Disc Cutter Research Articles

TBM performance analysis in very strong and massive rocks; case study: Kerman water conveyance tunnel project, Iran

ABSTRACT When TBMs are applied for tunnel excavation in very strong and massive rocks, the cutting mechanism happening under the disc cutters is converted from chipping to grinding. On the other hand, the most common TBM performance prediction models that have been developed assuming the occurrence of the chipping phenomenon would not be sufficiently accurate in grinding conditions. Therefore, this study aimed to develop a new empirical equation for estimation of the TBM performance in grinding conditions. In this regard, the database composed of actual measured TBM parameters (i.e. penetration rate and cutter load) and engineering rock properties (i.e. UCS, RQD in rock mass) was established using the data collected from a mechanised tunnelling project (the southern lot of Kerman water conveyance tunnel project, Iran) constructed in very strong rocks. Based on the established database, the statistical analyses were performed in order to develop a new TBM performance prediction model for grinding conditions. The proposed model provides a relationship between TBM penetration and cutter load for strong (UCS = 150–300 MPa) and massive rocks (RQD > 90) under grinding conditions.

Increasing the surface stability of the cutting tool through complex machining

Nowadays, the application of multilayer coatings is widely used to increase the abrasion resistance of cutting tools. Before applying the multilayer coating, the selected cutting tool was purified in a bath with a disc cutting surface from quick-cutting steel and carried out the process of ion-nitriding or chemical-thermal treatment. In this case, nitrogen and argon ions diffuse over the surface of the disc cutter. Ion alloying using low-energy high-precision electron beams followed this process. The processing was carried out on a single-chamber two-system magnetron installation “RITM-SP-M”. Finishing was carried out by disc milling with Swiss Platit π311 ((TiCr)N-(TiAl)N-(CrAlSi)N+ion nitriding, (TiCr)N-(TiAl)N-(CrAlSi)N(nATCRo3)), (TiAl)N+ion nitriding + ion alloying (NbHf), (TiAl)N, (TiAl)N+ion nitriding, diamond-like coatings).Such multilayer coatings were tested at the Navoi mining and metallurgical plant “Navoi machine-building plant”. Machined disc cutters have been tested on 34XH1MA which is difficult to machine.

The Influence of Confining Stresses on Rock Fragmentation, Thrust Force, and Penetration Energy in Sandstone Indentation Tests Using Disc Cutters

Hard rock Tunnel Boring Machines (TBMs) engaging disc cutters as cutting tools have been employed in considerable underground coal mines to accommodate the requirement of more stone drivage as operations are going deeper. This study conducted a set of disc cutter indentation tests to explore the influence of confining stresses on rock fragmentation, thrust force, and penetration energy on sandstone, which is commonly encountered in underground coal mines. The test results show that there exists a critical confining stress, under which the maximum thrust force and penetration energy keep increasing with confining stress mounting while the maximum thrust force and penetration energy will decrease or flatten if it is surpassed. By combining with previous studies and comparing the critical confining stress values to the rock mechanical properties’ values, the critical value is most likely to be of cohesion. For subsurface rock fragmentation, the Constant Cross Section (CCS) disc cutter indentation has denser cracks and their orientations are more lateral than those under the V shape one; the V shape disc cutter indentation is less sensitive to confining stresses, with no notable increase of crack number and crack reorientation with increasing confinement. Thus, the CCS disc cutter is more favorable than the V shape one from the perspective of rock fragmentation under confining stresses.

Introducing an empirical model for prediction of disc cutter life for TBM application in jointed rocks: case study, Kerman water conveyance tunnel

Disc cutters wear and need to be replaced when using tunnel boring machines (TBMs) to excavate through rock, often becoming a high ticket item on the list of consumables in tunneling operation. The empirical models used for predicting cutter life are commonly based on the properties of intact rock, while the impact of rock mass characteristics on cutter wear is often ignored or not properly taken into account. Joints and discontinuities tend to decrease the strength of rock mass, as compared to intact rock. Joint properties can affect the interactions between the rock and the disc cutter in the boring process. In other words, the cutter wear and life in a jointed rock mass are different than the wear rate in intact rock. In this study, field data including the geomechanical parameters and observed cutter life in the Kerman water conveyance tunnel (KWCT) project was analyzed using multivariable regression to offer a new empirical prediction model for prediction of cutter life in the jointed rocks. The model presented in this study shows that cutter life is a function of the total fracturing factor and rock mass strength, representing rock mass properties and Cerchar abrasivity index as intact rock property. Furthermore, boring in jointed rock is easier than an intact rock, and as a result, the cutter life increases. The validation results show that this model can offer a more accurate prediction of the disc cutter life in tunneling projects involving jointed rock masses.

Breakage Mechanism of Layered Sandstone Penetrated by TBM Disc Cutter

In this paper, the breakage mechanism of layered sandstone subjected to the TBM disc cutter was investigated. A series of typical layered sandstone specimens were prepared for true triaxial compression tests in the laboratory to simulate the disc cutter action at the tunnel face, and an acoustic emission (AE) system was used to monitor the breaking process during the penetration tests. Furthermore, a DV recorder was employed to capture the surface deformation. Then, the failure specimens were scanned by high resolution X-ray micro-CT. The results show that the failure mode of layered sandstone in terms of cracking transforms into local crushing with increasing confining stress. The propagation pattern of the cracks varies with the bedding inclination, which is distinctly different from intact rock. The results also indicate that the peak force presents linear variation with the confining stress and an increasing trend with the bedding inclination at the first penetration, and the failure mode of the second penetration is mainly related to the broken status from the first penetration.

Generalized cutting force model for peripheral milling of wood, based on the effect of density, uncut chip cross section, grain orientation and tool helix angle

The influence of the grain angle on the cutting force when milling wood is not yet detailed, apart from particular cases (end-grain, parallel to the grain, or in some rare cases 45°-cut). Thus, setting-up wood machining operations with complex paths still relies mainly on the experience of the operators because of the lack of scientific knowledge easily transferable to the industry. The aim of the present work is to propose an empirical model based on specific cutting coefficients for the assessment of cutting force when peripheral milling of wood based on the following input: uncut chip thickness and width, grain angle (angle between the tool velocity vector and the grain direction of the wood), density and tool helix angle. The specific cutting coefficients were determined by peripheral milling with different depths of cut wood disks issued from different wood species on a dynamometric platform to record the forces. Milling a sample into a round shape (a disk) allows to measure the cutting forces toward every grain angle into a sole basic diameter reduction operation. Force signals are then post-processed to carefully clean the natural vibrations of the system without impacting their magnitudes. The experiment is repeated on five species with a large range of densities, machining two disks per species for five depths of cut in up- and down milling conditions for three different tool helix angles. Finally, a simple cutting force model, based on the previously cited parameters, is proposed, and its robustness analysed.

Automated calculation of the profile of a disk cutter for the manufacture of helical grooves

The calculation of the profile of disk cutters, excluding undercutting for any complex profile of the helical groove, is proposed. The feature of the method is in the fact that the profile is specified by a small number of control points, which, using interpolation, is increased by tens or hundreds of times. The rational profile of the cutter is investigated depending on its three setting parameters. A numerical experiment was carried out for the profile of the cutter with the optimization of the setting parameters. Keywords: disk cutter, profile, helical groove, computer-aided design, calculation zov20@mail.ru

Parameters and operating modes of the coulter group of the sod seeder

For the implementation of strip overseeding, they are used by seed drills with disc cutters. Improving the sowing quality due to the compaction of the seed bed and the creation of a soil layer between the seeds and fertilizers is possible when removing the working bodies of seeds and fertilizers of the from the area of the circular knives. To ensure the incorporation of seeds and granulates at different soil levels, it is stage to determine the length of the fertilizer coulter cheeks and the permissible distance between working bodies. Dependencies for calculating rational parameters and operating modes of the developed coulter group are obtained. The calculated parameters make it possible to ensure the minimum spread of fertilizer granules along the planting depth and high stability of the soil layer thickness between the fertilizer and seeds. In the range of operating speeds of the seeder, the rational parameters of the coulter group have the following values: the angle at the top of the fertilizer coulter in the horizontal plane is 15-20°, the lip of the fertilizer coulter is 0.040-0.045 m, the width of the coulter bell is 0.02 m, the minimum distance between the coulters is 0.14-0.16 m.

Mechanical and Acoustic Emission Responses of Rock Fragmentation under Disc Cutter Penetration

To better understand the rock fragmentation mechanism and optimize cutter design and selection for rock excavation by TBM, a set of three-dimensional indentation tests was conducted with different rock and cutter types. Acoustic emission (AE) monitoring technique was employed to capture the information of the rock damage evolution real-timely. It is found that the penetration by using the constant cross section (CCS) cutter tends to induce inconspicuous rock chips formation before the sudden occurrence of the macrocrack, but that by using the V-type cutter tends to induce gradual rock fragmentation accompanied by the multiple local rock chips formation and the sawtooth force-penetration curve. Meanwhile, rock fragmentation models for CCS and V-type cutters were compared, and the spatio-temporal evolution of AE events was quantitatively analyzed to reflect the rock damage zone development process. Results indicate that the V-type cutter has greater penetration ability and the CCS cutter can cause larger unit damage zone radius. Microscopic observation by using the scanning electron microscope (SEM) reveals that the fracture mechanism for the crushed zone of rock is mainly shear type and that for the major crack is tensile type. It does not matter with rock types or cutter types.

Study on the symmetric bilinear initiating technique of deep-hole boulder blasting in the TBM tunnel excavation

The excavation of the deep-buried tunnel with tunnel boring machines (TBM) is often affected by boulder, which harm the cutter disc of the TBM. It is sometimes difficult to achieve the ideal blasting effect by the conventional blasting technology. In this study, a novel symmetric bilinear initiating (SBI) technique based on detonation wave collision was proposed to reduce the oversize boulders and improve the construction efficiency. The blasting parameters design and unit consumption of explosive were analyzed by using the empirical formula based on field tests in the Hongyan River Nuclear Power Plant (HRNPP) intake tunnel boulder blasting project. Numerical simulation models of the actual engineering parameters were also developed to reduce the risk of engineering test, and to analyze the detonation wave pressure, shock wave propagation, and crack state distribution. The results showed that the SBI technique obviously affects the detonation pressure distribution and crack state compared to the central point initiating (CPI) technique. Furthermore, different treatment methods of boulder were carried out in the field test. The results of rock sample size of the core-drill and TBM advance rate showed that it is possible to form better blasting effect when using SBI technique, and the results of blasting particle velocity also proved that SBI can improve the energy utilization rate of explosive. This study provides a novel method based on SBI system for the boulder blasting to ensure a safe and efficient TBM excavation.

Evaluating the influence of engineering geological parameters on TBM performance during grinding process in limestone strata

The chipping and grinding processes are the basis for understanding rock cutting during TBM excavation in hard rock conditions. The chips are produced when tensile fractures created by adjacent cutters propagate parallel to the tunnel face and coalesce whereas grinding occurs when fractures do not fully propagate through the rock and only fines are generated. Chipping is the normal and efficient boring process using machines equipped with disc cutters. Consequently, almost all of the models proposed for predicting the TBM penetration have been developed by the assumption that chipping is the dominant mode. It is obvious that these models are unable to predict correctly TBM performance when grinding is dominated in the rock cutting process. In this study, the relationships between engineering geological properties of the rock units (Cretaceous limestones) and operating and performance parameters of a refurbished EPB-TBM, employed for completion of SEL6 (the Southern Extension of Line 6, Tehran Metro) tunnel, were evaluated and analyzed. In this project due to limitations in the load capacity of the employed cutters and insufficient initial penetration in rock, the excavation was mostly carried out on grinding-dominated mode. So, the suitable data for establishing a special database and consequent analyses were provided. The established database composed of actual operating and performance parameters of the machine (i.e., cutterhead penetration and RPM and cutter load) and also engineering geological properties (i.e., UCS, alpha angle, GSI, and RQD) of limestone strata. Finally, by statistical analyses performed on collected and screened data (41 data sets), some simple, site-specific, empirical equations were developed to predict the TBM performance on grinding mode. In addition, according to the multivariate regression method, a significant relationship between the cutterhead penetration (PRev), the cutter load (Fn), intact rock strength (UCS), and geological strength index (GSI) was established, statistically. The obtained results demonstrate that this engineering geological-based model could provide a new applicable equation for accurately predicting TBM performance for similar geological conditions where grinding is dominant.

Operation power consumption and verification tests of a trenching device for orchards in Xinjiang based on discrete element

According to the agronomic requirements of orchard planting pattern and fertilization in Xinjiang, the soil particle models and a soil-trenching device interaction model were established by using discrete element simulation software in order to find out the law of influence of structure parameters and working parameters on the operation power consumption of a segmented cutting trenching device; moreover, its cutting process was simulated according to the response surface test design. According to the results of research on the influence of forward speed, cutter disk speed and cutter disk combination on the operation power consumption of the segmented cutting trenching device, the law of their influence on the operation power consumption in descending order is forward speed, cutter disk combination, cutter disk speed. According to the response surface test result, the following influential factor parameter combination has been obtained: forward speed 815 m/h, cutter disk speed 112 r/min, cutter disk combination A (cut angle 150°, bent angle 60° and working width 133 mm), cutter disk combination B (cut angle 180°, bent angle 90° and working width 166 mm), and trenching operation power consumption-optimization results were verified through field tests. According to the verification, the results showed a high accuracy of the simulation, with a relative error mean of 3.18% between the theoretical value and the field test value. This study can provide a reference for the energy-saving design of orchard trenching devices. Keywords: trenching device, discrete element, orchard, power consumption, simulation analysis, parameter optimization DOI: 10.25165/j.ijabe.20211401.5477 Citation: Ma C, Qi J T, Kan Z, Chen S J, Meng H W. Operation power consumption and verification tests of a trenching device for orchards in Xinjiang based on discrete element. Int J Agric & Biol Eng, 2021; 14(1): 133–141.

Theoretical and Experimental Results from Laboratory Tests by ILCM

The intermediate linear cutting machine (ILCM) is a machine designed to work on an intermediate scale between the full- and the small-scale. The reduced scale involves several advantages compared to full-scale tests, especially in terms of sample supplying and transportation. On the other hand, it has an impact on the testing conditions, resulting in a limitation of the cutting penetration and spacing during the test, as well as in a smaller disc cutter. This affects most of the results, which cannot be directly used for the on-site machine performance prediction. However, some experimental results provided in the literature show that the optimal spacing/penetration ratio is not significantly affected by the changes involved. On this basis, the results obtained from ILCM tests should provide reliable information about the optimal cutting conditions of a tunnel boring machine in massive rock mass. The work performed included the development of some improvements of the testing rig, as well as a modified ILCM testing procedure, according to the one typically used in standard LCM tests. The results provide information about the attitude of the tested lithotypes to mechanical excavation by means of disc tools, including the optimal cutting conditions. Additional work was developed in terms of detailed characterisation of the rock samples involved and assessment of the size distribution of the debris produced during the ILCM tests. Nevertheless, further tests are necessary, in order to assess the consistency of the experimental procedure employed and to investigate the scale effect.

Effect of Joint Orientation on the Breakage Behavior of Jointed Rock Mass Loaded by Disc Cutters

Effect of Joint Orientation on the Breakage Behavior of Jointed Rock Mass Loaded by Disc Cutters

A field parameters-based method for real-time wear estimation of disc cutter on TBM cutterhead

In hard rock TBM tunneling, the loss caused by disc cutter wear accounts for a large proportion of time and cost for the entire project. However, existing disc cutter wear prediction models mainly focus on predicting cutter consumption before construction and cannot predict the wear of each disc cutter. Moreover, the accurate rock parameters required in these models are challenging to obtain. Hence, these models are not capable of determining which cutter on cutterhead should be replaced during construction. To solve the problems mentioned above, this paper presents a novel field parameters-based method for estimating the wear of each disc cutter in real-time. The proposed method is implemented through the following steps. To begin with, a new health index is constructed and defined as the ratio of the rolling distance of a cutter in a small excavated section to its maximum rolling distance. Then, specific field parameters related to the new health index are analyzed and selected. Thereafter, the mapping model between the new health index and the specific field parameters is established based on a one-dimensional convolutional neural network. Finally, on the basis of the established model, the estimated health indices corresponding to all excavated sections of a disc cutter are accumulated to obtain its health status. The field data obtained from Mumbai metro tunnel was utilized to verify the effectiveness of the proposed method, which demonstrates that the proposed method can estimate the wear of each disc cutter in real-time with average accuracy as high as 87.8% on the test set. Therefore, the proposed method is capable of significantly reducing the time and cost of cutter inspection, replacement, and repair for TBM, thereby improve tunneling efficiency and reduce construction cost.

Analysing the Feasibility of a\xa0Full-face Cutting Machine for the Robominers Project

Several methods of excavation have previously been studied to choose the most suitable approach to be applied in the Robominers project. Compared to drilling and blasting and partial-face cutting, the full-face cutting option is regarded as one of the methods which can offer, among others, high advance rates and a safer working environment for the machinery. Current technologies of these methods, however, suffer from several limitations, such as the inability to bore very hard rocks, significant lack of geometrical flexibility in mine working areas, and low mobility due to large and heavy components. In this study, two of the most commonly applied small diameter full-face machines including the pipe jacking and the Boxhole Boring Machine (BBM) are studied with regards to their performance parameters. The pipe jacking machine option with a cutterhead consisting of disc cutters exhibits higher efficiency in excavation with only slightly lower production rates compared to a BBM with strawberry cutters. They are also much lighter machines. Yet, using the jacking concept means a limited driving length and does not apply to the Robominers. Therefore, the introduction of small gripper or shielded Tunnel Boring Machines (TBMs) can significantly improve the mobility. Their application, however, requires considering the risks of jamming in difficult ground conditions and the possible requirements of a support installation. These rock mechanics issues need to be carefully considered in the design of such machines. In addition, further studies are required to employ assisted cutting methods in very hard rocks and to increase the geometrical flexibility of these machines by lowering their turning radius.

WITHDRAWN: Development and optimization of cold rolled slitting machine process

Slitting machine is universally handled for trimming the unwanted edge part of broad sheet metal stock. A problem of camber formation at the time of cutting is quite common in cold rolling slitting machine. When the strip passes through skin pass operation, burr is formed due to friction which will result in bad surface finish and also when thrust force do not match with the pulling force results into camber covering edges of strips. The study focuses on the effects of cutting boundaries on specific strengths such as shear strength and thin line profile. Advancement in the cutting parameter is incorporated to eliminate the camber formation during the slitting operation. The study focuses on the effects of cutting boundaries on specific strengths such as shear strength and thin line profile. The scarp winding mechanism is developed considering the ergonomics of the workplace. The carrying of cutter discs consequently is found to be terribly little in comparison thereupon existing slitting methodology. Optimization of slitting process line is done by using Taguchi Method. Moreover, the paper provides a detailed CAD modeling and optimization for slitting operation which will enhance the operational parameters of the slitting machine.

Penetration behaviour of TBM disc cutter assisted by vertical precutting free surfaces at various depths and confining pressures

The ability to improve rock-breaking efficiency of tunnel boring machines in hard rock stratum is significant to improve driving speed and reduce construction cost and time. The undercutting method has been used to improve the rock-breaking efficiency of disc cutters, including the design of curved and multistage cutterheads. The limited radian of curved cutterheads and the number of multistage cutterheads, however, are restricted by the current manufacturing level. We explored mechanical response and rock-breaking efficiency assisted by water jet kerfs as the vertical free surface. We conducted a quasi-static penetration test of the disc cutter considering four kerf depths and three groups of confining pressures. We analysed the surface crack propagation and fractures inside the sample using acoustic emission and computed tomography scanning. We studied the influence of confining pressure and cutting depth of the water jet on penetration force, rock chips, and specific energy. We analysed the failure evolution and stress field of kerf specimens using numerical simulation. The results showed that increasing cutting depth relieved restraint stress and the resulting influence of the confining pressure on removed rock volumes and specific energy was not remarkable. We recommended a kerf depth of greater than 18 mm to reduce penetration force and significantly improve rock-breaking efficiency.

Bionic Design and Parameter Optimization of Rotating and Fixed Stem- and Leaf-Cutting Devices for Carrot Combine Harvesters

To solve the problems of the high rhizome damage and low net cutting during carrot combine harvesting, the following research was performed. The designed carrot stem- and leaf-cutting device was taken as the research object, and a bionic design idea was adopted. MATLAB software was used to extract and optimize the tibial curve of the mantis forelimb, and its shape was applied to the cutting edges of a single-disc rotating cutter and a straight fixed cutter, whose key structural parameters were determined. The kinematic and dynamic models of the cutter, stems, and leaves were established to explore the critical conditions of smooth cutting. A single-factor experiment was performed. The results show that the rhizome damage and the stems and leaf net cutting increased when the rotation speed of the clamping conveyor pulley increased. The flatness of the cutting surface first increased and subsequently decreased. At a speed of 102 r/min, the rhizome damage was 2.86%, the net cutting of stems and leaves was 92.82%, and the flatness of the cutting surface was 85.39%. The net cutting of stems and leaves and the flatness of the cutting surface increased as the disc cutter speed increased, while the rhizome damage decreased. When the rotation speed reached 165 r/min, the rhizome damage, the net cutting of stems and leaves, and the flatness of the cutting surface were 1.97%, 89.59%, and 91.48%, respectively. The bench test and field experiment results showed that the cutting performance of the optimized bionic cutter group is significantly better than that of the conventional knife group. The rhizome damage, net cutting of stems and leaves, and flatness of the cutting surface were 4.01%, 92.05%, and 84.05%, respectively, which meet the agronomic requirements for carrot harvesting.

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.