Tunnel Research Articles

Data-driven intelligent prediction of TBM surrounding rock and personalized evaluation of disaster-inducing factors

With the widespread application of tunnel boring machines (TBM) in underground tunnel construction, the accurate and real-time identification of geological indicators has become a key factor for ensuring construction safety. In this study, we introduced the nomogram method into the field of civil engineering for the first time to predict surrounding rock grades. Against the backdrop of a major water conservancy project in China, an in-depth analysis of construction data from the ascending phase was conducted to establish the relationship between surrounding rock grade predictions and key construction parameters. Compared with traditional models, the nomogram method has shown advantages in terms of prediction accuracy. Furthermore, by providing a personalized scoring mechanism for specific construction data, the nomogram method not only achieves the real-time prediction of rock grades but also clearly reveals the dynamic relationships between input parameters and rock grades, clarifying the entire prediction process. We identified the main factors related to rock grade prediction among TBM construction parameters, including the slurry conveyor belt speed, jacking pressure, cutterhead torque, cutterhead thrust, thrust pressure, and actual rotation speed. The training process revealed that the nomogram prediction model achieved optimal performance with seven input parameters, balancing accuracy and training time. According to the prediction results, the nomogram model’s area under the curve index is 0.92, providing greater accuracy than the traditional random forest model (0.89). Therefore, this study enhances the transparency and interpretability of model predictions by providing personalized assessments of construction parameters for predicting surrounding rock grades, overcoming the black-box issue of existing prediction methods and offering a novel and effective tool for rock grade prediction.

Study on the influence of slope on smoke overflow and temperature characteristics of carriages with lateral openings in subway fires

This research explores the impact of slope on fire hazards in train carriages with multiple lateral openings in underground tunnel fires. Utilizing FDS software, a comprehensive full-scale fire scenario is simulated to study smoke overflow and temperature distribution in inclined tunnels with slopes ranging from 0 % to 4 % and Heat Release Rates (1 MW–10 MW) under natural ventilation. The study reveals that smoke mainly originates from the upstream end door and the door near the fire source, with smoke overflow from the upstream end door increasing significantly with the slope. Fire power has minimal impact on smoke overflow. When fire power is large, the longitudinal temperature distribution inside the carriage exhibits an overall increasing trend with increasing slope. The maximum carriage temperature decreases steadily with the slope for Q˙ ≤ 5 MW, while the slope has less influence on temperature variation for Q˙ > 5 MW. A modified prediction model is proposed to forecast maximum ceiling temperature during fire scenarios, providing valuable insights for structural fire protection, fire detection, and smoke control in metro areas. This study enhances understanding of smoke movement and temperature distribution in train carriage fires in inclined tunnels, contributing to engineering practices.

Mechanical testing and numerical simulation of intelligent terminal structure of rockbolt used as a deformable support and for safety monitoring in rock engineering

The nonlinear mechanical behavior perception and deformation control of engineering rock masses are crucial technical challenges in the fields of underground engineering support and safety monitoring. An intelligent terminal structure (ITS) of rockbolts was designed for deformable support systems and safety monitoring in rock engineering applications. It is a type of device installed at the end of a traditional bolt. The ITS comprises two key components: a memory tooth and a yielding ring. This study introduces the design principle of an ITS in deformable rockbolt support systems. It proposes design parameters for the ITS in relation to the deformations encountered by engineering rockbolts. Tests were conducted to measure the ultimate bearing capacity and deformation of the ITS under pull-out conditions. The results demonstrate that the ITS of rockbolt undergoes deformation in the form of elongation as opposed to conventional bolts. Furthermore, finite element numerical simulations were conducted to investigate the mechanism of interaction between the memory tooth and yielding ring of the ITS. The numerical simulation results are consistent with the experimental results. The load capacity of the yielding ring exceeded that of the memory tooth. The field test results indicate that the dilatation of the surrounding rock mass causes ITS deformation in the diversion tunnel. The axial stress load exerted on the rockbolt is transferred to the ITS, leading to memory tooth breakage and compression deformation of the yielding ring. This mechanism allows the load and deformation of the surrounding rock mass to be reflected. The ITS not only serves as a deformable support system but also plays a significant role in monitoring the stress and deformation of the rock mass.

Characteristics of Pre-peak Mechanical Damage and Energy Evolution of Typical Hard-rock in Diversion Tunnel under Cyclic Loading-Unloading

An in-depth understanding of the pre-peak mechanical damage and energy-evolution characteristics of typical hard-rock in a diversion tunnel under cyclic load is of great significance to promote the safe and efficient construction of the diversion tunnel and the stability of surrounding rock. To study the pre-peak mechanical characteristics and the competition mechanism between energy storage and energy dissipation of typical hard-rock in a diversion tunnel under cyclic loading-unloading, combined with the internal drilling and blasting excavation of the actual engineering rock mass and the external vehicle cyclic load environment of the diversion tunnel, the cyclic loadingunloading tests of typical granite and tuff in diversion tunnel were carried out. Based on the analysis principle of mechanics and energy, the strain variables, modulus variables, energy variables and damage variables of granite and tuff under cyclic loading-unloading test were defined. The cyclic mechanical properties and energyevolution characteristics of granite and tuff under pre-peak load were analyzed. The competition mechanism between pre-peak energy storage and pre-peak energy dissipation of granite and tuff and the evolution law of strain damage variable and energy damage variable were revealed. The selection principle of rock sample size and the limitation of the test scheme were further discussed. The study of the damage evolution of rocks close to failure (pre-peak stage) under cyclic load is helpful to better understand the damage and failure mechanism of rocks in practical engineering problems. Keywords: Diversion tunnel, Cyclic loading-unloading, Granite/Tuff, Blasting cyclic load, Energy evolution.

Investigation on the Mechanical Characteristics of the Excavation of a Double-Line Highway Tunnel Underpass Existing Railway Tunnel under the Influence of Dynamic and Static Load

Research on the excavation mechanical properties of underpass tunnels has already had certain results, but only a few of them consider the effects of dynamic and static loads on the excavation mechanical properties of underground tunnels at the same time; particularly, there is a lack of research investigating double-line highway tunnels with angled underpasses of existing railway tunnels. In this paper, based on the tunnel project of the new double-line Shiqian Highway Tunnel passing under the Hurong Railway with an oblique angle, based on the method of over-advance geological prediction and investigations into the palm face surrounding the rock, the rock degradation caused by dynamic and static loads is quantified using the perturbation system. Additionally, the mechanical parameters of the rock under the influence of dynamic and static load coupling in the influence area of the cross-tunneling project are determined using the Hoek–Brown criterion, and the mechanical characteristics of the excavation of a tunnel under the double-lane highway tunnel passing under the existing railroad are constructed with the mechanical characteristics of the double-lane highway tunnel, taking into consideration the influence of the dynamic and static load coupling in a three-dimensional model. The results show that, in line with the new tunnel rock movement law for the top of the arch sinking, the bottom plate bulging, the side wall outward movement, the height and width of the arch, and the bottom plate arch show an increase with the tunnel excavation, while the side wall rock displacement effect is smaller; the left and right line tunnel disturbed area of the rule of change is similar; the existing tunnel bottom plate displacement is larger than the top plate and the left and right side wall, under the influence of the excavation time step. Typical profile point displacement is mainly determined by the distance from the excavation surface; von Mises stress extremes are observed in the top plate and side walls of the existing tunnel, which occur in the tunnel structure, and there are unloading and pressure-bearing zones in the bottom plate; the new tunnel has the same rock disturbance angle under the four calculation conditions and, based on the displacement control criterion, the excavation method is preferred and the upper and lower step blasting excavation method is recommended.

CFD Simulations to study the Effect of Ambient Temperature on the Ventilation in a Metro Tunnel under Different Heat Release Rate

Urban and inter-urban rail transport provide the most favoured commuting option for millions of individuals globally. In spite of massive investments of public money to develop rail technologies and related infrastructure such as tunnel systems, there remain challenges to ensuring safety in this area. Railway tunnels present specific and serious fire safety issues, based on their length and restricted width. Smoke and other emissions from fires are a central factor to be considered in relation to both structural safety and survival where tunnel fires occur. Patterns of smoke flow can impact upon how efficient exhaust systems are, and for naturally ventilated systems, establishing shaft smoke flow patterns in tunnel fires is a significant requirement. While earlier work has considered this issue, it has been based on standard atmospheric conditions, while external temperatures can influence smoke movement properties, heat distribution, and the pattern of smoke flows within vertically constructed shafts. This study takes the case study of an underground metro tunnel, applying computational fluid dynamics through ANSYS Fluent to simulate and examine the effects of more extreme external temperatures for fires of 5 and 15 mw occurring in this environment.

Numerical investigation on smoke control with new‐style horizontal smoke baffle in an immersed road tunnel

AbstractTo investigate the improvement induced by horizontal smoke baffles during lateral smoke exhaust, an immersed road tunnel with various horizontal smoke baffles positioned below the lateral exhaust vent was studied numerically. Together with the velocity field characteristics, the temperature distribution was investigated near the lateral smoke exhaust vent, followed by the analysis of lateral smoke exhaust efficiency under different horizontal smoke baffles. Results showed that after installing the horizontal smoke baffle, there was a significant decrease in the extracted cold air, while the high‐temperature smoke in the exhaust vent increases, indicating the plug‐holing is effectively suppressed. It is known that the efficiency of smoke exhaust increases when the length exceedance ratio of the horizontal smoke baffle is smaller than 100%, while it changes slightly when the baffle length continues to increase. When the width ratio of horizontal baffle is smaller than 40%, the efficiency of smoke exhaust increases with the baffle width and then changes slightly with a wider smoke baffle. With a larger aspect ratio, the wider and shorter lateral exhaust vent is beneficial for improving the lateral smoke exhaust. Under the current conditions, the case shows the optimal smoke exhaust performance with a horizontal baffle length exceedance ratio of 100%, a baffle width ratio of 40%, and exhaust vent aspect ratio of 3:1. Finally, an empirical model is developed to describe the improvement of smoke exhaust efficiency caused by horizontal smoke baffle. These outcomes are helpful to the design of lateral smoke extraction system in road tunnels.

Health assessment of TBM diversion tunnel structure based on AHP and AMV models

Health assessment is one of the important theoretical bases for deciding whether the diversion tunnel can operate safely and stably. A project of the TBM diversion tunnel is taken as the research object to ensure the normal operation of the diversion tunnel. Based on measured data and considering multiple safety aspects such as structural response, durability, and external factors of the diversion tunnel, a TBM diversion tunnel structural health evaluation index system is established. A new method for the TBM diversion tunnel structural health comprehensive evaluation based on Analytic Hierarchy Process-Matter Element Extension-Variable Weight Theory (AMV) is proposed to explore the impact of AMV fluctuation with the measured results of the indicators on the weight, closeness, and health grade of each evaluation index. The high sensitivity and high-risk evaluation indicators for the structural health of the diversion tunnels are identified. It is found that the variable weight varies with the changes in various indicator values, which can accurately evaluate the health status of tunnels in real-time. The characteristic values of the tunnel grade calculated by the AHP and the AMV are 1.589 and 1.695, respectively. The results of the corresponding interval diversion tunnel are the basic safety state of grade B. Except for the two evaluation indicators of concrete strength and slurry properties, the variable weight values and grade characteristic values of other evaluation indicators increase with the increase of indicator values. The four indicators of segment settlement, segment opening, segment misalignment, and segment cracks are more sensitive to the health of the TBM diversion tunnel. This AMV can accurately evaluate the health status of the diversion tunnel structure. The research results can provide references for later maintenance work and similar projects.

Investigation on evolution mechanism and treatment of invert damage in operating railway tunnels under heavy rainfall

Investigation on evolution mechanism and treatment of invert damage in operating railway tunnels under heavy rainfall

Field observations on the damage to road bridges after the 2023 Turkey Earthquake

A series of large-scale earthquakes occurred on February 6 in southern Turkey. The authors had the opportunity to join the Japan Disaster Relief (JDR) Expert Team and visit several damaged areas in Turkey from March 10 to 12, 2023. This article highlights damage cases of a road tunnel and several road bridges the authors observed around Antakya, Nurdağı, and Malatya. From the features of the observations, this article discusses the following three items for further study in the seismic design of road bridges: (1) seismic details for robustness, (2) seismic responses of bridges with longer natural periods, and (3) post-event inspection.

Research and application of bag filter system for railway ballast bed coal suction vehicles: An optimization and application study.

The current bag filter system used by railway ballast bed coal suction vehicles for cleaning coal dust from railway tunnels has low operational efficiency and generates significant volumes of dust. This paper describes a simulation test unit designed to enhance the dust removal performance in railway tunnels. The flow field inside the simulation test unit is investigated under different operating conditions through numerical simulations, and the variations in air volume and working resistance, total dust collection efficiency, and optimal operating parameters of a pulse cleaning system are identified through a series of experiments. The numerical results show that the pulse cleaning system does not significantly affect the uniformity of the flow field distribution at the bottom of the filter cartridge during the process of operation. The experimental research indicates that the simulation test unit satisfies the design requirements, achieving an average total dust removal efficiency of 99.93%. A field application shows that the total dust mass concentration at the operator position can be reduced from 335.8 mg∙m-3 to 4.2 mg∙m-3, effectively improving the operating environment within the tunnel.

A Coal Mine Tunnel Deformation Detection Method Using Point Cloud Data.

In recent years, the deformation detection technology for underground tunnels has played a crucial role in coal mine safety management. Currently, traditional methods such as the cross method and those employing the roof abscission layer monitoring instrument are primarily used for tunnel deformation detection in coal mines. With the advancement of photogrammetric methods, three-dimensional laser scanners have gradually become the primary method for deformation detection of coal mine tunnels. However, due to the high-risk confined spaces and distant distribution of coal mine tunnels, stationary three-dimensional laser scanning technology requires a significant amount of labor and time, posing certain operational risks. Currently, mobile laser scanning has become a popular method for coal mine tunnel deformation detection. This paper proposes a method for detecting point cloud deformation of underground coal mine tunnels based on a handheld three-dimensional laser scanner. This method utilizes SLAM laser radar to obtain complete point cloud information of the entire tunnel, while projecting the three-dimensional point cloud onto different planes to obtain the coordinates of the tunnel centerline. By using the calculated tunnel centerline, the three-dimensional point cloud data collected at different times are matched to the same coordinate system, and then the tunnel deformation parameters are analyzed separately from the global and cross-sectional perspectives. Through on-site collection of tunnel data, this paper verifies the feasibility of the algorithm and compares it with other centerline fitting and point cloud registration algorithms, demonstrating higher accuracy and meeting practical needs.

Numerical analysis of underground tunnel deformation: a case study of Midroc Lega-Dembi gold mine

Undertakings in underground mining are often complicated, particularly in situations where geotechnical conditions are not favorable. This study investigates the collapse of tunnels at the Lega-Dembi gold mine in Southern Ethiopia, an area characterized by weak talc formations. The persistent deformation of tunnels poses a threat to the safety of workers and mining operations. In this study, a numerical method that combines continuum and discontinuum approaches is employed to analyze tunnel failures. Additionally, the study evaluates the effect of geotechnical parameters on tunnel deformation, considering various support systems. The results indicate that a combination of rock bolts and shotcrete is effective in mitigating tunnel deformation. Furthermore, the study identifies the geological strength index and unconfined compressive strength as the most influential parameters on tunnel deformation. The findings also suggest appropriate support systems for managing underground instability and enhancing safety measures in weak geological formations.

Research on optimization strategy of TBM tunneling parameters based on stratum perception and simulation tunneling experiment

Real-time perception of surrounding rock stratum and optimization decision of tunneling parameters are of great significance for TBM safe and efficient tunneling. Taking a diversion tunnel in Xinjiang as the engineering background, 948 groups of tunneling data of surrounding rocks at all grades were collected. Aiming at the problem of unbalanced tunneling data of different grades of surrounding rock, the quaternion classification problem of surrounding rock grade is converted into the binary classification problem, and the surrounding rock stratum perception model is established based on EasyEnsemble algorithm. On this basis, a flow frame for optimization of all grades surrounding rock tunneling parameters is proposed, and the differences between the optimization results of exhaustive method, simulated annealing algorithm and ant colony optimization algorithm are compared. The results show that the prediction error of ant colony optimization model is less than 5 %, and the running time is only 1/12 ∼ 1/6 of the exhaustive method. Then, based on the self-developed model test equipment, a similar materials test block of surrounding rock stratum is configured, and a scale cutter head is used for simulation tunneling experiment. The experiment shows that the ant colony optimization model optimization result is the best combination of tunneling parameters, which shows that the proposed optimization flow frame of tunneling parameters has good applicability. Finally, the AdaBoost model was trained with unbalanced samples of various grades of surrounding rock, and the prediction results were statistically analyzed. The results showed that the AUC value of EasyEnsemble model increased by 11.33 % on average, the F-measure increased by 18.12 % on average, and the G-measure increased by 14.00 % on average compared with the AdaBoost model, indicating that data balance has a significant effect on improving the perception accuracy of surrounding rock stratum.

Intelligent prediction method for underbreak extent in underground tunnelling

Underground tunnel excavation using the drill-and-blast method often results in underbreak occurrences due to improper blasting parameters and complex geological environment. This underbreak phenomenon has a profound impact on tunnel safety, stability and construction costs. Traditional approaches for predicting underbreak extent (UE) through field measurements and theoretical models exhibit limitations in terms of accuracy and efficiency. Consequently, it is urgent to develop a novel approach for UE prediction in tunnelling operations. In this paper, extreme gradient boosting (XGBoost) is first applied as the foundational algorithm, and slime mould algorithm (SMA) is implemented for tuning hyper-parameters of XGBoost. Meanwhile, six chaotic maps are integrated with SMA to initialize the population and improve the optimization performance. Subsequently, a dataset of 250 samples is collected from three underground mines in China, involving ten influential factors (RMR, uniaxial compressive strength (UCS), vertical principal stress (σv), lateral pressure coefficient (λ), excavation area (EA), powder factor (PF), specific charge (SC), advance length (AL), periphery hole burden (HB)and periphery hole spacing (HS)). Additionally, four indices, i.e., coefficient of determination (R2), variance accounted for (VAF), mean absolute error (MAE) and root mean square error (RMSE), are used to evaluate the comprehensive performance of these proposed COSMA-XGBoost models and four common machine learning models. Finally, a parametric sensitivity analysis is performed, and the optimal intelligent model is applied in practical tunnelling projects. The results indicate that chaotic optimized SMA models have better convergence ability and higher accuracy compared with the original SMA model. Notably, the PSMA-XGBoost model outperforms other models as the R2, VAF, MAE and RMSE values for the testing set are 0.979, 95.79%, 4.176 and 4.884, respectively, whereas 0.968, 94.25%, 4.274 and 5.012, respectively for training set. EA, RMR and UCS exhibit significant effects on UE. In practical tunneling projects, the engineering application of the PSMA-XGBoost model demonstrates its feasibility and efficiency in predicting UE within underground tunnels.

Numerical Simulation and Application Research of Straight-Hole Cut Blasting with Empty Holes in Railway Tunnels

Numerical Simulation and Application Research of Straight-Hole Cut Blasting with Empty Holes in Railway Tunnels

Stochastic assessment of 3‐D tunnels in near‐fault ground motion using modified domain reduction method

AbstractA robust assessment of tunnels due to uncertainties present in soil and ground motion properties can affect the dynamic response of these structures. In this paper, a stochastic analysis considering an aleatory variability in shear velocity Vs by performing Monte Carlo simulations and assessing its influence on underground tunnels. To numerically assess the response of the soil‐tunnel system to near‐fault earthquake ground motion, the required computational domain usually spans multiple kilometers including both earthquake fault and the structure. Thus, these simulations are computationally expensive. An efficient alternative method, that is, the Domain Reduction Method (DRM), in which a modular two‐step methodology for reducing the computational costs in the large domain analysis is employed. A 3‐D soil‐tunnel structure interaction is modeled to simulate the response of tunnel subjected to an inclined earthquake fault. The numerical simulation of the soil‐tunnel‐fault system is conducted in an open‐source FE package called Multi‐hazard Analysis for STOchastic time DOmaiN phenomena (MASTODON) based on MOOSE framework. The interactive analyses are carried out for three distinct types of soils based on National Earthquake Hazards Reduction Program (NEHRP) provision, that is, soft, medium, and hard, by generating 130 realizations. The results provide many insights into the influence of local site effects, that is, frequency shift for the peak response and the importance of input ground motion characteristics that govern the response of underground structures. The dynamic response of the structure is very sensitive to the uncertainty in rock material properties, especially, the stiffness of the rock sample and the shear wave velocity.

High-Speed Railway Tunnel Bottom in Nearly Horizontally Soft and Hard Interlayered Strata: Deformation Mechanism and Countermeasures

High-Speed Railway Tunnel Bottom in Nearly Horizontally Soft and Hard Interlayered Strata: Deformation Mechanism and Countermeasures

Influence of incident angle on spalling damage of underground tunnels subjected to explosion waves

Tensile waves formed by the reflection of explosive stress waves at the free surface of a tunnel can lead to the destruction of the surrounding rock in the form of spalling. The incident angle of stress waves is an important factor affecting the characteristics of spalling. Theoretical calculations were conducted on the spalling thickness, spalling range, ejection velocity of rock fragments, and the furthest spalling distance in cases of normal incidence and oblique incidence, respectively. The variations of the spalling with the incident angle along the axial direction of the tunnel are presented. The results show that when the Poisson’s ratio of the medium is less than 0.26, the reflected longitudinal wave transforms from a tensile wave to a compressive wave within a certain range of the incident angle. As the incident angle increases, the thickness of the first spalling layer increases monotonically, while the total spalling thickness decreases monotonically. The critical condition of spalling is reached when the first spalling thickness equals the total spalling thickness. For an explosion 6 m away from the tunnel, the critical spalling distance obtained by oblique incidence is 1.67 m/kg1/3, and the peak particle velocity is 3.11 m/s. The critical spalling distance obtained by normal incidence is 5.64 m/kg1/3, and the peak particle velocity is 0.42 m/s. The theoretical results agree well with the on-site experimental data, indicating that the results of oblique incidence overestimated the critical peak particle velocity for spalling.

Intelligent ventilation-on-demand control system for the construction of underground tunnel complex

Intelligent ventilation-on-demand control system for the construction of underground tunnel complex