To explore the influence of grout rheological properties on the backfill grouting process, a rotational viscometer was first employed to measure the rheological behavior of cement-based grouts with different ratios, analyzing the effects of various ratios on rheological parameters. Subsequently, combined with Herschel-Bulkley model and fluid simulation software, a numerical model for backfill grouting was established. Finally, the grouting process and effectiveness under the influence of factors such as location and number of grouting holes, grouting pressure, and grout ratios were investigated. The results indicate that yield stress and consistency coefficient are primarily affected by the water-binder ratio, but this influence diminishes when the water-binder ratio exceeds 0.85. The rheological index is noticeably influenced by the water-binder ratio, bentonite-water ratio, and cement-fly ash ratio, yet exhibits poor regularity. During grout filling, the top region undergoes 4 stages of evolution, whereas other regions experience only 2 stages. Positioning grouting holes near the vault can improve the filling effectiveness in the top region, and increasing the number of grouting holes accelerates the filling rate but reduces the total grout volume during the rapid growth stage. Increasing the water-binder ratio or decreasing the bentonite-water ratio reduces yield stress, thereby enhancing filling speed and volume. Increasing grout density delays early-stage filling but benefits the accumulation of total grout volume in later stages. Since excessive pressure at middle grouting holes suppresses later-stage filling speed and volume, achieving optimal filling performance requires the maximum pressure at upper grouting holes and minimum pressure at middle grouting holes.

To clarify the stress characteristics and failure mechanism of inclined bolt joints in subway shield tunnel segments, firstly, full-scale tests were designed and carried out on 2 adjacent segment standard blocks based on the supporting engineering. The stress-strain development law of concrete in each part of the inclined bolt segment joint during bearing was analyzed, and the failure process of the segment joint was studied in stages. Then, a numerical model was established to compare the failure process and characteristic change laws of segment joints under 2

To address the engineering problem of aggravated micro-pressure wave hazards at the portal of a 400 km · h^-1 high-speed railway tunnel, this study investigates the radiation characteristics of micro-pressure waves under the coupled effects of actual terrain and buffer structures. Based on the three-dimensional unsteady compressible Navier-Stokes equations and the SST k-ω turbulence model, and using the tunnel equivalent diameter D (10 m) as the characteristic scale, the study systematically examines the radiation characteristics, including peak wave pressure, waveform, attenuation laws, and spatial directivity, of micro-pressure waves under conditions with and without buffer structures at the tunnel exit; it also studies simple flat terrain and semi-cut-semi-fill actual terrain. The results show that the buffer structure pre-radiates micro-pressure waves through side openings, effectively reducing the intensity of micro-pressure waves in the axial direction (directly in front of the tunnel alignment, azimuth θ=0°) at the tunnel portal. The buffer structure effectively reduces the peak value and alters the waveform at 2D, but causes an increase in peak value at 8D, and also enhances micro-pressure waves in lateral directions (e.g., θ=+45°, +90°). Terrain variation has a relatively weak influence on micro-pressure waves in the tunnel axis direction but significantly affects the areas on both sides: the peak micro-pressure wave at the cut (θ>0°) is greater than that on simple flat terrain, while the peak at the fill (θ<0°) is the lowest. The cut slope has a concentrating effect on micro-pressure waves in the area below the cut top, whereas the fill terrain disperses the propagation paths, leading to lower peak values. The attenuation rate of micro-pressure waves is smallest along the tunnel axis and accelerates significantly as the azimuth angle θ increases; for the same azimuth angle, the attenuation at the cut is greater than that at the fill. The directivity of micro-pressure waves is significantly influenced by the buffer structure and actual terrain. When the propagation distance reaches 5D, the influence of the buffer structure becomes negligible, and terrain dominates the directivity - simple flat terrain exhibits axial directivity, while the semi-cut-semi-fill terrain shows directivity in the [0°, +45°] interval due to the concentrating effect of the cut and the dispersing effect of the fill. The research results provide an important theoretical basis for optimizing and design of buffer structures and terrain treatment at the portals of 400 km/h high-speed railway tunnels.

By means of three-dimensional CFD numerical simulation method, the spatiotemporal distribution law of aerodynamic pressure on the tunnel wall and vehicle surface in the horizontal and vertical directions during single vehicle passage and double vehicle intersection of CR400 EMU with a speed of 400 km ∙ h^-1 is studied, and the negative pressure area and boundary conditions on the tunnel wall and vehicle surface are quantified. The results indicate that the aerodynamic pressure inside the tunnel can be correlated with parameters such as vehicle type, train speed and tunnel length to form a theoretical model. When different types of single vehicle pass through the tunnel at a speed of 400 km ∙ h^-1, the difference in peak aerodynamic pressure acting on the tunnel wall is limited. Compared with the CR400BF EMU, the CR400AF EMU only increases the positive peak of aerodynamic pressure by 1.1% and the negative peak of aerodynamic pressure by 0.9%. The aerodynamic pressure on the surface of the EMU shows high uniformity in both the horizontal and vertical directions. During single vehicle passage and double vehicle intersection, the surface of the vehicle body is basically in the same pressure state at the same time. At different tunnel lengths, when the speed of the EMU is 400 km ∙ h^-1, the negative pressure of the expansion wave at the center of the tunnel and the negative pressure of the high-speed train body itself are superimposed when a single vehicle passes through the tunnel, and the negative peak value of the aerodynamic pressure borne by the body reaches -4.60 kPa. When 2 vehicles intersect at different positions with a constant speed inside the tunnel, the maximum negative pressure occurs at the intersection condition of the tunnel center, and the negative peak value of the aerodynamic pressure reaches -9.68 kPa. When 2 vehicles intersect at a constant speed in the center of the tunnel, there is an unfavorable velocity boundary that significantly strengthens the negative pressure effect in the intersection negative pressure area.

To address the mechanism analysis and treatment of inverted arch uplift and track slab cracking in an in-service tunnel, a combined approach of field structural disease characteristic analysis and laboratory tests was adopted to explore the disease mechanism of inverted arch uplift deformation and track slab cracking in an in-service tunnel of the Shanghai-Kunming Railway. According to the analysis of structural cracking characteristics and disease mechanism, integrated treatment measures of "grouting anchor pipe installation - bedrock grouting and removal - reconstruction of inverted arch structure" was proposed. These measures were adopted to guide the construction of the background project, and the evolution laws of the contact stress between the bedrock and the inverted arch was monitored and analyzed during the construction process. The results indicated that: the expansion deformation of bedrock upon water exposure was the main cause of local uplift of the inverted arch and other supporting structures, leading to increased internal forces, uneven deformation, and cracking; factors such as bedrock bearing capacity reduction, stress concentration induced by local high in-situ stress, and uneven stiffness and stress distribution in the invert arch structure further exacerbated the risk of non-coordinated deformation and cracking in the bedrock-invert arch system; the contact stress between the bedrock and the reconstructed inverted arch showed a phased evolution pattern, initially increasing slowly and then gradually converging to stability. The average contact stresses at three monitoring sections were 167.83, 169.51 and 165.82 kPa, respectively, which ensured the stability and safety of the tunnel structure. The treatment measures in combination with the disease mechanism analysis effectively prevented and controlled inverted arch uplift and structural cracking in the in-service tunnel. The research results provide a design scheme and engineering application reference for the treatment and prevention of similar engineering diseases.

To investigate the characteristics of the initial compression wave associated with tunnel sonic boom in long high-speed railway tunnels and analyze its correlation with the occurrence of tunnel sonic boom, full-scale tests were carried out in a long tunnel. Taking the formation mechanism of tunnel sonic boom and the propagation path of the initial compression wave as the starting point, the longitudinal distributions of the aerodynamic pressure and pressure-gradient peak of the initial compression wave inside the tunnel before and after the occurrence of sonic boom were comparatively analyzed. The influence of train speed on these peak values during sonic boom occurrence was clarified, and the effects of portal hood configuration and train type on tunnel sonic boom were discussed. The results show that, under the action of nonlinear effects, the initial compression wave is progressively steepened during propagation, thereby inducing tunnel sonic boom. For the tested tunnel, regardless of whether sonic boom occurs, the aerodynamic pressure peak of the initial compression wave along the tunnel longitudinal direction first increases and then decreases. When sonic boom occurs, the pressure peak of the initial compression wave near the train exit end is higher than that near the entry end. Taking a train speed of 340 km · h^-1 as an example, the positive peak, negative peak, and peak-to-peak value of the aerodynamic pressure of the initial compression wave at the measurement point near the exit end increase by 36.53%, 11.22%, and 20.71%, respectively, compared with those near the entry end. With increasing speed, the probability of tunnel sonic boom increases, and the variation rate of the aerodynamic pressure peak of the initial compression wave from the train entry end to the middle section of the tunnel is higher than that at lower speeds. When sonic boom occurs, the pressure-gradient peak of the initial compression wave increases sharply after propagating a certain distance, and the increase near the train exit end is significantly greater than that near the entry end; at 340 km · h^-1, the difference between the two reaches nearly ninefold in the tested tunnel. When sonic boom occurs, the pressure-gradient peak inside the tested tunnel is proportional to the train speed raised to the power of 6.5-9.6, whereas when sonic boom does not occur, it is proportional to the train speed raised to the power of 3.5-4.6. In addition, compared with the recessed portal hood, the oblique portal hood is more effective in mitigating the occurrence of tunnel sonic boom.

The 25 Hz phase-sensitive track circuit faces a broken rail detection problem due to the presence of a bypass path. As a result, the variation law of the receiving end voltage under broken rail conditions has not been clarified in the field operation for a long time. To provide a theoretical basis for eliminating potential safety hazards, based on the multi-conductor transmission line (MTL) modeling method, multiple sections along the bypass path of a 25 Hz phase-sensitive track circuit are equivalently represented as a single bypass section. A six-port network is adopted to analyze the voltage and current relationships between the broken rail section and the bypass section. These sections are linked through the impedance bond (IB) and the earth to form a coupling circuit, which is then used to establish a bypass-path model of the 25 Hz phase-sensitive track circuit and derive the corresponding MTL equations. Based on the principle of transformer mutual-inductance circuits, the voltage and current relationships of IBs at the sending and receiving ends of the broken rail section are analyzed. The boundary-condition parameter matrix of IB is derived, and the longitudinal distribution of voltage and current under broken rail conditions of the 25 Hz phase-sensitive track circuit is obtained. A decoupling algorithm based on the IB boundary-condition is proposed. The bypass-path model and the decoupling algorithm are validated through laboratory and field tests. Considering that the receiving voltage in the bypass path is non-zero under broken rail conditions, the effects of the IB connection scheme, break location, ballast leakage, and cross-bond distance on the receiving voltage are investigated. The results show that, for sections with IBs fully connected, the receiving voltage increases as the break location approaches the mid-section and as the ballast resistance increases. For sections with the sending-end or receiving-end IB disconnected, the receiving voltage increases as the break location approaches the end where the IB remains connected, and it first rises and then falls as the ballast resistance increases. When the cross-bond distance exceeds 2 km, the receiving voltage becomes nearly invariant, and 2 km can be used as a reference value. A higher receiving voltage under broken rail conditions makes broken rail detection more difficult. Therefore, it is recommended that, for sections with fully connected IBs, broken rail detection be tested using a criterion of a 40% drop in receiving voltage, whereas for sections with the sending-end or receiving-end IB connection disconnected, broken rail detection be tested by removing the single-rail connecting wire at the IB-connected end.

To further enhance the intelligent recognition, assessment, early warning, and active prevention and control capabilities of high-speed railways in responding to risks such as natural disasters, perimeter invasion/foreign object intrusion, and external environmental safety, a method for active perception and early warning of the operational environment safety of high-speed railways is proposed based on the concept of active control of high-speed railway operating environment safety. By analyzing the action mechanism and spatiotemporal evolution patterns of the main influencing factors on the operational environment safety of high-speed railways, the disturbance mechanisms of various risk sources on train operation are revealed. On this basis, a situational awareness method for the operating environment safety across full spatiotemporal scenarios is designed, covering refined forecasting of meteorological disasters, multi-modal fusion-based recognition of perimeter invasion/foreign object intrusion, and intelligent perception of external environmental hazards through air-space-ground collaboration. Corresponding intelligent assessment and early warning models are then constructed, and active control and emergency response strategies are formulated. The results show that the accuracy of refined gale situational awareness for wind speed forecasting reaches 93%. Compared with the existing similar intelligent methods, the transmission delay of alarm information from system generation to train's beyond-visual-range terminal display is reduced from 2.364 s to 1.651 s. This method can provide a systematic solution for engineering applications and demonstrate promising prospects for practical implementation.

To optimize the layout of railway rescue trains and enhance railway emergency rescue efficiency in China,the genetic-simulated annealing hybrid algorithm is improved based on the arc risk quantification. First, a multi-dimensional risk quantification evaluation index system for the railway network is constructed. Through the Entropy Weight-TOPSIS method, risk quantification evaluation is conducted on each arc segment of the network. Then, combined with coverage theory, an optimal layout model for railway rescue trains is established with objectives including network rescue coverage rate, rescue time satisfaction, and rescue train layout cost. Secondly, the Multi-Phase Adaptive Simulated Annealing Genetic Algorithm (MP-ASAGA) is designed to solve the model. The solution process is divided into the exploration phase focusing on searching for the global optimum and the development phase focusing on accelerating convergence, with different evolutionary strategies applied in each phase to improve the algorithm's solving performance. Finally, a case study using actual railway network data from a railway bureau in China is conducted for calculation and validation. The results show that compared with the original layout scheme of the railway bureau in the case study, the optimal railway rescue train layout scheme obtained by the proposed method achieves an improvement of 8.99% in network rescue coverage rate, and an improvement of 11.62% in rescue time satisfaction. This method can provide corresponding theoretical support for the layout optimization of railway rescue trains and the enhancement of rescue efficiency.

To address the data security risks arising from the explosive growth of railway passenger transport data, the core lies in achieving intelligent identification and dynamic protection of sensitive information. Then, an intelligent identification technology for sensitive data in railway passenger tickets based on data knowledge base is proposed. Firstly, a three-level knowledge base of "laws and regulations-industry standards-enterprise norms" is constructed. Secondly, combined with historical railway passenger ticket data, a multi-level intelligent identification algorithm for sensitive data is designed, thereby efficiently and accurately identifying sensitive information in multi-modal data. On this basis, the graph technology is finally introduced to construct a data asset and sensitive data lineage graph, and based on the topological relationship of data flow, the efficient propagation of sensitive information labels among related data nodes is achieved. The results show that the sensitive information identification efficiency of the proposed technology reaches about 217 000 messages per second in structured data processing, which is almost twice as high as the traditional solution. In unstructured data processing, through domain knowledge graphs injection, the F₁ value of sensitive entity recognition is increased to 91.24%, and the context misjudgment rate is reduced to 5.88%. The accuracy of text extraction and sensitive information recognition of multimedia images reaches 93.71%. This technology can significantly improve the accuracy and processing efficiency of sensitive data identification in railway passenger tickets.