Cutter Head Research Articles

Working Face Stability of Box Shield Tunneling under Non-Uniform Support Pressure

This paper proposes a theoretical model for the stability analysis of a box tunnel face in non-cohesive soils considering the uneven distribution of support pressure caused by multiple cutter heads and screw conveyors. The support pressure distribution on the tunnel face is concave. Accordingly, the failure mechanism is composed of a prism and a wedge, both including three blocks. The relatively smaller support pressure acting on the middle blocks lead to the tendency of slide. Assuming that the support pressure acting on the side blocks is obtained using the active earth pressure coefficient, the support pressure acting on block II can be achieved by limit equilibrium analysis considering the interactions between the blocks. The influences of strength parameters and geometric parameters on the tunnel face stability are discussed in the parametric analysis. For comparison, numerical analysis is conducted in the commercial software OptumG3. It is found that the results given by the proposed model agree well with those from the numerical model. Therefore, the rationality of the proposed model in predicting the collapse geometry is verified.

Design Method of Anti-Damage and Anti-Crack for Main Parameters of Tunnel Boring Machine Cutter Head

Design Method of Anti-Damage and Anti-Crack for Main Parameters of Tunnel Boring Machine Cutter Head

Probabilistic Life Prediction of Tunnel Boring Machine under Wearing Conditions with Incomplete Information

This paper developed a data analysis approach to estimate the probabilistic life of an earth pressure balance (EPB) tunnel boring machine (TBM) under wearing conditions with incomplete information. The marginal reliability function of each system component of TBM is derived based on data collected from the site. The structure of the failure framework was determined based on the evaluation of influencing factors, including the wearing of the cutter head panel and screw conveyor. The joint distribution model was built by utilizing the best-fit copula function and the remaining reliable mining distance can be predicted from this model. Real data of the remaining thickness of the wearing resistance structure of the cutter head panel and screw conveyor from an earth pressure balance (EPB) TBM were captured. A realistic metro tunneling project in China was utilized to examine the applicability and effectiveness of the developed approach. The results indicate that: (1) With the selection of normal distribution and Gumbel copula as the best-fit marginal distribution function and copula function, the reliable mining distance was predicted as 4.0834 km when the reliability equaled 0.2. (2) The copula function was necessary to be considered to assess the joint distribution of the reliability function, as the predicted mining distance reduces significantly to 3.9970 km if assumed independent. (3) It enables the user to identify the weak component in the machinery and significantly improve the reliable mining distance to 4.5075 km by increasing the initial thickness of the screw conveyor by 0.5 mm. This approach can be implemented to minimize the risk of unintended TBM breakdown and improve the tunneling efficiency by reducing unnecessary cutter head intervention during the mining process.

A Critical Investigation on the Reliability, Availability, and Maintainability of EPB Machines: A Case Study

Tunnelling is a vital geotechnical engineering feature of underground transportation systems that is potentially hazardous if not properly investigated, studied, planned, and executed. A reliability, availability, and maintainability (RAM) analysis is one of the main practical techniques in machinery-based projects to recognize the failure and repair rates of machines during or after their operations. RAM analysis of mechanized tunneling can help to manage the project safety and cost, and improve the availability and performance of the machine. There are several methods to obtain and predict the RAM of a system, including the Markov chain simulation and other statistical methods; however, the result of the analysis can be affected by the selected method. This paper presents the results of a critical investigation on the RAM of the Earth pressure balance machines (EPBMs) used in developing an urban metro project in Isfahan, Iran. The five kilometer length of the first line of the Isfahan metro project was excavated using EPBMs over four years. After overhauling the EPBMs and making some minor changes, excavation of the second line started, and to date, about 1.2 km has been excavated by the refurbished machines. In the present study, a RAM analysis has been applied to electrical, mechanical, and cutter head subsystems of the EPBMs in Lines 1 and 2 of the Isfahan metro project over an 18- and 7-month period of machine operation, respectively. The results show that the estimated availability, A(t), determined by the Markov method, is closer to reality but cannot be propagated to reliability R(t) and maintainability M(t) analysis. It was also revealed that by predicting the required maintenance and proper planning, the overall availability of the EPBM was improved from 45% in Line 1 to 61% in Line 2. The outcomes of this study can be used in the future planning of urban tunneling projects to estimate machine, staff, and logistic performance with the least possible error, and appropriately arrange the factors involved in the system.

Needle selector failure detection based on piezoelectric sensor and driver co-location characteristics

Aiming at the problem of the malfunction of knitting machines caused by the unstable operation of the piezoelectric needle selector during the jacquard process, a state detection scheme for the piezoelectric needle selector that integrates the sensor and drive function co-located is proposed. The motion state of bimorph piezoelectric cantilever beam and its bi-directional piezoelectric effect in the jacquard process of piezoelectric needle selector are analyzed. Electrical and dynamic models were established for the electrical characteristics inside the bimorph piezoelectric cantilever beam and the dynamic characteristics of the cutter head and baffle of the needle selector. The signal detection circuit is designed to realize the real-time detection of the piezoelectric needle selector state by analyzing the time domain and frequency domain characteristics of the electrical signal. The results show that in the normal working state of the piezoelectric needle selector, the internal electric signal of the piezoelectric driver has two characteristic frequencies, which are between 155 and 180 and between 1630 and 1670 Hz, and the time for the piece to swing to the limit position is relatively long under abnormal working conditions.

Research on Strata Deformation Induced by EPB Tunneling in Round Gravel Stratum and Its Control Technology

Recently, many studies have been conducted on the stratum deformation induced by earth pressure balance (EPB) shield tunneling in soft soil and sand. Movement laws vary largely among different strata. However, at present, relevant research mainly focuses on soft soil and sand, whereas little attention has been paid to the movement law of round gravel stratum with higher instability. In this study, a field monitoring test was carried out on the EPB shield machine when it passes through the round gravel stratum. Based on the analysis of monitoring results under different chamber earth pressures, thrust force, the torque of the cutter, grouting pressure, and grouting volume, the relationships between shield tunneling parameters and their influence on the disturbance of the surrounding soil mass were investigated. It was found that the surface deformation shape of the monitoring section of the south and north lines conforms to the Gaussian curve. The vertical deformation of the stratum at the tunnel axis is the largest. The maximum value is observed when the cutter head reaches the monitoring section. The horizontal deformation reaches a maximum value at the stage of the shield tail pass section. The strata deformation is not only related to the strata properties but also has a strong positive correlation with the shield tunneling parameters. The chamber earth pressure is the main factor affecting the stratum deformation before the arrival of the cutter head, and the grouting volume is the main factor affecting the strata deformation during the stage of the shield tail pass section.

Prediction of Tunnelling Parameters for Underwater Shield Tunnels, Based on the GA-BPNN Method

Reasonable tunnelling parameters for underwater shield tunnels play an important role in maintaining driving efficiency and safety. In this paper, a neural network method was developed to predict tunnelling parameters. Soil properties and geometric parameters were taken as inputs for the neural network, which output the tunnelling parameters, such as advancing thrust, rotation, penetration, torque of the cutter head, and support pressure. In order to improve the stability of the neural network, a genetic algorithm (GA) with a global searching ability was used to optimize the initial weight of the neural network (GA-BPNN). The accuracy of the algorithm, based on GA-BPNN, was studied through an underwater shield tunnel project. The results showed that the integration of GA into the neural network significantly improves the prediction ability for shield tunnelling parameters, especially for adjustable parameters. Later, the developed GA-BPNN model was further utilized to predict and set the range of shield tunnelling parameters in fine sand stratum of high risk. Through a comparative analysis of tunnelling parameters, the reasons leading to ground instability have been found out, and the effectiveness of ground pre-reinforcement has been verified.

Design and Simulation Analysis of a Flexible Clamping and Conveying Device of a Green Leafy Vegetable Cutting and Bundling Integrated Machine

In order to improve the harvesting production efficiency of green leafy vegetables, this paper designs and simulates the flexible clamping and conveying device of the green leafy vegetable cutting and bundling integrated machine. Through theoretical calculation and 3D modeling, the design optimization of key components is carried out in this paper. The cutter head of the guillotine cutting and throwing device is a wheel cutter type. The throwing blades are axially symmetrically distributed on the cutter head, and the movable blades are radially distributed at equal angles and are located in the middle of the two throwing blades. The electronic control system of the wrapping device uses a pressure sensor to cooperate with the baling device to realize automatic wrapping after baling. In addition, the drive chassis of the machine is a hydrostatic drive system, which is convenient for step-less speed change and automatic control within a certain range. Through the simulation study, it can be seen that the flexible clamping and conveying device of the green leafy vegetable cutting and bundling integrated machine proposed in this paper can meet the industrialization needs of green leafy vegetables.

Big Data-Based Performance Analysis of Tunnel Boring Machine Tunneling Using Deep Learning

In tunnel boring machine (TBM) construction, the advance rate is a crucial parameter that affects the TBM driving efficiency, project schedule, and construction cost. During the operation process, various types of indicators that are monitored in real-time can help to control the advance rate of TBM. Although some studies have already been carried out in advance rate prediction, the research is almost all based on statistical methods and shallow machine learning algorithms, thereby having difficulties in dealing with a very large amount of monitored data and in modeling the time-dependent characteristics of the parameters. To solve this problem, a deep learning model is proposed based on the CNN architecture, bidirectional Long Short-Term Memory module, and the attention mechanism, which is called the CNN-Bi-LSTM-Attention model. In the first step, the monitored data is processed, and the CNN architecture is adopted to extract features from the data sequence. Then the Bi-LSTM module is adopted to obtain the time-dependent indicators. The significant features can be addressed by the added attention mechanism. In the model training process, the rotation speed of the cutter head (N), thrust (F), torque (T), penetration rate (P), and chamber earth pressure (Soil_P) are adopted to predict the advance rate. The influence of the training periods on the model performance is also discussed. The result shows that not only the data amount, but also the data periods have an influence on the prediction. The long-term data may lead to a failure of the advance rate of TBM. The model evaluation result on the test data shows that the proposed model cannot predict the monitored data in the starting stage, which denotes that the working state of TBM in the starting stage is not stable. Especially when the TBM starts to work, the prediction error is big. The proposed model is also compared with several traditional machine methods, and the result shows the excellent performance of the proposed model.

Study on Comprehensive Technology of Preventing Mud Cake of Large Diameter Slurry Shield in Composite Stratum

When large-diameter slurry shields are tunneling in a composite stratum with a high clay content, the cutter head may form a mud cake. After the mud cake is formed, it will cover the cutter and reduce the opening rate of the cutter head, thus reducing the penetration of the cutter and the driving speed. Based on a road upgrading project, this paper studies the prevention and treatment of a mud cake and forms a set of comprehensive treatment methods. For a large mud cake, through theoretical analysis, two calculation methods of the cutter head sealing coefficient are obtained, and the cutter head sealing coefficient relationship model is established. Comparing the calculated cutter head’s actual opening coefficient with the required cutter head opening coefficient can provide a judgment basis for the time of manual warehousing. For medium and small mud cakes, the numerical simulation is carried out based on the cutter head and the scouring system, the distribution characteristics of the flow field near the cutter head are analyzed, and the angle of the central scouring hole is optimized. For a small mud cake, hydrogen peroxide is selected as an additive through microscopic mechanism analysis. The effect of the hydrogen peroxide solution concentration on dissolving a mud cake is obtained through laboratory tests, and its effectiveness is verified through field tests. The research results can provide a reference for the mud cake prevention of slurry shields in similar strata.

Study on parameter analysis and damage mechanism of water jet combined with mechanical cutter head breaking concrete

For concrete buildings, the tasks of maintenance and reconstruction will rapidly increase with time, and concrete breaking is one of the important technical processes. In this study, it proposed the water jet combined with mechanical cutter head breaking concrete technology, which has advantages in efficiency, safety and quality compared with mechanical breaking concrete buildings. To reveal parameter influence rules and damage mechanism of water jet combined with mechanical cutter head breaking concrete, it investigated the experiment of water jet combined with mechanical cutter head breaking concrete under different water jet parameters by orthogonal experiment and numerical simulation. Within the range of water jet parameters studied in this experiment, the order of sensitive factors of water jet parameters is the diameter of the nozzle > the impact time > the water pressure > the jet target distance. Compared with the mechanical breaking methods, the working pressure of the mechanical cutter head can reduce by 10.00%–36.67% in water jet combined with mechanical cutter head. The optimal water jet parameter combination is the 360 MPa of water pressure, the 6 mm of jet target distance, the 80 s of impact time, and the 0.5 mm of diameter of the nozzle. Moreover, based on the smooth particle hydrodynamics (SPH) method, it established the numerical model of water jet combined with mechanical cutter head breaking concrete, verified by the crack propagation state inside the concrete based on computer tomography (CT). The results demonstrated that at the initial stage of water jet impacting concrete, compressive stress and shear stress caused craters formation; at the stage of continuous impact of water jet, cracks formation in concrete was mainly caused by tensile stress; at the initial stage of mechanical cutter head pressing concrete, concrete was mainly subjected to compressive stress and shear stress resulting in craters development; at the stage of mechanical cutter head penetrating concrete, cracks development was mainly caused by compressive stress and shear stress. The results can provide theoretical supports for the water jet combined with mechanical cutter head breaking concrete buildings.

Model Test of TBM Tunnel Crossing Large Dip Angle Fault Zone under High In Situ Stress

In order to study the effect of fracture zone on tunnel stability under high ground stress and to reveal the disaster mechanism of fracture zone surrounding rock compressor, the TBM tunnel of Fragrant Furnace Mountain Tunnel in the F12 fracture zone in Dali I section of central Yunnan was experimentally studied. The results show that the TBM cutter head has a significant effect on the surrounding rock pressure in the range of 0.43 D~0.5 D (hole diameter), with a maximum increase of 1.19-fold. As the measurement point approaches the tunnel contour, the displacement of surrounding rock increases. As TBM traverses the fracture zone interface, the displacement of surrounding rock increases at the maximum rate. The effect of TBM shear rock formation failure on the internal displacement of rock formation is 1.21 D in the front and not more than 1.5 D in the top. Sliding and loosening of the fault zone looser above the interface can easily lead to blockage of the fault zone, and the pressure of the surrounding rocks at front edge does not affect more than 1.73 H (the length of horizontal projection of the fault zone interface). Therefore, in the course of construction, the interface of fracture zone should be promoted to reduce the construction risks.

Hybrid multibody system method for the dynamic analysis of an ultra‐precision fly‐cutting machine tool

AbstractThe dynamics of an ultra‐precision machine tool determines the precision of the machined surface. This study aims to propose an effective method to model and analyze the dynamics of an ultra‐precision fly‐cutting machine tool. First, the dynamic model of the machine tool considering the deformations of the cutter head and the lathe head is developed. Then, the mechanical elements are classified into M subsystems and F subsystems according to their properties and connections. The M‐subsystem equations are formulated using the transfer matrix method for multibody systems (MSTMM), and the F‐subsystem equations are analyzed using the finite element method and the Craig–Bampton reduction method. Furthermore, all the subsystems are assembled by combining the restriction equations at connection points among the subsystems to obtain the overall transfer equation of the machine tool system. Finally, the vibration characteristics of the machine tool are evaluated numerically and are validated experimentally. The proposed modeling and analysis method preserves the advantages of the MSTMM, such as high computational efficiency, low computational load, systematic reduction of the overall transfer equation, and generalization of its computational capability to general flexible‐body elements. In addition, this study provides theoretical insights and guidance for the design of ultra‐precision machine tools.

Head removal enhances planarian electrotaxis.

ABSTRACTCertain animal species utilize electric fields for communication, hunting and spatial orientation. Freshwater planarians move toward the cathode in a static electric field (cathodic electrotaxis). This planarian behavior was first described by Raymond Pearl more than a century ago. However, planarian electrotaxis has received little attention since, and the underlying mechanisms and evolutionary significance remain unknown. To close this knowledge gap, we developed an apparatus and scoring metrics for automated quantitative and mechanistic studies of planarian behavior upon exposure to a static electric field. Using this automated setup, we characterized electrotaxis in the planarian Dugesia japonica and found that this species responds to voltage instead of current, in contrast to results from previous studies using other planarian species. Surprisingly, we found differences in electrotaxis ability between small (shorter) and large (longer) planarians. To determine the cause of these differences, we took advantage of the regenerative abilities of planarians and compared electrotaxis in head, tail and trunk fragments of various lengths. We found that tail and trunk fragments electrotaxed, whereas head fragments did not, regardless of size. Based on these data, we hypothesized that signals from the head may interfere with electrotaxis when the head area/body area reached a critical threshold. In support of this hypothesis, we found that (1) smaller intact planarians that cannot electrotax have a relatively larger head-to-body-ratio than large planarians that can electrotax, and (2) the electrotaxis behavior of cut head fragments was negatively correlated with the head-to-body ratio of the fragments. Moreover, we could restore cathodic electrotaxis in head fragments via decapitation, directly demonstrating inhibition of electrotaxis by the head.

Experimental Study on Shield Tunneling Control in Full Section Water-Rich Sand Layer of Collapsible Loess

Taking China’s first application of domestic shield tunneling in a water-rich sand layer for crossing a high-speed railway as research background, the influence of changes in the shield tunneling parameters on ground settlement is analyzed based on field tests, and a construction control method suitable for shield tunneling under a risk source in a water-rich sand layer is proposed. The test results show that the use of 10% sodium bentonite as the soil modifier for soil pressure balance shield tunneling into the water-rich sand layer has advantages, while adding 50% loess into the bentonite slurry in the gravel sand layer can greatly improve the impermeability of the soil; the settlement of soil can be effectively reduced by using the special segment with grouting holes for deep grouting and applying the adaptive transformation of the shield cutter. Based on the statistical analysis results, a reasonable range for the cutter head torque, cutter head speed, chamber pressure, bentonite injection volume, and advanced speed in the water-rich sand layer can provide a construction control basis for similar projects and provide data support for the compilation of relevant specifications.

Study on launch tunnelling parameters of a shield tunnel buried in pebble soil with existing pipelines base on discrete continuous coupling numerical method

A computational scheme coupling the particle flow code in three dimensions and fast Lagrangian analysis of continua in three dimensions techniques is implemented to evaluate the coupling effects of different discrete and continuous coupling computing modes under a gravity stress field. Based on the optimal coupling mode that can consider the computational efficiency and coupling effect, a three-dimensional discrete-continuous coupling numerical model is established to realize the dynamic excavation of a shield tunnel. The effects of launch excavation chamber filling rates and shield tunnelling control parameters on the ground surface and pipeline settlement in the initial stage are examined. With the increase in the initial chamber filling rate, the convergence rate of the surface and pipeline settlements increases, and the total settlement significantly decreases. Moreover, although the disturbance range of shield tunnelling to the strata decreases, the thrust and torque of the shield machine increase. As the cutter head speed varies, the settlement of the surface and pipeline and thrust of the shield machine do not significantly change. However, the torque of the shield machine significantly increases with the increase in the cutter head rotation. The tunnelling speed, ground disturbance range, and shield torque are weakly correlated; however, as the tunnelling speed increases, the thrust of the shield machine increases and the stratum displacement tends to be uplifted. With the increase in the screw conveyor rotation speed, the settlement of the surface and pipeline increases, and the thrust of the shield machine decreases. The torque of the shield machine, range of ground disturbance, and screw conveyor rotation speed are only weakly correlated. The thrust and torque calculated using the coupling numerical model are close to the measured values, which demonstrates the reliability of the coupling numerical model.

Working Mechanism and Parameter Optimization of a Crushing and Impurity Removal Device for Liquid Manure

Aiming to solve the problems of easy clogging and high energy consumption of multi-way fertilization devices for liquid manure, a crushing and impurity removal device for liquid manure was designed by combining the physical characteristics of liquid manure and impurities, and building the corresponding test bench. The proposed device could crush flexible impurities such as straw and filoplume and intercept hard impurities with high density. The main structural parameters of the device were determined according to the survey analysis and the theoretical design. The influences of cutter head shape, cutter edge angle, cutter shaft speed, and cutting clearance on the disqualification rate and energy consumption of straw crushing were obtained by a single-factor experiment. Furthermore, the Box–Behnken central composite design method of the response surface was employed to investigate the effects of the cutter shaft speed, cutting clearance, and cutter edge angle on the disqualification rate and energy consumption of straw crushing. In addition, the working parameters of the device were optimized by employing the response surface method. On this basis, the mathematical relationship model among the disqualification rate, energy consumption, and all influencing factors was established. The results show that the optimal combination of working parameters includes a cutter shaft speed of 312 r/min, a cutting clearance of 1.4 mm, and a cutter edge angle of 45°. From the prediction model, the predicted failure rate was 4.15%, and the predicted energy consumption was 47.53 J. The verification experiment was then performed under the optimal combination of working parameters. The obtained disqualification rate was 4.08% and the energy consumption was 47.56 J, which met the design and work requirements.

Design and Optimization of Working Parts of Vertical Spiral Ditching Machine Based on Milling Force and BP Neural Network Model

The existing vertical spiral ditching machine mainly works in flat orchards, and the structural design of ditching components does not match the design of power transmission system, which leads to high ditching power consumption and poor ditching stability. According to the needs of deep application of organic fertilizer in orchards, a spiral cutter was designed to alleviate the common problems of high power consumption and poor stability of ditching machine and reduce the power consumption of ditch cutting. Therefore, the motion parameters and structural parameters of the spiral cutter are optimized. Using ANSYS preprocessor, the finite element model of cutting soil with spiral cutter is established, and the implicit functional relationship between milling force factor and instantaneous cutting thickness is established by using BPNN (BP neural network). On the basis of the established prediction model of milling force, orthogonal experiments were carried out to obtain the best combination of cutter head rotation speed, slotting depth, and advancing speed with minimum power consumption: 20.16 rad/s, 0.3 m, and 0.12 m/s. By investigating the influence of various working parameters on the power consumption of ditching machine, the analysis basis is provided for selecting reasonable working parameters of ditching machine.

Geometry design, meshing analysis and error influences of face-hobbed cycloidal bevel gears with double circular-arc profile for a nutation drive

As the core components of nutation drive, the internal meshing pair of bevel gear must be delicately designed to achieve desirable operational performances for the transmission device. For this purpose, this paper designs a face-hobbed internal meshing pair of cycloidal bevel gears with double circular-arc profile (DCAP). First, a cutter head with DCAP cutting edges is designed to generate the tooth surface of internal gear pair. Then, the tooth geometry of the external and internal bevel gears are derived according to the meshing theory. Finally, a finite element model is developed to simulate the meshing characteristics of the gear pair. The simulation results reveal that the proposed face-hobbed cycloidal bevel gear pair with DCAP has higher contact/bending strength, better load sharing and smaller transmission error compared with the logarithmic spiral bevel gear pair with DCAP. The effects of four typical manufacturing errors on meshing characteristics of the proposed bevel gear pair are investigated to provide fundamental references for the tolerance design of cycloidal bevel gears.

Design and fabrication of multi cutting hack saw machine

The growth of Indian manufacturing sector depends largely on its productivity & quality. Productivity depends up on many factors one of the major factors being manufacturing efficiency with which the operation/activities are carried out in the organization. productivity can be improved by reducing the total machining time, combinating the operations etc. In the case of mass production where variety of jobs is less and quantity to be produced is huge, it is very essential to produce the job faster rate. This is not possible if we carry out the production by using general purpose machines. The best way to improve the production rate (productivity) along with quality is by the use of special purpose machine. Usefulness and performance of the existing radial cutter machine will be increased by designing and manufacturing of multi cutter head attachment. This paper details with design and development of multi cutter head for cycle time optimization of the component.