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Rapid acquisition of rock structure information during tunnel construction is crucial for optimizing subsequent construction strategies and avoiding engineering rock disasters. In this regard, this study proposes the best time to obtain rock structure information on the tunnel face during the construction period. By summarizing relevant studies on rock information acquisition locally and abroad and combining them with the actual situation during the construction of the Lushan Tunnel, this study analyzed the factors affecting the quality of rock information acquisition during the construction period and the approximate range of the optimal timing of acquisition. We also conducted experiments on the concentration of respiratory dust and the concentration of total dust on each section of the Lushan Tunnel construction site and explored the optimal timing of acquiring rock information on the tunnel face by conducting several dust experiments at the construction site. The results showed that the best time to obtain information was before the erection of the steel arch, which was also the best time for the engineers to conduct mechanical characterization of the tunnel face and the lining inspection of the tunnel. The optimal acquisition timing identified in this study is crucial for improving the accuracy of rock information acquisition and guiding subsequent construction programs. [ABSTRACT FROM AUTHOR]

Excess pore water pressure (EPWP) induced by shield tunneling has a significant influence on the stability of the tunnel face, post-construction settlement, and the mechanical behavior of the tunnel lining. However, the three-dimensional and unsaturated property of the soil field is seldom considered in current research. Considering the non-uniform radial convergence model, a modified three-dimensional displacement solution induced by shield tunneling was established first. Then based on unsaturated EPWP elastic theory, a reliable and efficient method is developed to expedite the evaluation of EPWP distribution in three-dimensional saturated and unsaturated clay soil. The validity of the method is confirmed through comparison with field test and numerical outcomes. The analysis examples demonstrate that negative and positive EPWP are generated above the tunnel crown and beneath the tunnel invert, respectively. In the vertical direction, the negative EPWP exhibits a decreasing trend ahead of the heading face and an increasing trend behind it. Along the longitudinal direction, the influence zone of EPWP extends to 1D ahead of and 6D behind the heading face. With the decrease of soil saturation, the EPWP values tend to diminish. The maximum EPWP values observed in saturated conditions can be 16.13 times higher than those under unsaturated conditions. [ABSTRACT FROM AUTHOR]

During the assembly of concrete segments into a tunnel lining, small geometric imperfections are unavoidable. In the longitudinal joints, they lead to contact deficiencies, which affect the eccentricities of the forces transferred through them. This influences the development of internal forces along the lining's circumference. However, it is often not realistically considered in structural calculations. In this paper, the effects of longitudinal joints assembly imperfections on the lining's internal forces were investigated by employing finite element models for various lining configurations. The results show that assembly imperfections have an unfavorable effect on the internal forces in most cases. Depending on the loading situation, this can lead to more required reinforcement and higher utilization ratios in the segments field and joints compared to perfectly assembled linings. Stiffer and less deformable configurations are at higher risk of experiencing more severe effects. In systems at risk, an individual assessment is recommendable. Therefore, a simplified method is introduced that requires a significantly reduced modeling effort and calculation time and lower software capabilities. [ABSTRACT FROM AUTHOR]

This study aims to investigate the influence of the tiny soil arch effect generated by the soil between the steel tubes in the ring direction of the tunnel overrun tube shed on the force deformation of the steel tubes during the working period. By assuming the arch effect axis between the steel tubes is circular and intercepting any three adjacent steel tubes on the tunnel contour line to establish a vertical coordinate system, the equation of the arch axis and the coordinates of the arch top were derived. Referring to the calculation theory of the peripheral rock pressure of the Taishaki tunnel, the peripheral rock pressure borne by the steel tubes of the pipe shed under the consideration of the micro‐arch effect was derived. Assuming the pipe shed acts as a semi‐infinite long beam on Pasternak's two‐parameter elastic foundation, the pipe shed was divided into four sections axially based on the initial support application status and the tunneling position of the working surface. The controlling equations for each section were analyzed and solved. The theoretical deflection curves of the pipe shed were obtained using actual engineering construction parameters and were validated by monitoring the settlement values of the soil layer above the tunnel using multipoint displacement meters. The study shows that the initial support application status and the tunneling position of the working surface significantly affect the functioning mechanism of the pipe shed, causing it to play different roles at different stages. When the working surface advances to the target section, the pipe shed exerts a beam arch effect; when the working surface tunnels beyond the target section, the pipe shed exerts a combined beam effect. The deflection change trend of the pipe shed with the advancement of the working surface is characterized by rapidly increasing, rapidly decreasing, and slowly decreasing stages, with the maximum deflection change occurring above the working surface position. Considering the micro‐arch effect, the theoretical deflection changes are larger and closer to the actual engineering situation compared to the existing theory that does not consider the micro‐arch effect. The results provide theoretical references for the design and implementation of tunnel overrun pipe sheds, moving beyond mere engineering experience and validating new methods for monitoring the deformation of surrounding rock during tunnel construction, effectively ensuring construction safety during tunnel excavation. [ABSTRACT FROM AUTHOR]

This paper presents an IoT-based solution for detecting grouting voids in tunnel construction using the Raspberry Pi microcomputer. Voids between the primary and secondary tunnel linings can compromise structural integrity, and traditional methods like GPR lack continuous feedback. The proposed system uses embedded electrical wires in the secondary lining to measure conductivity, with disruptions indicating unfilled voids. The Raspberry Pi monitors this in real time, uploading data to a cloud platform for engineer access via smartphone. Field tests were conducted in a full-scale, 600 m long tunnel to evaluate the system's effectiveness. The tests demonstrated the system's accuracy in detecting voids in various tunnel geometries, including straight sections, curves, and intersections. Using only the proposed void detection system, the largest void detected post-grouting was 1.8 cm, which is within acceptable limits and does not compromise the tunnel's structural integrity or safety. The system proved to be a cost-effective and scalable solution for real-time monitoring during the grouting process, eliminating the need for continuous manual inspections. This study highlights the potential of IoT-based solutions in smart construction, providing a reliable and practical method for improving tunnel safety and operational efficiency during grouting operations. [ABSTRACT FROM AUTHOR]

Using the complex variable method, an elastic analytical solution of the ground displacement caused by a shallow circular tunneling is derived. Non-symmetric deformation relative to the horizontal center line of the tunnel cross-section is used as a boundary condition. A comparison between the proposed analytical method and the Finite Element Method is carried out to validate the rationality of the obtained analytical solution. Two parameters in the Peck formula, namely the maximum settlement of the ground surface center and the width coefficient of settlement curve, are fitted and determined. We propose a modified Peck formula by considering three input parameters, namely the tunnel depth, tunnel radius, and the tunnel gap. The influence of these three parameters on the modified Peck formula is analyzed. The applicability of the modified Peck formula is further investigated by reference to six engineering projects. The ground surface displacement obtained by the explicit Peck formula is in good agreement with the field data, and the maximum error is only 1.3 cm. The proposed formula can quickly and reasonably predict the ground surface settlement caused by tunnelling. [ABSTRACT FROM AUTHOR]

In order to investigate the stress and strain state of the surrounding rock and the effect of supporting structure of the deep buried tunnel through the fault zone in mountainous area, taking Lianfeng Mountain Tunnel Project as the research background, based on ABAQUS large-scale finite element numerical computation program, the mechanics calculation model of the construction of the deep buried tunnel through the fault zone was established, and the change rule of the structural stress state and the horizontal and vertical settlement rule of the mountain after the tunnel excavation and lining were studied. The results showed that the settlement in the fault zone during tunnel excavation was much larger than that in the normal rock body; the stress difference between the surrounding rock and the peripheral mountain body at the fault zone was larger, and the stress difference at the junction with the normal mountain body was larger; the settlement caused by tunnel excavation affected the range of 50 m, and the settlement at the center of the twin tunnels increased with the increase of vertical height; the excavation of the second tunnel in the construction of the twin tunnels caused the increase of the strain of the first tunnel. [ABSTRACT FROM AUTHOR]

Copyright of Railway Construction Technology is the property of Railway Construction Technology Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Railway Construction Technology is the property of Railway Construction Technology Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Railway Standard Design is the property of Railway Standard Design Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The construction of tunnels excavated by the conventional method in densely populated urban environments requires an adequate characterization of the loads acting on the primary lining during the excavation process, to ensure that the ground is deformed and stresses around the tunnel are relieved, simultaneously complying with the failure and serviceability limits of international standards while minimizing damage to nearby structures. In this paper, common lining design criteria are revisited, through the numerical simulation of an instrumented tunnel section which is part of a 4.5 km long metro line currently under construction in Mexico City. Key needs for improvement in current design approaches are identified. The tunnel was instrumented with load cells, extensometers, and topographical references for convergences and divergences. A three-dimensional finite difference model of the instrumented section was developed, and the load transfer mechanisms between the excavated soil and the primary lining were analyzed. Then, the numerical simulation of the contribution of the secondary lining in the overall stability for sustained load was established, along with the expected ground settlements, which can significantly affect nearby structures. Results gathered from this research are key for updating lining design criteria for urban tunnels built in stiff brittle soils. [ABSTRACT FROM AUTHOR]

Segmental tunnel linings have a complex structural behavior that is difficult to predict. Full-scale in situ structural monitoring allows us to gain access to these structures, observe the acting mechanisms, and better understand the actual structural behavior under realistic boundary conditions. In a recent structural monitoring project in Frankfurt, Germany, strains, deformations, and temperatures were measured at the segmental lining of a twin-tube tunnel boring machine (TBM) tunnel. Hereby, internal forces were back-calculated from the strain measurements. The results of the monitoring are presented and discussed in this paper. The measurements began immediately after the assembly of the segments and have been performed continuously over several years. Because of that, it was possible to observe that the internal forces differ significantly between the construction stage and the final state. During the construction stage, the internal forces develop quickly within hours after ring assembly, showing a distribution along the lining's circumference that is hard to predict. Almost all radial deformations occur during this period and remain unchanged afterward. After this first early phase, a period of stress redistribution follows, including significant changes in the internal forces. At its end, the stable, final state is reached. In this state, the internal forces match better with expectations. In the monitored areas, the stresses during the construction stage slightly exceeded those of the final state, which should be avoided for economic reasons. Additional investigations regard the temperature development within the lining, the influence of the second tube construction on the already built tube, and the development of longitudinal ring interaction over time. The latter significantly influences the structural behavior, but its development is often subject to uncertainties. In this case, it was observed that the longitudinal interaction decreases considerably over time. Practical Applications: In the structural design of segmental tunnel linings, structural or geotechnical engineers have various options regarding the available calculation methods and modeling strategies. All of these options are part of the state of the art, and the selection is up to the engineer. However, the results can be quite different depending on the chosen option. Consequently, uncertainties remain regarding the real linings' internal forces and structural reliability. The actual mechanisms can be identified by investigating the real structural behavior of segmental tunnel linings with in situ structural monitoring. Then, with back-analyses, on the one hand, it can be tested to determine how well different calculation methods and modeling strategies correspond to reality. On the other hand, the monitoring data can contribute to improving existing calculation methods, developing new modeling approaches, and establishing more detailed recommendations or optimizations regarding the design and construction of segmental tunnel linings. This paper presents findings derived from a structural monitoring project on a segmental lining. Different mechanisms and aspects, sometimes uncertain or debatable in tunnel design, are discussed regarding their real in situ appearance. The gained data will also be used for further back-analyses and investigations. [ABSTRACT FROM AUTHOR]

• An effective method is proposed to analyse the longitudinal mechanical response of shield tunnel during its construction. • The influence of the shearing dislocation of circumferential joints on the uplift of shield tunnel is fully considered. • A coefficient is introduced to accurately calculate the dynamic buoyancy generated by the synchronous grouting. • The effect of the equivalent shear stiffness of shield tunnel on the lining uplift is quantitatively analysed. During shield tunnelling, longitudinal deformation occurs in the shield tunnel structure owing to the buoyancy generated by the synchronous slurry, which has adverse effects on the assembly quality and even the structural integrity of the segmental ring structure. However, the current longitudinal beam-like model for analysing the uplift response during shield tunnel construction adopts the Euler–Bernoulli beam to describe the shield tunnel. This model does not consider the shearing dislocation effect, causing errors in the structural longitudinal deformation analysis. In this context, this study proposes a shield tunnelling uplift model based on the Timoshenko beam theory, which can effectively consider the shearing dislocation effect, aiming to evaluate the longitudinal response of shield tunnels more accurately. A Pasternak two-parameter foundation with springs reflecting the resistance of the overburden with different thicknesses was adopted to simulate the supporting effects of the synchronous grouting layer and surrounding soil layer composite on the tunnel, considering the influences of both the shearing effect of the foundation and tunnel buried depth on the shield tunnel uplift. The dynamic buoyancy coefficient, determined through an inverse analysis of the field measurement data, was introduced to accurately calculate the magnitude of the dynamic buoyancy generated by the flow of synchronous slurry. The proposed model was validated by comparing its results with actual measurements. The uplift characteristics of the shield tunnel during construction were obtained by using the proposed model in an actual project. It was found that the longitudinal analysis model for shield tunnel uplift based on the Euler–Bernoulli beam theory underestimates the uplift and overestimates the internal forces generated during shield tunnelling. [ABSTRACT FROM AUTHOR]

Diseases such as voids behind the initial support of the tunnel will lead to problems such as lining rupture and concrete damage in the tunnel structure, which seriously affects the driving safety in the tunnel. In tunnel construction, ground penetrating radar is frequently employed as a method for detecting hidden defects. However, when the cavity size is small, there will be a large error when the original radar data is directly interpreted, which cannot meet the needs of practical engineering. To enhance the precision in tunnel detection, the Finite-Difference Time-Domain method is used to simulate various small cavities of different shapes located behind the primary support lining of the tunnel, and the study involves examining the electromagnetic response characteristics of different kinds of holes. The migration techniques of KIRCHHOFF, F-K, and reverse time are employed to reconstruct the hole target. Furthermore, digital morphology is employed to enhance the clarity of the image. Finally, the edge detection technology is used to further extract the hole features. After that, small cavities of different shapes are buried in the established outdoor concrete model box and radar detection is carried out. The detection position of the reconstructed radar image and the actual position of the cavity in the model box are verified. The results show that compared with KIRCHHOFF migration and F-K migration, the image processed by reverse time migration is clearer and more intuitive, and can restore the contour of small holes well. The research findings can serve as a reference for the interpretation of radar data of the cavity behind the initial support of the tunnel. [ABSTRACT FROM AUTHOR]

The steel rib and the lattice girder are two typical steel arch frames used in the primary lining of the New Austrian Tunnelling Method (NATM) highway tunnel. In the process of tunnel construction, it is necessary to choose the support method according to the mechanical properties, durability, construction difficulty, and economic benefits. In order to analyze the mechanical characteristics of steel arch frames, a loading and measurement test system for steel arch was designed, and destructive tests were carried out on a three-bar lattice girder, four-bar lattice girder, and I-beam steel rib. The steel utilization coefficient was introduced to compare the mechanical properties of the different types of steel frames. The results show that the I-beam steel rib has the largest steel utilization coefficient, but it is not well combined with concrete. Among the lattice girders, the three-bar W-shaped lattice girder uses the least amount of steel under the same load, which reduces the construction cost and is worth applying and popularizing. Additionally, the steel utilization coefficient of different types of lattice girders can be optimized through the ratio of steel bar diameters. It is proved that the steel utilization coefficient can provide a reference for the evaluation and selection of steel frames for the primary lining of highway tunnel engineering. [ABSTRACT FROM AUTHOR]

The segment misalignment is a common defect in the segment installation of a shield tunnel construction, due to the complexity and uncertainty of its construction conditions. This raises a concerning about the safety of the segment lining for the shield tunnel. In this paper, the integrated numerical models with surrounding rock, peastone grouting and segment lining were built using three-dimensional finite element method, by introducing two kinds of misaligned defects of segments. One was the misalignment that elongated the horizontal axis of the transversal ring section of segment lining, another was the misalignment between adjacent rings of segments. To eliminate the impact of boundary on numerical results, seven rings of segments are built for the three-dimensional finite element models, and the middle ring is dealt with for the results analysis under V-class surrounding rock, including the circumferential stress of outer and inner layers of the segment, the contact stress on joint surface between segments, and the stress of locating pins between adjacent rings. Results indicate that the two kinds of misaligned defects create pronounced impact on tensile stress of segment at the bottom and the crown segments, respectively, which produces a greater tensile stress to increase cracking risk even abrupt fracture of segment. However, the misaligned defects have a slight impact on the contact stress and the locating pins stress. Therefore, attention should be paid to the cracking of bottom or crown segments in the segment lining of shield tunnel. [ABSTRACT FROM AUTHOR]

In order to predict groundwater pressure on tunnel linings with embedded drainage networks, as needed in the design of tunnels under high water pressure, a coupled hydraulic model is proposed by incorporating seepage in the surrounding rocks and pressurized flow in the networks. The model is executed using the software Comsol Multiphysics and applied to analyses of a high-speed railway tunnel in China. Comparative analyses indicate that the model is more comprehensive and accurate than existing models in the literature. For rocks with low hydraulic conductivities (< 3 × 10−5 m/s), the water pressures calculated from the existing models are about the same as those from the proposed model; however, for rocks with medium to high hydraulic conductivities (> 3 × 10–5 m/s), the existing models may err on the unsafe side by significantly underestimate the water pressures. Moreover, the more permeable the rock, the greater the underestimation of the water pressure on the lining. Meanwhile, some valuable suggestions for the embedded drainage networks are obtained through parametric analysis based on the proposed model. The proposed model is valuable for designing linings with embedded drainage networks for tunnels under high water pressure. [ABSTRACT FROM AUTHOR]

Current tunnel design provisions do not consider the shear resistance of transverse reinforcement in precast concrete tunnel lining (PCTL) segments. Such reinforcement is often designed as a minimum for shrinkage and temperature resistance. This study evaluated the behavior and shear strength of PCTL segments reinforced with glass fiber‒reinforced polymer (GFRP) bars with and without closed shear ties. A total of five full-scale rhomboidal PCTL specimens with a 1,500 × 250 mm rectangular cross section and an arched length of 2,100 mm were constructed and tested under three-point loading up to failure. The testing parameters included the configuration of the transverse reinforcement (bars versus closed ties), the spacing of closed shear ties, the longitudinal reinforcement ratio, and concrete strength. The load–deflection behavior, cracking, failure mechanisms, shear capacities, and strain in the reinforcement and concrete are discussed herein. The results indicate that all specimens experienced shear failure because of the diagonal tension failure or shear compression mode. The presence of shear stirrups enhanced the structural performance of the GFRP-reinforced PCTL segments. In addition, increasing the closed-tie ratio, longitudinal reinforcement ratio, and concrete strength increased the shear strength of the segments. A comparison between the test results and predictions made with the critical shear crack theory (CSCT) was introduced in the theoretical approach to evaluate the applicability of existing FRP design code provisions. The predictions produced according to FRP design codes can be classified between conservative and nonconservative predictions. The modified CSCT yielded predictions closest to the experimental values with an accuracy of 98%. [ABSTRACT FROM AUTHOR]

To explore the stress state of lining structures in a tunnel traversing a water-rich fault zone, the long-term in-situ stress monitoring of surrounding rock, initial steel arch frames, and secondary lining concrete were conducted in a red-bed mudstone section of a tunnel under construction in Gansu. The force patterns of the tunnel structure were analyzed during the water and mud outburst control period in the water-rich fault. The results show that moisture seepage from the water-rich fault results in a maximum surrounding rock pressure of 498.28 kPa on the crown during construction. Following the application of the secondary lining, the pressure decreases gradually, but the pressure on the inverted arch continues to rise, reaching a peak of 352.75 kPa. The initial steel arch supports display a clear asymmetrical force distribution, with greater force on the upper outer side than the lower. Maximum compressive stress occurs at the crown and right waist, where the right waist experiences bending and breakage due to stress from fault activity. Inside the arch, stress distribution is lower at the top and higher at the bottom, with the greatest compressive stress on the left side of the inverted arch. Overall, the secondary lining concretes comply with the safety factor requirements of tunnel. The crown and right waist, being directly impacted by the water-rich fault, sustain the maximum concrete compressive stress. Continuous moisture penetration from the fault zone to the tunnel's base rock post-construction prolong the stress stabilization period for the inverted arch, increasing the risk of floor heave during long-term operation. It is crucial to monitor the deformation of the tunnel base during operation. These results offer valuable insights for optimizing reinforcement strategies and formulating drainage plans in similar tunnel projects. [ABSTRACT FROM AUTHOR]

Despite significant achievements in the field of tunnel construction, adequate methods for their dynamic calculation under transportation load (loads from moving transport within the tunnel) are still practically nonexistent. Particularly significant challenges arise during the calculation of shallowly embedded tunnels. Using the mathematical modelling method, such a calculation was performed for a tunnel supported by a circular cylindrical homogeneous lining. In the presented work, a shallowly embedded tunnel reinforced with a two-layer lining is considered. When creating the mathematical model, the tunnel is represented as a circular cylindrical twolayer shell located in an elastic half-space. The load-free horizontal boundary of the half-space (ground surface) is parallel to the shell axis. Dynamic equations of elasticity theory in Lamé potentials are used to describe the motion of the internal thick layer of the shell and the surrounding body. The vibrations of the external thin layer of the shell are described by classical shell theory equations. The equations are represented in moving Cartesian and cylindrical coordinate systems associated with a load moving uniformly along the inner surface of the shell. Based on the obtained solution to the problem and numerical experiments, the stress-strain state of the two-layer lining of a shallowly embedded tunnel and the surrounding rock body is investigated under the action of a uniformly moving axisymmetric normal load. It is established that at the ground surface when the lining has a rigid contact with the rock body, the displacements and stresses are lower compared to when the contact is sliding. [ABSTRACT FROM AUTHOR]

Large buried depths, extensive tunnel lines, and challenging geological conditions are characteristics of tunnel construction. There is a rising need for high-quality disaster source prospecting in advance, particularly for water-bearing structures. Due to its high sensitivity to aquatic conditions, the electrical resistivity method is frequently utilized in forward tunnel prospecting. However, the configurations of the electrical resistivity method commonly used in tunnels are limited by the narrow space of the tunnel. Their capacity for depth sounding is constrained, and precise detection is challenging. In light of the requirements of fine detection and the limits of existing methods, as well as the advantages of the borehole resistivity detection method in detection accuracy and depth, we conducted research on three distinct types of borehole resistivity configurations in tunnels. We calculated and analyzed the potential characteristic curves of three different types of borehole configurations, as well as quantitatively evaluated their depth. The model test is made to invert and contrast the information gathered by various gadgets. The advantages and disadvantages of various borehole resistivity settings for tunnels are thus demonstrated. [ABSTRACT FROM AUTHOR]

In order to study the influence of shield tunneling on existing high-speed railway lines. Combined with centrifuge test and three-dimensional numerical simulation, the dynamic response of shield tunnel undercrossing existing high-speed railway tunnel was studied, and the influence of settlement joint and steel pipe pile reinforcement on existing tunnel was analyzed. The results show that: (1) the construction joints of existing tunnels significantly reduce the shielding effect of existing high-speed railway tunnels on the ground; (2) The settlement value of the existing tunnel caused by double-line shield tunnel construction needs to be controlled by steel pipe pile reinforcement to meet the requirements of the specification; (3) The double-line shield tunnel construction has little effect on the internal force of the existing high-speed railway tunnel, and the reinforcement of the high-speed railway tunnel lining meets the stress requirements. [ABSTRACT FROM AUTHOR]

Aiming to address the problem of construction and environmental risks in tunnel construction through the soil–rock mixture backfill area, this paper carried out a seismic dynamic response model test of a pile-supported tunnel based on practical projects. Firstly, the stress–strain curves and failure characteristics of the soil–rock mixture in the study area were obtained through triaxial tests, and based on this, similar materials for the model test were developed. Then, a vibration table model test was devised to investigate the seismic dynamic response of the pile–tunnel structure. The findings revealed the following: when subjected to seismic waves, the soil–rock mixture stratum displayed a "skin effect" in its acceleration response, indicating that closer proximity to the surface led to heightened horizontal acceleration responses; the horizontal peak acceleration of the grouting mixture stratum in the vertical direction exhibited a "Zigzag" pattern; the peak values of strain response and bending moment in the tunnel lining cross-section exhibited an "X" shape and inverted "V" shape, respectively. The bending moment at the pile crown increased alongside the peak value of the input seismic wave acceleration. The maximum surface settlement in the model ranged from 0.5 to 1 cm, with the tunnel–pile structure effectively mitigating surface settlement. [ABSTRACT FROM AUTHOR]

In order to ensure the safety of the Beijing–Shanghai high-speed railway during the construction and operation of the shield tunnel on Line R1 of the Jinan Metro, a numerical simulation of geological disturbance during the underpass of the small-radius stacked tunnel was carried out. We analyzed the mechanism of geological deformation and the construction factors affecting settlement and found that bridge settlement far exceeded safety standards without taking safety control measures. In this regard, safety control technologies such as setting isolation pile sleeve valve pipes, controlling shield tunneling parameters, grouting control technology, and trolley support technology have been proposed. Monitoring was conducted on the uneven settlement of the bridge surface, the internal and external stresses of the pipe segments, and the soil pressure they were subjected to. The results showed that the surface settlement of the bridge after safety control measures was controlled within the safety standard range, and the stress and soil pressure changes of the pipe reinforcement were within the allowable range, further verifying the effectiveness of the safety control measures. [ABSTRACT FROM AUTHOR]

In recent years, to effectively mitigate the issue of urban traffic congestion, tunnels have become widely used new type of road. However, when the soil layer is excavated and disturbed, the resulting vibration affects the safety of the buildings above it, especially for ancient buildings that are very sensitive to vibrations. Taking the White Tower in Hangzhou as an example, in this paper, the vibration response propagation of large-diameter shield tunnel excavation to adjacent ancient towers is studied through field measurements. The vibration response of the unexcavated south line tunnel is predicted by using 3D numerical analysis software, and the optimal construction parameters are obtained. The study found that the frequency domain component of the White Tower bedrock vibration caused by shield tunneling is mainly 5–20 Hz, and the vibration response attenuates significantly beyond 40 m. Further, reducing the propulsive force can reduce the vibration response of the White Tower; therefore, controlling the propulsion and reducing the tunneling velocity can reduce the vibration response. [ABSTRACT FROM AUTHOR]

The confining pressure has a great effect on the internal force of the tunnel. During construction, the confining pressure which has a crucial impact on tunnel construction changes due to the variation of groundwater level and applied load. Therefore, the safety of tunnels must have the magnitude of confining pressure accurately estimated. In this study, a complete tunnel confining pressure time axis was obtained through high-frequency field monitoring, the data are segmented into a training set and a testing set. Using GRU and RNN models, a confining pressure prediction model was established, and the prediction results were analyzed. The results indicate that the GRU model has a fast-training speed and higher accuracy. On the other hand, the training speed of the RNN model is slow, with lower accuracy. The dynamic characteristics of soil pressure during tunnel construction require accurate prediction models to maintain the safety of the tunnel. The comparison between GRU and RNN models not only highlights the advantages of the GRU model but also emphasizes the necessity of balancing speed accuracy in tunnel construction confining pressure prediction modeling. This study is helpful in improving the understanding of soil pressure dynamics and developing effective prediction tools to promote safer and more reliable tunnel construction practices. [ABSTRACT FROM AUTHOR]

The assumption of an isotropic material behaviour is still common practice for tunnel design. Strictly speaking, this assumption is only valid if the influence of directional dependencies on the resulting deformations and stresses is marginal. In lithologies that have a high degree of anisotropy, such as shales and phyllites, the orientation characteristics of material properties such as strength and stiffness should be taken into account in order to avoid serious misinterpretations of the bearing capacity and deformation characteristic of the surrounding rock and the tunnel lining. The main focus is to accurately distinguish between the different types and terminology of anisotropy. [ABSTRACT FROM AUTHOR]

The issue of water seepage poses a significant challenge in tunnel infrastructure. Wet areas are commonly used to evaluate the degree of water seepage in tunnel projects. To investigate the feasibility for numerical simulation to predict a wet area, we selected concrete test blocks with two types of defects—holes and cracks—as the research specimens. Numerical models for various seepage conditions were constructed using TOUGH2, and the results were validated through laboratory experiments. Additionally, the Shenjiamen Subsea Tunnel was simplified into a numerical model, employing TOUGH2 to forecast its future wet area performance within the scope of national standards. The outcomes of our research revealed that point seepage and line seepage exhibited circular and elliptical morphologies, respectively. Moreover, external water pressure and defect size exerted a significant influence on the expansion of the wet area. Notably, the impact of crack width surpassed that of hole diameter. Encouragingly, the numerical models generated using TOUGH2 for unsaturated concrete demonstrated excellent agreement with laboratory test results concerning the geometry, size, and pattern of the wet area. These findings signified the potential of TOUGH2 numerical simulation as a valuable tool in predicting the lifespan of tunnels. [ABSTRACT FROM AUTHOR]

In the context of long-distance cross-basin water transfer projects, the water conveyance tunnel serves as a pivotal component in mitigating regional disparities between economic development and water resources allocation. However, in high seismic-intensity areas of southwest China, geological complexities and densely distributed active faults present formidable challenges. Consequently, the construction of water conveyance tunnels necessitates traversing one or more active fault zones. This study examines the impact of an adaptive tunnel structure in the presence of fault dislocation, focusing on the Xianglushan Tunnel, a constituent of the Central Yunnan Water Diversion Project. Taking the Longpan-Qiaohou Fault F10-1 as a case study, we assess the influence of active faults on the anti-dislocation adaptive structure of the Xianglushan Tunnel, considering factors such as displacement, relative deformation, maximum principal stresses, and longitudinal equivalent internal force in critical tunnel sections. Numerical calculations validate the efficacy of this adaptive structure in reducing induced internal forces and deformations of the tunnel lining. The results show that, under the influence of strike-slip dominated fault movement, one side of the tunnel exhibits tensile stress, with a magnitude of approximately 5 MPa. The maximum normal and tangential deformation of the hinge joint is concentrated in the central section of the fault zone. The incorporation of an articulated adaptive design significantly enhances the stress state of lining under dislocation condition. These research results directly inform the engineering design and construction of water conveyance tunnels traversing active fault regions, providing valuable guidance for related tunnel construction endeavors. [ABSTRACT FROM AUTHOR]

In recent years, point cloud segmentation technology has increasingly played a pivotal role in tunnel construction and maintenance. Currently, traditional methods for segmenting point clouds in tunnel scenes often rely on a multitude of attribute information, including spatial distribution, color, normal vectors, intensity, and density. However, the underground tunnel scenes show greater complexity than road tunnel scenes, such as dim light, indistinct boundaries of tunnel walls, and disordered pipelines. Furthermore, issues pertaining to data quality, such as the lack of color information and insufficient annotated data, contribute to the subpar performance of conventional point cloud segmentation algorithms. To address this issue, a 3D point cloud segmentation framework specifically for underground tunnels is proposed based on the Segment Anything Model (SAM). This framework effectively leverages the generalization capability of the visual foundation model to automatically adapt to various scenes and perform efficient segmentation of tunnel point clouds. Specifically, the tunnel is first sliced along its direction on the tunnel line. Then, each sliced point cloud is projected onto a two-dimensional plane. Various projection methods and point cloud coloring techniques are employed to enhance SAM's segmentation performance in images. Finally, the semantic segmentation of the entire underground tunnel is achieved by a small set of manually annotated semantic labels used as prompts in a progressive and recursive manner. The key feature of this method lies in its independence from model training, as it directly and efficiently addresses tunnel point cloud segmentation challenges by capitalizing on the generalization capability of foundation model. Comparative experiments against classical region growing algorithms and PointNet++ deep learning algorithms demonstrate the superior performance of our proposed algorithm. [ABSTRACT FROM AUTHOR]

With the increasing complexity of engineering environments in tunnel construction, some projects are located in areas with adverse geological conditions, including areas prone to fault movements and other geological hazards. Fiber-reinforced concrete can significantly enhance structural performance in such challenging conditions. Currently, the application of high-performance steel-polypropylene fiber in tunnel linings and its anti-fault performance are quite limited. Therefore, this paper focuses on studying the application of steel-polypropylene mixed fiber-reinforced concrete in tunnel lining under reverse fault movements. In this paper, the constitutive relationship of mixed fiber-reinforced concrete is modified based on literature data. Utilizing the Najar formula, fiber-related variables were designed, and a three-dimensional numerical simulation model of a reverse fault tunnel was established. By designing various parameter combination cases, the structural response of tunnel linings was calculated and studied. then the influence patterns of mixed fiber parameters on the anti-fault performance of tunnel linings are summarized, the relationships between main variables are explored, and a reasonable value range for the two fibers is determined, which can provide guidance for practical engineering. [ABSTRACT FROM AUTHOR]

To examine the distribution of the plastic zone of the surrounding rock subjected to various expansion approaches used for the existing tunnels, this article deals with the distribution and thickness of the plastic zone of the surrounding rock subjected to one-sided expansion excavation (1SEE), two-sided expansion excavation (2SEE), and surrounding expansion excavation (SEE). First, the mechanical model of tunnel expansion is established and the initial stress field 1SEE and expansion stress field of tunnel surrounding rock are analyzed. The finite element model of tunnel expansion is developed to examine the plastic zone distribution in the presence of various tunneling approaches. The obtained results reveal that with the growth of expansion size, the plastic distribution area grows, with a maximum increase rate of 138.5%; the difference of each position reduces, with the difference value of each part less than 0.2 m. The plastic zones of 2SEE and SEE approaches are almost symmetrically distributed around the tunnel center line, and the invert and vault of the SEE tunnel are excavated at the same time, the excavation size is the same, and the difference in plastic zone range is small. With the rise of the lateral pressure coefficient, the distribution pattern of the plastic zone changes from X-type to butterfly-type and then to ellipse-type. [ABSTRACT FROM AUTHOR]

Single-layer tunnel lining using shotcrete has the significant advantages of reducing the tunnel excavation volume and saving construction materials, which has been gradually applied in tunnel construction. The high-performance concretes are generally adopted in single-layer tunnel lining for enhancing the bearing capacity of the tunnel lining, whereas the single-layer tunnel lining may still induce damages due to the adverse conditions such as shallow buried depth of the tunnel, and further study related to its application condition is thus required. This paper presents a study of the single-layer tunnel lining with shotcrete employed for supporting the large-span tunnel, in which the reinforcement ribs are also adopted in the single-layer lining for improving the lining stiffness and strength. The study is implemented using numerical simulation, focusing on the safety and performance variation of the single-layer tunnel lining influenced from the varied lining thicknesses and shallow buried depths of the tunnel. The results shows that the single-layer tunnel lining has the obvious advantage of toughness in significantly absorbing large deformation of surrounding rocks and improving the ability to resist lining cracking. The results also demonstrate that the single-layer tunnel lining with shotcrete and reinforcement ribs can safely support the large-span tunnel, in which the stability and safety of the large-span tunnel are confirmed from both the tunnel deformation and lining stresses. Moreover, the factors related to both the lining thickness and shallow buried depth of the tunnel have great influence on the single-layer tunnel lining with shotcrete and reinforcement ribs, in which the insufficient lining thickness and excessive shallow buried depth of the tunnel can induce the damages of the single-layer tunnel lining due to shotcrete stresses exceeding its strength. This study provides some references of employing the single-layer tunnel lining with shotcrete and reinforcement ribs for supporting large-span tunnel. [ABSTRACT FROM AUTHOR]

To reduce traffic congestion and meet the demand for rail transportation, the diameters of shield tunnels are constantly expanded. The super-large diameter, deep depth and long distance of super-large-diameter shield tunnels, coupled with the limitation of existing structures on underground construction space, cause many problems in the construction of these tunnels, such as affecting existing structures. This study takes a shield project in Wuhan as the research object, uses the finite element method to simulate the influence of super-large-diameter shield tunnelling on the displacement of the existing Line 5 tunnel segments, and analyzes the influence of the isolation pile arrangement and length on the isolation effect. The analysis indicates that (1) the displacement of Line 5 decreases with an increasing horizontal center distance between the tunnels and increases with an increasing vertical center distance between the tunnels, with a maximum displacement of 17.9 mm; (2) the displacement direction and position of the maximum displacement of Line 5 vary with changes in the vertical center distance between the tunnels, but remain essentially constant with changes in the horizontal center distance; and (3) the isolation piles closer to the shield tunnel improve support, with its isolation effect on the Line 5 segment becoming limited. [ABSTRACT FROM AUTHOR]

Groundwater pressure is the main cause of debonding (i.e. tensile failure) of the sprayed waterproofing membrane interface within composite sprayed concrete lined (SCL) tunnels. It is critical to understand the failure mechanisms, the right approach to numerical simulations of its effects and the practical implications on lining design and membrane interface testing methodology. This paper addresses these issues. The paper first presents a conceptual relationship between the possible groundwater pressure application locations and the stress state, and hence the potential failure mechanisms of the membrane interface in composite SCL tunnels. To quantify stresses in a fully bonded membrane interface, two numerical modelling approaches for the membrane interface with different levels of complexity are introduced. Example numerical analyses of composite beams and whole composite SCL tunnels with a fully bonded membrane interface are provided. The results confirm the conceptual relationship between water application location, the stress state and the potential failure mechanism of the membrane interface. The results also showed that the two numerical modelling approaches proposed are both able to simulate the effects of groundwater pressure on the stress states of the membrane interface and tunnel lining forces. The implications on tunnel design and testing programmes for a sprayed membrane interface are discussed. [ABSTRACT FROM AUTHOR]

To accurately predict ground settlement caused by shield tunnel construction, a prediction method of ground settlement considering the support effect of the tunnel lining structure is studied in this research. First, based on the Maxwell–Betti power interchange theorem and considering the lining supporting effect of a circular shield tunnel, an analytical formula for ground loss caused by tunnel construction is derived by constructing two groups of elastic mechanical model calculation models for different stress states. The calculation method of ground loss with the influence of the lining support is optimized and improved. Second, considering the tunnel construction method and the lining support effect, the Loganathan formula is improved, a theoretical formula for a vertical displacement field for shield tunnel construction is deduced, and the ground settlement prediction model of a circular shield tunnel construction is established. Finally, the method is compared with other calculation methods, such as the Loganathan method, and three tunnel engineering cases are predicted and analyzed. The results show that the prediction results are closer to the actual monitoring settlement value, verifying that this method has good adaptability and reliability in actual tunnel engineering. [ABSTRACT FROM AUTHOR]

With the continuous development of urban underground spaces, new underground engineering approaches are becoming more similar to existing operating tunnels. Existing research is typically concerned with the impact of a single project, such as a new tunnel or deep excavation, on existing shield tunnels. There are few studies on the influence of both excavation and overcrossing tunneling on operational tunnels. Taking a section ranging from the Chengzhan Station to the Jiangcheng Road Station of Hangzhou Metro Line 7 as a case study, this study analyzes the automatic monitoring data of the existing tunnel within this section. Through data analysis, the influences of deep excavation and shield tunneling on the vertical settlement, horizontal displacement, segment convergence, and differential settlement of the tunnel ballast of the adjacent existing line segment are assessed. The influence of deep excavation and overcrossing tunneling on multiple disturbances of existing line tunnels is summarized. This study will be useful for similar projects involving deep excavation next to existing tunnels and overcrossing tunneling, as it will help clarify the protection range of existing lines and determine the displacement alarm value of existing structures. [ABSTRACT FROM AUTHOR]

Fire hazards can cause severe and irrecoverable damage to reinforced concrete (RC) tunnel linings. Historically, major fire events have led to months of downtime and millions of dollars of losses owing to repair costs and affected operations. The potential threat to the serviceability of transportation networks emphasizes the need to establish a standardized and effective post-fire damage assessment method to guide repairs and restore functionality. This paper proposes a fire damage assessment framework for RC tunnel linings that integrates advanced modeling with visual inspections, non-destructive testing and material sampling. The framework quantifies fire damage to RC tunnel linings in terms of surface discoloration, crack width, concrete spalling, sectional temperatures, strength loss of materials and residual displacement. A damage classification system is proposed based on a collection of international guidelines and feedback from industry experts to map damage metrics and repair strategies. A case study, using data from recent experiments, is conducted to demonstrate the applicability of the proposed framework and the benefits of the information obtained from numerical modeling. This framework can also be integrated with risk-assessment methods to optimize the fire design of tunnels with associated active and/or passive fire protection. [ABSTRACT FROM AUTHOR]

We present a scanning tunneling microscopy (STM) technique to simultaneously measure the topography, the local tunnel barrier height (d I /d Z), and the differential conductivity (d I /d V). We modulate the voltage and tip piezo with small sinusoidal signals that exceed the cut-off frequency of the STM electronics and feed the tunneling current into two lock-in amplifiers (LIAs). We derive and follow a set of criteria for the modulation frequencies to avoid any interference between the LIA measurements. To validate the technique, we measure Friedel oscillations and the subtle tunnel barrier difference between the h c p and f c c stacked regions of the Au(111) herringbone reconstruction. Finally, we show that our method is also applicable to open feedback loop measurements by performing grid I (V) spectroscopy. [ABSTRACT FROM AUTHOR]

A method to perform spectrum analysis on low power signals between 0.1 and 10 THz is proposed. It utilizes a nanoscale antiferromagnetic tunnel junction (ATJ) that produces an oscillating tunneling anisotropic magnetoresistance, whose frequency is dependent on the magnitude of an evanescent spin current. It is first shown that the ATJ oscillation frequency can be tuned linearly with time. Then, it is shown that the ATJ output is highly dependent on matching conditions that are highly dependent on the dimensions of the dielectric tunneling barrier. Spectrum analysis can be performed by using an appropriately designed ATJ, whose frequency is driven to increase linearly with time, a low pass filter, and a matched filter. This method of THz spectrum analysis, if realized in the experiment, will allow miniaturized electronics to rapidly analyze low power signals with a simple algorithm. It is also found by simulation and analytical theories that for an ATJ with a 0.09 μ m 2 footprint, spectrum analysis can be performed over a 0.25 THz bandwidth in just 25 ns on signals that are at the Johnson–Nyquist thermal noise floor. [ABSTRACT FROM AUTHOR]

In recent decades, the permanent single-layer tunnel lining has been developed to meet the requirements of the deep-buried and over-long tunnel projects. In this study, macro-synthetic polypropylene (PP) fiber-reinforced shotcrete was designed for the permanent single-layer tunnel lining. Uniaxial compressive tests were carried out on the three rock–shotcrete composites (G-NSC, S-NSC and S-FSC) with two types of rocks [granite (G) and sandstone (S)] and two types of shotcretes [normal shotcrete (NSC) and fiber-reinforced shotcrete (FSC)] to investigate the failure mechanism of the composites. Combined with X-ray computed tomography (X-CT) and digital image correlation (DIC) technologies, the meso-structures of shotcrete, the strain development, crack propagation and damage evolution laws of different composites were analyzed. The results showed that macro-synthetic PP fiber increased the porosity and the volume of large-diameter pores of the shotcrete. The microcracks mainly emerged and propagated in the shotcrete for G-NSC, but occurred and gathered near the rock–shotcrete interface of sandstone-based composites. Besides, macro-synthetic PP fibers can greatly increase the ductility of the composite, and cracks tended to propagate along with the interface between aggregates and mortar in FSC. Finally, damage calculation model based on the dissipated energy was proposed for the rock–shotcrete composites. [ABSTRACT FROM AUTHOR]

Among several works, constructions in rock masses are the most complex in engineering, due to many uncertainties of the environment. Tunnel construction is a case in point. A common problem found in tunnel excavations with the use of explosives is the occurrence of overbreak beyond the boundary line of the tunnel. Many researchers worldwide have proposed forecasting techniques based on the use of regression models or machine learning, however, these require many samples and variables, such as the explosive rate and rock mass. Predicting overbreak before blasting is essential in project management, as it can modify parameters of the blasting plan, design, schedule and employee safety. Therefore, this study sought to employ an exponential smoothing model, which could predict the percentage (%) of overbreak in a tunnel section, based solely on the previous overbreak values. This time series methodology has never been used before in tunnel excavations, although it is used in the financial market. The technique was tested in one Brazilian tunnel. The model proved to be very efficient in predicting overbreak in tunnel construction, since it can be adjusted at each advance. The model can be adjusted as a function of α: where α is close to zero, the model prioritizes past events, while for α close to 1, it prioritizes recent events. The best fit occurred with α = 0.9; 0<α<1. [ABSTRACT FROM AUTHOR]

With the increasing demand of transport construction in coastal areas, seabed instability around tunnels subjected to ocean waves and protection of the tunnels are becoming increasingly important. Current analytical solutions on the seepage field around subsea shield tunnels induced by waves are generally based on the impermeable lining, without considering the permeability. Furthermore, previous studies seldom take account of the influence of nonlinear wave loads under the sloping seabed terrain. For better tunnel stability, this paper presents a new set of analytical solutions for predicting Stokes wave-induced seepage pressure responses around a shield tunnel in a sloping seabed considering the influence of the permeable tunnel lining. The accuracy of the presented solutions is then verified by comparison with the numerical solution and experimental data, showing reasonable alignments. Moreover, parametric analyses are also performed to assess the influence of wave characteristics, seabed properties, and tunnel lining permeability on seepage pressure responses, in which the distribution of the excess pore pressure response outside the lining and excess pore pressure around the tunnel circumference is described in detail. In general, the analytical solutions provide an effective insight into the wave-induced seepage pressure response around a shield tunnel, which can serve as a credible theoretical basis in the preliminary design of tunnels. [ABSTRACT FROM AUTHOR]

Supports are typically installed to maintain the stability of tunnels in rock. The supporting forces and their spatial distributions are important quantities in tunnel and lining design. Analytical solutions can provide rapid predictions of the mechanical responses for the entire ground and lining; however, the rock–lining interaction under realistic conditions in shallow tunnel construction is still not fully considered in the current analytical research due to mathematical difficulties. This study provides a semi-analytical approach to accurately address the elastic stress and displacement around shallow lined tunnels induced by tunnel excavation and lining installation with full consideration of the rock–lining interaction and the lining thickness, stiffness and installation time. Based on the complex variable theory and conformal mappings, the stress and displacement of the rock and lining are expressed by potentials in the form of Laurent series. A few coefficients in these series are determined, and the relationships among the other coefficients are established by the boundary conditions. The optimisation model is then proposed by satisfying the compatibility conditions at several points along the rock–lining interface with minimum error, by which all the coefficients in the potentials of the rock and lining are finally addressed. The semi-analytical approach is verified by the good agreement between the results of the semi-analytical and numerical models under the same assumptions. A parametric study is performed to investigate the influence of the key parameters on the stress and displacement of the ground and lining. The proposed semi-analytical approach can rapidly and precisely provide the mechanical field of rock and lining, and the code can be provided to interested readers. [ABSTRACT FROM AUTHOR]

China is gradually transitioning from the "tunnel construction exploration era" to the "tunnel high-quality construction and operation era", and the maintenance demand of highway tunnels has increased sharply. Therefore, there is an urgent need for an evaluation method to evaluate the service reliability of highway tunnels, so as to provide reference for tunnel maintenance personnel to carry out maintenance work. Taking highway tunnels as the research object, this paper extracts three parameters, including length, maximum width and fractal dimension, from the binary image of highway tunnel lining cracks. The standard for dividing the length of the highway tunnel section is 500m as the tunnel section, and a section disease sample space including multiple highway tunnels is constructed. The EM clustering algorithm was used to determine the number of graded grades of disease, and the relative Euclidean distance was used as the evaluation index to divide the safety grade of the tunnel into five grades: normal, degraded, inferior, deteriorated and hazardous. The partial least squares method is used to establish the lining service reliability evaluation formula and verify the residual of each sample point in the sample space. The smaller the average value of the residual, the better fitting effect of the established evaluation formula. The service reliability evaluation method proposed in this paper is applied to engineering practice and compared with the expert scoring method and the national standard method, which proves that the evaluation method in this paper has the advantages of strong visibility, simple evaluation method, and is conducive to engineering practice. [ABSTRACT FROM AUTHOR]

The rapid development of urbanization has changed the traffic and transportation in the central area. The change of the surrounding rock and structural stress state of the project under construction caused by the tunnel construction in the same period has caused great harm to its safe use and casualties. Shield construction technology can achieve safe excavation and lining, with high degree of automation. And it is a relatively common construction method at present. But its adaptability to section size and section environmental conditions is poor. In view of this, from the analysis of construction monitoring data, the study established a longitudinal model considering lateral effects from the perspective of lateral characteristics. It also achieved stress assessment and improvement through lateral deformation calculation, segment ring bolt calculation and formula correction. The experimental results showed that the opening at the circumferential seam of the right line of the test tunnel under this method is 8.9 mm. The radius of curvature is 758 mm, and the safety assessment level of longitudinal deformation is 3. This method can effectively guarantee the safety of shield tunnel construction and has good guiding value for tunnel management and maintenance. [ABSTRACT FROM AUTHOR]