Abstract:Bedded rock is a common sedimentary rock type in underground engineering environment, and anchor support technology is generally used to strengthen bedded rock. In order to study its mechanical response under complex engineering stress environment, Yunnan red sandstone, marble glue, screw and epoxy resin were selected as raw materials and the test samples were made by cutting and bonding. Triaxial compression test was used to investigate the effects of different interface dip angles and confining pressures on the mechanical properties of anchored and unanchored stratified rocks. The results showed that the failure of the sample experienced pore compaction, linear elasticity, stable crack growth, unstable crack growth and post-peak failure, and its strength, deformation parameters and crack growth pattern were significantly affected by confining pressure. The increase of confining pressure can prolong the elastic deformation stage and improve the residual strength and ductility. The failure modes of specimens with different angles under confining pressure are split failure, tensile shear failure and pure shear failure. Confining pressure has a comprehensive enhancement effect on the mechanical properties of anchored and stratified rocks, which not only enhances the compressive strength and shear resistance of rocks, but also improves the post-peak ductility of rocks. This study provides strong support for further understanding of rock mechanical properties and engineering applications.

Abstract:Because the structural vibration in rail transit has a deep impact on safety and environment, in order to control the vibration of the plate structure, the amplitude-enhanced device can be used to increase the stiffness and mass of the vibration absorber, and the amplitude-enhanced vibration absorber is periodically arranged on the plate. Based on the null space method and the energy method, a new band gap calculation method is improved, which overcomes the difficulty of constructing the shape function under the periodic boundary condition, and greatly improves the calculation efficiency. Using this method, the band gap characteristics of a plate with periodically attached AMVAS are studied. The vibration mode law of the starting and ending points of the band gap are studied, and the influence of the amplification coefficient and mass ratio of the amplitude enhancement device on the band gap is discussed. In addition, the vibration transmissibility of periodic plate structures with amplitude-enhanced vibration absorbers and ordinary vibration absorbers is compared and analyzed. The results show that the appropriate amplification factor and mass ratio can effectively enhance the low frequency vibration reduction effect of the device. The amplitude enhanced vibration absorber has the effect of increasing the attenuation amount and broadening the attenuation range, and has a significant effect on the vibration control of the specific frequency of the periodically arranged plate structure. The research results can provide theoretical basis for vibration and noise reduction in the field of rail transit.

Abstract:In order to consider the nonlinear characteristics of rock and soil materials in slope stability analysis, a rigorous upper bound variational analysis method for slope stability based on the deep-seated failure mechanism is proposed. Based on the upper bound theorem of limit analysis, a rotational failure mechanism of homogeneous slope was established. The sliding surface and its stress under limit state were obtained according to the Euler equation of variational principle, variational transversality conditions and boundary conditions. The implicit function for the critical slope height was established via the energy balance equation, and the critical height of slope was optimized by particle swarm optimization algorithm. The slope factor of safety (FOS) was obtained. By comparing , it is found that the potential sliding surface and the distribution of principal stress on the slope obtained by the proposed method are in good agreement with the calculation results of OPTUM G2 and FLAC 3D, and the error of safety factor is small. The results show that the variational analysis method can effectively evaluate the stability of homogeneous slope with sliding below the slope toe.

Abstract:To investigate the structural vibration characteristics of parallel transfer subway stations under the mutual influence of trains on different lines, this study integrates vehicle-track coupling dynamics analysis, finite element simulation, and field tests at subway stations. It analyzes the transmission characteristics of vibrations within buildings and the impact of combined train operations on structures, offering vibration reduction suggestions. The results indicate that platform vertical vibrations predominantly occur within the 30~80 Hz frequency range, with distinct peaks at 36, 47, 67 Hz. Due to the superposition of incident and reflected waves at the top layer, vibrations are amplified there, with an average amplification of 4.50 dB, and the lateral transmission attenuation rate is approximately 0.51 dB/m. When trains operate simultaneously on both lines, the Z vibration level at central sampling points above the lines is higher. To comply with vibration limits, the entry speed should be restricted to no more than 22 km/h. The vibration reduction fastener achieves an effect of 3.80 dB. Except for its inherent frequency range of 11~14 Hz, the steel spring floating plate exhibits significant vibration reduction in other frequency bands, notably reaching 28.00 dB at the 80 Hz band.

Abstract:Whether the transverse stiffness similarity of the model shield tunnel is reasonable or not is directly related to the accuracy of the cross-sectional deformation of the model shield tunnel during the model test. In order to study the design method of segment ring of model shield tunnel, the similarity and processing materials of the model shield tunnel segment ring were analyzed. Different types of model tunnel segment rings were designed and tested. The relationship between vertical displacement and horizontal displacement of segment ring and vertical loading of shield tunnel with different models was obtained. The results show that: some polymer materials have certain creep properties, and it is recommended to avoid using polymer materials with this characteristic to make model shield tunnel segment rings; the creep of nylon material is small, which can be selected as the material for processing model tunnel segment ring. Due to the complexity of the influencing factors of the bending stiffness of the assembled joint, when it is necessary to simulate the longitudinal joint of the segment, it is recommended to simulate the longitudinal joint of the segment by slotting. The bending stiffness of the joint can be controlled by the width and depth of the slotting. The design and processing of modified homogeneous ring are simple. If the shield tunnel is studied by scale test and the model shield tunnel is designed as modified homogeneous segment ring, it is recommended to use steel plate as the material for processing the model shield tunnel.

Abstract:To address the difficulty in identifying echoes from near-surface railhead defects caused by near-field interference, this paper establishes an ultrasonic sound-field model in rails based on the Huygens integral, and combines numerical simulations and experiments to investigate the effects of probe frequency and piezoelectric element size on the sound-field distribution and defect-echo features. The results show that, as the element size increases from 10×10 mm to 20×20 mm, the near-field length increases from 11.9 mm to 51.4 mm; as the frequency increases from 1 MHz to 4 MHz, the near-field length increases approximately linearly, while the peak sound pressure decreases overall with increasing frequency and element size. In the near field, defect echoes overlap significantly with the initial pulse, making near-surface railhead defects difficult to distinguish; in the far field, the echo separation improves and the detection accuracy increases markedly.

Abstract:In view of the susceptibility of high-speed railway insulator detection to climatic and environmental factors, as well as the deficiencies in accuracy and efficiency, this study proposes an improved algorithm ABFPYOLOv8. This method first constructs a C2f-AFE module to strengthen the extraction ability of global contextual features and suppress complex background interference. Subsequently, the neck network is replaced with a BCNeck structure to enhance the ability to capture target details. Furthermore, the Powerful-IoU loss function is employed to optimize the localization performance and reduce the false detection rate. Additionally, a 160 × 160 small target detection head is added to enhance the recognition ability of small-sized insulators. Experimental results indicate that, compared with the original YOLOv8n model, the ABFP-YOLOv8 model achieves improvement in mAP@50 and mAP@50-95, increase in inference speed, despite reduction in the number of parameters. This suggests that the algorithm is highly suitable for deployment in mobile detection terminals and scenarios with complex and variable detection environments.

Abstract:The return system is an important component of the traction power supply system. Under the direct power supply mode, the traction return system consists of multiple circuits with a complex structure. If the return is not smooth, it may cause the supporting fittings to melt and burn, seriously threatening the safety of railway operation. This study aims to analyze the mechanism of support fittings melting and burning caused by traction return system faults under direct power supply mode, clarify its key influencing factors, and provide theoretical basis for fault diagnosis and troubleshooting of traction return system. Firstly, an in-depth analysis was conducted on the current distribution characteristics in the traction return system, and a simulation model of the traction power supply return system based on CDEGS was established; Then, the current and potential distribution characteristics were simulated under typical fault conditions such as normal working conditions, ungrounded contact wire pillars, and ungrounded return lines; Further comparative analysis was conducted on the influence of different soil resistivity and grounding resistance on the distribution of system current, and the reasons for the melting and burning of pillar fittings were summarized. The simulation results show that under normal operating conditions, the maximum return ratios of the return line and the through ground line are 37.00% and 19.00% respectively; When the return wire is not grounded, the proportion of return wire and through ground wire return is 47.34% and 10.10% respectively. At this time, some current flows into the through ground wire through the pillar, and the maximum current passing through the pillar can reach 74.73 A. There is a maximum voltage difference of 40 V between the return wire and the pillar. When the return wire is not grounded, there is a voltage difference between the return wire, pillar, and through ground wire, and a large current flows through the supporting fittings on the pillar. The combined effect of the two causes the supporting fittings to heat up and melt. In actual operation, it is necessary to strengthen the investigation of ungrounded return lines to avoid the occurrence of such faults.

Abstract:In order to solve the problem of high transportation costs in the process of multi-vehicle loading, a multi vehicle loading problem that considers both transportation costs and transportation safety was studied. Firstly, under the premise of infinite vehicle loading capacity, a mathematical model for vehicle loading was constructed to minimize the cost of using vehicles and consider load balancing for the problem of vehicle loading of multiple vehicle types and varieties of goods. Secondly, variable neighborhood search algorithm was proposed to solve the problem. Finally, based on the idea of "personification", neighborhood operators such as tail box operator, large vehicle to small vehicle operator, one large vehicle to two small vehicle operator, two small vehicle to one large vehicle operator, and shaking operator to heavy-duty vehicles were designed and applied to the variable neighborhood search algorithm. The example data results demonstrate that compared with traditional intelligent optimization algorithms, the variable neighborhood search algorithm constructed in this paper has strong global search ability. The model and algorithm can reduce the number of vehicles from 4 to 3 while ensuring load balance, thereby reducing vehicle costs by 17.44%. The average loading rate is increased from 0.69 to 0.89, and improving the average vehicle loading rate by 28.99%. The optimization effect is significant. The model and algorithm constructed in this article can greatly save the transportation costs of logistics enterprises, improve transportation profits, and help logistics enterprises improve quality, reduce cost, and increase efficiency while ensuring transportation safety.

Abstract:A smart vehicle decision-making model based on deep reinforcement learning and risk assessment is proposed to solve the problem of safe driving decisions for vehicles in highway environments. Firstly, a Bayesian based position uncertainty quantification method is proposed for modeling and quantifying driving risks; Then, a self attention mechanism is introduced into the decision model to help vehicles perceive potential dangers in complex scenes and avoid dangerous decision execution; Finally, a simulation environment was constructed on the Highway env simulation platform, and the model was trained and tested using simulation experiments. Multiple experimental comparisons were also designed. The results show that the proposed RA-PPO-Mul model achieves 98% safety rate and higher driving efficiency, which is superior to the traditional reinforcement learning model and the model that only introduces a single module.

Abstract:Addressing the challenges of highway pavement defect, such as diverse categories, significant scale variations, and high background complexity, an improved YOLOv7-based highway pavement defect detection algorithm is proposed. Firstly, an explicit vision center module is integrated into the neck network to comprehensively capture both global and local information of input features, thereby enhancing the feature extraction capability for small targets. Secondly, a feature fusion module RFECSP, is designed to mitigate the issue of low detection accuracy caused by the loss of detail information and interference from irrelevant background regions, by reinforcing the feature fusion for multi-class and multi-scale defect. Finally, the MPDIoU loss function is employed to further improve the network's convergence speed and detection accuracy. The results demonstrate that the algorithm exhibits excellent effectiveness in detecting roadway pavement defect, effectively meeting the requirements for detecting cracks or potholes in highway pavements.

Abstract:Accurate prediction of the state of health (SOH) of power batteries was essential for extending the service life of new energy vehicles and ensuring driving safety. To address the limitations of BP neural networks in feature extraction, sensitivity to initial parameters, and local optima issues, a WPD-GA-BP-based prediction method was proposed. First, feature parameters were extracted using capacity increment analysis, and key features related to SOH were selected using Pearson correlation. Next, wavelet packet decomposition was applied to multi-scale reconstruct the label values, enriching the feature set. Finally, a genetic algorithm optimizes the BP neural network’s initial weights and thresholds, avoiding local optima and improving prediction accuracy. The results show that, compared to the pre-improvement WPD-BP and BP models, WPD-GA-BP reduces the maximum error to less than 1.5%, significantly improving prediction performance. It outperforms SVR and LSTM models, achieving the highest R2 and the smallest MAE and RMSE, demonstrating stronger accuracy and stability in predicting power battery SOH.

Abstract:In order to recover the mechanical energy during the vibration of the vehicle suspension, a vibration mechanical energy recovery was conducted based on the designed vibration energy harvesting magnetorheological (MR) damper and charging circuit module. The proposed vibration energy harvesting MR damper is modeled for power generation performance based on COMSOL software, and the charging capability for 1.2 V lithium battery is also analyzed combined with Simulink for co-simulation. The full-bridge rectifier circuit is designed and fabricated, and the experimental test system is also built. The generating electricity abilities of the induction coils in series are tested under the sinusoidal displacement excitation with frequency of 4 Hz and amplitude of 8mm. The test results show that the induction coils in series can generate power of 0.13 W, and it is lower than the simulated value of 0.22 W. The reason is that the mechanical vibration energy is relatively weak and there exists circuit loss. In addition, the charging energy from the damper to the 1.2 V lithium battery is about 1.44 mAh within 40 s, and it needs 1 667 s to be fully charged. The relevant results show the developed MR damper has a good charging ability.

Abstract:In order to achieve rapid and accurate testing of the longitudinal loads of open-top wagons for heavy haul, the theory of grid-insensitive structural stress method was introduced. A calculation method for dynamic structural stress under multi-channel dynamic excitation was proposed, and a scheme for finding strain measurement points of the longitudinal load of the vehicle body based on modal decoupling was formed. The dynamic response test during the running on the railway line was carried out. Taking the data of the tested dynamic strain measurement points as the simulation target, the longitudinal dynamic load of the vehicle body was identified by using the load inversion method with time-domain iteration. The results show that: for the C70E open-top wagon, the modal decoupling measurement points of the longitudinal load are located behind the center plate of the vehicle body, with a horizontal distance of 115 mm from the small cross beam on the floor and a vertical distance of 135 mm from the upper cover plate of the center sill; the longitudinal load inverted under the dynamic excitation system has the same waveform as the longitudinal load tested by the traditional coupler. Due to the absence of the influence of the coupler buffer, the coupler force load obtained by inversion under the dynamic excitation system is more accurate than that of the traditional coupler testing method. The longitudinal load inversion method based on the vehicle body strain can conduct rapid testing on the premise of ensuring accuracy, providing an important means for the longitudinal load testing of railway freight vehicle bodies in the future.