design theory, material selection, and construction techniques. Firstly, based on different fundamental theoretical models, the paper analyzes the factors influencing the mechanical response of precast slabs, fatigue verification equations, and design parameters, summarizing the structural design methods for prefabricated pavements. Secondly, the impact of novel materials on the mechanical properties and durability of pavements is summarized from the aspects of leveling layers, precast slabs, and joint materials. Finally, the paper systematically elaborates on the construction processes of prefabricated pavements, including the construction methods of leveling layers, lifting and connecting techniques for pavement panels, and joint treatment technologies. Additionally, the paper proposes suggestions for future research directions, aiming to provide theoretical references and practical guidance for the appli-cation and promotion of prefabricated pavement technology.

Abstract:In order to study the characteristics of indoor vibration and secondary noise of buildings induced by 160 km/h urban subway, a long-term monitoring system was deployed in a building room along a new urban express line to carry out long-term vibration and noise monitoring. Based on the analysis of a large number of monitoring data,the characteristics of indoor vibration and secondary structural noise of buildings along the highspeed underground line are studied,and the changes of vibration and noise characteristics at different driving speeds are studied. The analysis results show that each frequency band of indoor vibration induced by subway has a certain degree of dispersion. In the 25.0~125.0 Hz frequency band,the dispersion degree of the frequency-divided vibration level is lower than that of other frequency bands. The dispersion of the frequency-divided sound pressure level of each frequency band of indoor secondary structural noise induced by subway is significantly greater than that of the frequency-divided vibration level of indoor vibration induced by subway. The difference between secondary structural noise and background noise is mainly concentrated in the 31.5~125.0 Hz frequency band. The correlation between the vibration frequency-divided vibration level and the secondary structural noise frequency-divided sound pressure level in the subway-induced room is large in the frequency band of 31.5~100.0 Hz. After the speed increases, the correlation between the vibration level and the secondary structural noise does not increase significantly, but the dispersion degree of the vibration and secondary structural noise monitoring data decreases. After the speed increases, the vibration frequency division vibration level increases at 20.0~50.0 Hz, while the secondary noise sound pressure level of the structure increases only at 31.5 Hz.

Abstract:The creep compliance function is usually expressed by a Prony series model when using finite element codes to calculate the creep effects of concrete structures. To address the physically meaningless phenomenon of negative, oscillatory and unstable parameters when using traditional single methods (such as the conjugate gradient method and the LM algorithm) to fit Prony series models to experimental creep function data, this paper proposes a novel hybrid intelligent optimization method for Prony series parameter identification. The method establishes an objective optimization function with penalty terms and combines a simulated annealing-genetic hybrid intelligent algorithm with nonlinear programming methods to constrain parameter identification within physically meaningful ranges. Subsequently, a simple and practical calculation formulation for the Prony series was proposed by parameter analysis. It was shown by numerical examples that the proposed method not only effectively eliminates the drawbacks of conventional approaches, but also gives the identification with relative errors below3%. The Prony expression of creep function can be directly applied to the development of finite element software program in calculating the creep effect of concrete structures.

Abstract:The application of UHPC in bridge engineering is becoming increasingly common. In order to further study the fatigue performance of RD welded joints in steel UHPC composite bridge decks,fatigue tests and nu-merical simulations were conducted on RD welded joints of steel bridge decks under simulated wheel loads. The fatigue cracking behavior and stress distribution of specimens under central loading conditions were analyzed, and the fatigue life of RD welded joints was predicted using structure stress method. A 3D solid finite element model of RD welded joints with UHPC overlay was established based on ABAQUS software. Static loads were applied to the model,and node forces and moments at the crack initiation section were extracted to calculate the equivalent structure stress. The fatigue performance of RD welded joints was evaluated using the master S- N curve in the structural stress method,and compared with the predicted results of the hot spot stress method and critical distance theory. The research results indicate that under the central loading condition,the weld seam connecting the cover plate and the U- rib is subjected to tensile stress,and the tensile stress gradually increases and tends to stabilize in the middle of the weld seam. Fatigue cracks first initiate at the vulnerable part and propagate in stages along the thickness direction of the plate until fracture; After being reinforced with UHPC,the end effect of the weld seam in the RD welded joint is significantly reduced,and the structural stress value in the middle of the weld seam is greatly reduced,with a maximum reduction of 87.2%. At the same time,the UHPC layer and the cover plate form a whole to jointly bear the load,making the structure stress distribution tend to be flat,significantly improving the fatigue stress state of the steel bridge deck; Compared with the hot spot stress method and critical distance theory,the prediction results given by the structure stress method are more conservative and closer to the experimental values,with a prediction error of only 8%. For steel-UHPC composite welded joints,the predicted values given by the structure stress method reach infinite fatigue life. Overall,the structure stress method can effectively evaluate the fatigue performance of steel bridge decks,accurately predict the fatigue life of welded components at a lower cost,and assist in formulating maintenance strategies. It has broad practical prospects in the field of steel structure bridges.

Abstract:In recent years, ballastless track systems in high-speed railways have developed rapidly, but studies on carbon emission characteristics and precise calculation methods during the construction phase remain limited. This paper conducts a comprehensive quantitative analysis of carbon emissions during the construction phase of CRTS Ⅲ slab ballastless track in high-speed railways. The PROMETHEE-Ⅲ method is used to rank carbon emission factors, and a ballastless track construction carbon emission database is built using MySQL. The proposed models quantify the per-kilometer carbon emissions of embankment, bridge, and tunnel sections. Concrete accounts for 41.06%~43.52%, steel accounts for 52.90%~54.53%, with materials contributing up to 96.00% of total emissions. Results show that embankment sections produce significantly higher carbon emissions than bridge and tunnel sections. Concrete and steel are the dominant emission sources. Sensitivity analysis reveals that steel emission factors have the strongest impact on total emissions, followed by concrete.

Abstract:In order to better grasp the changes in the mixing uniformity of reclaimed asphalt pavement (RAP), the dynamic process of the evolution of RAP mixing uniformity at different mixing speeds was simulated. Firstly, based on the discrete element method (DEM) to simulate the RAP mixing process under different mixing speeds, we analyze the mixing uniformity change and internal mechanism of the old aggregate agglomeration crushing; Secondly, on the basis of agglomerate crushing, we further analyze the uniformity evolution process of the new and old aggregates; Finally, we use the 3D printing technology and image processing to analyze the mixing uniformity change of the new and old aggregates in the chamber under different mixing speeds. There is a process of agglomerate crushing from fast to slow, The inflection times of the fitted curves of dispersion factors of old aggregate agglomeration at 5, 10, 15, 20 r/min mixing speeds are 10.92, 6.69, 5.48, 4.12 s, respectively. the further the agglomerates are away from the center of mixing, the more obvious the trend of speed and force changes in mixing, and the more homogeneous the mixing is. The inflection times of the fitted curves of disper-sion factors of old and new aggregates at 5, 10, 15, 20 r/min mixing speeds are 17.05, 8.74, 5.66, 4.26 s, respectively. The uniformity of the mixing of the old and new aggregates under different mixing speeds is slightly different between the indoor experiment and DEM, but all of them reach the inflection point of uniformity around 4 s. The change of mixing uniformity of RAP is a complex dynamic process, and the mixing speed is a key factor that cannot be ignored to affect the mixing uniformity.

Abstract:To investigate the seismic safety performance of shield tunnels under geothermal source effects, based on Xi’an Metro Line 10 project, finite element numerical simulation was adopted to reproduce the seismic response of shield tunnels under geothermal sources, and the influence of different relative positions between geothermal sources and the tunnel was analyzed. The results show that geothermal sources significantly amplify the stress levels in tunnel segments near the heat source while reducing the joint opening displacements in these areas, with minimal impact on sections far from the heat source. The distance between the heat source and the tunnel affects the stress levels in tunnel segments but has little influence on joint opening displacements. Geothermal sources significantly affect joint opening displacements and stress in shield tunnels near the heat source but have negligible impact on parameters such as acceleration and tilting angles. The research can provide reference for the design of similar working condition in the future.element

Abstract:In order to explore the elastic wave propagation pattern in the ballastless track structure on the periodic bridge, the ballastless track-bridge coupling structure is considered as a four-layers Timoshenko beam coupling model including rail, slab, bed plate and bridge. The plane wave expansion method-energy method was used to solve its dispersion characteristics. The accuracy of the proposed method was verified by comparing with the results of the finite element method. Then, based on this method, the influence of structural stiffness change on elastic wave propagation was explored, and the formation mechanism of band gap in the dispersion characteristics was clarified. The results show that there are two band gaps in the ballastless track-bridge coupling structure within 0~50 Hz, and when the longitudinal stiffness is large, the initial frequency and cut-off frequency are mainly affected by the longitudinal stiffness of each connecting layer. The first and second cut-off frequencies increase with the increase of the stiffness of the glide lamella and the stiffness of the fastener, respectively. This study provides a theoretical reference for the vibration reduction of the ballastless track structure on the bridge.

Abstract:Leakage detection is a critical measure to ensure the proper operation of hazardous waste landfills. Traditional manual visual inspections are inefficient, and hazardous waste can affect the health of workers.A method based on instance segmentation is proposed to detect leakage. The method uses a camera mounted on an inspection robot to capture video images, the YOLOSeg-EViT network performs instance segmentation. Experimental results show that the algorithm achieves a mean average precision of 75.7%, and when detecting with a 1 280×720 pixel resolution video, the detection is 54.4 frames per second. On an edge computing platform, the algorithm reaches mean average precision 75.1% and 33.1 frames per second. The leakage detection algorithm effectively identifies leakage, improves the detection efficiency, and prevents workers from being exposed to hazardous substances, making it highly practical.

Abstract:Image contents in road scenes are usually complex, with significant differences in scale and shape between different objects, and lighting and shadows can make the scenes difficult to recognize. However, existing semantic segmentation methods often fail to effectively extract and fully integrate multi-scale semantic features, resulting in poor generalization ability and robustness. To address these issues, this study proposes a semantic segmentation network model that fuses multi-scale Transformer features. Firstly, the CSWin Transformer was employed to extract semantic features at various scales, accompanied by the introduction of a feature refinement module (FRM) to enhance the semantic discrimination capability of deep, fine-grained features. Secondly, an attention aggregation module (AAM) was adopted to separately aggregate features across scales. Finally, by integrating these enhanced multi-scale features, the semantic expression ability of the features was further enhanced,thereby improving segmentation performance. Experimental results demonstrate that this network model achieves an accuracy of 82.3% on the Cityscapes dataset, outperforming SegNeXt and ConvNeXt by 2.2 percentage points and 1.2 percentage points, respectively. Moreover, it attains an accuracy of 47.4% on the highly challenging ADE20K dataset, surpassing SegNeXt and ConvNeXt by 3.2 percentage points and 2.8 percentage points, respectively. The proposed multi-scale Transformer feature fusion model not only achieves high semantic segmentation accuracy, accurately predicting pixel semantic categories of road scene images, but also has strong generalization performance and robustness.

Abstract:In the current domain of air traffic, frequent flight conflicts and departure flight delays within airport systems are increasingly becoming key factors that affect the efficiency of flight operations and passenger satisfaction. By considering the resource constraints of airport systems, the concept of“airport satisfaction”is introduced. The objectives of optimization include minimizing the total delay of departure flights, maximizing the sum of satisfaction across all airports, and maximizing the overall measure of fairness within the airport system. A collaborative sequencing model for departure flights in the terminal area of airport clusters is established, and an elitist strategy-based non-dominated sorting genetic algorithm is designed to solve the Pareto optimal solution for the collaborative sequencing problem of departure flights in the terminal area of airport clusters. An empirical analysis was conducted using the terminal areas of three airports in the Beijing-Tianjin region as examples. The experimental results show that compared to the first-come-first-served scheme, the total flight delay was reduced from 7 796 seconds to 5 029 seconds, a decrease of 35.5%, with the average delay per flight dropping from 159 seconds to 103 seconds. The average satisfaction of flights reached 0.786 7, and the overall measure of fairness among airports in the cluster was 0.004 4. The proposed optimization method can significantly reduce the total delay of departure flights in airport systems, improve overall flight satisfaction, and achieve the fair and efficient use of resources.