Tunneling Machine Research Articles

The rock fragmentation and crack propagation under TBM tunneling based on particle flow code

Abstract The rock fragmentation and crack propagation of anisotropic rock induced by tunnel boring machine (TBM) tunneling is studied in this paper. First, a numerical model based on the 2D particle flow code (PFC2D) is established and calibrated to reveal the four stages of rock fragmentation. In Stage I (indentation depth 0–0.4 mm), the indentation force beneath the cutterhead increases and decreases dramatically with the accumulation and release of mechanical energy. Such a phenomenon indicates that a hydrostatic core (crushed zone) can be observed. In Stage II (indentation depth 0.4–1.1 mm), many median cracks propagate dramatically with the indentation force. Meanwhile, the hydrostatic core is pushed because the mechanical energy of the cutterhead is reaccumulated in the specimen. In Stage III (indentation depth 1.1–2.6 mm), lateral cracks begin to develop due to the further increase in indentation depth. In Stage IV (indentation depth 2.6–5 mm), the lateral cracks and median cracks continue to propagate, and rock chips can be found on the sides of the cutterhead. Then, with increasing confining pressure, lateral cracks begin to gradually develop and the maximum angle of lateral cracks is 70.5°. Furthermore, the magnitude of the intrusion velocity can seriously influence the evolution of the indentation force during Stages III and IV because of the accumulation and release of mechanical energy. The accumulation and release of mechanical energy are more obvious with a higher intrusion velocity of the cutterhead.

Substantiating rational parameters for a stull-timbered device of the selective heading machine

Purpose. To carry out the studies of proposed options for overlapping to support excavation roof and ensure roof maintenance to avoid collapse and protect people and mechanisms. To study a specified goal, an expert assessment of the existing tools to maintain roof rocks in the working area where people and mechanisms are engaged has been carried out. Methodology consists in applying software and computer simulation of interaction processes of mining rocks with arched design options. Findings. A short analysis of the most commonly applied structures to provide temporary fastening of preparatory and permanent mine workings has been carried out. The options for a roof design and the elements for temporary fastening are proposed. The parameters for four sectional overlapping have been substantiated. The loads acting on the roof-supporting structure and the coefficients required to determine the rock loads, the strength of some roof layers and "soil" as well as the forces in the rack hydraulic cylinder have been calculated. Originality. Applying temporary arched fastening in the working area of a tunneling machine promotes reducing a number of technological operations and manual labor employment as well as enhancing maintenance personnel safety. The speed of tunneling works is supposed to increase. Practical value. It is based on the analysis of a selective heading machine performance with an easily collapsed roof, study results to achieve a constructive machine improvement are presented. Its components may vary depending on mining and geological conditions of the work. The obtained parameters are verified by calculations and design solutions. The minimum mass of the fastening that provides both rigidity and strength of the structure is significantly reduced. Obtained results can be applied in underground tunneling and other similar works as well as in constructing roads and railways. The design of the device gives the possibility to adjust the height depending on the mine roof condition.

Prediction of geology condition for slurry pressure balanced shield tunnel with super-large diameter by machine learning algorithms

Real-time and precise prediction of geological conditions is extremely beneficial to the safe and efficient construction of slurry pressure balanced shield machines (SPBMs), especially for super-large diameter tunnels. Machine learning algorithms provide an effective way to predict geological conditions and have been successful in hard-rock tunnel boring machine (hard-rock TBM) tunnels or earth pressure balance shield machine (EPBM) tunnels. However, the effectiveness of machine learning in predicting geological conditions for super-large diameter SPBM tunnels is still unknown. This study systematically demonstrated the application of machine learning algorithms to the prediction of geological conditions in super-large diameter SPBM tunnels based on field data from the Heyan Road crossing river tunnel. The relationship between SPBM parameters and geological conditions was first evaluated, and subsequently, an adaptive model was proposed to determine the number of input variables. The performance of three algorithms, random forest (RF), AdaBoost, and support vector machine (SVM), in rock mass classification, and seven algorithms, multi-objective random forest (MORF), single-target-RF, regressor chain-RF, single-target-AdaBoost, regressor chain-AdaBoost, single-target-SVM, and regressor chain-SVM, in formation percentage prediction, were compared. The results showed that machine learning algorithms can effectively predict the geological conditions in super-large diameter SPBM tunnels. Specifically, RF had the best performance in rock classification compared with AdaBoost and SVM. MORF outperforms the other six algorithms in terms of formation percentage prediction. Additionally, sensitivity analysis indicates that the newly proposed parameters, including slurry system parameters and cutter type, have a clear positive effect on the performance of geological condition prediction.

A Comparative Performance Evaluation of IPv4/IPv6 Using Network Simulation and Virtualization Tools

Internet users are expected to grow from 4.5 billion in 2020 to 5.3 billion by 2023. In terms of the population, this represents 66% of the global population. However, the growth of connected devices and internet users is going very fast. Not yet as the number of the internet of things (IoT) applications such as video surveillance, smart meters, and tracking and the machine to machine increased as well. The address space of the IPv4 cannot meet these requirements and this growth in the connected devices. According to that another IP address scheme designed to meet the requirements and the needs for the IoT & M2M and the growth of the number of internet users. This is the IPv6 which consist of 128 bit and can provide a huge number of addresses. The limitation of the addressing space was solved by the IPv6 but the problem arises in the migration from IPv4 to IPv6 as the migration cannot happen overnight so transition mechanisms developed to allow the communication between both IPv4 and IPv6 network. This paper aims to study the performance parameters such as the delay, the throughput, and the TCP establishment time which could be affected by the transition mechanism. The methodology that used in this project is using a network simulation tools such as GNS3 and virtual box to simulate the network scenarios and network performance check such as Wireshark and iperf3 tools to analyse the traffic. The results in this project show that if the delay is the main concern, then the tunneling machine will be the best choice, behind that when the TCP flow playing an important role for the network engineer then the tunneling machine will be the best option. However, the dual-stack method is considered the best in terms of throughput.

Jamming of the double-shield tunnel boring machine in a deep tunnel in Nyingchi, Tibet Autonomous Region, China

The Duoxiongla tunnel in Nyingchi, Tibet Autonomous Region, China passes through a gneissic formation, with a maximum 830 m thick overburden. The tunnel was excavated by a double-shield tunnel boring machine (TBM) and three shield jamming accidents occurred during the construction, which adversely affected the construction progress. In order to prevent the shield machine from jamming again, numerical simulations were conducted to investigate the shield jamming accidents. In addition, the contact relationship between double-shield and surrounding rocks when the TBM entered squeezing ground and the changes in frictional resistance to be overcome during the excavation process were studied. The effects of injection of lubricants and over-cut on reducing the shield jamming risk were explored. Finally, the jamming criterion was proposed by comprehensively considering the surrounding rock strength, in-situ stress, surrounding rock deformation, and reserved gap. The results show that the sequence of surrounding rocks that come into contact with and squeeze the TBM can be influenced by the gap between shields and surrounding rocks, and the locations where the three shield jamming accidents happened are consistent with the actual advancing lengths of the TBM in the formation with extrusion deformation. The method of injecting lubricants at the contact position between surrounding rocks and shields fails to release the jammed TBM. Over-cut can widen the gap between surrounding rocks and shields, which reduces the risk of shield jamming. The assessment of jamming in the Duoxiongla tunnel based on the established jamming criterion is consistent with the actual engineering excavation conditions and can provide reference for judging shield jamming during TBM excavation in other types of squeezing ground.

Calculation of surface settlement and pile foundation deformation caused by shield machine tunnelling along curve section

The shield machine tunnelling along the curve section causes more disturbance to the surrounding environment than the straight section. Pile foundation is the most commonly used foundation form in high-rise buildings, and high-rise buildings have extremely high requirements for controlling non-uniform deformation. Therefore, it is necessary to study the surface settlement and the deformation law of pile foundations caused by shield machine tunnelling along the curve section. Considering the shield machine tunnelling factors along the curve section and the coupling effect of piles and soil, the analytical calculation formula of the ground settlement and the pile foundation deformation caused by the shield machine tunnelling along the curve section is deduced. According to the actual project situation, a finite difference model (FDM) is constructed, and the correctness of the FDM and analytical prediction formula is verified by comparing the on-site monitoring data. The research shows that the error among the FDM results, the analytical prediction results, and the on-site monitoring data are small, and the surface settlement and pile foundation deformation meet the construction control standards. The friction resistance of the shield shell, the integrative gap at the shield tail (IGST), and the over-cutting gap (OG) are the main factors leading to the surface settlement. However, the shield shell friction and OG are the main reasons leading to the inner settlement of the curve section being more prominent than the outer side. The difference in the pile foundation settlement on both sides of the curve section is slight, the maximum settlement difference rate is 1.8%, and the maximum horizontal deformation rate of the pile foundation on the inner and outer sides is 9.2%, which shows that the horizontal deformation of the pile foundation is more sensitive to the asymmetrically distributed construction factors.

Predicting variation of multipoint earth pressure in sealed chambers of shield tunneling machines based on hybrid deep learning

In order to avoid safety accidents caused by the unbalance of earth pressure in the chamber during the tunneling process of shield tunneling machine, it is very crucial to make a scientific and accurate dynamic prediction of earth pressure change. Therefore, a hybrid deep learning model is built by using discrete wavelet transform (DWT), one-dimensional convolution neural network (1DCNN) and long-short term memory (LSTM), implementing the scientific prediction of multipoint earth pressure variation trend in this paper. The DWT is introduced to reduce noise in training data, reduce training cost, and improve training accuracy; the 1DCNN is employed to extract features quickly and reduce the training time of LSTM; in order to further improve the prediction performance of the model, the Ranger optimizer is used to optimize the LSTM, which not only improves the prediction accuracy, but also makes the training process of the prediction model more stable. Finally, the validity of the model is verified based on the actual construction data. The results show that the overall and local earth pressure variation trends in the sealed chamber are clearly visible, which can provide decision-making basis for the shield machine to realize automatic, intelligent and safe excavation construction.

DEM-continuum mechanics coupling simulation of cutting reinforced concrete pile by shield machine

Based on the discrete element method (DEM) - continuum mechanics coupling method, a numerical simulation analysis is carried out to model cutting some existing bridge piles that have invaded Beijing Metro Line 12. Firstly, the macroscopic parameters of the reinforced concrete pile and the soil stratum where the shield tunneling machine traversed are calibrated using uniaxial compression and Brazilian test through a series of numerical tests. In this paper, the procedure of building up a DEM-continuum mechanics coupling model is presented, then the model is applied to simulate the process of cutting the pile foundation using the earth pressure balanced (EPB) shield machine. The influences of different advancing parameters on the displacement of the pile bottom, the thrust force, and the torque of the EPB shield machine are investigated. The simulation-calculated results, such as thrust force and torque of the shield machine, are in good agreement with the theoretical method in previous studies and the corresponding monitored data in the field. Finally, a method based on the thrust of a single cutter is proposed to improve the theoretical model so that it can consider the effects of cutting bridge piles.

Regulating bulkhead pressure of EPB shield machines through DEM modeling and data mining

Proper regulation of the earth pressure on the bulkhead of earth-pressure balanced (EPB) shield tunneling machines is significant to ensure safe construction. This study proposes a procedure for regulating the bulkhead pressure by combining numerical simulations and data mining, and applies the procedure to a metro line constructed in sandy pebble stratum using EPB shield. Firstly, the relationship between the bulkhead pressure and the pressure on the tunnel face is carefully obtained from discrete element modeling, and the required supporting earth pressure is derived by considering the arching effect. Secondly, aided with the machine learning method, a model is constructed for predicting the average bulkhead pressure per ring according to the operational parameters (i.e., the average driving speed and the rotation speed of the screw conveyor). Given the target value of the bulkhead pressure, the optimal values of the operational parameters are obtained from the model. In addition, an autoregressive moving average stochastic process model is developed to monitor the real-time fluctuation of the bulkhead pressure and guide the actions taken in time to avoid dramatic fluctuations. The results indicate that the pressure difference between the tunnel face and the bulkhead is considerable, and the consideration of the arching effect can avoid overestimating the bulkhead pressure. A combination of the machine learning model and the stochastic process model provides a plausible performance in regulating the bulkhead pressure around the target value without dramatic fluctuation.

Laboratory experiments and discrete element modeling on the surface failure induced by EPB tunneling: The effects of cutterhead open ratio and relative tunneling depth

This paper presents laboratory tests and high-fidelity numerical simulations to examine the ground failure induced by Earth Pressure Balance (EPB) Shield Tunneling in granular soils. Specifically, we designed and conducted laboratory tests using a reduced-scale EPB Shield Tunnel machine, and built corresponding three-dimensional (3D) discrete-element method (DEM) models to simulate the dynamic excavation process and to gain further understandings of the mechanisms of the ground movement. The study is particularly focused on the combined influences of the cutterhead open ratio and the relative tunnel depth on the ground motions and stress perturbations during the EPB tunneling, which remain understudied in existing studies. The results show that the open ratio of the cutterhead has significant effects on the ground failure in granular soils, especially in cases of relatively shallow tunnels. The larger the open ratio of the cutterhead, the wider the surface and subsurface settlement trough and the greater the soil pressure in the chamber. The pressure distribution in the soil chamber with a larger cutterhead open ratio is significantly more non-linear than that of the case with a smaller cutterhead open ratio. For a given cover-to-diameter ratio (C/D) of the tunnel, the width parameter (k) is generally constant regardless of the depth for the case with a large cutterhead open ratio, especially in the relatively shallow tunnels, while it increases non-linearly with the depth for the case with a small cutterhead open ratio, especially in relatively deep tunnels. Furthermore, soil arching mechanisms are analyzed qualitatively with respect to different cutterhead open ratios and C/Ds. The study demonstrates quantitatively the response of ground surface to the cutterhead open ratios and C/Ds as well as the associated ground failure mechanisms through a combination of laboratory experiments and 3D DEM simulations, providing further insights into the ground behaviors during the dynamic EPB tunneling process.

Wear mechanism and life prediction of the ripper in a 9‐m‐diameter shield machine tunneling project of the Beijing new airport line in a sand‐pebble stratum

AbstractTool wear is a noteworthy problem in the process of shield tunneling, and the degree of wear varies with stratum. The sand‐pebble strata in Beijing are typically mechanically unstable. However, many subways are buried wholly or partially in sand‐pebble strata. Taking the Beijing New Airport line tunneling project as research background, this study evaluated the wear characteristics of the multiconfiguration rippers of a 9‐m‐diameter spoke‐type shield tunneling machine in a sand‐pebble stratum. The wear values of five ripper teeth and ripper flanks were analyzed based on field‐measured data from the Beijing New Airport line project. As the analytical results show, the wear value generally increases as the installation radius enlarges with the rise of cutting trace length. The wear of the 190‐rippers was divided into five categories: pedestal wear, ripper teeth collapse, uniform wear, ripper teeth falling off and ripper flank wear. Uniform wear of the ripper teeth and ripper flank wear were the two abrasion types of the 190‐rippers. The teeth of the 155‐rippers mostly maintained their cutting capacity under the protection of the 190‐rippers. A wear prediction model of linear fitting field data was developed for a 190‐ripper face to obtain the optimum shield driving distance in the sand‐pebble stratum. The average wear coefficients of the 190‐ripper before and after replacement matched well, being 0.045 and 0.066 mm/km, respectively. The results of this study provide a theoretical reference for tool wear prediction in shield construction under similar geological conditions.

Effects of laser energy density and path on residual stress of remanufactured key components for shield tunneling machine

Due to the abrasion and high cost of key components for shield tunneling machines, the failed or worn components are remanufactured by laser melting deposition (LMD) with paraxial powder feed. However, the residual stresses distributed in the cladding layer reduce the service life of remanufactured parts. In this paper, an experimental study is presented on residual stresses along the depth direction of cladding with varied laser energy density and deposition path. Residual stress in Fe-based coating and heat-affected zone (HAZ) is characterized by X-rays with the method of layer-removal. The microstructural evolution and the phase structure of laser deposited cladding layers are analyzed. The results indicate that the residual stresses, in the range of −624 to −86 MPa in the cladding layer, are mainly compressive while the tensile stresses (in the range of 200–550 MPa) are primarily in the heat-affected zone (HAZ). With the increase of the thickness of the cladding layer, the depth of the zero stress layer increases. The main phases in the cladding layer are α-Fe and γ-Fe. The microstructure in the top layers of the cladding consists of fine, equiaxed grains while in the lower layers, the grains are distinctly cellular.

Refinement Study on Pressure Relief Zone of Gas Extraction Borehole Considering Roughness

Pre-pumping of coal seam gas by gas extraction borehole is an effective measure to manage gas. The existing study concluded that the pressure relief zone of the roadway is difficult to seal, and thus the sealing depth of the gas extraction borehole should generally exceed the pressure relief zone of the roadway. Based on the relationship between roughness and GSI, a numerical simulation was carried out with the engineering background of the 22200 machine tunnel of the E8 coal seam of the Sixth Mine of Pingdingshan Tianan Coal Industry Company Limited. The results of numerical simulation and field experiments show that: (1) the quantitative standard of whether the borehole has “air leakage” or whether the surrounding rock cracks around the borehole are connected to the free surface can be characterized by permeability; (2) the variation rate of relative permeability has an inflection point at 2–4 m from the free surface of the roadway wall; (3) the dividing point of whether the surrounding rock cracks around the borehole are connected to the free surface can be set at 6 m, which is located in the pressure relief zone. (4) when the sealing depth of the coal roadway is 6 m and the sealing depth of the rock roadway is 5 m, there is no gas leakage in the borehole, that is, there is an area where a crack is not connected with the free surface of the roadway in the pressure relief zone.

Multiscale Variational Autoencoder Aided Convolutional Neural Network for Pose Estimation of Tunneling Machine Using a Single Monocular Image

With the rising demand of underground construction, intelligent tunneling techniques have been increasingly studied to improve the safety and efficiency of construction. The self-positioning technology of tunneling machines is the cornerstone of intelligent tunneling, which is particularly challenging \textcolor{blue}{due to} the extreme environments of the underground tunnels. In this paper, a novel robust and real-time six degrees of freedom (6-DoF) pose estimation strategy is proposed for tunneling machines based on the computer vision and deep learning methods. A monocular camera is attached to the tunneling machine, and employed to capture the images of the artificial feature object that is set far behind the tunneling machine. A novel multi-scale variational autoencoder aided convolutional neural network (MSVAE-CNN) model is developed to estimate the current absolute 6-DoF pose of the tunneling machine in an end-to-end manner using a single monocular image, in which the multi-task variational learning scheme is able to enhance the generalization and robustness of the model and the multi-scale structure can improve the learning ability of the neural network. In our numerical experiments, a Motion Capture System is utilized to assist the acquisition of training dataset. The experimental results demonstrate the efficacy of the proposed MSVAE-CNN based pose estimation method.

A shield tunneling method for enlarging the diameter of existing tunnels: Experimental investigations

As for the construction of a metro line, excavated stations usually serve as departure and receiving shafts of the shield tunneling machines, used for drilling of station-to-station tunnels. However, the shield tunneling machines may reach the stations before their excavation. In order to avoid stopping of tunneling to wait for the completion of the station, a Shield Twice Tunneling Method (STTM) is developed and applied to a real engineering example. It permits the station-to-station tunneling machines to pass through the stations first. Subsequently, larger-diameter shield tunneling machines are driven from one end of the station to the other one. The resulting tunnels serve as side-platform stations. A model test, simulating the tunneling process of the larger-diameter shield tunneling machines, was carried out. It was designed according to the concept of equivalent specific energy. The experimental results corroborate the rationality of the selected tunneling machine and of its equipment with cutters. In addition, suitable tunneling parameters are provided. The average values of the thrust forces and the torsional moments are predicted, based on the results of the model test. They agree with the monitored results on site. This demonstrates the usefulness of the model test. Application of the STTM to a real engineering project shows that the entire construction period was reduced by 45%.

Analysis of working face stability during obstruction removal from a box tunnel machine

Analysis of working face stability during obstruction removal from a box tunnel machine

Full scale study of pile response to EPBS tunnelling on a Grand Paris Express site

This article presents a full-scale experiment on the effect of EPBS tunnelling on pile foundations in the Paris area. Three cast in-situ piles, instrumented with strain gauges and optical fibre cables, were installed at different distances from tunnel axis with various pile base positions to monitor pile strains as the EPBS progresses. This paper investigates pile – soil differential settlements at ground surface, axial load variations, shaft friction mobilization, base load variations, bending moments and pile structural failure possibility. The pile behaviour changed depending on the pile position with respect to the tunnelling machine, with the main changes occurring during the passage of the EPBS beneath or at pile level. Estimation of pile behaviour based on simplified modelling was confirmed by the field monitoring.

Coupling dynamic characteristics of tunnel boring machine cutterhead system with multi-source uncertainties

During tunnel boring machine (TBM) tunneling, the violent vibration of the cutterhead system is the major cause of structural failure and engineering accidents. There are many uncertain coupled factors of the cutterhead system, which can lead to inaccurate vibration analysis and difficulty predicting the dynamic response. In this study, coupling dynamic characteristics under multi-source uncertainties of the TBM cutterhead system were analyzed. First, a geological uncertain coupling model and disc cutter uncertain coupling model were established. Then, the load interval boundaries with multi-source uncertainties under different working conditions were obtained and the load interval boundary was combined with the cutterhead dynamic model to establish a dynamic model with multi-source uncertainties. Finally, a dynamic characteristic analysis was carried out using a real-world engineering example to validate the model. The results show that when multi-source uncertainties are considered: (1) The maximum increase in the radial load amplitude and corresponding load interval median are about 137% and 73%, respectively. The maximum increase in the overturning moment amplitude and the load interval median are roughly 92% and 93%, respectively. (2) Under typical working conditions, the maximum increase in the stability vibration response boundary is about 92% for the radial displacement response, with a maximum increase in overturning angle displacement of 70%. (3) The optimum mass fraction of the cutterhead center block is around 46.5%, resulting in the smallest vibration amplitude. The results provide a theoretical reference for the design of cutterhead structures for vibration reduction.

Prediction and analysis of slurry shield TBM disc cutter wear and its application in cutter change time

Disc cutter is mainly used in cutting through hard rock. Disc cutter wear is inevitable during tunnel boring machine (TBM) tunneling, and excessive wear can lead to a decrease in tunneling efficiency and increase construction risks. Therefore, the importance of predicting the disc cutter wear accurately and arranging the cutter change plan can never be overemphasized. In this study, disc cutter wear data and replacement records for three shield chamber openings were analyzed, which were collected from a water conveyance tunnel project in Guangdong, China. It was found that the normal wear failure accounted for approximately 76.19%, while the abnormal wear failure accounted for 23.81%, and the range of tools to be replaced due to normal wear continues expanded as the tunneling distance increased. Based on the observed wear data, it is found that the wear rate of edge tools is much lower than that of center tools, which does not conform to the normal wear rules. Subsequently, a new disc cutter wear prediction model was developed considering energy conversion and uneven thrust distribution for explaining this problem. The determination method of the energy conversion coefficient k and thrust distribution coefficient b was proposed, and they had been obtained from the wear data in the first replacement. On the other hand, the proposed model has higher accuracy in both cutter wear and cutter change range prediction compared with the existing models. However, the prediction accuracy of the proposed model will decrease with the increase of the tunneling distance, so the undetermined coefficients k and b need to be updated in a timely manner.

Deep learning analysis for energy consumption of shield tunneling machine drive system

Inaccurate estimation of energy from the shield driving system may result in serious energy loss and low tunneling efficiency. A deep learning network is developed in this study to optimize the energy consumption of cutterhead drives in a shield tunneling system. The proposed model, KCNN-LSTM, cooperates convolutional neural network (CNN) and long short-term memory predictor (LSTM) based on clustering algorithm to realize accurate energy consumption forecasts. First, geological conditions, shield operational parameters, and geometry are characterized and identified using a feature extraction strategy. The proposed model is used to decompose the energy consumption values and extract the sequential and implicit features of nonlinear interactions. The prediction is then applied to a real tunnel field case study. The modeling results are evaluated by comparing its performance with the reproduced Naïve predictor and other proven deep learning networks including recurrent neural network (RNN), CNN, and LSTM. The comparisons reveal that the proposed model outperforms the other conventional techniques in predictive accuracy. The KCNN-LSTM model provides an accurate and feasible tool for adjusting the energy consumption of cutterhead drives in shield tunneling.