Tunnel Lining Research Articles

Experimental Study on the Stress and Failure Mode of a Shield Tunnel Lining Under Asymmetric Thrust

This paper develops the "formation–shield tunnel segment–reaction frame model test system." The force and failure modes of the segment under different curvature radii and different left- and right-hand thrusts are compared and analyzed. The analysis results include the following. (1) Under asymmetric thrust, the axial force, bending moment, and deformation of the segment present an asymmetric distribution. With the increase in the ratio of the thrust between the lateral and inner jacks of the turn, the loading step of the damage inside the segment lining structure is advanced. (2) With the increase in the radius of curvature, the bending moment and deformation of the segment lining decrease, but the magnitude of the sudden change in the axial force of the segment structure increases accordingly. (3) The failure locations of the segment structure are mostly concentrated at the joints between the vault and the arch. With the increase in the jack thrust ratio, the cracks caused by segment structure failure also increase, transverse crack extension occurs where the force on the outside of the turn is large, and the peeling phenomenon occurs.

A novel numerical framework to simulate mechanical response and damage characteristics of mountain tunnels under faulting

This paper presents a novel numerical framework that can simulate the mechanical response and damage characteristics of mountain tunnels under faulting more precisely and efficiently. Both the submodeling and two-stage models are adopted in the framework. The submodeling technique is used to obtain a precise simulation of tunnel-fault interaction while ensuring computational efficiency. The two-stage models can acquire accurate initial stress of the tunnel lining and simulate the tunnel-rock interaction during fault movement, which can also achieve the transition from static to dynamic analysis. The computational efficiency can be improved by about 73 % via the proposed numerical framework compared to the conventional numerical analysis when keeping the same mesh sizes. Moreover, overall lining damage indices and cross-sectional ovalization are introduced to quantitatively evaluate the respective damage and deformation of the tunnel lining cross-section, and damage level classifications for tunnel lining under faulting are established. Parametric sensitivity analyses are performed to investigate key factors affecting the mechanical damage behavior of mountain tunnels under strike-slip faulting, including fault dislocation, fault zone width, and the tunnel-fault intersection angle. The increasing fault dislocation causes larger tunnel-rock interaction around the fault plane, making the damage and deformation of tunnel lining around the fault plane more severe. The fault zone width has a significant impact on the damage and deformation range of tunnel lining. The tunnel-fault intersection angle contributes great influence on the magnitude and range of tunnel lining damage and deformation. The tunnel lining would suffer relatively severe damage and deformation when the two fault blocks move away from each other along the tunnel axial.

Confining Pressure Forecasting of Shield Tunnel Lining Based on GRU Model and RNN Model

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.

Experimental investigation of seismic performance of segmental tunnel with secondary lining under strong earthquake

To assess the seismic performance of large-diameter tunnels in soil ground with and without secondary lining, large scale shaking table tests with geometrical ratio of 1:15 were conducted. The model tunnels were grouped as a tunnel only with segmental linings (Single lining), a tunnel liner with additional semi-ring secondary lining (Semi-ring), and a tunnel with additional full-ring secondary lining (Full-ring). Transverse excitations input from shaking-table were designated as Shanghai artificial accelerogram with magnitudes from 0.3 to 1.0 g. Measurements were made mainly on the time histories of acceleration responses, cross-sectional deformation, extension/closure at longitudinal joints of segmental linings, and earth pressure on external surface, of the model tunnels. Comparison the seismic responses of the tested models gives the effects of secondary lining as: 1) the distribution of acceleration responses on segmental linings is significantly different in the case of single lining model; 2) dynamic normal earth pressure on the external surface of the segmental linings increase along depth, but in different patterns; 3) the constraint effects of semi-ring secondary lining on extension/closure of longitudinal joints are not significant in the upper half of segmental lining. Furthermore, with the increase of earthquake intensity, the constraint effects of full-ring secondary lining on both cross-sectional deformation and extension/closure of longitudinal joints become more remarkable, compared with those of the semi-ring secondary lining.

Experimental study on the damage performance and forced response of concrete lining in fault-crossing tunnel

Understanding the adverse effects of tunnel crossing active faults on tunnel structures is crucial for ensuring their safe operation and construction. This paper presents the results of a series of model tests conducted at a scale of 1:40 using a fault sliding test box. Three sets of fault comparison tests were carried out, namely: (1) the tunnel does not cross the fault, (2) the spring stiffness is reduced, and (3) the model is not reinforced. The objective was to study the failure characteristics of tunnels crossing active faults. The findings reveal that when the hanging wall moves downwards, cracks appear on the surrounding rock surface of the hanging wall, specifically above the tunnel lining crossing the fault. The lining is significantly damaged within the range of − 30–+ 30 cm. All points of axial force exhibit an increasing compression trend. The section of axial force and bending moment near the fault fracture surface is notably larger than that far from the fault fracture surface. The safety factor of the entire structure decreases sharply after dislocation, making the tunnel more susceptible to cracking at various locations such as the vault, arch waist, left and right arch feet, and inverted arch. It has been proven that the shear compression of the fracture surface during fault dislocation is the main cause of longitudinal through cracks in the lining. The use of springs with higher stiffness effectively ensures the reciprocating dislocation of the upper and foot walls, with long duration and large displacement, providing a better simulation of the dislocation of active faults.

Model test on frost heaving pressure induced by frozen partial ponding behind tunnel lining in cold region

For tunnels in a cold region, the research of frost heaving-induced pressure (FHIP) due to frozen partial ponding is carried out based on certain theoretical assumptions. However, there is few research using the laboratory experiment to investigate the evolution of FHIP with time and space. Therefore, in this paper, to study the mechanism of the FHIP induced by frozen partial ponding of tunnel in the cold region, a three-dimensional geotechnical model test equipment only considering frost heave loads on lining is developed, in which the cold air of environment can be blown into the tunnel. Accordingly, the variation law of FHIP and the temperature field in the surrounding rock under the freezing condition are discussed. Moreover, a three-dimensional cone shape constrained model is developed to predict FHIP by considering the differences of the ponding depth, the stiffness of the surrounding rock and lining, which is further validated by comparing with experimental data. Results indicate that when the FHIP occurs, the temperature in the surrounding rock starts to drop rapidly with time. This proposed model can evaluate the FHIP caused by a frozen partial ponding with any cone shape and size. To account for the effect of time, the theoretical and semi-empirical model is further developed based on the three-dimensional cone shape constrained model. Comparisons with experimental data demonstrate that the modified theoretical and semi-empirical model well predict the evolution law of FHIP. This research can provide theoretical references to reveal the spatio-temporal evolution of the FHIP for partial ponding of tunnels in the cold region.

Failure investigation of the tunnel lining in expansive mudstone – A case study

When studying the deformation characteristic of tunnel lining in the expansive surrounding rock, most research focuses on the expansion effect of surrounding rock after water absorption, while seldom considers the softening effect caused by water absorption at the same time. Therefore, based on a failure case of a tunnel in expansive mudstone in northern China, this paper investigates the expansion characteristics of the mudstone and the deformation as well as the failure law of tunnel lining through laboratory tests, field monitoring and numerical simulations. The results show that the mudstone exhibits significant water disintegration and softening characteristics, with a noticeable deterioration in strength. The clay mineral content of the mudstone is 68.8 %, and evaluations of various indicators indicate moderate expansion potential. The failure modes at the crown of the preliminary lining are compressive failure, which are coincident with that of field monitoring. The expansion of the surrounding rock leads to a sharp increase in the internal forces of the preliminary lining, significantly weakening its safety and causing large deformation even damage. The maximum deformation of lining reached 449 mm, necessitating the dismantling and rebuilding of the damaged preliminary lining. Therefore, in the design and construction of tunnels in mudstone, considering the expansive potential is essential to ensure the safety of the project.

An Iterative Calculation Method for Internal Forces and Deformation of Curved Tunnel Lining

The accurate prediction of lining forces and deformations is crucial for the design of arched tunnel lining. However, in traditional tunnel structural mechanics methods, the distribution shape of the surrounding rock elastic resistance (SRER), as well as the zero point and maximal point locations of SRER, are not clearly defined. In this paper, an iterative calculation method is proposed based on the gradual convergence of the unitized values of SRER and total displacement (TD) of the lining, and the one-to-one functional relationship between the two in the stability process of the surrounding rock and lining. In this method involves using the initial displacement caused by the pressure of the surrounding rock pressure is used to initiate the iterative process, and iterative calculation is carried out until the errors between the unitized value of SRER and the unitized value of TD of the lining structure meet the error requirements. This enables precise determination of the SRER and TD. In order to verify the effectiveness of the proposed method, a case study is conducted on the tunnel of Lianghe Expressway tunnel in Yunnan province, China. The results showed that when the semi-lining structure is divided into unit blocks and the average error of consistency is required to be less than 1e-3, it takes about 20 iterations are needed to meet the error requirement. Furthermore, the accuracy of the calculated results is verified through site-measuring experiments. This method provides an effective tool for failure analysis of arched tunnel lining structures.

Realistic long-term stress levels in a deep segmented tunnel lining, from hereditary mechanics-informed evaluation of strain measurements

Realistic estimation of stresses in segmented tunnel linings is a challenge tackled herein by means of a hybrid, i.e. computational-experimental, approach. Thermistor-equipped vibrating wire strain gauges were installed (i) into concrete samples undergoing one year-long uniaxial creep tests under the environmental conditions of the tunnel site, and (ii) into the tubbings making up the tunnel lining of the Koralm tunnel. The data obtained from the creep tests allow for calibration and validation of an integro-differential thermo-viscoelastic model. The creep function combines a power-law for short-term creep with a logarithmic law for long-term creep. The corresponding relaxation function is determined by means of Laplace-Carson transformation, inversion, and back-transformation. This is the basis for translating the circumferential strain histories measured in the tubbings of Ring 2013 in Koralm tunnel KAT3 into circumferential and longitudinal stress evolutions. They are mainly due to mechanical ground-shell interactions. The corresponding degree of utilization increases during the first four months after ring installation, and remains virtually constant thereafter. Stress fluctuations due to seasonal temperature variations play only a minor role. With regards to a long-term prognosis, it is very interesting to note that the strain measurements recorded in the tubbings, when plotted as function of the logarithm of time, follow bi-linear trends. These trends can be extrapolated to 150 years, the targeted service life of newly built tunnels in Austria. Throughout this period, the viscoelasticity-based estimates of the stresses in the vicinity of the strain sensors stay temporally constant, at some 40% of the strength of concrete.

TunGPR: Enhancing data-driven maintenance for tunnel linings through synthetic datasets, deep learning and BIM

Non-destructive Testing (NDT) techniques and data-driven technologies are increasingly applied in underground infrastructure maintenance, which can facilitate predictive monitoring for informed decision-making. Ground Penetrating Radar (GPR) is extensively utilised in rapid condition assessment of tunnel linings, particularly for detecting defects that lead to unforeseen changes of dielectric properties of materials. In this paper, a prototyped framework is proposed, namely TunGPR, for GPR-based tunnel lining assessment by incorporating Building Information Modelling (BIM), synthetic database and deep learning-enabled interpretation. The first module integrates laser-scanned point clouds and GPR Scan-to-BIM of tunnel lining with geological model. Subsequently, interoperability is achieved between the geo-integrated BIM and GPR simulation software. From the dielectric model retrieved from the BIM model, a database is established, considering a variety of condition combinations (i.e., voids, cavities, delamination, and water intrusion) leveraging domain randomisation and Finite-Difference Time-Domain (FDTD) modelling, as well as monitored field data. The dataset is then fed into the diagnostic module underpinned by a dual-rotational Convolutional Neural Network (CNN) that is customised to enhance accuracy and automation of hyperbola detection. Lastly, a preliminary risk assessment matrix is implemented into the BIM model for data management and action prioritisation. These efforts serve as an initial step to validate the feasibility and effectiveness of the GPR-enabled data-driven maintenance for tunnel linings in a BIM-centred framework.

Experimental study on mechanical properties of sprayed ECC under quasi-static and cyclic loading

The tunnel lining will be subjected to the cyclic action of high ground stress during service. However, there is a lack of research on the damage evolution mechanism of sprayed engineered cementitious composites (ECC) under cyclic loading. Herein, we studied the strain rate effect and fatigue damage evolution mechanism of sprayed ECC by conducting compression and bending tests at different quasi-static strain rates and high-stress cyclic loading-unloading compression and bending tests. The results show that with the increase of strain rate, the compressive peak stress and bending strength of sprayed ECC show an upward trend, as well as the increase of the change rate. At 8.3 × 10−3 s−1, the compressive SGF is 1.52, with an energy storage limit density of 0.501MJ/m3. At 2.1 × 10−2 s−1, the bending SGF is 1.52, with a peak fracture energy of 49.29 J. In addition, under the compression test, the tensile shear failure of specimens develops from finer double shear planes to coarser multiple shear planes. Under the bending test, the position of the main crack of specimen is gradually transferred from the mid-span to both sides. Under high stress cycle test, the input energy and dissipation energy of the two tests have the similar trend, showing “U” type. The variation of elastic energy and dissipation energy conversion rate exhibits a “U” type with different directions. At the last loading, the dissipation energy conversion rate of compression test is 46.8%, while that of bending test is 70.4%. The damage variable of specimen increases significantly with the increase of the number of cycles, accompanied by an increase in the degree of breakage. In addition, the damage variables based on deformation characteristics are higher than those based on energy characteristics.

Research on the Mechanism of Frost Heaves Caused by Void Water Accumulation behind the Lining of High-Speed Railway Tunnels in Cold Regions

(1) Background: Lining voids and macroscopic water freezing are both prominent issues that threaten driving safety in high-speed railway tunnels. With the continuous expansion of the scale of high-speed rail tunnels in extremely cold areas in China, the issues of lining voids, water accumulation, and frost heaving have triggered heated discussions. The need to reveal the frost-heave mechanism is urgent. (2) Methods: Firstly, a simulation experiment of the frost heaving of accumulated water was carried out based on the discharge conditions of accumulated water. Secondly, a numerical model was used to study the evolution process of frost heaves caused by accumulated water in voids. Finally, a drainage coefficient was introduced to propose a method for calculating the frost-heave force of accumulated water in voids. (3) Results: The blockage of the drainage channel leads to the generation of frost-heave force; the freezing/thawing process of the void water develops from the thinnest part to the thickest part of the void edge, and the freeze/thaw cycle of the water body causes the frost-heave force to become greater and greater in the evacuated cavity. The higher the height and the closer the drainage channel is to the hollow bottom, the greater the frost-heave force when the accumulated water freezes. (4) Conclusions: When the evacuated water freezes, it develops from the thinner edge to the thicker center. The magnitude of the frost-heave force is affected by the freeze/thaw cycle, the height of the evacuated cavity, and the position of the drainage channel.

A Coupled Rock-Pipe Hydraulic Model for Predicting Groundwater Pressure on Tunnel Linings with Embedded Drainage Networks

A Coupled Rock-Pipe Hydraulic Model for Predicting Groundwater Pressure on Tunnel Linings with Embedded Drainage Networks

Investigation of a new reverse drainage construction and the pressure-reducing effect of a tunnel in a water-rich karst location

It is quite simple to create cracking, leaking, and other disasters in the tunnel during operation because water-rich karst tunnels are subject to the action of the high head. If the drainage is not timely, this results in high-pressure water collection around the tunnel lining. The study was conducted depending on Tongzi Tunnel to resolve the issue of water pressure encountered by water-rich karst tunnel lining under high head action and to lessen the issue of operational tunnel illness under long-term water pressure. The mechanical reaction of the number of reverse drainage holes and the size of pipe diameter at the raised arch under various water heads on the tunnel construction was studied using model testing in combination with numerical simulation analysis. It was discovered that using the traditional drainage system would subject the supine arch to extremely high-water pressure, which is often hard to efficiently remove. The major issue causing the elevated arch bulging tragedy is that water pressure in the elevated arch increases as head height increases. High water pressure in the raised arch may be efficiently dealt with using the suggested reverse drainage approach. The pressure reduction rate compared to the traditional drainage method achieved 13.6 % for the investigation of the fractured Tongzi tunnel reverse drainage holes, which had a total of five holes with a diameter of roughly 100 mm. Reverse drainage structures have the potential to save project costs while also realizing “point to point” pressure reduction at the elevation arch of the tunnel and have positive effects on total tunnel pressure reduction. The study's findings can serve as a guide for designing and building comparable water-rich karst tunnel constructions as well as for maintaining drainage systems while they are in use.

A numerical investigation of the behavior of a tunnel with adaptive anti-dislocation measures subjected to the action of fault dislocation

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.

Study of the damage characteristics and corrosion mechanism of tunnel lining in a sulfate environment

Sulfate corrosion is one of the main causes of tunnel lining deterioration. An accurate understanding of the damage characteristics and corrosion mechanism of sulfate-corroded tunnels is the basis for the anti-corrosion design and damage control of the tunnel lining. Based on a project concerning a sulfate-corroded tunnel in the mountainous area of Southwest China, this study conducted a field investigation and laboratory tests and, combined with existing research data, summarized the damage characteristics and corrosion mechanism of this type of tunnel and proposed the characteristic corrosion state of tunnel lining in a sulfate environment. The results show that 1) sulfate corrosion led to leakage, surface spalling crystallization, and strength loss, and the corrosion typically occurred at the arch waist and arch foot. 2) Physical and chemical corrosion occurred in the tunnel lining, and the corrosion products included sodium sulfate, calcium carbonate, gypsum, ettringite, and thaumasite. 3) In China, this type of tunnel is mainly located in the Southwest and Northwest, and its lining is in a special state of “one-sided accelerated corrosion.”

Multi visual images fusion approach for metro tunnel defects based on saliency optimization of pixel level defect image features

The multi-vision defect sensing system, lining composed primarily of IRT and RGB cameras, allows for automatic identification and extraction of small surface ailments, greatly enhancing detection efficiency. However, the presence of various issues like train vibration, inconsistent lighting, fluctuations in temperature and humidity leads to the images showing inadequate uniformity in illumination, blurriness, and a decrease in the level of detail. The above issues have led to unsatisfactory fusion processing results for multiple visual images and increased missed detection rates. To address the above-mentioned issue, multi visual images fusion approach for subway tunnel defects based on saliency optimization of pixel level defect image features is proposed. The approach initially analyses the train’s motion status and image blurring conditions. It then eliminates the dynamic blurring in the image. Secondly, Image weights are allocated based on the uniformity of visible light image illumination in the tunnel, as well as real-time temperature and humidity. Finally, image feature extraction and fusion are performed by a U-Net network that integrates channel attention mechanisms. The entire experiment was carried out on a dataset consisting of leakage data from the tunnel lining of Shanghai Metro and tunnel defect data from Beijing Metro. The experimental results demonstrate that this approach improves the image pixel value variation rate by 39.7%, enhances the edge quality by 23%, and outperforms similar approach in terms of average gradient, gradient quality, and sum of difference correlation with improvements of 15.9%, 7.3%, and 26.6% respectively.

Numerical Simulation of Mechanical Characteristics and Safety Performance for Pre-Cracked Tunnel Lining with the Extended Finite Element Method

The service performance of tunnel lining is affected by crack properties and development states. In this paper, numerical simulation models were established to investigate the mechanics characteristics and safety performance for lining structures under different cracks based on the extended finite element method (XFEM). Analyze multiple quantitative factors in simulation, including changes in crack location, crack length, and crack distribution range in the lining structure. The axial force and bending moment of the preset cracks in the lining structures were first studied. The maximum safety factor attenuation rate (Dkmax) was proposed to analyze the impact of longitudinal and annular cracks on the safety performance. The axial force at the vault of the lining arch is the most significantly affected by the combined longitudinal cracks at multiple locations. When the length of a longitudinal crack increases from 1 m to 6 m, the axial force value at the crack point decreases by 33.77%, 36.15%, and 11.32%. However, the bending moment value increases by 4.47 times, 2.50 times, and 1.69 times. Under the influence of longitudinal cracks in an “arch crown + arch shoulder”, “arch crown + arch waist”, and “arch crown + arch shoulder + arch waist”, the axial force in the arch vault increased by 21.55%, decreased by 17.52%, and decreased by 13.45%. The distribution pattern of the bending moment under the influence of circumferential cracks shows convexity at the arch shoulder and arch foot, and concavity at the arch waist and side walls. The safety factor scatter curve with longitudinal cracks shows a gradual transition from a “W” shape to a “U” shape. The safety factor curve with circumferential cracks presents an approximately symmetrical wave-shaped distribution.

3D Deep Learning for Segmentation of Masonry Tunnel Joints

Historic masonry lined tunnels form a large proportion of the world’s railway tunnel stock. However, as many of these date from the second industrial revolution over 150 years ago, they typically contain large areas of structural deterioration. Masonry spalling is a pervasive form of surface damage and its severity, defined by the depth of spalling, is indicative of a tunnel’s structural condition. Current tunnel spalling condition assessment procedures are largely manual, so the extent of spalling observed on many historic tunnels presents a challenge for timely and cost-effective assessment. Automated machine learning based workflows have shown substantial potential for automating and reducing the subjectivity of the assessment process. A key step in these workflows involves segmenting the location of masonry joints from 3D point clouds of the tunnel lining in order to isolate masonry block locations. The most prevalent method is to unroll 3D tunnel lining data into 2D before applying U-Net based convolutional neural networks to segment joint locations. However, recent developments in 3D point based neural networks enable semantic segmentation to be conducted directly on the input point cloud. Point based methods such as KPCONV provide 3D feature characterization and enable semantic segmentation of a wider variety of tunnel geometries by default, since a handcrafted unrolling strategy is not required. This study conducted a performance comparison between 3D KPCONV, 2D U-Net, and XGBOOST feature classifier based joint identification techniques. In order to effectively compare a real-world use-case where time consuming manual data labelling should be minimized, the methods were only trained on a 9.94m section of tunnel. It was found that a 2D U-Net combined with tunnel unrolling workflow could be more successfully trained on the case study dataset and due to effective transfer learning, achieved superior performance to KPCONV and XGBOOST methods.

Implementation of an enhanced fiber optic sensing network for structural integrity monitoring at the Brenner Base Tunnel

The reliable assessment of deformation characteristics along tunnel linings is essential to understand ongoing structural processes during construction and operation. Conventional monitoring techniques may involve limitations, either in the spatial or the temporal resolution and do not deliver the overall deformation behavior along the entire lining. Distributed fiber optic sensing (DFOS) has significantly evolved in recent years to monitor large-scale civil infrastructure, with scientific sensing designs being realized within various research projects. The technology can be advantageous for in-situ tunnel monitoring since the distributed strain and temperature sensing feature delivers a more complete picture of the linings’ structural deformation behavior.This paper introduces the design and realization of an enhanced distributed fiber optic sensing network inside concrete tunnel lining segments, currently being implemented at the Brenner Base Tunnel. The construction is one of the largest civil infrastructure projects world-wide and will be globally the longest underground railway connection with a total length of about 64 km once completed. The designed DFOS system, consisting of more than 35 km sensing cable overall, provides distributed strain and temperature information along numerous tunnel cross-sections, spread over more than 30 km tunnel drive and two different construction lots. After installation, measurements are being continuously performed, autonomously evaluated, and transferred to the ACI online visualization dashboard in real time. It can be shown that fiber optic sensors have considerably developed from research into innovative practice and are capable to extend or even to replace conventional, geotechnical sensors.