TBM Tunneling Research Articles

A New Self-Sensing Fiber Optic Anchor to Monitor Bolt Axial Force and Identify Loose Zones in the Surrounding Rock of Open TBM Tunnels.

TBM has been widely used in underground engineering and construction, but there is no precedent for the application of open TBM in the inclined shafts of coal mines, which brings new challenges to the support system. The distribution of the axial forces on anchors and the range of loosening of the surrounding rock are crucial considerations in tunnel support design. Existing methods for measuring the axial forces in anchors and determining the extent of loosening in the surrounding rock typically remain at the inspection level, lacking long-term and real-time monitoring capabilities. This paper presents a new self-sensing anchor with embedded optical fibers (made using an improved stirrer) and proposes an intelligent tunnel rock monitoring system. The paper also outlines a method for identifying loosening zones in surrounding rock based on monitoring data and theoretical analysis. Installing self-sensing anchors in the deep sections of the rock surrounding a tunnel provides three-dimensional, round-the-clock real-time monitoring of the axial forces acting on the anchors, using new technology and methods to recognize the deformation characteristics of loosening zones within the surrounding rock. This new self-sensing fiber optic anchor was first applied to an open TBM tunneling project in an inclined shaft in the Kekegai coal mine, and monitoring data indicate that self-sensing optical fiber anchors can accurately reflect stress patterns in real time. The axial force curve can be divided into four segments: the borehole area, the loosening zone, the stable zone, and the anchoring zone. Consequently, it accurately identifies the thickness of loosening zones at different positions within the tunnel's surrounding rock. This information is compared and verified against results obtained from bolt dynamometers and borehole inspection. On this basis, an intelligent monitoring system was established to provide a basis for making engineering construction decisions, which makes tunnel construction smarter and helps technicians timely adjust TBM driving and support parameters.

Full-scale test of disc cutter rotary cutting in TBM tunnelling: a case study of Mawan granite in Shenzhen, China

Understanding the distribution of cutting force provides a foundation for the design and optimization of cutterhead layout. The simulation of rotary cutting with a large cutting radius remains a challenge for laboratory tests. In this study, taking the driving condition of the Mawan Tunnel located in the Guangdong-Hong Kong-Macao Greater Bay Area as a case study, a full-scale rotary cutting platform with large cutting radius was used to investigate the rock-breaking effects. Rotary cutting with cutting depths of 1–8 mm and cutting radii of 200–1400 mm were carried out on the granite testing platform using a 19-in disc cutter. The normal force, rolling force, and side force during the cutting process were systematically monitored. Moreover, the time–frequency characteristics of the rock breaking process and the effects of cutting depth, cutting radius and stress state on the average and peak loads were investigated. The results show that the average normal force and rolling force increased with increasing cutting depth, while the side force was less affected by cutting depth through the Boltzman model analysis. The average normal force and rolling force were not significantly affected by the cutting radius, but the average side force decreased as a power function with increasing cutting radius, and showed a stable side force when the installation radius exceeded 1000 mm. The dominant frequency of the cutting force was 0–1.2 Hz, exhibiting notable low-frequency characteristics. Additionally, the ratio of peak to average (RPA) with respect to triaxial cutting force demonstrated an increase with the growth of cutting depth, while RPA in terms of side force exhibited a corresponding growth with the increasing cutting radius. In particular, the cutting force characteristics of the cutterhead obtained in this study can inform the layout of disc cutters and real-life TBM operations, thereby avoiding severe overloading of internal disc cutters.

Development of a Novel TBM Tunnelling Test Platform and Its Application in Rock–Machine Interaction Analysis

Development of a Novel TBM Tunnelling Test Platform and Its Application in Rock–Machine Interaction Analysis

Case study on the influence of rock brittleness on the TBM tunnelling performance

Brittleness is an important mechanical property of rock. Accurately evaluating rock brittleness and its influence on the TBM tunnelling performance is necessary. In this work, via two practical engineering cases, with the aim of overcoming the difficulty of penetrating extremely hard rock (breccia fused tuff) in the Zhuxi\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$Z{\ ext{huxi}}$$\\end{document} project, the influence of rock brittleness on the TBM tunnelling performance was studied via comparative analysis with that Nabang\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$Nabang$$\\end{document} project. Seven commonly used rock brittleness indices based on stress‒strain curves were summarized, and a brittleness evaluation method suitable for extremely hard rock was determined by introducing the normalized specific energy to obtain brittleness indices for two lithologies (breccia fused tuff and biotite hornblende plagioclase gneiss) in two projects. The influences of rock brittleness on penetration and the specific energy were compared and analysed. The results showed that the brittleness indices B3\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$B3$$\\end{document} and B5\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$B5$$\\end{document} were more suitable for evaluating rock brittleness. Rock brittleness influenced the TBM tunnelling performance, but this influence gradually decreased with decreasing uniaxial compressive strength (UCS\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$UCS$$\\end{document}), which is obviously less than that of the rock strength. When the UCS\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$UCS$$\\end{document} was lower than 150 MPa, the TBM tunnelling parameters could be adjusted within a significant margin to eliminate the influence of rock brittleness, which could be ignored when predicting the tunnelling performance. When the UCS\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$UCS$$\\end{document} was greater than 150 MPa, rock brittleness imposed a notable influence on the tunnelling performance, which must be considered when predicting the tunnelling performance. This research could provide reference data for evaluating the hard rock brittleness index and accurately predicting the TBM tunnelling performance in engineering practice.

Correction: Developing Estimation Equations for the Cerchar Abrasivity Index of Rocks Applicable to TBM Tunnels

Correction: Developing Estimation Equations for the Cerchar Abrasivity Index of Rocks Applicable to TBM Tunnels

Multi-source seismic geological ahead-prospecting for TBM tunneling in fractured strata: improved strategies and case studies in a water conveyance project, China

Multi-source seismic geological ahead-prospecting for TBM tunneling in fractured strata: improved strategies and case studies in a water conveyance project, China

Wear prediction study considering TBM hob slip

Aiming at the problem of serious tool wear and untimely tool change affecting the construction efficiency when TBM is digging in microfractured tuff strata, the hob wear prediction study is carried out based on engineering examples. By analysing the rock-breaking mechanism of hob wear, a linear wear rate model and a life prediction model considering hob slip are derived based on the CSM model and the abrasive wear theory; the wear rate and the wear amount at the tool change point are further calculated by the prediction model in comparison with the measured value, and the furthest digging distance of the hob is calculated by the life prediction model. The results show that: the relative error between the measured average wear rate and the calculated linear wear rate considering the hob slip is 5.3%; the life prediction model predicts that the longest digging distance of the positive hob is 857 rings and the shortest distance is 198 rings. The results of the study are of guiding significance for the prediction of tool wear and the selection of the timing of opening and changing the hob in TBM tunneling.

Development of Grouting Quality Evaluation System for a Shield TBM Tunnel Using the Impact-Echo Method

Development of Grouting Quality Evaluation System for a Shield TBM Tunnel Using the Impact-Echo Method

Hybrid deep learning-based identification of microseismic events in TBM tunnelling

For TBM’s safe and efficient tunnelling, the microseismic monitoring technique has been widely applied in rockburst warning. However, useful microseismic events are often mixed with noisy events, which seriously affects warning accuracy. To this end, this study proposes several hybrid deep learning-based microseismic identification approaches in TBM tunnelling, where recurrent neural networks directly treat monitored microseismic events as time series and avoid complex feature pre-extraction, and grey wolf optimization and attention mechanism are embedded to optimize model hyper-parameters and recognize value information. Additionally, the learning curve and early-stopping strategy are also integrated to reduce overfitting and underfitting risks. Results in a real TBM-excavated water conveyance tunnel indicate that the bidirectional long short-term memory network model combined with grey wolf optimization and attention mechanism achieves the greatest identification performance among discussed models and provides an effective support for intelligent identification of microseismic events under TBM tunnelling environments.

MatDEM-based study of disc cutter force model in open TBM tunnels: Incorporating installation radius and synergistic effects

The prediction of rock cutting force is critical for tunnel boring machine performance and cutterhead design. This paper presents a novel model for rock cutting force prediction based on the Colorado School of Mines (CSM) model, which incorporates the installation position of disc cutters by introducing installation radius and synergistic effect factors. Linear cutting tests in the laboratory and large-scale rotary cutting simulations in MatDEM software were conducted to examine the impact of these factors. Results indicate that the normal and rolling forces increase and stabilize as the installation radius increases. The synergistic effect produces three force modes in a cutting circle, with mode α having the largest cutting force, mode β having a smaller force, and mode γ having the smallest force. The impact of installation radius and synergistic effect varies with rock-cutter parameters. Multiple regression analysis was used to determine the introduced factors. The proposed model was validated with rock strength and operation data from the Irtysh River conveyance project. The results demonstrate that the proposed model outperforms the CSM model in predicting cutting force in field conditions.

Numerical Analysis of the Single-Directionally Misaligned Segment Behavior of Hydraulic TBM Tunnel

The misalignment of segments in installation is a common issue in the construction of TBM tunnels. This raises a question of whether misalignment affects the operation safety of a hydraulic TBM tunnel. Using a water transfer engineering project as an example, this paper built a three-dimensional finite element model composited with segment, grout layer and surrounding rock for the numerical analysis of the behavior of single-directionally misaligned segments. The crown or invert segment was separately misaligned towards to the center of segment ring in a value of 5 mm, 10 mm, 20 mm, 30 mm or 40 mm. The strength grade of the segment concrete was C50. A weaker surrounding rock composed of V-class rock was considered for the tunnel. The results indicate that the misalignment of the crown or invert segment, respectively, creates the tensile stress in the inner surface of the corresponding segment, the tensile stress will be over the limit of C50 concrete when the misalignment is over 30 mm, indicating a risk of concrete cracking. The contact surfaces of the segment ring basically remain in compression, and the locating pins between the segment rings exhibit an evident increase in tensile stress at misaligned positions. The key points that can be obtained from this study are that a special supervision is needed to ensure the accuracy of segment installation, and strengthening measures are needed for existing misaligned segments.

Analysis of quartz content in muck based on artificial intelligence algorithms and laser-induced breakdown spectroscopy in TBM tunneling

Analysis of quartz content in muck based on artificial intelligence algorithms and laser-induced breakdown spectroscopy in TBM tunneling

Developing Estimation Equations for the Cerchar Abrasivity Index of Rocks Applicable to TBM Tunnels

Developing Estimation Equations for the Cerchar Abrasivity Index of Rocks Applicable to TBM Tunnels

Classification and Prediction of Rock Mass Boreability Based on Daily Advancement during TBM Tunneling

Classification and Prediction of Rock Mass Boreability Based on Daily Advancement during TBM Tunneling

Study on the Information Evolution Law of Water-resistant Rock Mass During Fault Water and Mud Inrush in TBM Tunnels

Study on the Information Evolution Law of Water-resistant Rock Mass During Fault Water and Mud Inrush in TBM Tunnels

Improved TBM side cutter life prediction method considering rock integrity and TBM tunnelling attitude

Improved TBM side cutter life prediction method considering rock integrity and TBM tunnelling attitude

Hydromechanical analysis of slurry infiltration with coupled CFD–DEM method

AbstractThe tunnel face stability is closely related to the migration behavior and clogging mechanism of the slurry particles in granular soils, which is not yet fully understood. In this study, the coupled computational fluid dynamics–discrete element method (CFD–DEM) is adopted to investigate the infiltration behavior of slurry at the particle scale. The full Johnson–Kendall–Roberts (JKR) contact model describing interparticle behavior that accounts for cohesion present even when particles are microseparated after collisions is adopted for clay‐clay or clay‐sand particles and the Hertz–Mindlin model is used for sand‐sand particles. Through simulations, the mechanism of the slurry particle's blockage is identified as physical, frictional and cohesive modes, and slurry particle migration usually undergoes the process of aggregation‐destruction‐migration‐reassembly. Meanwhile, the influences of pressure, cohesive force, and particle shape on infiltration are also analyzed. The results indicate that high pressure lengthens the infiltration path and increases the infiltration rate. The increase in cohesion enhances the effective clogging of the sand column by the slurry, and particles with smaller sphericity are more likely to clog in the sand column. These findings may enhance our understanding of the slurry infiltration mechanism and its practical application in TBM tunneling.

Mechanism of radial chain rockbursts in a deep granite TBM tunnel under the influence of weak band

Radial chain rockbursts (RCRs) in deep-buried TBM tunnels have prolonged durations and can pose significant safety risks. Further research is needed to deepen our understanding of the mechanisms of recurrence of rockbursts under the influence of structure plane. In this study, the geological characteristics, occurrence characteristics, microseismic (MS) activity laws, and rock mass fracture mechanism of several RCRs influenced by weak band were summarized to reveal the mechanism of recurrence of RCRs. Research shows that under the influence of weak band, (1) RCRs tends to occur in the area where the dip angle is large, and the strike intersects with the tunnel direction at a large angle and forms a small angle with the maximum principal stress. The width of the weak band typically ranges from 0.01 to 1 m, which is positively correlated with the final depth of rockburst pit. The strength of the weak band is relatively “soft” compared to the surrounding bedrock. (2) The depth of each rockburst pit in RCRs gradually decreases, the time interval between adjacent rockbursts gradually increases, and the maximum thickness of rock block in each rockburst gradually increases. (3) The maximum MS energy of MS events and the maximum apparent stress gradually decreased in the development process of RCRs. The region of stress concentration gradually extended to deeper zone, and the distance difference between stress concentration region and sidewall during each rockburst occurrence stage gradually decreased. (4) The effect of weak band on RCRs attributes to the excavation induced local stress concentration near the weak band, and the interface between the weak band and surrounding rock controls the boundary of the rockburst body. The “chain effect” of RCRs mainly shows that the promotion effect of the previous rockburst on the subsequent rockburst, by promoting the stress and rock fracture transferring to the deep zone, and the proportion of shear fractures increases.

Prediction method of TBM tunnel surrounding rock classification based on LSTM-SVM

TBM tunnel surrounding rock classification is a key indicator for supporting decision-making and ensuring safe construction. And predicting the surrounding rock type accurately in advance is of great significance for TBM intelligent construction. This paper established the surrounding rock classification model based on support vector machine (LIBSVM), including preprocesses historical tunneling parameters, extracts data information that can accurately reflect the relationship between rock and machine, analyzes the correlation between different parameters and surrounding rock categories, and obtains highly relevant parameters. Based on the long short-term memory (LSTM), the prediction model of total thrust, cutter head torque, gripper pressure, cutter head rotate speed, and propulsion speed are established, which is the strongly correlated parameters with surrounding rock. Combining the parameter prediction model with the surrounding rock classification algorithm, the LSTM-SVM tunnel surrounding rock classification prediction model is established. The results showed that the coefficient of determination of the total thrust model, the cutter head torque, the gripper pressure, the cutter head speed, and the propulsion speed were 0.9825, 0.9396, 0.9974, 0.9843, and 0.9636. The overall prediction accuracy of the surrounding rock category can reach 86.0686%, which can provide a certain reference for predicting the surrounding rock condition in a short distance.

SSFLNet: A Novel Fault Diagnosis Method for Double Shield TBM Tool System.

In tunnel boring projects, wear and tear in the tooling system can have significant consequences, such as decreased boring efficiency, heightened maintenance costs, and potential safety hazards. In this paper, a fault diagnosis method for TBM tooling systems based on SAV-SVDD failure location (SSFL) is proposed. The aim of this method is to detect faults caused by disk cutter wear during the boring process, which diminishes the boring efficiency and is challenging to detect during construction. This paper uses SolidWorks to create a complete three-dimensional model of the TBM hydraulic thrust system and tool system. Then, dynamic simulations are performed with Adams. This helps us understand how the load on the propulsion hydraulic cylinder changes as the TBM tunneling tool wears to different degrees during construction. The hydraulic propulsion system was modeled and simulated using AMESIM software. Utilizing the load on the hydraulic propulsion cylinder as an input signal, pressure signals from the two chambers of the hydraulic cylinder and the system's flow signal were acquired. This enabled an in-depth exploration of the correlation between these acquired signals and the extent of the tooling system failure. Following this analysis, a collection of normal sample data and sample data representing different degrees of disk cutter abrasions was amassed for further study. Next, an SSFL network model for locating the failure area of the cutter was established. Fault sample data were used as the input, and the accuracy of the fault diagnosis model was tested. The test results show that the performance of the SSFL network model is better than that of the SAE-SVM and SVDD network models. The SSFL model achieves 90% accuracy in determining the failure area of the cutter head. The model effectively identifies the failure regions, enabling timely tool replacement to avoid decreased boring efficiency under wear conditions. The experimental findings validate the feasibility of this approach.