Search Results (310)

Conventional drilling and coring methods are inherently limited to providing one-dimensional geological data, which hinders accurate characterization of the spatial distribution of rock mass structures and properties. Mechanical disturbances during drilling often cause core breakage, further compromising the fidelity of in situ geological representation. This study proposes an integrated approach combining borehole optical imaging and GPR to enhance the characterization of rock mass structures. A dynamic exploration method is introduced, defined as an adaptive drilling layout workflow based on phased information feedback. The fundamental concept, key assumptions, boundary conditions, and field implementation procedures of this dynamic survey are systematically described. The integrated method is applied to a high-speed railway investigation project in the Tengzhou section, Shandong Province, China, where six boreholes were surveyed using both techniques. Results demonstrate that fused analysis of borehole optical images and GPR data effectively reveals rock morphology, fracture distribution, joint systems, and fractured zones. Optical imaging provides high-resolution orientation data at the borehole wall. Borehole GPR extends detection radially into the surrounding rock mass. Together, the two methods enable spatially enhanced characterization and partially mitigate the azimuthal ambiguity inherent in single-borehole radar measurements. A triangular borehole survey scheme is shown to be feasible for locating subsurface anomalies. The proposed method effectively reduces borehole requirements compared to conventional grid layouts. Through the integrated analysis of optical imaging and GPR data, common anomalous features can be successfully identified. The method demonstrates practical applicability for detecting fractures with apertures greater than 1 cm and meter-scale cavities. Good consistency between the two techniques validates the feasibility of this integrated approach. The method’s limitations, including resolution constraints and detection omission risks, are explicitly acknowledged, and risk control strategies are proposed. Overall, the dynamic exploration approach reduces investigation costs and accelerates project timelines. It also provides a practical framework for the spatial characterization of rock mass discontinuities with minimal borehole requirements. Full article

The impact of short-distance lateral shield tunneling threatens the safety of operational high-speed railways (HSRs). To address the engineering challenge of “how to select isolation pile density under fixed cost constraints,” this study focuses on the Xi’an Metro shield tunnel section passing laterally adjacent to the Daxi and Zhengxi Passenger Dedicated Lines. Under the constraint of identical total economic costs, two isolation pile schemes—low-density and high-density—were established to investigate the control patterns of different densities on HSR bridge piles and surrounding ground surface deformation. A three-dimensional (3D) numerical model was developed for the lateral shield tunneling process. Combined with field-measured data, numerical simulations were conducted for corresponding construction stages to analyze the disturbance effects of shield tunneling on HSR piers and the surrounding ground, as well as the deformation restraint performance of isolation piles. The results indicate that the high-density isolation pile scheme (pile spacing: 2.0 m; pile length: 22 m) provides superior control compared to the low-density scheme (pile spacing: 4 m; pile length: 28 m). Following single- and double-track excavation, the vertical displacement of HSR piers was reduced by 0.6 mm and 1.1 mm, respectively—a reduction of 40–74%. Furthermore, the pier displacement along the depth direction shifted from non-uniform to relatively uniform. The difference in surface settlement between the two schemes was only 0.2 mm, suggesting that isolation pile density has a marginal impact on ground deformation. The horizontal displacement of high-density isolation piles stabilized at 1.7–1.9 mm, with vertical heave ranging from 1.2 to 1.4 mm. The lateral displacement profile exhibited a regular “double-C outward expansion” shape, which is better suited to the characteristics of water-rich sand layers. Initial excavation causes significant disturbance to the original strata, necessitating enhanced stress field protection measures. The high-density scheme is recommended for engineering applications, as it achieves optimal control of bridge pile deformation under cost constraints and meets regulatory specifications. Full article

Reliable high-precision positioning in railway tunnels is essential for intelligent train operation and safety monitoring, yet GNSS signals are severely degraded by blockage and multipath. This paper proposes a deployment-oriented numerical framework to optimize pseudolite layouts in tunnels by explicitly modeling visibility obstruction and controlling worst-case geometry along the train trajectory. A high-fidelity 3D tunnel–train model is established, in which line-of-sight (LoS) availability is screened under vehicle occlusion and trajectory-level geometric quality is evaluated accordingly. Instead of optimizing only the average PDOP, the proposed framework minimizes the trajectory 90th-percentile PDOP (qPDOP) to suppress tail-risk geometric degradation, while interpreting PDOP as an error amplification factor that directly affects positioning reliability under measurement noise and local multipath. The core contribution is a Voronoi-partition-constrained improved genetic algorithm (IGA) for tunnel pseudolite deployment. Voronoi partitioning enforces segment-wise coverage by requiring at least one pseudolite in each partition cell and avoids clustering-induced blind zones. Meanwhile, the IGA incorporates improved search and constraint-handling mechanisms to satisfy practical engineering requirements, including feasible installation regions, minimum spacing, mounting-face balance (ceiling/side walls), communication range, and continuous satellite visibility. Comparative simulations and ablation studies demonstrate that the proposed method achieves more uniform coverage and significantly improves full-trajectory geometric stability, reducing high-quantile PDOP and mitigating local spikes in occlusion-sensitive sections under cost-constrained sparse deployments. The proposed framework provides a practical and flexible toolchain for designing positioning-oriented pseudolite infrastructures in underground transportation environments. Full article

To address the challenge of surrounding rock instability in deep-buried tunnels crossing fractured fault zones, this study focuses on the Xigu Tunnel of the Lanzhou–Hezuo Railway. A combination of laboratory triaxial tests, an optimized multi-source advanced geological prediction workflow, and a site-specific parameter-weakened Mohr–Coulomb numerical simulation is employed to systematically reveal the physical–mechanical properties, spatial distribution, and deformation response of fractured rock masses under excavation-induced disturbance. The triaxial test results show that the average peak strength of the surrounding rock reaches 149.04 MPa; however, significant variability is observed among samples, and the failure mode exhibits a typical brittle–shear composite feature. The measured cohesion and internal friction angle are 20.57 MPa and 49.91°, respectively, indicating high intrinsic strength of individual rock blocks. Nevertheless, due to the presence of densely developed joints and crushed structures, the overall mass is loose and highly sensitive to dynamic disturbances such as blasting and excavation, revealing a unique mechanical paradox of high-strength rock blocks with low overall rock mass stability in deep-buried fractured zones. Joint TSP (Tunnel Seismic Prediction Ahead) and ground-penetrating radar (GPR) prediction reveals decreased P-wave velocity, increased Poisson’s ratio, and intensive seismic reflection interfaces; a quantitative index system for identifying the boundaries of narrow deep-buried fractured zones is proposed based on these geophysical characteristics. Combined with geological face mapping, these results confirm the existence of a highly fractured zone approximately 130 m in width, characterized by well-developed joints, heterogeneous mechanical properties, and localized risks of blockfall and groundwater ingress. The developed numerical model, with parameters weakened based on triaxial test and geological prediction data, effectively reproduces the deformation law of the fractured zone, and the simulation results agree well with field monitoring data, with peak displacement concentrated at section DK4 + 595, thus accurately identifying the center of the fractured belt as a key engineering validation result of the integrated technical framework. During construction, based on the identified spatial characteristics of the fractured zone and the proposed targeted support insight, enhanced dynamic monitoring and targeted support measures at the fractured zone center are required to ensure structural safety and long-term stability of the tunnel. This study develops an integrated engineering-oriented technical framework for deep-buried tunnels crossing narrow fractured zones, and provides novel mechanical insights and quantitative identification indices for such complex geological engineering scenarios. Full article

This study conducts an in-depth investigation into the left–right lifting height deviation in the main lifting and lining device of the SQS-300K tunnel and bridge clearance cleaning vehicle under specific working conditions. Through field measurements and theoretical analysis, the research highlights the typical characteristics of this issue in transition curves (with a maximum deviation of 50 mm) and its adverse effects on track geometry. A systematic hydraulic–electrical synergistic optimization scheme using independent cylinder control is proposed to address the problem. Field tests show that the maximum deviation is reduced to below 10 mm after optimization. The findings not only resolve the technical challenges encountered in the field application of the SQS-300K machine but also provide a theoretical foundation and practical technical support for the optimized design, precise control, and condition maintenance of lifting and lining devices in similar large-scale railway maintenance machinery. This contribution is significant for ensuring railway operational safety. Full article

Large-span bridges with bluff body girders are susceptible to vortex-induced vibration (VIV) due to their low frequency, light mass, and relatively low damping ratio, affecting fatigue life and serviceability. While research progress has been made on VIV mechanisms and control measures, systematic investigations on the application of vortex generators (VGs) to narrow Π-shaped railway girders remain scarce, and the potential synergistic effect of combining VGs with conventional aerodynamic measures has not been explored. To address this gap, wind tunnel tests were conducted on a 1:50 scale sectional model of a narrow Π-shaped steel girder for a railway cable-stayed bridge. The experimental program systematically investigated the VIV response of the original girder and evaluated the suppression effectiveness of conventional aerodynamic measures (vertical stabilizers, deflectors, modified fairings) and spanwise control using VGs. Parametric optimization of VG height (0.1 H–0.2 H, where H is the girder height), spacing (2/3 L₀ and L₀, where L₀ = 12.5 m is the standard segment length), and installation position (upper fairing, lower fairing, girder bottom) was performed. Results show that under wind angles of attack from −5° to +5° and a damping ratio of 0.36%, the original girder exhibits pronounced vertical VIV with a maximum RMS amplitude of 0.025 m, approximately 3.15 times the code limit. Conventional measures alone fail to adequately suppress VIV. However, the optimal combination of VGs (height 0.2 H, spacing L₀, installed on the lower fairing) with a 0.5 m wide, 15° inclined deflector effectively suppresses VIV under wind AOAs of 0°, ±3°, and –5°, achieving suppression below the measurable threshold. This study contributes the first comprehensive parametric investigation of VGs for narrow Π-shaped railway girders, reveals a synergistic effect when combining VGs with deflectors, and incorporates practical engineering constraints (such as aesthetic requirements) into the optimization process. Full article

Active support systems are being increasingly applied in the control of large deformation in soft rock tunnels, and exploring the bearing characteristics of prestressed anchor bolts is of great engineering value for improving the long-term stability of tunnel structures. To address the problems of insufficient quantitative characterization of the bearing performance of prestressed anchor bolt support in soft rock tunnels and the difficulty of small-scale model tests in revealing the synergistic bearing law of support and surrounding rock, this study took a 350 km/h double-line high-speed railway tunnel as the prototype and established a large-scale tunnel structure model test system to conduct comparative tests under three working conditions: unsupported, ordinary bolt support, and prestressed anchor bolt support. By monitoring the tunnel failure process and mechanical response of the support structure throughout the test, the failure modes, bearing capacity, deformation characteristics, and axial force distribution of anchor bolts of tunnels under different support forms were systematically analyzed to quantitatively reveal the active support mechanism and bearing strengthening effect of prestressed anchor bolts. The results show that the design bearing capacity of the tunnel model with prestressed anchor bolt support is increased by 127.3% and 31.6% compared with that of the unsupported and ordinary bolt support models, and the ultimate bearing capacity is increased by 120.0% and 43.5%, respectively. Its secant stiffness in the initial loading stage reaches 80.0 kPa/mm, which is five times that of the ordinary bolt support and can effectively restrain the early plastic deformation of the surrounding rock. When the design bearing capacity is reached, the tensile stress of prestressed anchor bolts accounts for 40.2~69.8% of the ultimate tensile strength, with a more uniform axial force distribution and a much higher utilization rate of material mechanical properties than ordinary anchor bolts, which can fully mobilize the bearing potential of deep rock mass and realize the synergistic bearing of support and surrounding rock. This study accurately quantifies the bearing strengthening law of prestressed anchor bolts on tunnel support systems and clarifies the core mechanism of their active support. The research results provide important experimental basis and theoretical reference for the optimal design and engineering application of prestressed anchor bolts in soft rock tunnel engineering. Full article

Taking the Daliang Tunnel of the Lanzhou–Xinjiang High-speed Railway crossing a reverse strike-slip fault as the engineering background, seismic damage investigations of the Daliang Tunnel and other cross-fault tunnels under earthquake action were conducted. Using 1:50 meso-scale model tests, experimental analyses were carried out on the lining strain response, internal crack development and failure, and surrounding rock pressure variation during fault dislocation. The failure modes and mechanisms of tunnels crossing reverse strike-slip faults were thoroughly explored. Meanwhile, a three-dimensional numerical model of the Daliang Tunnel was established to investigate the influence of dislocation modes with structural zonation within the fault zone on the surrounding rock response. The results indicate that the damage and strain response of the tunnel lining are mainly distributed within the fracture zone, predominantly characterized by combined oblique shear and compression failure. Due to the displacement of the lining induced by strong surrounding rock movement, surrounding rock pressure exhibits considerable variation at the boundaries of the fracture zone, accompanied by certain void detachment phenomena. The overall deformation of the tunnel crossing the reverse strike-slip fault presents an “S”-shaped pattern, which is consistent with the numerical simulations. The compression and dislocation morphology of the sidewalls within the rupture surface is in good agreement with the point cloud plan view. The compressive deformation and strain of the surrounding rock are most significant within the rupture surface. Meanwhile, the soft-to-hard transition segments between the new fracture zone and the rupture surface, as well as between the rupture surface and the influence zone, exhibit a trend of first decreasing and then increasing. Full article

Prefabricated lining is increasingly used in railway tunnels due to its advantages of environmental friendliness, high construction efficiency, and convenience. However, the existence of block joints weakens structural integrity, and the segmentation optimization of prefabricated lining remains a challenge especially for irregular lining. Based on the Yongfengcun tunnel in the Fuzhou Ganghou Railway Project, the nonlinear mechanical behaviors of joint stiffness were investigated under axial force, bending moment and shear force. A beam–spring model was established by considering the bending and shearing stiffness of block joints, and the mechanical behaviors were analyzed efficiently by Python 3.9 and ABAQUS 2025 for 572 segmentation schemes. Based on a Delphi questionnaire, three key indicators including horizontal convergence, bending moment amplitude and length variance were selected as independent optimization objectives. The stable Pareto frontier was obtained using the NSGA-II algorithm. Application in the Yongfengcun tunnel fully verified the effectiveness of the method. Full article

Accurate and reliable train localization is critical for rail safety, particularly on regional and rural lines where traditional track-based infrastructure (e.g., balises, track circuits) is often too costly. Global Navigation Satellite Systems (GNSSs) offer a potential solution, but their performance degrades significantly in obstructed environments such as tunnels, forested areas, and deep cuttings commonly present on rail. This study presents a real-world case study of a GNSS-only navigation performance measurement on a regional railway track. Using a mass-market GNSS receiver and a high-precision reference system, the study analyses the position accuracy. Results highlight the limitations of GNSS-only navigation, particularly in meeting accuracy requirements for critical applications such as track distinction. To address these challenges, the study presents a comparative review of Alternative Positioning, Navigation, and Timing (A-PNT) methods. The technology level points to a multi-sensor fusion approach to ensure resilient, cost-effective rail localization for future intelligent and autonomous rail systems. Full article

To elucidate the evolutionary patterns and influencing factors affecting the stability of the surrounding rock during tunnel excavation in ductile shear zones, this study takes the tunnel section within the ductile shear zone of the mountain area as a case study. Numerical simulation methods were employed to analyze vertical deformation, plastic zone development, and stress redistribution characteristics of the surrounding rock under a three-step excavation approach. Furthermore, this research investigates how burial depth and surrounding rock grade impact stability. The findings indicate that during the tunnel excavation process, the vertical deformation, plastic zone, and extrusion deformation at the face exhibit significant phased characteristics. Notably, the weak zone of the fractured surrounding rock serves as a concentrated area of deformation. Upon completion of the excavation, the maximum settlement observed at the arch top reached 246.07 mm. The plastic zone primarily experienced shear failure and showed a tendency to stabilize after reaching section Y = 35 m during excavation. The burial depth exerts a significant influence on the stability of the surrounding rock. As the burial depth increases from 400 m to 550 m, there is an observable upward trend in the settlement at the top of the arch, uplift at the bottom of the arch, and maximum principal stress; notably, the rate of increase for maximum principal stress remains stable. The instability mechanism of the surrounding rock, primarily characterized by shear failure, has not altered. The classification grade of the surrounding rock serves as a critical factor influencing stability. The vertical deformation scale, extent of plastic zones, and values for maximum principal stress in Grade IV surrounding rock are considerably smaller than those observed in Grade V. Enhanced mechanical properties and integrity within the rock mass can significantly improve stability conditions for surrounding rocks. These research findings provide a theoretical foundation and engineering reference for optimizing support systems in tunnels traversing ductile shear zones. Full article

When a tunnel traverses an inclined coal seam, the coal-tunnel angle α of the seam significantly alters the stress distribution in the surrounding rock, its failure mode, and the loading conditions on the support structure. This study investigates the influence of coal-tunnel angle α on surrounding rock stability and support structure loads, with the No. 1 Meijiaxiang Tunnel on the Wengma Railway in Guizhou Province serving as the engineering case. An integrated approach combining laboratory tests, numerical simulations, and engineering verification is employed. Laboratory tests were conducted to determine the basic mechanical properties of the limestone and coal. A refined 3D finite element model was developed in MIDAS GTS NX to analyze the effects of coal-tunnel angle α (α = 30°, 45°, 60°, 75°, 90°) and different construction methods on surrounding rock deformation, plastic zone development, and the stress state of the initial support. The results indicate that the coal-tunnel angle α significantly influences tunnel stability. Both crown settlement and the plastic zone extent decrease notably as α increases. Among the construction methods, the reserved core soil method most effectively controls surrounding rock deformation, but induces greater stress concentration in the initial support. Furthermore, for the most unfavorable case (α = 30°), an optimization analysis of the cyclic advanced length for the reserved core soil method was conducted. It is shown that using an 8 m advanced length can effectively control settlement while significantly reducing support stress and bolt axial forces. With its integrated methodology and detailed parameter analysis, this study provides a valuable theoretical and practical reference for optimizing the design and ensuring the safe construction of similar tunnels traversing inclined coal seams in complex soft–hard interbedded strata. Full article

Point cloud technology, characterized by its high-precision 3D geometric acquisition in complex railway environments, has become a cornerstone for the intelligent detection, monitoring, and maintenance of railway infrastructure. This paper provides a systematic review of point cloud applications across critical railway scenarios, encompassing track geometry extraction, infrastructure component identification, tunnel and bridge modeling, clearance and encroachment analysis, and structural condition monitoring. We evaluate various mobile and stationary acquisition platforms alongside their typical data processing workflows. Furthermore, this review synthesizes cutting-edge advancements in processing algorithms, with a focus on feature extraction, semantic segmentation, and the transformative impact of deep learning and artificial intelligence on data fusion. Notably, the paper explores the synergy between point clouds and computational mechanics, specifically the construction of high-fidelity digital twins through multi-physics coupling to enable real-time simulation of structural stress distribution and damage evolution. We critically analyze persistent technical bottlenecks, such as acquisition efficiency, monitoring precision, data fragmentation, environmental interference, and the complexities of multi-modal data fusion. Finally, the paper outlines future research trajectories, focusing on autonomous intelligent sensing, multi-sensor integration, and the comprehensive digital transformation of railway infrastructure management, aiming to provide a robust theoretical framework and technical roadmap for the sustainable intelligentization of global railway systems. Full article

During the excavation of the Guadarrama railway tunnels, part of the Spanish high-speed rail network (AVE), distinct wear patterns were observed among four types of disc cutters employed in tunnel boring machines (TBMs). The central question addressed in this study is whether the differences in wear—specifically in the Abrasivity Value Steel (AVS) recorded for the four cutter types—are attributable to variations in their inherent wear resistance or to the variability of the tested lithologies and the testing procedures. If the latter hypothesis is confirmed, it would imply that substituting one cutter type for another would not result in significant changes in consumption rates, and that the observed variations would be primarily associated with lithological differences rather than cutter design. This paper presents a real case study concerning the selection of disc cutters for two TBMs used in the excavation of the Guadarrama tunnels. The rock mass encountered consisted predominantly of granite and gneiss. Full article

Dense and complex underground structures impose stringent requirements on shield tunneling. In the close-proximity construction of super-large-diameter shield tunnels, challenges may arise, including adverse impacts on the normal operation of existing structures, as well as difficulties in ensuring the bearing capacity and deformation control of these structures during excavation. This study, based on the stratigraphic conditions of the Chengdu area, employs FLAC3D 7.0 version software to simulate the section where the Shuanghua Road Tunnel underpasses both Metro Line 10 and the Chengdu-Guiyang High-Speed Railway. The main conclusions are as follows: (1) Tunnel underpassing induces uneven settlement in the metro tunnel, with a maximum settlement reaching 47.7 mm. The settlement trough exhibits a twin-peak morphology during dual-line construction. When a single super-large-diameter tunnel line crosses the existing structural cluster, the maximum settlement is located directly above the crossing point. During dual-line crossing, the maximum settlement shifts towards the midpoint between the two new tunnel lines. (2) As the left line of the new tunnel approaches the existing structure, the cross-sectional deformation of the existing structure is “pulled” towards the direction of the excavated new tunnel. After the new left line moves away, the cross-sectional deformation gradually recovers to a bilaterally symmetrical state. (3) The tunnel cross-section undergoes dynamic “compression-tension” convergence changes during the construction process, with a maximum longitudinal tensile convergence of −1.28 mm. (4) During the underpassing of the existing structural cluster by the super-large-diameter tunnel, the maximum torsion angle is approximately −0.016°, occurring at the moment when the shield machine head first passes directly beneath, located directly above the new tunnel. The torsion angle of the existing structure is greatest during the first underpassing event, and the maximum torsion angle during the second underpassing is lower than that during the first. This study reveals the composite deformation mode of “settlement-convergence-torsion” during the underpassing of existing structural clusters by super-large-diameter shield tunnels, providing a theoretical basis for risk control in similar adjacent engineering projects. Full article