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To investigate wear characteristics of tunnel boring machine (TBM) disc cutter rings interacting with types of rock, a range of wear tests were performed on a TBM cutter test rig, and laboratory-scale disc cutters were used in the experiments. The mass loss, vertical load, temperature field, wear mechanism and change rule of cutter tip for the disc cutter rings were obtained during the tests. The results indicate that the rock types and properties of rock exhibit great influences on the cutter wear. The variation of the weight loss testing with different types of rock is partially explained by the discrepancies of vertical load, cutting temperature, and the transition of wear mechanisms. In addition, the test results show that the wear characteristics of cutter rings are mainly affected by uniaxial compressive strength (UCS) rather than equivalent quartz content (EQC) for types of rock. This study will benefit the design of cutter rings with enhanced wear resistance.

As a key component of tunnel boring machines (TBMs), the disc cutter ring and its structural parameters are closely related to the TBM tunneling quality. Literature review shows that investigations on optimization design methods for cutter ring structure are seriously insufficient. Therefore, in this paper, a multiobjective optimization design model of structural parameters for disc cutter rings is developed based on the complex geological conditions and the corresponding cutter ring structure design requirements. The rock breaking capability, energy consumption, load-bearing capability, wear life, and wear uniformity of disc cutter are selected as the objectives, and the geometric structure of cutter rings, ultimate load-bearing capability, and cutterhead drive performance are determined as constraints. According to the characteristics of this model, a self-adaptive multipopulation genetic algorithm (SAMPGA) is utilized to solve the optimization problem, and the Fuzzy analytical hierarchy process (FAHP) is employed to calculate weight coefficients for multiple objectives. Finally, the applicability of the proposed method is demonstrated through a case study in a TBM project. The results indicated that the rock breaking performance and service life of the disc cutter are improved after optimization by using the proposed method. The utilization of SAMPGA effectively solves the premature local convergence problems during optimization. The geological adaptability should be considered in the cutter ring structure design, which can be realized by using the proposed method based on the suitable weight coefficients.

The construction efficiency and quality of tunnel boring machines (TBMs) is largely determined by the service life of cutting tools, which is the result of contact loads in the crushed zone between cutter ring and rock. In this paper, a series of rock breaking tests were conducted with a 216 mm diameter disc cutter and concrete samples. Based on the superposition principle, the distribution of contact loads between disc cutter and rock were obtained by using the truncated singular value decomposition (TSVD). The results show that both the peak value and the whole numerical distribution of the radial strains on the cutter ring increase with the increase of the penetration. The distribution curves of the contact loads show an approximate parabola going downwards, which indicates contact loads are more concentrated. The front non-loading area with a ratio from 1.8% to 5.4% shows an increasing trend with the increase of penetration. However, the change of rear non-loading area is not obvious. It is believed that the conclusions have guidance for the study of rock breaking mechanism and manufacturing process of the disc cutter.

The disc cutter is the main rock cutting tool of a tunnel boring machine (TBM), and its wear directly affects the cutter change decision. Therefore, real-time monitoring of disc cutter wear has become an urgent technical problem for boring machines. In this study, an online monitoring system based on an eddy current sensor is designed to monitor disc cutter wear in real time. The effects of three types of rock and muddy water mixture on the measurement data are compared. Results show that measuring the eddy current distance can solve the problem of inaccurate measurement after the disc cutter is covered by rocks. Besides, the error data of this method in measuring disc cutter wear are analyzed. A function test is performed for similar disc cutters on a multi-function disc cutter performance test bench, and a real-time continuous test is conducted for the wear of two disc cutters in a certain TBM project. With a comparison of monitored and measured results, it shows that the error is less than 1 mm, which indicates that the system exhibits stable transmission and high accuracy in measurement and meets engineering requirements.

To study the wear characteristics of disc cutter rings, cutter-rock wear tests between cutter rings with six types of hardness and three typical types of rock are carried out based on the liner cutting machine (LCM). The wear mechanism and wear depth are also studied with a laser microscope. The research results show that the wear mechanism of cutter rings is micro cutting when the disc cutter rings wear against sandstone. The wear loss, wear depth and morphology of wear debris change insignificantly with the increase of the hardness. When the cutter rings wear against rust stone, the wear mechanism of cutter rings presents furrow deformation, followed by micro cutting with the increase of the hardness. When the hardness is increased to 57.5 HRC, the cutter wear mechanism begins to show brittle fractures. With the increase of the hardness, the wear loss and wear depth are decreased, but the decrease speed slows when the hardness is increased to 57.0 HRC. When disc cutter rings with different types of hardness wear against gneiss, the wear law is, on the whole, consistent with that in the case of rust stone. Finally, the rule for selecting the appropriate blade shape for cutter rings with different types of hardness when wearing against three typical rock formations is obtained based on the shape changes of the cutter blades.

To improve the excavation efficiency of Tunnel Boring Machines (TBMs), the free-face-assisted rock cutting method induced by TBM disc cutter (FM) was explored and the differences between the FM and the conventional Cutting Method (CM) were also compared based on a series of rock cutting tests. The results show that when the free face distance is less than a critical value, the FM can promote the tensile failure of the rock and the formation of big rock debris effectively. Moreover, the cutting efficiency and the cutting forces including normal force, rolling force and side force of the disc cutter under the FM are also significantly reduced and improved, respectively, compared to that under the CM. The FM can be applied in multi-stage cutterhead TBMs to improve the cutting efficiency and reduce the failure of the disc cutter, the research results indicate that the free face distance should be controlled within 80 mm to use the free face effectively.

To improve the wear resistance of disc cutters for tunnel boring machines (TBMs), this study is devoted to investigating the effects of rocks and cutter ring properties on the wear behaviors of dis...

Geological adaptability matching design of a disc cutter is the prerequisite of cutter head design for tunnel boring machines (TBMs) and plays an important role in improving the tunneling efficiency of TBMs. The main purpose of the cutter matching design is to evaluate the cutter performance and select the appropriate cutter size. In this paper, a novel evaluation method based on multicriteria decision making (MCDM) techniques was developed to help TBM designers in the process of determining the cutter size. The analytic hierarchy process (AHP) and matter element analysis were applied to obtaining the weights of the cutter evaluation criteria, and the fuzzy comprehensive evaluation and technique for order performance by similarity to ideal solution (TOPSIS) approaches were employed to determine the ranking of the cutters. A case application was offered to illustrate and validate the proposed method. The results of the project case demonstrate that this method is reasonable and feasible for disc cutter size selection in cutter head design.

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.

The disc cutters of tunnel boring machine (TBM) are installed with different polar angles. This causes the cutting depth difference between adjacent disc cutters on the tunnel face. A rock-cutting model was established to study the rock fragmentation law between adjacent disc cutters with different polar angles based on particle flow code (PFC). The influence of polar angle of adjacent disc cutters on rock cracks and stresses under different cutter spacing and penetration was studied. Research shows that polar angle difference leads to the discontinuity of rock-fragmentation process by adjacent cutters. The effect of rock-fragmentation is influenced by the cutting depth difference between adjacent cutters. The effect of rock-fragmentation performed best, meanwhile large rock blocks were flaked when the difference of cutting depth is half of the penetration. Too large or small difference of the cutting depth will cause high specific energy consumption of rock fragmentation. The specific energy consumption is relatively small when the difference of cutting depth is half of the penetration.

A series of numerical simulations were performed to investigate the influence of side free surface on the rock fragmentation induced by single TBM disc cutter. The JH-2 model combined with a Rankine tensile cracking softening model was adopted to define the rock constitutive model to simulate the rock dynamic fracture process. The distance that allows for cracks just to extend to side free surface under a given penetration is defined as the critical distance, which distinguishes the rock fragmentation patterns between induced by disc cutter close to side free surface and conventional single cutter. The former rock fragmentation pattern is that rock chips in the form of wedge-shaped block spalling from rock specimen due to tensile cracks intersection. From the mean rolling force and the rock debris mass, the specific energy to reflect cutting efficiency was calculated for different distances to side free surface. The cutting efficiencies of former patterns are far higher that by conventional single cutter. The rock macro-fracture patterns and cutting efficiency were then compared with those obtained from linear cutting experiments. The critical distance for Baiyun granite is about 100 mm obtained from experiments, in good agreement with that deduced from numerical simulations. The height difference between the inner and outer cutterhead of the two-stage cutterhead should be more than 220 mm and the distance from first disc cutter on the inner cutterhead to free surface should be less than 100 mm for granite ground.

Disc cutter performance evaluation and selection is one of the typical and challenging kinds of Multiple criteria decision-making (MCDM) problems. To improve the construction efficiency as well as decrease cost of tunnel boring machine (TBM) project, it is essential to evaluate the cutter performance according to the geology and construction demand. This paper develops a novel hybrid fuzzy MCDM approach to address this kind of MCDM problems in the fuzzy environment. To determine more justified weights for criteria with consideration of subjective and objective weights, a hybrid weight-determining method that integrates fuzzy AHP, entropy weight (EW), and game theory (GT) is presented. The fuzzy comprehensive evaluation and fuzzy TOPSIS are combined to obtain the evaluation results with consideration of both quantitative and qualitative criteria. The proposed approach is applied to a case study of disc cutter performance evaluation, and the final rankings of alternatives with the weights of the criteria are discussed. To verify the evaluated results, a comparative study is carried out with engineering practical data, the proposed approach, and some classical MCDM methods. Additionally, a sensitivity analysis is performed based on varying the criteria weights. The investigations show the proposed approach is reasonable, robust, and effective, which can be a precise decision-making aid to deal with many practical MCDM problems in a variety of engineering areas.

Disc cutter is the main rock breaking tool of TBM. It is angled worn frequently because of locked-rotor; as a result, monitoring relevant operating parameters of TBM disc cutter has become an urgent technical problem. This paper studies nondestructive and non-contact online detection disc cutter rotational speed method of based on eddy current sensor: applies eddy current sensor to detecting six 2 mm-high metal bumps setting on the disc cutter, so as to detect the rotational speed of disc cutter. K60 MCU is applied as the main control core. The experimental results show that the on-line rotational speed monitor system of disc cutter features high anti-jamming ability and is reliable.

In order to study rock breaking characteristics of tunnel boring machine (TBM) disc cutter at different rock temperatures, thermodynamic rock breaking mathematical model of TBM disc cutter was established on the basis of rock temperature change by using particle flow code theory and the influence law of interaction mechanism between disc cutter and rock was also numerically simulated. Furthermore, by using the linear cutting experiment platform, rock breaking process of TBM disc cutter at different rock temperatures was well verified by the experiments. Finally, rock breaking characteristics of TBM disc cutter were differentiated and analyzed from microscale perspective. The results indicate the follows. 1) When rock temperature increases, the mechanical properties of rock such as hardness, and strength, were greatly reduced, simultaneously the microcracks rapidly grow with the cracks number increasing, which leads to rock breaking load decreasing and improves rock breaking efficiency for TBM disc cutter. 2) The higher the rock temperature, the lower the rock internal stress. The stress distribution rules coincide with the Buzin Neske stress circle rules: the maximum stress value is below the cutting edge region and then gradually decreases radiant around; stress distribution is symmetrical and the total stress of rock becomes smaller. 3) The higher the rock temperature is, the more the numbers of micro, tensile and shear cracks produced are by rock as well as the easier the rock intrusion, along with shear failure mode mainly showing. 4) With rock temperature increasing, the resistance intrusive coefficients of rock and intrusion power decrease obviously, so the specific energy consumption that TBM disc cutter achieves leaping broken also decreases subsequently. 5) The acoustic emission frequency remarkably increases along with the temperature increasing, which improves the rock breaking efficiency.

Disc cutter consumption takes up a large part of the cost of TBM construction, and the analysis of the wear of disc cutters can provide design guidance for the cutter head and cutter arrangement in practice. Data analysis of the disc cutter wear capacity of engineering 6859 m in Yinsong, Jilin (the diameter of cutter head is 7,920 mm) shows that the wear capacity of the inner disc cutter (under the same cutter space) is linear to the position where the cutter is installed on the cutter head. Therefore, a formula for calculating the wear rate of the inner disc cutter is based on establishment of the disc cutter installation radius. In accordance with the slope coefficient (A) of the wear rate of the disc cutter, the influence of tuff and granite on it is analyzed at first, then the difference of seven different prediction model combinations of penetration (P), rock uniaxial compressive strength (UCS) and thrust (Fn) under single action and combination action are analyzed. Then, it shows that the single action based on P is the best with the R2 of 0.7156 and the wear rate of the inner disc cutter based on P and UCS is the best for combination action with the R2 of 0.726.

Disc cutter is a tool that EPB shield machine uses in fragment hard rocks in the construction of a subway tunnel in Jinan. Many disc cutter rings fractured during the tunnelling process in April to May 2018. Based on the force characteristics of the cutter ring, a comprehensive analysis was performed to investigate the base materials, residual stress, mechanical properties, metal flow line, and micro morphologies of the fracture cutter ring to identify the fracture causes. The cutter ring fracture type was quasi-cleavage fracture. Moreover, the test result showed that tensile strength and toughness of the cutter ring was lower than the regular cutter ring. The direction of the initial crack is perpendicular to the cutter ring edge. A collection of banded precipitates and oxides were distributed among the grains by metallographic test, scanning electron microscope (SEM) and energy dispersive spectrometer (EDS). It increased internal defects in the cutter ring and reduced the mechanical properties of the cutter ring. These defects are the main factor that causes the cutter ring fracture during karst formation tunnelling with large impact loads. Besides, excessive residual stress was another of the cutter ring fracture. The uneven distribution of residual stress and cutter ring hardness also indicated uneven heating of the cutter ring during manufacturing and heat treatment. Finally, some suggestions which aimed at EPB shield machine tunnelling progress and cutter ring manufacturing were put forward as well.

A novel optimization methodology for the disc cutter designs of tunnel boring machines (TBM) was presented. To fully understand the characteristics and performance of TBM cutters, a comprehensive list of performance parameters were investigated, including maximum equivalent stress and strain, specific energy and wear life which were closely related to the cutting forces and profile geometry of the cutter rings. A systematic method was employed to evaluate an overall performance index by incorporating objectives at all possible geological conditions. The Multi-objective & Multi-geologic Conditions Optimization (MMCO) program was then developed, which combined the updating of finite element model, system evaluation, finite element solving, post-processing and optimization algorithm. Finally, the MMCO was used to optimize the TBM cutters used in a TBM tunnel project in China. The results show that the optimization significantly improves the working performances of the cutters under all geological conditions considered.

According to the cutting characteristics of progressive spiral movement by rotary cutting of the disc cutter, using the broken theory of interaction of compression and shearing, the three-axis force rotary cutting mechanical model of disc cutter was established and the influence of installation radius, the phase difference and the cutter space on the mechanics of disc cutter were analyzed. The results show that on the same radial line of tunneling interface, the boring distance of cutting tools installed on a different radius is not equal. The cutting radial line of tunneling interface is a polyline and its height is determined by phase angle and penetration of cutting tools. Both phase difference and the installation radius between adjacent disc cutters have little effect on the vertical force and rolling force, but increase with the increase in cutter spacing. In addition, when increasing phase difference and cutter space bilaterally, and reducing installation radius simultaneously, the lateral force would be improved. Related results have been verified on100 t rotary tool cutting test platform.

On the basis of reasonably simplifying the structure of disc cutter, the rolling force is used as the vibration source and based on equivalent stiffness method, the method to establish a general vibration differential equation of rolling rock in the rolling direction is further discussed. Through theoretical derivation, a conclusion can be drawn that the range of the vibration frequency is ωf-1.414ωf. Finally, taking an experimental disc cutter rolling concrete as the example, under the certain cutting condition, the vibration model is established and then the vibration frequency is calculated which is approximate equal to 17, 000HZ, so as to lay a theoretical foundation for further analyzing the dynamic performance of the cutter in rock-breaking process.

A series of numerical experiments was performed to simulate rock fragmentation by TBM (Tunnel Boring Machine) disc cutter. We used the large non-linear dynamic finite element software ANSYS/LS-DYNA to simulate three-dimensional dynamic process of two disc cutters cutting soft rock. The information such as when disc cutters combined, the fore disc cutter's has effect on the rear disc cutter under different cutting phase angle, and the soft rocks stress field of the disc cutters at its corresponded load steps and so on are obtained, what's more, the results had been carefully analyzed. The simulation results shows that, with the increase of phase angle of the two adjacent disc cutters, there is little change in the average lateral force and the average rolling force of the rear cutter. When the phase angle equals to 120°, the average vertical force obtains its minimum, and the maximal external lateral force of the rear cutter is larger than its maximal internal lateral force, then the lateral unbalance force points to inside. This conclusion provides basic data for the structural design of cutter head and engineering construction maintenance. The conclusion can be used as a guide for the further research of TBM cutters' rock fragmentation mechanism and can provide a reliable foundation for the improvement of the design of TBM cutters.

On the basis of reasonably simplifying the interaction process of TBM disc cutters and rock on tunneling surface, the shape of effective breaking pit is used as the lower boundary condition of vibration system and based on the equivalent stiffness method, two general differential equations of TBM disc cutter for vertical vibration are established, which are respectively suitable for hard rock, soft rock and soil. Taking an experimental disc cutter rolling granite as the example, through dynamic simulation, results show that vibration acceleration increases linearly with increased depth of the effective breaking pit and linear velocity of disc cutter and Nonlinearly decrease with increased width of the effective breaking pit; Besides satisfying the strength requirement, the selection of bearings and the design of cutter shaft should give dual attention to dynamics performance.