Disc Cutter Research Articles

Prediction Model for Normal and Flat Wear of Disc Cutters during TBM Tunneling Process

The accurate prediction of disc-cutter wear has been a longstanding topic that affects the tunneling efficiency and performance of tunnel boring machines, especially the prediction of flat wear extent in mixed ground. In the present study, a novel method for predicting the wear depth of the disc cutter is proposed based on energy analysis. Initially, the critical condition for the occurrence of normal and flat wear is determined. Subsequently, according to the geometry of disc cutters and the relationship between wear loss and friction work, the normal and flat wear depth of the disc cutter are obtained, respectively. By comparing calculated wear with Ren's prediction model and a case study, the effectiveness of the present model was verified. Finally, the influences of penetration depth and installation radius on cutter wear in mixed ground were analyzed. The research results indicate that the critical condition for the occurrence of flat wear is that the resistance moments acting on disc cutters exceed the driving moment. In addition, it was found that flat wear extent was much larger than the normal one. The disc cutter is prone to wear abnormally in mixed ground. Sensitivity analyses on penetration depth and installation radius show that wear from of disc cutters is determined by penetration depth. Furthermore, both normal and flat wear exert positive correlations with installation radius. The present work may provide some primary understanding about the determination of the critical condition for the occurrence of flat wear under different engineering environments.

Development and Performance Evaluation of an Integrated Disc Cutter System for TBMs

Changing the cutter is an essential procedure in tunnel boring machine (TBM) operations. The danger and low efficiency of manually replacing the disc cutter has led engineering equipment designers to study technologies to automate the changing of cutters. The key step is to design a new integrated disc cutter (simplifying the replacement process) to facilitate robot operation. Until now, the design and research of new integrated disc cutter systems has mainly relied on inspiration. In this paper, a solution space of a certain configuration of an integrated disc cutter system based on topology theory was designed. The evaluation system for the solution space was constructed by the analytic hierarchy process (AHP), and the optimal scheme of the configuration was finally obtained. In addition, experiments and simulations show that the structural strength and anti-loosening performance of the new disc cutter system meet the engineering requirements. Application of topology theory and the new evaluation system provides useful theoretical analyses and guidance for the design of new cutter systems.

Probabilistic analysis of the disc cutter failure during TBM tunneling in hard rock

TBM disc cutters used in a long-distance tunneling particularly in cutting through hard rock would undergo substantial and intense wear. The cutting efficiency may greatly reduce and potentially facing complete suspension if the worn-out cutters were not ascertained in a timely manner. Due to the uncertainty of both geological and technical factors, it is undoubtedly arduous to predict the failure of the disc cutter. In this study, the rock abrasiveness and strength properties of 267 rock specimens, including 9 different rock types were investigated. The uncertainty characteristics of the rock abrasiveness and TBM operational parameters were summarized based on the collected data. The rock abrasiveness, compressive strength, tensile strength, TBM advancing rate and rotation speed of the cutter head were considered as random variables in this study. A probabilistic analysis was performed to investigate the cutter failure and cutters group failure in hard rock excavation. The results show variability in the geological and technical factors withhold an important influence on the cutter failure, in particular on the cutters group failure. It is therefore essential to analyze the performance of the cutter wear in the probabilistic framework to avoid overestimation of the cutters’ lifespan. Lastly, a reliability design chart is proposed for the adoption in the industries to estimate the potential failure of the cutter.

Experimental Study on the Evolution of Argillization of Mudstone and Cutter Wear during the TBM Tunnelling

Argillization is a process in which clay‐bearing rocks disintegrate into the clay under the action of high temperature, pressure, and water. When tunnel boring machines (TBMs) excavate in the mudstone, argillization takes place, causing the clogging of the TBM cutterhead. As a result, the penetration rate drops gradually. Abnormal wear might occur. To investigate the evolution of argillization of mudstone and cutter wear during the TBM tunnelling, a series of rotary indentation tests were carried out on the self‐designed experimental bench for different loading times. During the test, the temperature and penetration depth of disc cutters were measured in real time. After loading, microstructures of cutting grooves, slacking mudstone, and worn cutter ring were observed by stereomicroscope. Consequently, the evolution of argillization in mudstone and cutter wear were investigated. Experimental results indicate that the argillization process of mudstone by disc cutter can be divided into three stages: mechanical cutting stage, deterioration of mudstone and the formation of slacking mudstone stage, and adherence of slacking mudstone stage. Specifically, at mechanical cutting stage, the rock was cut by cutter directly, causing high frictional heat. Then the microstructure of mudstone was deteriorated due to the water‐weakening mechanisms, temperature effect, and mechanical activation effect. Finally, the slacking mudstone was adhered to the disc cutter. Correspondingly, due to the argillization of mudstone, the disc cutter wear goes through the mechanical wear stage, argillization wear stage, and secondary wear stage in sequence. This investigation reveals the rock cutting mechanism of TBM considering the argillization of mudstone. Furthermore, it provides some references for design and operation of the TBM.

Study on the breaking process of jointed rock mass by disc cutters based on digital image correlation and infrared thermography

Jointed rock masses are frequently encountered during the TBM excavation. To investigate the rock breakage mechanism of jointed rock mass by disc cutter and precursory information before rock failure, a series of indentation tests were performed on shear rheological test system. During the test, breaking process of specimens were recorded by digital image correlation system and thermal infrared imager simultaneously. Therefore, the strain fields and thermal infrared images of jointed rock mass by disc cutters were obtain. The experimental results show that the failure process of jointed rock mass can be divided into four stages: compaction stage, linear elastic stage, residual failure transition stage and post-failure stage. Besides, the characteristic of strain fields shows a good accordance with that of infrared radiation temperature fields at each stage. The failure of rock samples is dominated by shear failure, and the localized temperature rise is an important infrared precursor of rock fracture and instability. The experimental results are of great significance to the deep understanding of the breaking mechanism of jointed rock mass and warnings of engineering disasters.

Numerical simulation analysis of coal rock crushed by disc cutter based on ABAQUS

In view of the lack of research on the mechanism of disc cutter cutting coal rock during the tunnelling process of coal mine rescue tunnel equipment, the ABAQUS software was used to establish the finite element model of single disc cutter crushing coal rock, and the influence of penetration and cutting speed on the rock breaking force during the process of disc cutter crushing coal rock was analyzed. The results show that the average cutting force increases linearly with the penetration and cutting speed. The maximum vertical force of the disc cutter at a penetration of 5mm is 2.6 times that at a penetration of 2mm. The impact of the disc cutter cutting force at a penetration of 3mm is obvious. The average rolling force at a cutting speed of 0.8 rad/s is twice that of a cutting speed of 0.2 rad/s. The impact of the disc cutter cutting force at a cutting speed of 0.5rad/s is obvious. Comprehensively considering the influence of penetration and cutting speed on the average value and fluctuation range of disc cutter cutting force, choosing a moderately large penetration and a large cutting speed parameter combination will help to achieve rapid and safe coal mine emergency rescue tunnelling. The method in this paper provides a basis for the optimization of the cutterhead tunnelling parameters during coal rock cutting.

Исследование процесса оборота почвенного пласта новым корпусом дискатора на нераскорчеванных вырубках

Исследование процесса оборота почвенного пласта новым корпусом дискатора на нераскорчеванных вырубках

On the Use of Microscale Abrasion Test for Determining the Particle Abrasivity

Abstract Particle abrasivity is an important concept for helping to select materials for pumps and for disc cutters in underground excavation, and specific ASTM standards are available for making these selections. However, for manufacturing processes in which abrasive action is their core, the particle size range is approximately a few micrometers. The evaluation of particle abrasivity using the microscale abrasion test matches this range of particles for this purpose, but relatively few investigations using this kind of method have been conducted. The aim of this investigation is to use the microscale abrasion test to evaluate the particle abrasivity, avoiding changes on the ball surface and on the particle size distribution. Samples of quenched AISI D2 tool steel were used for tests. The wear mode was dependent on the testing time. Alumina (Al2O3) particles presented a lower abrasiveness when compared to boron carbide (B4C) ones, confirmed by the higher wear coefficient found in the latter after reaching the steady-state regime. This behavior was evidenced by the number of active particles in the contact, which showed that there were a larger number of B4C particles than Al2O3 during the contact at all sliding distances. The particle abrasivity is discussed in terms of significant characteristics of slurries: particle shape, particle size distribution, hardness-to-elastic modulus ratio, zeta potential, and density. As the controlling of those characteristics seems to be very important, particle abrasivity is a concept that needs to be improved besides the test system used for that purpose.

Analysis of Grinding and Chipping Processes beneath Disc Cutters of Hard Rock Tunnel Boring Machines (Case study: Uma-Oya water Conveyance Tunnel, SriLanka)

Analysis of Grinding and Chipping Processes beneath Disc Cutters of Hard Rock Tunnel Boring Machines (Case study: Uma-Oya water Conveyance Tunnel, SriLanka)

Modular milling cutter with inner-cooling network

The big sized milling cutters are expensive tools and are not appropriate for small batches production. Making these tools more versatile, able to fit to different kinds of processes and shapes of the parts to be machined is a must. As well, cooling the cutting area is very important. The existing end-mill cutters are designed to feed internally with coolant only the teeth on the front side. The paper presents a concept of a modular tool, made of elementary disk cutters, able to be reconfigured to get different shapes and sizes. The main element of novelty the paper claims is the inner cooling system of the complex tool. The special design of the elementary milling cutters and of the shaft they are mounted on make the tool able to lead jets of coolant to every insert, no matter where they are placed, on the cylindrical or on the front side of the milling cutter. A network of channels drilled in the shaft and in the body of elementary milling cutters make this possible. The capability to splash with coolant under high pressure all the cutting edges do not depend on the number of teeth of the tool. Being delivered from inside the cutting tool, the coolant splashes directly on the contact surface between the inserts and workpiece, which makes cooling more efficient.

Numerical Simulation and Experimental Verification of Disc Cutter Rings in Die Forging Process

In order to study the forming law of the disc cutter ring in the independently researched die, the finite element model (FEM) of disc cutter ring for die forging has been established and the die forging process has been simulated by the plastic forming software. The metal flow field, temperature field, stress and strain field of the filling process were obtained by simulation. The exerted force of the die was also simulated and analyzed; thus, the die forging process was optimized. Based on the designed process parameters and simulation results, the experimental study on die forging forming of cutter ring was carried out. The comparison shows that the numerical simulation results are in good agreement with the experimental results, which proves that the die forging model of disc cutter ring in this paper is feasible.

Predicting TBM performance in soft sedimentary rocks, case study of Zagros mountains water tunnel projects

Soft rock formations are widespread throughout the mountainous regions of the world including the mountains of western and southern Iran. Therefore, it is very common to pass through soft rock formations while building long tunnels for various purposes in the mountainous regions. The soft sedimentary rocks are frequently found in Zagros Mountains located in the south and west of Iran, where most of Iran's water conveyance projects (long and deep tunnels) have been constructed or are under construction. The behavior of these rocks in tunneling projects has received much attention in the past decades, but some features comprising the boreability and performance of tunneling machines in such rocks have received little attention. Many of these sedimentary rocks, especially those composed mainly of clay minerals, exhibit “non-structurally controlled” behavior in deep tunnels and below the groundwater level, and are completely continuous. During loading by disc cutters, these rocks usually exhibit plastic behavior, and the formation of chips in these rock types are often different than brittle and discontinuous rocks. Obviously, this necessitates the development of special models to predict the TBM performance in these rocks. In this study, the machine performance in soft rock formations along some of the Zagros Mountains water tunnel projects has been investigated. Efforts have been made to develop a special empirical model for continuous (intact) soft rock formations to complement the models presented in previous studies. Evaluation of the relationships between different geological and machine performance and operating parameters in these projects indicated that there is a strong correlation between intact rock properties (uniaxial compressive strength) and two parameters including penetration and cutter load. New empirical models developed based on statistical analyses of machine performance in these projects are presented for predicting TBM performance in similar conditions.

Fabrication and Evaluation of a Cabbage Harvester Prototype

A cabbage harvester prototype was fabricated and tested to save time, cost, and labor for harvesting. This harvester was designed for harvesting operations to drive the prototype and control the harvester. The single-row prototype harvesting meets the functional requirements of the physical properties of the Egyptian cabbage. The performance of the harvester prototype was evaluated on two shapes of cutter disc, four cutter disc speeds, and four cutter disc angles; these parameters were assessed at 88% moisture content of the cabbage head and average forward speed of 1.5 km/h. The results demonstrated that the serrated edge cutter discs and 900 rpm disc speed produced actual productivity of 12.56 ton/h, 2.28 kW power requirements, 0.18 kW h/ton specific energy requirement, and of 3.66 $/h operating cost. It turns out that the harvester did not do major harm to the cabbage and less than 4% damage. Operating the harvester at the optimum parameters saves cost and time compared with manual harvesting.

Rock Breaking Performance of Two Disc Cutters of Tunnel Boring Machine for Safe Tunneling in Unstable Coal Rock Stratum

In unstable coal rock formations, the rescue channels should be constructed through safe and efficient tunneling. The rock breaking performance of the tunneling equipment directly hinges on the cutter-head layout. Focusing on the conditions of unstable coal rock formation, this paper adopts the extended Drucker-Prager (D-P) plastic model to define the properties of bedrock materials of the coal rock with low mechanical strength and poor homogeneity. Then, a finite-element model was established on ABAQUS for the coal rock cut by two disc cutters, and used to simulate the breaking of the coal rock and the peeling of slags from the bedrock. On this basis, the authors analyzed the influence of cutter spacing (30, 35, 40, and 45mm) over cutting force, rock breaking amount, and specific energy under two cutting methods: simultaneous cutting and sequential cutting. Finally, a cutter deployment strategy was designed for safe and efficient tunneling in unstable coal rock formations. The results show that: Under simultaneous cutting, as the cutter spacing increased from 30 to 35mm, the rock breaking amount increased, while the specific energy declined; as the cutter spacing further rose from 35 to 45mm, the rock breaking amount dropped, while the specific energy increased. Under the coal rock conditions in our research, the optimal cutter deployment strategy is: simultaneous cutting with cutter spacing of 35mm. The research results provide theoretical support for the cutter-head design of rescue equipment for collapsed coalmines.

Full-scale granite cutting experiments using tunnel boring machine disc cutters at different free-face conditions

This study presents the results of full-scale hard rock (granite) cutting experiments using tunnel boring machine disc cutters at different free-face conditions. Rolling cutting tests are conducted on a full-scale rotary cutting machine with a commercial constant cross-section disc cutter with a diameter of 432 mm. Three free-face conditions are prepared for the tests: vertical free faces, inclined free faces (with different heights and cut spacings), and narrow kerfs. The rock-cutting force, rock-cutting trajectory, specific energy, and shape of the representative rock chip are analyzed and compared for each test. The major results are as follows. First, for the granite subjected to vertical free-face conditions, the cut spacing should not be larger than the critical value of 140 mm in order to break the rock successfully with high efficiency. Second, the free face that is closer to parallel to the penetration direction exhibits a decreased rock-cutting force and improved rock-cutting efficiency. Third, narrow kerfs are not as effective as vertical and inclined free faces for assisting rock breaking. Therefore, to exploit the advantages of narrow kerfs, they should be prepared close to the cutting path, with spacings of less than 40 mm for the studied granite. Fourth, the applied grain-based discrete element method is effective for numerical analysis of the rock-cutting process because the rock-fragmentation performance is very similar to that in the laboratory tests.

Experimental studies using a new portable linear rock cutting machine and verification for disc cutters

This study aims at verifying the experimental results of a newly developed portable linear rock cutting machine (PLCM) and its usability for proper selection, design and predicting performance of TBMs instead of full-scale rock cutting machine. PLCM minimizes some of the disadvantages of full-scale linear rock cutting machine (FLCM) such as requiring experienced manpower to run the tests, large blocks of rock samples, which are usually difficult to obtain and expensive, and time consuming procedures. Relieved and unrelieved cutting tests at different depths of cut are performed in this study on different rock samples with the PLCM by using a mini-scale constant cross-section (CCS) disc cutter having a diameter of 145 mm and a tip width of 4.7 mm and the FLCM by using a real-life CCS disc cutter having a diameter of 432 mm and a tip width of 12 mm. Line spacing is 20 mm for mini scale disc cutter and 60–80 mm for real-life disc cutter in cutting tests in relieved mode. The results from both of the experimental devices are correlated for using prediction of cutting performance parameters of FLCM, which is commonly preferred and well-proven testing device for predicting the performance of any type of mechanical miner excavating hard rock. Then, another set of rock sample is obtained from Uskudar-Umraniye-Cekmekoy (UUC) metro tunnel construction site using EPB TBMs, of which their field performance (penetration and/or cutting rate, specific energy) and operational parameters (TBM thrust, cutterhead torque, power and rotational speed) are recorded. Based on the PLCM tests performed on the samples obtained from the field, the performance of the TBM is estimated theoretically (deterministically) and compared with the realized field performance to verify the results of the PLCM tests. The results indicate that the experimental cutting performances of the PLCM and the FLCM are well correlated and the PLCM can be used for predicting performance, design and selection of TBMs excavating hard rocks. Additional studies are required for developing more reliable models for predicting excavation performance.

Optimum design of the peripheral cutters’ specification on the head profile for hard-rock TBMs

One of the most important goals in the design of the TBMs is to optimize the arrangement of the peripheral cutters on the cutterhead layout. Peripheral cutters refer to the cutters installed on the curved area near the periphery of the TBM cutterhead. This optimization is essential to improve TBM performance (e.g. penetration rate) and to control the interaction of the cutters (e.g. cutter normal force) with the tunnel face. The actual penetration of the peripheral cutters in the tunnel face is relatively lower which leads to lower applied normal force. To avoid ridge formation between these cutters and to prevent high asymmetric forces applied to the flanks of the cutters, it is necessary to gradually reduce the cutter spacing in the peripheral region of the cutterhead. The evaluation of the design specifications of the peripheral cutters, including spacing, tilt angle, and normal force is typically relying on experience and engineering judgment. To improve such strategies and to achieve an efficient design for the cutterhead lace design, an optimization method is introduced based on the statistical analysis of the cutterhead design details of various TBMs from around the world, as well as the principal of using the optimum ratio of spacing to the cutter contact area (S/Acon). The results of this method provide the optimum spacing of disc cutters and their corresponding tilt angles and normal forces for the peripheral cutters. In developing relationships for the peripheral cutters’ normal forces, graphical methods are utilized to calculate the actual cutter contact area and the actual cutter indentation area for different values of cutter tip width, cutterhead curvature radius, and tilt angle. In this regard, a multivariate regression formula is presented to evaluate the actual indentation area. To illustrate the steps presented in this method, an example is provided and the details of the design procedure and its final results are explained. The results of the proposed method establish a new foundation to improve the design process of hard-rock TBMs to help prevent structural damages and low performance.

A TBM advance rate prediction method considering the effects of operating factors

Due to the widespread use of Tunnel Boring Machines (TBMs) in China, all affected parties involved in related construction of projects have proposed higher requirements for the controllability of TBM construction periods. Consequently, this report proposes a new TBM advance rate prediction method. By mining TBM construction data obtained from a project diverting water from the Songhua River to cities in the middle region of the Jilin Province in China (hereinafter referred to as the “Songhua River Diversion Water Supply Project”) and analysing the varying rules of the tunnelling parameters under different surrounding rock conditions, this report proposes a corresponding relationship relating the surrounding rock conditions, reduction coefficient of the disc cutter thrust (Fn) and cutterhead rotation speed (N), and establishes a TBM penetration rate (PR) prediction model, which is affected by factors associated with the operator’s control. Furthermore, after investigating and summarizing the TBM construction processes of several projects, TBM downtime is classified and evaluated to obtain the TBM utilization factor (U). Based on the PR and U, a TBM advance rate (AR) prediction model is established. The established AR model was applied to a water diversion project in the Xinjiang Uygur Autonomous Region of China. This engineering practice has demonstrated that the operator adjusts the PR according to the surrounding rock conditions, and the prediction of the PR affected by the operating factors has been proven accurate. Furthermore, the prediction method of U obtained by evaluating the downtime is simple and feasible. Overall, the results indicate that the proposed AR model possesses satisfactory predictive performance.

Disc cutter wear prediction based on the friction work principle

As the main rock-breaking tool of the tunnel boring machine, wear of the disc cutter is affected by geological conditions, equipment factors, and tunneling parameters when it interacts with rock. Because of the complex factors affecting disc cutter wear, it is difficult to accurately predict the wear of the disc cutter. In this study, the rock-breaking mechanism and the force of the disc cutter were analyzed, and a theoretical prediction model of disc cutter wear was established based on the friction work principle. The parameters in the disc cutter wear prediction model were determined by simulation, and a prediction method of disc cutter wear is proposed. Finally, the wear prediction model of the disc cutter was verified by field wear data. The results show that the average error between the predicted value of the disc cutter and the actual wear data from the field is 16.1%. The wear prediction model of the disc cutter has high accuracy and adaptability. The research results provide an effective method for wear prediction of the disc cutter, which is of great significance and engineering value for cutter replacement and construction management.

The performance of TBM disc cutter in soft strata: A numerical simulation using the three-dimensional RBD-DEM coupled method

Though disc cutters are widely used in mixed strata, eccentric wear of disc cutters in soft part of mixed strata is still an important factor influencing the efficiency and cost of TBM tunnelling. The eccentric wear of disc cutters is closely related to their motion state, however, in-depth research on this issue are still less. This paper introduces a three-dimensional RBD-DEM coupled method, adopting a newly developed RBD coupling calculation program in which the mutual interaction between disc cutters and strata was considered. Based on this method, the cutting process of disc cutter was simulated and the performance of disc cutter was investigated. The results show that the slip ratio decreases as the depth of penetration depth increases, however, the degree of influence is not obvious in terms of a critical value of penetration depth, on the contrary, if the penetration depth is too large, the slip ratio fluctuation increases. At the same penetration, linear velocity does not have significant effects on slip ratio, but it can have great effects on the torque of the disc cutter, especially the torque at the start-up phase. Existing eccentric wear would lead to the periodic fluctuations of angular velocity and enlarge both the rolling force and thrust force, therefore, existing wear will accelerate eccentric wear.