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Mechanical performance of TBM cutterhead in mixed rock ground conditions
Abstract
The mechanical performance of TBM cutterhead including thrust, torque, eccentric force and overturning moment was calculated and analysed in different mixed rock ground conditions. The calculation model was built by identifying the rock type under each cutter using a ray intersection algorithm and calculating the cutting forces of each cutter using the CSM model. The mixed rock ground conditions were simplified as rock type distribution and rock strength classification. In the present paper, the rock distributions of the Layer-Banded Rock (LBR) and Random-Distributed Rock (RDR) types were considered. The influences of rock strength (Uniaxial Compressive Strength: UCS, Brazilian Tensile Strength: BTS), rock locations and number of rock layers were studied. For verification, a boring experiment was designed and conducted using an experimental cutterhead with 14 disc cutters. The rock box was poured with concrete C20, C40 and C60 layer by layer to prepare the LBR condition. The average torque and thrust of the calculation model and experiment were in good agreement. Some conclusions were drawn from the study on the rock strength, rock locations, area percentages of different rock layers and number of rock layers. And hence, some suggestions were proposed to enhance the tunnelling efficiency and reduce damage to the cutterhead.
... Obviously, cutterhead-block interaction involves front blocks and corner blocks, while rear blocks bear no cutterhead-block interaction. The cutter-rock interactive forces have been widely investigated through LCM (linear cutting machine) laboratory tests (Gertsch et al. 2007;Cho et al. 2013), RCM (rotary cutting machine) laboratory tests (Xia et al. 2012;Geng et al. 2016), numerical simulation (Cho et al. 2010;Yang et al. 2016;Xiao et al. 2017), theoretical analysis (Roxborough and Phillips 1975;Rostami and Ozdemir 1993) and in situ tests (Gong et al. 2007;Yin et al. 2014). Interactive forces acting on a cutter are usually composed of normal contact force, tangential force and side forces, which are related to the cutter's geometrical size, penetration extent, spacing and cutting speed (Roxborough and Phillips 1975;Rostami and Ozdemir 1993). ...
... Actually, the interactive forces fluctuate during TBM advancing in real projects (Gong et al. 2007;Farrokh and Rostami 2009;Yin et al. 2014). For hard rock TBMs, the normal force is in a range of 0-400 kN and the tangential force lies between 0 and 35 kN as noted in many numerical (Cho et al. 2010;Yang et al. 2016;Xiao et al. 2017) and experimental analyses (Gertsch et al. 2007;Cho et al. 2013;Geng et al. 2016;Gong et al. 2007;Xia et al. 2012;Yin et al. 2014). The cutting coefficient (CC), which is defined as the ratio of the tangential force to the normal force, has been shown to be within a range of 4-14% (Gertsch et al. 2007;Farrokh and Rostami 2009;Cho et al. 2013). ...
... Only front blocks and corner blocks will experience cutterhead-block interaction. To determine whether a cutter acts on block B or not can thusly be simplified as an equivalent problem of determining whether a point is in a polygon or not (Geng et al. 2016;Hormann and Agathos 2001), through which the number of active cutters on block B can be determined. ...
It is important to consider machine–block interaction when assessing the stability of tunnels excavated by tunnel boring machine (TBM) in blocky rock mass as the behavior of rock blocks changes with TBM progression. The cutterhead motion (advancement and rotation) alters the geometry of rock blocks and the cutters acting on the block. As a consequence, the contact forces between the cutterhead and rock blocks change, which leads to the variation of block kinematics and stability. This paper extends the traditional block theory to analyze the life-cycle behavioristics (morphology, mechanics, kinematics and stability) of rock blocks during TBM tunneling considering TBM–block interaction. The morphology analysis follows the traditional block theory but considers TBM–block interaction. The cutterhead–block interaction is decomposed into a normal component and a tangential component, both of which depend on cutterhead motion. The removability conditions and mechanical equations for three traditional translational modes and two rotational modes are derived, based on which the kinematics and stability of rock blocks during TBM tunneling can be determined. Implementation of the proposed methodologies in reflecting the dynamic evolution of block behavioristics in the process of TBM tunneling is demonstrated through a generic example.
... As for the LBR mixed ground condition, new approaches have been proposed by which the mechanical performance parameters of cutterhead including torque, thrust, and eccentric force and overturning moment can be estimated (Geng et al., 2016;Rostami, 2008). Geng et al. (2016) introduced a calculation method and validated it by a laboratory scale test. ...
... As for the LBR mixed ground condition, new approaches have been proposed by which the mechanical performance parameters of cutterhead including torque, thrust, and eccentric force and overturning moment can be estimated (Geng et al., 2016;Rostami, 2008). Geng et al. (2016) introduced a calculation method and validated it by a laboratory scale test. These methods can be applied to performance prediction investigations. ...
... However, depending upon the strength parameters of the harder rock formation, a low penetration rate is anticipated (Qi et al., 2015). To avoid such unfavourable delays, modifications on the TBM cutterhead such as using a combination of drag bits and disc cutters or using high strength material disc cutters or even larger disc cutters with higher load bearing capacities are recommended (Geng et al., 2016;Yi et al., 2014). As for more abrasive rocks, all of the steel structures and tools in contact with abrasive rock need to be wear protected efficently. ...
Mixed-face grounds could be frequently experienced during TBM tunneling in hard rocks. As a consequence, this condition brings about potential difficulties for the tunneling operation such as an escalation in the disc cutter consumption and undesirable TBM performance. In this paper, the performance of a hard rock double-shield TBM in mixed-face ground conditions of a limited chainage of Kerman water conveyance tunnel is discussed and analyzed accordingly. The water transmission Complex from Safa dam to Kerman was initially designed to transfer a proportion of Jazmourian watershed to the city of Kerman. This complex encompasses a tunnel with the length of 38 kilometers divided into two main lots in south and north. Frequent and intermittent lithological variations originated from intruded dykes and igneous plutons in a limited chainage of tunnel in the southern part led to high disc cutter consumption, local damages to the cutterhead and consequent reductions in the TBM advance rate. The main lithology of the rock mass in this region is consisted of Diorites and Agglomerates. Besides, the existence of a fault with crushed zones in the tunnel path direction further aggravated the situation. In a detailed analysis on the disc cutters consumption, various cutter wear mechanisms including flat wear and multi-flat wear, extension of cracks on the cutter rings and breakage occurred in the cutter rings and bearing were identified as a result of mixed-face grounds as well as too much abrasivity of rocks in some sections. In order to improve understanding upon mixed-face condition in hard rock TBMs, a description of Kerman water conveyance tunnel components and geology is firstly presented as a case study. Subsequently, the main operational problems encountered in the specific chainage of tunnel being subject to mixed-face grounds are explained with an emphasis on different possible mechanisms of disc cutter wear. The distribution of damage cutters on the cutterhead are analyzed in detail and optimum performance parameters for excavating through these zones are presented. Lastly, some measures are suggested by which the negative impacts of such circumstances can be minimized.
... Modeling the distribution of disc cutters and drag cutters on the cutterhead in different excavation faces can reflect the cutting process of cutters more intuitively when the cutterhead is rotating, but such models are very scarce. Geng et al. [4] fixed the positions of each tool and stratum in the coordinate system, identified the types of rocks under each cutter using a ray intersection algorithm, and then utilized the Colorado School of Mines (CSM) model to determine the cutter cutting forces. However, the model was only applied to the layer-banded rock (LBR) and the random-distributed rock (RDR) conditions. ...
... When Rs is 0%, 50%, and 100%, the values of the torque, thrust, and power hardly fluctuate. The present conclusions agree with some previous research by Geng et al. [4] and Zhang et al. [5], which shows the viability of our model. Figure 10 depicts the variation of cutterhead torque, thrust, and total power with various penetrations when the cutterhead is spinning. ...
In this paper, a theoretical estimation model of TBM thrust, torque, and power in the rock–soil interface (RSI) of mixed ground is developed, including a new force model for the drag cutter that accounts for chamber pressure and soil friction. A distribution model of the disc cutters and drag cutters on the cutterhead adaptable to different excavation surfaces is built in order to visualize the cutting process as the TBM cutterhead rotates, and a program is created and that runs smoothly using the Python version 3.8, which can recognize the numbers and calculate the forces of the disc cutters and drag cutters in the soft and hard strata, respectively. Then, combining with friction forces and chamber pressure calculated by the program, the variation in torque, thrust, and power are produced. Subsequently, a new index (MPPI), which considers both the thrust of the TBM and cutterhead torque, for forecasting TBM tunneling performance in composite strata is presented. The reliability of the index as well as the estimation model are validated using data from an actual project to offer recommendations for future tunneling projects.
... Rong et al. (2019) developed a quantitative relationship between operational parameters and tool wear. In order to reduce cutter wear and enhance tunneling efficiency, Geng et al. (2016) calculated and analyzed the performance of a tunnel boring machine (TBM) cutterhead, including the thrust, torque, eccentric force, design, and overturning moment under different geological conditions. Amoun et al. (2017) investigated the influence of geological parameters and operational factors on tool wear and concluded that the increase of TBM thrust, earth pressure, and torque generally leads to the rise of cutter consumption. ...
Tool 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.
... Such highly specific models are often closely associated with the use of artificial intelligence models (Armaghani et al., 2019;Salimi et al., 2019;Gao et al., 2020;Li et al., 2020;Afradi and Ebrahimabadi, 2021;Zhou et al., 2021a). In particular, research into small-diameter tunnelling performance in soil and loose rock has been largely neglected, and predictions are based on the experience of TBM manufacturers and contractors (Geng et al., 2016;Macias et al., 2020;Goodarzi et al., 2021;Lehmann et al., 2022). More strikingly, the projects in the databases used for the TBM prediction can be quite old (going back to the 1960 s) and thus neglect advancements in machines technology. ...
... The calculation of the thrust is based on parameters such as uniaxial compressive strength, opening ratios of the cutterhead, tensile strength, and borehole diameters [9]. Additional theoretical studies can be found in [10], [11], [12], and [13]. Theoretical modelling usually focuses on analyzing the thrust of a single cutter. ...
It is difficult for tunnel boring machine (TBM) operators to respond for safe and high-efficient construction without accurate reference parameters such as the TBM thrust. A new hybrid model (MRFO-AT-TELM) combining an improved two-hidden-layer extreme learning machine (AT-TELM) and manta ray foraging optimization (MRFO) algorithm is proposed to predict TBM thrust with 12 selected input featuring parameters. The affine transformation (AT) activation function is used to improve the performance of TELM. Input weights and bias of AT-TELM are optimized using the MRFO algorithm. The performance of the proposed model is validated with TBM construction data collected from the Yin-Song Project in China and compared with other models. Input data of the first 30, 60, and 90 seconds of the rising period are analyzed. Results show that the proposed model is superior to the other models and with 90-second data as input outperforms that with 30 and 60-seconds data. The proposed model and the selected input features are validated in a new project. The thrust prediction model can be embedded into the TBM construction intelligence system and thus help improve construction efficiency.
... Typical tests include the cutter wear test (Bruland, 1998), the linear cutting machine (LCM) test (Balci, 2009;Cho et al., 2013;Tumac and Balci, 2015;Entacher and Schuller, 2018;Zhang et al., 2018), and the rotary cutting machine (RCM) test (Qi et al., 2016;Pan et al., 2018;Peng et al., 2018). For an instance, a testing apparatus which can examine an actual fullscale cutterhead is recently developed (Geng et al., 2016). Although this approach testing each machine part is valid, an assembly of these numerous components can still present a risk to any defect as a whole intact machine. ...
Construction of urban tunnels using a tunnel boring machine (TBM) is often favored over drilling-and-blasting based excavation method. Often, TBMs are customized and re-used in fields. However, little effort has been made to verify the status quo of the reused TBM prior to its placement, and no apparatus or method is available to examine the excavation performance of whole, assembled TBMs. Therefore, we present a newly developed apparatus which can examine the excavation performance of small cross-section TBMs with the cutterhead diameter of ∼3.5 m at full scale. The equipment was verified with a rock-like concrete specimen, in which the excavation of TBM was examined while varying the thrust and cutterhead rotational speed. The test results reveal the positive impact of thrust on the penetration rate (PR) and penetration depth (Pe), as well as a linear relationship between PR and the cutterhead speed. This proves that the presented full-scale TBM excavation testing method is capable to produce reliable and remarkably consistent results. The presented full-scale excavation testing method can be used to examine the functionality of a TBM of interest and further explore the effect of different ground conditions, such as rock strength, joints, and weathering, and the effect of different cutterhead design, including the number of cutters, cutter shape, and cutter location.
... It can provide theoretical basis for design the better pick cutting performance type cutting pick. Zheng KH et al. [25][26] proposed a numerical three-dimensional (3D) mesoscopic approach of pick cutting complex coal seams, which could investigate the effects of the 3D meso-structure on the failure patterns and fracture mechanism. ...
Shearer provide an effect solution for mining coal, and the cutting performance of pick largely accouts for the ability of a shearer and mining performance. We conducted pick cutting coal experiments in different seam forms on the coal and rock cutting teasted. According to the rotary cutting mechanical model of single pick cutting coal seam, combined with the strength condition of coal seam and coal-rock interface, the rotary cutting mechanical model of pick cutting coal seam with coal-rock interface is established. The stress strain and strength condition of the area in and around the interface are analyzed based on the coal-rock interface crushing theory, which provides basis for further research on the cutting mechanical model of single pick crossing the coal-rock interface. According to the analysis on the ampulitude domain, the phenomenon that force increment between the pick cutting rock and uniform coal seam linearly increases with the increase of compressive strength difference between coal seam and coal-rock interface, and the load fluctuation keep a positive correlation with the compressive strength. Analysis on the signals of the pick cutting coal seam with coal and rock interface at different conditions shows that some basic properties of the cutting load changes over times. In addition, the coal seam with coal-rock interface appears larger impact load and other time-domain characteristics.
... Shi et al. [8] put forward a method for calculating the cutterhead torque by taking into account the cutterhead structure, cutting principle, and geological conditions. Additionally, Zhou et al. [9] and Geng et al. [10] studied the factors that influence the thrust and torque of cutterheads and derived a model for calculating the relevant thrust, torque, overturning torque, and other external loads. Xia et al. [11] modified the cutterhead overturning moment calculation model and analyzed the mechanical performance of a typical TBM cutterhead under different working conditions. ...
The cutterhead of a full-face rock tunnel boring machine (TBM) is constantly subjected to varying impact and dynamic loads during tunneling processes, resulting in relatively large vibrations that could easily lead to fatigue cracking of the entire machine and affect the tunneling performance and efficiency. To explore the dynamic characteristics of the TBM mainframe, a TBM from a water-diversion project is investigated in this research. According to the TBM vibration transmission route, an equivalent dynamic model of the TBM mainframe is established using the lumped-mass method in which the relevant dynamic parameters are solved. Additionally, the dynamic response characteristics of the TBM mainframe are analyzed. The results indicate that the vibration levels in three directions are approximately the same, the multi-directional vibration of the cutterhead is more intense than that of other components, and the vibration and external excitation exhibit identical change trends. A set of vibration field tests is performed to analyze the in situ dynamic responses of the mainframe and verify the correctness of the dynamic model. The theoretical and measured acceleration values of the TBM mainframe have the same magnitude, which proves the validity of the dynamic model and its solution. The aforementioned results provide an important theoretical value and practical significance for the design and assessment of the TBM mainframe.
... The most recent literature, i.e. Geng et al. [14], to a great extent refers to the references listed above and thus confirms this impression. Most papers discussing MFC related to hard rock TBM tunneling deal with simultaneous occurrence of different rocks at the face. ...
The effects of so-called Mixed Face Conditions (MFC) on hard rock TBM tunneling in several cases have been object of disagreement between clients and contractors. A main reason for this is that no precise definition exists of MFC related to hard rock tunneling. Of the two main international organizations related to tunneling and rock engineering, ITA defines MFC as simultaneous occurrence of rock and soil at the face, while ISRM has no particular definition. In literature, various definitions of MFC have been proposed based on the ratio of UCS of the strongest and the weakest rock at the face. In very few cases important factors such as stratigraphy and structural geology have been taken into account. Simultaneous occurrence of hard and soft rock at the tunnel face will cause vibrations of the TBM cutter head, with the consequences this may have on TBM operation, performance and cutter wear. The main intention of this paper is to give recommendations on what should realistically be classified as MFC in hard rock tunneling. Also, recommendations are given on how hard rock TBMs should best be operated to cope with varying hard and soft rock conditions at the tunnel face.
... where F n is the normal force, F t is the rolling or tangential force, n n and n t are the unit vectors of normal and tangential forces determined by the cutter position relative to the excavation face, respectively . Full scale laboratory cutting tests, modeling based on force estimation formulas, and numerical simulation can also be utilized to calculate the magnitude of cutting forces exerted on a single disc cutter (Gertsch et al., 2007;Cho et al., 2010;Xia et al., 2012;Geng et al., 2016). ...
... The excavation face reaches the unfavorable region when F c is around 8%, 28% and 54%, which implies the TBMground system in an unstable state for the performance torque fluctuates greatly. Geng et al. (2016) got the similar result that if the percentages of soft and hard rocks are close to each other when the TBM cutterhead in two-layer banded rock condition, a high eccentric force and overturning moment are observed. Tóth et al. (2013) discovered that the most significant decrease in PRev when the F c ranges from 0 to 30% based on the data analyzed from the DTSS tunneling project in Singapore. ...
... The first Slurry TBM was launched at Yingmentan station in the right tunnel of the Y-M section, and had a total of 365 rings and a distance of 438 m were bored. The average advance rate of the first 365 rings was 1.95 rings per day, which is much lower than the common rate (20 rings per day) of a Slurry TBM (Jung et al., 2011;Geng et al., 2016). This is because when the Slurry TBM was tunnelling towards the riverbed, the content and size of the cobbles increased, which made the breaking and pumping of the clasts more difficult. ...
The slurry tunnelling boring machine (TBM) was used to construct the tunnel of the Lanzhou Metro Line 1 undercrossing the Yellow River, China. The ground is characterized by sandy cobble with high cobble content. There are many challenges for slurry TBM tunnelling in sandy cobble ground because the cobble is hard to break and transport. This paper focuses on the performance of slurry TBM tunnelling, summarizes the lessons of shield driving and suggests countermeasures for the cobble breaking and disposal including cutterhead improvement, double pebble crusher and clasts collection tank. The chamber pressure and grouting pressure during the driving process were recorded and compared with the theoretical ground stress. The key parameters including the thrust force of cylinders, advance rate, torque and rotation speed of the cutterhead were recorded and analysed. Field test results show that the surface settlement induced by slurry TBM tunnelling in sandy cobble ground can be well controlled and the longitudinal surface settlement can be predicted by the Attewell formula and modified Attewell formula. This paper provides a good reference for slurry TBM tunnelling in sandy cobble ground.
... Alsahly et al. (2016) advanced finite element modeling of excavation process by TBMs. Geng et al. (2016) studied at mechanical performance of TBM cutterhead in mixed rock ground conditions. Liu et al. (2017) suggested a predictive model of TBM performance for granite formations. ...
Tunnel boring machines (TBMs) are designed to excavate underground spaces and widely used in tunneling, civil and mining projects. TBM performance prediction substantially deals with the evaluation of machine's penetration rate and the number of consumed disc cutters. There are various methods and equations to predict the TBMs performance in the literature. In this paper, we predicted the penetration rate and number of consumed disc cutters in Beheshtabad water conveyance tunneling project, one of the major water conveyance tunneling projects in Iran, using Artificial Neural Network (ANN) and Support Vector Machine (SVM) methods. Results showed that both approaches are very effective but SVM yields more precise and realistic findings than ANN.
... Jebelli et al., 2010;Wu et al., 2015;Yin et al., 2017), variably weathered granite and rock (e.g. Grødal et al., 2012;Jain et al., 2014;Schneider et al., 2012;Wu et al., 2016) and mixed ground conditions (Geng et al., 2016;Rostami, 2016;Shirlaw, 2016). However, despite research into the performance of EPB machines in mixed ground conditions, there is still a need to enhance shield tunnelling performance, depending on ground conditions and operational factors. ...
... The excavation face reaches the unfavorable region when F c is around 8%, 28% and 54%, which implies the TBMground system in an unstable state for the performance torque fluctuates greatly. Geng et al. (2016) got the similar result that if the percentages of soft and hard rocks are close to each other when the TBM cutterhead in two-layer banded rock condition, a high eccentric force and overturning moment are observed. Tóth et al. (2013) discovered that the most significant decrease in PRev when the F c ranges from 0 to 30% based on the data analyzed from the DTSS tunneling project in Singapore. ...
Tunnelling in rock–soil interface mixed ground has often been faced with cutterhead torque fluctuation, a reasonable penetration rates to reduce the torque fluctuation and improve tunnelling efficiency is of great significance. In this paper, the cutting torques model was established. Torque changes with the rotation angle of cutterhead has been studied when the cutterhead in rock–soil interface with different hard rock area ratios (Fc). The results show that the average torque of cutterhead increases with the increase of Fc. The torque fluctuation cannot be eliminated, and torque fluctuation reaches its maximum when the Fc is about 10%–20%, which most likely to cause blockage and damage for the cutterhead. Such compound stratum sections should be avoided as far as possible when designing of tunnel lines. In the case of the same average torque, the penetration does not decrease linearly with the increase of Fc because of torque fluctuation. The penetration decreases slightly when the Fc reaches 10%–20%, and decreases obviously when the Fc exceeded 30%. The reason is that the penetration needs to be reduced to decrease the torque as well as torque fluctuation; when Fc reaches 60%, the penetration reaches the lowest; when Fc exceeds 60%, the penetration increases slightly to improve the tunnelling efficiency because torque fluctuation is reduced.
... Jebelli et al., 2010;Wu et al., 2015;Yin et al., 2017), variably weathered granite and rock (e.g. Grødal et al., 2012;Jain et al., 2014;Schneider et al., 2012;Wu et al., 2016) and mixed ground conditions (Geng et al., 2016;Rostami, 2016;Shirlaw, 2016). However, despite research into the performance of EPB machines in mixed ground conditions, there is still a need to enhance shield tunnelling performance, depending on ground conditions and operational factors. ...
The wear of excavation tools is considered to be one of the critical factors affecting the scheduling of shield tunnel construction. There is presently no effective countermeasure to prevent severe wear of excavation tools during tunnelling operations in complex geological formations. In addition, such wear is likely to lead to other problems, such as face instability and an unfavourable rate of tunnel advancement. The study reported in this paper analysed the various factors that affected the wear and performance of excavation tools during earth pressure balance machine tunnelling at the Ma-Lian section of line 9 of the Guangzhou metro, China. It was found that tunnelling in mixed ground conditions (upper soft and lower hard strata) led to severe wear of the cutter discs, resulting in additional costs and schedule delays. The foam expansion ratio, concentration of foaming agent and the foam injection ratio were measured to be 20, 2·5% and 40% respectively. Pre-grouting and effective soil conditioning were also found to prevent excessive wear of the cutter discs and surface collapse incidents caused by face instability.
... Some activity on this topic has taken place in recent years, as the TBM market seems to be growing in Asia. Research on this topic has mainly taken place in the state key laboratories in China, and has also been done by researchers in Turkey and Korea [1,[3][4][5][6]. The focus of these activities has been to make the machines more effective, primarily to address the dire need and pressure to improve the speed of tunneling and increase efficiency. ...
The success of a tunnel-boring machine (TBM) in a given project depends on the functionality of all components of the system, from the cutters to the backup system, and on the entire rolling stock. However, no part of the machine plays a more crucial role in the efficient operation of the machine than its cutterhead. The design of the cutterhead impacts the efficiency of cutting, the balance of the head, the life of the cutters, the maintenance of the main bearing/gearbox, and the effectiveness of the mucking along with its effects on the wear of the face and gage cutters/muck buckets. Overall, cutterhead design heavily impacts the rate of penetration (ROP), rate of machine utilization (U), and daily advance rate (AR). Although there has been some discussion in commonly available publications regarding disk cutters, cutting forces, and some design features of the head, there is limited literature on this subject because the design of cutterheads is mainly handled by machine manufacturers. Most of the design process involves proprietary algorithms by the manufacturers, and despite recent attention on the subject, the design of rock TBMs has been somewhat of a mystery to most end-users. This paper is an attempt to demystify the basic concepts in design. Although it may not be sufficient for a full-fledged design by the readers, this paper allows engineers and contractors to understand the thought process in the design steps, what to look for in a proper design, and the implications of the head design on machine operation and life cycle.
... Gertsch et al. [6] measured the vertical force, rolling force, and lateral force load spectrum of a 17-inch-diameter cutter with coarse-grained red granite. Geng et al. [7] performed cutter experiments on rocks with various hardnesses and verified the CSM model proposed by Rostami based on the experimental data. Many scholars subsequently used the numerical method to solve the force of the cutter. ...
Tunnel boring machine (TBM) is seriously damaged due to excessive vibration, and its anti-vibration design is the key of the drive system design. At present, the coupling model between the gear load imbalance and the electronic control strategy is difficult to be established. The actual cutterhead vibration and the motor output torque law are unknown, which make the TBM system dynamical model different from the actual situation. The calculation accuracy is difficult to estimate. In this paper, the electromechanical coupling model of TBM’s main drive system is established. The real-time dynamic load of each pinion is taken as the input disturbance of the electrical system, and the real-time output torque of each motor calculated by electrical system is inputted as the dynamic model load. Compared with the measured data, the error of the maximum amplitude of the radial acceleration is less than 20% and the dynamic torque amplitude is 9.55%. At the same time, the results show that with the rotation of the cutterhead, the loads between the motors, the output torque, and the gear radial vibration are periodically changed. When the motor load difference is maximum, the motor output torque difference is 49% of the average output torque, and the maximum amplitude of large ring gear and pinion radial vibration amplitude is 1.5–2 times the average.
... Tunnel boring machines (TBMs), as dedicated engineering machines, are widely employed in tunnel constructions due to their high excavation efficiency and excellent safety [1,2]. TBMs are applicable for various grounds including the rock, soil and soil-rock mixed grounds [3]. When tunneling in rock ground, the disc cutters installed on the TBM cutterhead are the most efficient and popular cutting tools to cut the hard rock [4,5]. ...
To study the wear behaviors of the tunnel boring machine (TBM) disc cutter ring under drying, water and seawater conditions, a series of cutter-rock wear tests were conducted based on the self-designed TBM cutter performance test bench. The results indicate that the wear behaviors of the cutter ring are affected significantly by wear conditions. The largest mass loss of the cutter ring is under the drying condition, followed by the seawater condition, and the smallest is under the water condition. The differences in mass loss were explained by the cutter force, wear mechanism, and wear debris etc of the cutter ring. These results can provide some references for the wear resistance design and service life prediction of the TBM cutter ring.
... They proposed that the fluctuation amplitude and frequency of the torque were minimal when α = 50% and maximum when α = 30% or α = 70%. Geng, Wei, Meng, and Macias (2016) analysed the mechanical performance of hard rock tunnel-boring machines (TBMs) in mixed rock ground by means of analytical methods and experimental validation. For a two-layer layered-banded rock (LBR) condition (Tóth`s classification, Tóth et al., 2013), the eccentric force and overturning moment are the greatest when the percentage of soft rock and hard rock is nearly equal, and such a condition is detrimental to the cutterhead and main bearing of the TBM. ...
Micro-disturbance construction in mixed ground is a major challenge in shield tunnelling construction. It has a high tendency to trigger clogging risks when mix shield tunnelling is performed in mixed ground containing mudstone, which has some undesired influences on the shield tunnelling performance and settlement control, especially when passing near buildings. This study focused on the characteristics of the tunnelling parameters of mix shield tunnelling in mixed ground and the settlement control measures for such a situation. A K-means clustering was conducted to investigate the relationship between the mixed ratio (the height ratio of mudstone in the excavation face) and the tunnelling parameters and silhouette evaluation was used to determine the optimal number of clusters. We also employed the K-means++ algorithm to select the initial centroids. The results of the analysis indicate that the slurry pressure in the excavation chamber (SPexcavation), total thrust and torque significantly increased while the penetration rate slowed down with the increase in λ. When 0.15 ≤ λ < 0.6, the fluctuation in the average value of SPexcavation is the greatest, which is unfavourable for settlement control. Based on studies regarding the protection of adjacent buildings in the Nanning metro line 1, it is beneficial to modify the slurry properties, slow down the advance speed and increase the cycle time when tunnelling in mudstone. The control of the SPexcavation is the first priority, and automatic monitoring along with sufficient grouting is essential for the protection of adjacent buildings.
... Lan et al. (2016) proposed a non-destructive and non-contact online method to detect disc cutter rotational speed or cutter jamming on the basis of eddy current sensor. Geng et al. (2016) set up a model to analyse the mechanical performance (thrust, torque, eccentric force and overrunning moment) of TBM cutterhead in different mixed rock ground conditions. A boring experiment was conducted using an experimental cutterhead with 14 disc cutters for verification. ...
Sequential sampling methods have gained significant attention due to their ability to iteratively construct surrogate models by sequentially inserting new samples based on existing ones. However, efficiently and accurately creating surrogate models for high-dimensional, nonlinear, and multimodal problems is still a challenging task. This paper proposes a new sequential sampling method for surrogate modeling based on a hybrid metric, specifically making the following three contributions: (1) a hybrid metric is developed by integrating the leave-one-out cross-validation error, the local nonlinearity, and the relative size of Voronoi regions using the entropy weights, which well considers both the global exploration and local exploitation of existing samples; (2) a Pareto-TOPSIS strategy is proposed to first filter out unnecessary regions and then efficiently identify the sensitive region within the remaining regions, thereby improving the efficiency of sensitive region identification; and (3) a PE&V learning function is proposed based on the prediction error and variance of the intermediate surrogate models to identify the new sample to be inserted in the sensitive region. The proposed sequential sampling method is compared with four state-of-the-art sequential sampling methods for creating Kriging surrogate models in seven numerical cases and one real-world engineering case of a cutterhead of a tunnel boring machine. The results show that compared with the other four methods, the proposed sequential sampling method can more quickly and robustly create an accurate surrogate model using a smaller number of samples.
The disc cutters of shield machines exhibit unsatisfactory adaptability and performance during the soft–hard varied strata tunneling process. To analyze the rotation state, cutting performance, and adaptability of disc cutters during shield tunneling in soft–hard varied strata, the Holmquist Johnson Cook and Federal Highway Administration constitutive models are introduced to numerically simulate the failure process of materials on the excavation face and to calculate the load of disc cutters. Additionally, the parameters of the models are modified based on laboratory disc cutter excavation test results. The results of numerical calculation can reflect the load level and the behavior of the disc cutters during operation. The tangential loads of the disc cutters during the cutting of four typical soft-strata excavation face models are numerically calculated, thus providing reference values for the starting torque of the disc cutters. A greater penetration is suggested for soft-strata tunneling to allow the disc cutters to rotate smoothly and continuously as well as to guarantee a better cutting effect. The disc cutters in the center of the cutterhead should be specified with a lower starting torque to prevent uneven wear, rotation stagnation, cutterhead clogging, and other adverse phenomena.
The cutter layout of a full-face tunnel boring machine (TBM) directly affects its tunneling efficiency. The revolving diameter of the center cutter is small, and the double-edged design results in its rock breaking mechanism and force characteristics being significantly different from those of the single-edged cutter. The gage cutter is installed on the transition arc of the cutterhead, and the installation inclination complicates its movement and force. In this paper, by taking sandstone as the research object, the composite rock breaking models of the center cutter group and the gage cutter group of a compound TBM are separately established based on the three-dimensional particle discrete element method. The numerical models are verified by comparing results with the full-scale rotary cutting laboratory test. From the view point of the force characteristics of a single cutter, the propagation of rock cracks between adjacent cutters, the overall mechanical properties of the cutterhead, the load characteristics and layout form of the double-edged center cutter, and the installation angle range of the gage cutter were studied. Results demonstrate that the use of a cross-shaped center cutter layout can reduce the force of a single cutter ring and the overall load of the cutterhead, which is conducive to TBM stability during tunneling. Therefore, it is recommended that a cross-shaped layout for the double-edged center cutter of a rock formation compound TBM should be used. To improve the stability and service life of the cutter, we recommend setting the installation angle of the innermost gage cutter of the rock formation compound TBM to about 9°, and the installation angle of the outermost gage cutter should not exceed 70°.
This paper proposed a new index for evaluation of disc cutter life during earth pressure balance (EPB) tunnelling. This new index was defined as the ratio of accumulated cutter radial wear to working time of the shield machine. With this new index, the measured disc cutter wear can be transformed into a time series data. To predict cutter wear with construction process, an ensemble intelligent model integrating one-dimensional convolutional neural network (1D-CNN) and gated recurrent unit (GRU) was developed via incorporating the proposed cutter wear index. A multi-step-forward prediction mode was adopted to train the ensemble model to predict cutter wear in advance. Field data collected from an EPB tunnelling section in Guangzhou-Foshan intercity railway, Guangzhou, China, was used for validation. Results showed that the proposed index and ensemble model can predict wear of a certain cutter with high accuracy. Three other sequential deep networks were employed for comparison to verify the applicability of the proposed index and ensemble model. The proposed index and ensemble model is convenient to be used on site and can predict wear of a certain cutter on cutterhead to help determine which cutter to be replaced during real-time construction.
Based on the theory of hydraulic self-reversing and pressurization, a variable cross-section squeeze pulse water jet rock breaking platform was built. When the nozzle diameter is 0.5 mm, the granite erosion and crushing experiments under different driving pressures are carried out, and the depth, volume and specific energy consumption of the erosion pit are analyzed. The results show that the device can achieve intermittent injection after pressurizing the input fluid at a rate of 5.8 times. Meanwhile, the pressurization process of fluid is divided into ascending section, stable section and descending section. Compared with the continuous water jet with the same peak output pressure, the depth of destroyed granite is increased by 129 %–288 %, the volume of broken granite is increased by 37 %–121 %, and the specific energy consumption per unit of crushing volume is reduced by 21 %–74 %. The device can use low-pressure fluid to effectively crush granite.
Considering the failure mechanism of pick cutting coal & rock, combined with the cutting load test, the single pick load of cutting coal & rock is obtained and analyzed, based on the load of single coal & rock caving load change process in time domain analysis, establish the fold catastrophe theory model of cutting load, qualitative analysis, the change rule of cutting load and provide theoretical basis for the further study of cutting load. The single fracture load equation in cutting was obtained by numerical fitting, the load characteristics and change rule were analyzed by catastrophe theory, the coal–rock cutting system dynamics model was established. The mutation characteristics of coal and rock breaking process for pick pressing into the coal and rock until spallation are revealed, and the mutation mechanical model taking the load as disturbance factor is established. The stiffness of the cutting system plays an important role in cutting. The dynamic crushing load change process of coal–rock cutting mechanical system can be well described by catastrophe theory.
Rock-soil interface mixed ground (RSI) is often encountered in tunnel construction. The excavation loads of tunnel boring machines (TBMs) are controlled by the interaction characteristics between TBM and rock/soil layers. The different properties of rock and soil cause the varying interaction range and stress distribution. Currently, there have been several studies available to estimate excavation loads under RSI, and the conclusion is that the total loads increase with increasing the rock layer proportion in the excavation face. However, the previous studies cannot take the difference of rock / soil properties into account, except for the calculation of cutters loads. Therefore, the interaction characteristics between RSI and TBM is unclear. This paper analyzes the interaction characteristics between TBM’s main components and complex geological conditions (e.g., layered soil, layered rock, and RSI condition). A model is proposed to calculate the total thrust and total torque assuming quasi-static equilibrium of the tunneling equipment. The rationality and applicability of the model are discussed and verified by two typical projects. Furthermore, the geological adaptability is discussed in terms of the excavation difficulty and the matching relationship between total torque and total thrust. The results indicate that when the rock layer proportion in the excavation face increases, the reduction of overall extrusion and friction loads is 1.5 times higher than the increase of disc cutters breaking load. The total loads and the ratio of the total torque to total thrust decrease approximately linearly. There is a power function relationship between the excavation difficulty index and the penetration depth. The results of this study provide an important reference for the total loads design of equipment propulsion systems and the parameter adjustment during tunnel construction.
The cutterhead of a tunnel-boring machine (TBM) is the main weighted part in the process of tunneling and bears loadings in different directions. A fatigue failure of a cutterhead would severely affect the construction progress and safety. Therefore, it is of great importance to study the fatigue reliability of its cracks. In this study, the area of the cutterhead with a higher stress was found using static strength analysis and we analyzed the dynamic stress characteristics. In addition, the stress intensity factor of a cutterhead crack was calculated using the submodeling technique, and the crack propagation mechanism and damage characteristics of a cutterhead crack were also analyzed. Then, combined with crack fatigue theory, we proposed a fatigue reliability evaluation method based on the Joint Committee on Structure Safety method (known as the JC method), and the effects of different factors on the reliability were discussed for different geological conditions. The results show that the crack propagation was of the open and tear types in the deepest part of the crack tip, but there are three kinds of propagation modes at both ends. As the initial crack depth increased, the fatigue reliability of the cutterhead decreased significantly. The reliability was positively correlated with the crack shape ratio. However, there were no significant relationships between the reliability and the depth of the critical crack.
The main drive system is the core of a Tunnel Boring Machine (TBM). The force transmission law of this system is extremely complicated, which leads to severe vibration, structural failure, and safety hazards. Therefore, the dynamic analysis and the study of the vibration transmission law of a TBM main system under different working conditions are very important. In this study, a novel testbed for a hard rock TBM main system and a multi-DOF coupling dynamics model were built by considering the external excitations of the cutters, the time-varying meshing stiffness of the gear teeth, the meshing error, the clearance, and the stiffness of the main bearing. A wireless vibration monitoring system was built on the testbed. Experiments under typical working conditions were done to verify the dynamic model. Finally, the dynamic response of the system was analyzed. The results showed that the maximum error of the theoretical and actual dynamic response was 18.1%, and the dynamic model could be used to analyze the vibration of an actual TBM. The vibration law of the testbed was close to the actual TBM, so the testbed could be used for the vibration law analysis of the actual TBM under other working conditions. The study of the vibration law under different working conditions and different digging parameters could be used to guide the intelligent tunneling of the TBM.
TBM and roadheader are two dominating excavation machines in underground tunnelling projects. The performance of these two tunnelling machines has been reviewed and analysed individually by many researchers from multiple points of view. However, there are almost no studies that have made an extensive comparison between these two machines, mostly from financial points of view. The current study is intended to characterize both financial and technical status of these two mechanical tunnelling machines in one of the biggest coal mines in Iran. The main objective of this study is to define the best method and equipment that meets a predefined economic goal, which is mainly to maximize the net present value. To this end, a technical and financial model based on the geomechanical and financial parameters involved in the project has been prepared and the financial part of the project has been carried out by applying COMFAR III financial analysis software. Subsequently, a sensitivity analysis of the model was conducted in order to evaluate the effect of involved parameters on the project. According to the results, a roadheader has better economic justification than a TBM, while the TBM has a better advance rate than the roadheader.
Optimization in TBM cutterhead design is essential for increasing its performance. Lace design for the cutters, buckets, and manholes in the cutterhead, is one of the major considerations in the design of the hard rock TBMs. An optimum lace design is necessary to avoid cutterhead deviation, vibration, and stress concentration during its operation. TBM manufacturers usually utilize two common lace designs of radial and spiral configurations. Despite the presence of many advantages for these two designs, each of them has its own disadvantages which may cause difficulties in achieving an efficient design of the cutterhead. This paper introduces a new TBM cutterhead lace design in which all three normal, side, and rolling forces are considered. The new force and moment balancing relationships are presented. With the consideration of the problems of the radial and spiral configurations, a new method of “uniformly distributed lace design” is introduced and the steps of achieving the final layout of the cutterhead is explained with its required parameters. On the basis of an example, a comparative study is made among three methods of applying radial, spiral, and uniformly distributed lace designs. The results show that the new method is very efficient in both uniformly and symmetrically distributing the cutters, buckets, and manholes on the cutterhead surface with no boundary conflicts. It also has the advantage to have low unbalanced forces and moments.
As a crucial rock crushing equipment, the raise boring machine (RBM) has been widely used in underground engineering construction, especially in the construction of shaft wellbores. Herein, experiments and measurements were carried out in a hydropower station construction project. By loading a set of engineering parameters, data from the four parameters of pulling force, torque, rotation speed and drilling speed of the drill pipe were obtained. The research results show that torque in the rock breaking process has no correlation with the rotation speed and is linearly related to the pulling force. Increasing rotation speed or pulling force can both clearly improve rock breaking efficiency; however the effect from pulling force is greater. This experimental method is able to find the best engineering parameters so that the RBM can obtain minimum energy consumption for rock breaking.
Cutter cutting tests for the cutter placement in the cutter head are being conducted through various studies. Although the cutter spacing at the minimum specific energy is mainly reflected in the cutter head design, since the optimum cutter spacing at the same cutter penetration depth varies depending on the rock conditions, studies on deciding the optimum cutter spacing should be actively conducted. The machine learning techniques such as the decision tree-based regression model and the SVM regression model were applied to predict the optimum cutter spacing ratio for the nonlinear relationship between cutter penetration depth and cutter spacing. Since the decision tree-based methods are greatly influenced by the number of data, SVM regression predicted optimum cutter spacing ratio according to the penetration depth more accurately and it is judged that the SVM regression will be effectively used to decide the cutter spacing when designing the cutter head if a large amount of data of the optimum cutter spacing ratio according to the penetration depth is accumulated.
This paper conducts a simulation experiment research on cutter-head vibration characteristics by evaluating a soft-hard mixed stratum (the upper layer is silty soil, whereas the lower layer is moderately weathered granite of maximum UCS 142.0 MPa and slightly weathered granite of maximum 210.0 MPa). The ratios of hard rock and soil within the tunnel face were designed to be 1:1 and 1:2. Then, the cutter-head and stratum model were subjected to vibration analysis by reasonably deployed accelerometers. Results show that: 1) different conditions of heterogeneous strata mainly affected the acceleration amplitude and frequency distribution of cutter-head, in other words, the stronger hard rock, the larger the strength difference between the hard rock and soil within a tunnel face, the larger the vibration acceleration and the more concentrated the vibration frequency distribution; 2) the radial and circumferential vibration acceleration of the cutter-head in different positions were not largely different; however, axial accelerations were largely different. The axial vibration accelerations first increased and then decreased along the radial direction of cutter-head. Considering the difference between Multi-Mode Boring Test System and real cutter-head structure, the radius of joint between the cutter-head and the flange plate should be reasonably increased according to the ratio of hard rock in tunnel face; 3) with the increasing difference between the strength of the hard rock and soil, the circumferential and axial vibration acceleration multiplied. Thus, the soil remarkably reduces the vibration of the cutter-head. These results can provide some evidence of potential application for advancing manufacturing practice for cutter-head and disc cutter of shield machine.
The cutterhead system is a core component of TBM equipment, which works in the extremely severe environment, and the strong impact loads result in severe vibration, crack, damage failure and other engineering failures. Accordingly, the key for cutterhead system structure design and parameter matching is to evaluate and predict cutterhead tunneling performance reasonably. In this paper, a prediction method for TBM cutterhead dynamic tunneling performance is proposed under the typical composite geological conditions, based on the CSM model of multi-cutters and cutter loads field test data. Then an actual TBM cutterhead of a water conservancy project is taken as an example, a spatial three-dimensional separation zone model for cutterhead tunneling is established under the typical geological condition, and the parameters influence rules of cutterhead tunneling performance are analyzed. The results show that, the cutterhead loads and specific energy change rules with different parameters are basically similar. Moreover, under the condition of penetration p=10mm, the cutterhead bending moment coefficient of variation magnitude exceeds 20%, which is the maximum, and the normal cutter spacing optimal value is 95mm. Also, when the normal cutter spacing is kept constant in 85mm, the penetration has a greater influence on the torque and specific energy coefficient of variations, which is increased from 2mm to 10mm, and the two indexes decrease by about 73%. It is indicated that proper increase of penetration is beneficial to reduce the vibration fluctuation degree of torque and specific energy. The proposed method of TBM cutterhead dynamic tunneling performance and the analysis results can provide theoretical basis and design reference for TBM cutterhead layout and tunneling parameters matching.
To investigate the surrounding rock deformation and fracture mechanism of mixed-face ground under tunnel boring machine (TBM) tunnelling, tests of a mixed-face ground model with TBM tunnelling were conducted by using a self-developed 3D large-scale simulation test machine and TBM excavation equipment. A fibre Bragg grating sensor and a distributed optical fibre sensor have been installed along the micro-pressure cell and are used to monitor the variation of stress, strain and displacement in the surrounding rocks while ‘uncoordinated deformation is observed at the interface’ during the excavation process. By comparing the experimental observation obtained in the soft and hard rocks located near the interface, a significant difference is observed in the deformation and stress measurement. The fractures observed in the shallow layer of the surrounding rock mass were mainly tensile fractures and tensile shear fractures, and pressure shear fractures were observed at a certain depth of the surrounding rock during TBM tunnelling. The results not only provide reference data on the mechanical behaviour of mixed surrounding rocks during tunnelling by TBM but also can guide construction units to prevent and control the disaster of TBM in tunnelling through mixed-face ground.
With the aid of 3D acoustic emission (AE) monitoring system, the cracking process of granite under compressive stress condition and its effect on the hydro-mechanical properties is experimentally studied. The granite is taken from Beishan area, a preferable region for high-level radioactive waste (HLW) disposal in China. The experiment results suggest that the rock failure and degradation of mechanical properties are essentially related to the propagation and coalescence of induced cracks. Using an anisotropic damage tensor proposed by Shao et al., the damage evolution during the whole loading process is studied according to the experimental data. It is revealed that the damage evolution is mainly initiated with the appearance of nonlinear mechanical behaviour, and accelerated close to the failure point and in post-peak region. The estimated damage variable in lateral direction is found be globally higher than the value in vertical direction. The recorded AE events indicate that cracking process of granite could be accelerated due to the existence of hydraulic pressure. As a result, much lower compressive strength is obtained under same effective confining pressure in hydro-mechanical coupling tests. A similar tendency of damage and permeability is noticed, and the permeability variation in granite is found to be negligible before the coalescence of microcracks. Finally, an empirical relation is proposed to describe the influence of damage evolution and confining pressure on permeability variation.
In this paper, by taking into account the periodically varying mesh stiffness in multiple pinions transmission and the speed–torque characteristics of variable frequency motor drives, the dynamic model for the revolving system of tunnel boring machine (TBM) has been established. Based on the soft ground/hard rock assumption of mixed-face conditions and the analysis of cutting force on each disc cutter and each drag bit, the time-varying excavation torque on the TBM cutterhead in mixed-face tunnelling is obtained. The dynamic excavation torque and cutterhead rotation speed are discussed and compared for TBM tunnelling in several typical mixed-face conditions, which are characterized by the area percentage of soft ground on the excavation face and the uniaxial compressive strength (UCS) of rock. The results show that the excavation torque may run up to a critical value and fluctuate greatly in extremely adverse excavation environments, which may lead to an unexpected TBM stoppage and even a catastrophic failure of the drive motor. To decrease the penetration per revolution in time through applying a lower advance velocity and a higher cutterhead revolution will significantly reduce the excavation torque and effectively avoid such situations.
It is important that the compliance design of tunnel boring machine (TBM) is performed to improve the efficiency and reduce the failure accidents when they excavate in the heterogeneous geologic strata. The equivalent excavating model of the heterogeneous geologic strata has been established based on the typical geological structure in the tunnel construction. The load behavior of the individual cutters was discussed. The mathematical description of total torque on the cutterheads is given in terms of the load of cutter and their locations. The correlation between the torque behavior and the rotating angle of cutterheads is investigated. The results show that fluctuation of torque is dependent on the ratio of hard rock and soft soil on the excavating face. When the percentage of the soft soil is 30%, the fluctuant amplitude is maximum, which may lead to the blockage and failure accidents of driving system. It is in agreement with the engineering case in the Shanggongshan tunnel construction. It can be used in the compliance design of the TBM.
Based on the shield tunnel construction in complex strata in Guangzhou second tunnel line, an idea of composite metro shield machine is brought forward, and the shield function and its technique parameter are studied and analyzed with the adaptability of cutterhead, cutter, geological condition. The excavation mode theory, the transition between different excavation modes and different excavation parameters are studied, and some technical problems, such as the excavation difficulties problem, the low efficiency problem, the high cost problem, the trouble in distortion control of the shield excavation, are solved. Furthermore, in order to control the excavation direction of the shield more effectively and avoid the cracking and the dislocation of segment, the reason of direction warp is analyzed; and some control methods are presented. In order to avoid mud in clay strata and water gushing in water-enriched geology, the technique of sediment improvement is studied. In order to guarantee the security of nearby building and the routine traffic condition of Beijing-Guangzhou Railway, some credible techniques, such as synchronous grouting technique, construction monitoring technique, the variation of excavation parameters to control tunnel deformation, are adopted.
This paper investigates the performance of tunnel boring machines (TBMs) in rock-soil mixed-face ground based on TBM tunneling projects in Singapore. Currently several methods are available to estimate TBM tunneling performance in homogenous rock or soil. However, the existing models cannot be effectively applied to predict TBM penetration rate in mixed ground. The tunnels in this study were excavated in adverse mixed-face ground conditions. The geological profiles and the TBM operational parameters are compiled and analyzed. The influence of different geological face compositions on the performance of the TBMs is studied. The statistical analysis shows that there is a possible correlation between the mixed-face ground characteristics and the TBM advancement. Different approaches are used to find a reliable model. Finally, a method is proposed to predict the TBM performance in mixed-face ground for project planning and optimization.
The recent development of larger shield-driven tunnels has for consequence that the tunnel face consists more frequently of multi-layered formations. However, most tunnel designs are still currently conducted in the homogeneous soil condition. In this study, a series of 1-g plane model tests and FEM analyses were carried out to investigate the influence of the layered soils in terms of their relative stiffness and thickness on the lining behavior (i.e. inner force and convergence). The numerical results were found to agree reasonably well with the results obtained from the model tests. For multi-layered formation, a linear increase of the relative thickness of the sandy layer could reduce non-linearly the magnitude of both the moment and the convergence. The distributions of the bending moment and of the convergence along the tunnel perimeter were found to be strongly dependent on the relative stiffness of the layered formations. However, the multi-layered condition has little effect on the thrust force under the condition of this test. In view of these results, some discussions on the applicability of the widely used homogenized design model for the multi-layered soil condition are finally presented.
The TBM tunnelling technique initially focused on the soft rock environment. As the technique developed towards stronger machines, more powerful motors and larger cutters, hard rock TBM tunnelling became a routine task. Today, there are few ground conditions where the TBM technique is not feasible. A certain and in some cases serious limitation is, however, represented by varying ground conditions, such as dykes, faults, weakness zones or even soils/soft rock, combined with hard rock. This is commonly referred to as mixed-face conditions. Variable geological conditions may call for customised machine design, and in the development of the design, geological knowledge is crucial. An identification of scenarios that may cause a threat to the successful implementation of the TBM-method, is more important than for conventional drill and blast tunnelling, as the latter has a greater flexibility.
This paper focuses on the analysis of the TBM performance recorded during the excavation of the Lötschberg Base Tunnel. The southern part of the tunnel was excavated by two gripper TBMs, partly through blocky rock masses at great depth. The jointed nature of the blocky rock mass posed serious problems concerning the stability of the excavation face. A detailed analysis has been carried out to obtain a relationship between the rock mass conditions and the TBM performance, using the Field Penetration Index (FPI). In blocky rock conditions, the FPI is defined as the ratio between the applied thrust force and the actual penetration rate. A database of the TBM parameters and the geological/geotechnical conditions for 160 sections along the tunnel has been established. The analysis reveals a relationship between the FPI and two rock mass parameters: the volumetric joint count (Jv) and the intact rock uniaxial compressive strength (UCS). Through a multivariate regression analysis, a prediction model for FPI in blocky rock conditions (FPIblocky) is then introduced. Finally, other TBM performance parameters such as the penetration rate, the net advance rate and the total advance rate are evaluated using FPIblocky.
A scheme for providing stability measures for a tunnel excavated in mixed-ground conditions using chemical grouting is described. Typical geotechnical problems encountered during excavation are highlighted. An analytical approach for calculating the required thickness of grouted soil was developed. Grout characteristics to achieve the required behaviour are described, along with the recommended sequence of construction. A methodology employing finite element analyses to predict the tunnel behaviour during construction is proposed. It was utilized in designing the excavation support. Predictions compared well with actual field measurements.
As the use of hard rock TBMs constantly continues to grow, so are the experiences gained in these projects and the challenges that need new solutions. Cutterhead modeling has been a successful tool used by the industry at various levels of sophistications relative to the end use. These models are based on the estimation of the cutting forces and can be used for cutterhead design optimization as well as performance estimates. While these models have proven to be useful in these areas, there is still room for improving their accuracy to account for different rock features and rock mass properties. New and emerging technologies in cutter and machine manufacturing can be assisted by the use of these models in optimizing their use or assessing their potentials. This paper reviews the state of the art of modeling used for design and performance prediction of hard rock TBMs. A brief overview of the available models will be offered and their strength and shortcomings will be discussed.
The Kranji tunnel is part of the Deep Tunnel Sewerage System in Singapore. It is approximately 12.6 km in length. Along the tunnel alignment, all the ground is composed of granite with different weathering grades (from fresh rock to residual soil). The changing ground from hard rock to mixed face and soft ground (and vice versa) at the tunnel level was anticipated. The tunnel depth along the route is between 15 m and 50 m. Two EPB TBMs were deployed at this tunnel with a bored diameter 4.90 m. These machines were designed so that both hard rock and soft ground could be excavated. The cutter head was equipped with a combination of both rippers and disc cutters. During the excavation, it was found that the frequency of the ground change between hard rock and residual soil is much higher than that expected. Due to the frequently changing ground, correspondingly the tunnel boring machine (TBM) operation mode had to be transferred frequently from hard rock tunnelling to transition mode and to earth pressure balance (EPB) close mode. It resulted in great difficulties for the TBM in an optimized operation condition. These difficulties included high cutter wear and flat cutters, tunnel face instability, water inflow at weathering interface, and time delays. In order to overcome these problems and speed up the tunnelling progress, the TBM used in the north drive was modified to attempt the frequently changing ground. The performance of the modified TBM was highly improved. However, the highly abrasive and frequently changing mixed face ground still caused high cutter wear, especially flat cutter wear. These posed many challenges to the equipment and the tunnel crew.
Point-in-polygon is one of the fundamental operations of Geographic Information Systems. A number of algorithms can be applied. Different algorithms lead to different running efficiencies. In the study, the complexities of eight point-in-polygon algorithms were analyzed. General and specific examples are studied. In the general example, an unlimited number of nodes are assumed; whereas in the second example, eight nodes are specified. For convex polygons, the sum of area method, the sign of offset method, and the orientation method is well suited for a single point query. For possibly concave polygons, the ray intersection method and the swath method should be selected. For eight node polygons, the ray intersection method with bounding rectangles is faster.
Development of TBM boring test bench
- Z Xingjian
- L Puqing
- H Fei
Xingjian, Z., Puqing, L., Fei, H., 2013. Development of TBM boring test bench. Tunnel
Construction 33, 615-618 (in Chinese).