Cutter Head Research Articles

Formation process of paste HDN slurry in gravel stratum

At present, due to the complex geological conditions and long-distance drive, scheduled and unscheduled cutter head intervention maintenance during shield tunneling has become a major innovation in shield engineering in China. Therefore, paste HDN has been successfully applied to cutter head intervention under pressure, but corresponding research work on its film-forming mechanism and process is lacking. Film-forming experiments and theoretical analysis of the paste indicated that the film-forming process of the paste during gravel-stratum formation can be divided into two stages: Seepage blocking of the forming pore diameter and forming of a mud cake on the excavation surface. The seepage process was completed almost instantaneously, and the forming process of a 5–10 cm mud cake required 1–2 days. In addition, a mud diffusion model was established for investigating the mud infiltration process. The results of the aforementioned experiments were applied to the cutter head intervention of Guangzhou Metro and Lanzhou Metro, and this application ensured the efficient and safe completion of the intervention task.

Study on the optimum grouting materials and their performance in the TBM tunnel collapse reinforcement project

Considering the water inrush and collapse accident involving a tunnel boring machine (TBM) in a tunnel of the Qingdao Metro Line 1, the difficulties in grouting reinforcement in the collapse area were analyzed in order to avoid the adverse effects of grouting on the TBM equipment. The zoning governance method was chosen to solve these problems. The performance requirements of grouting materials for different areas were analyzed, after which the key properties of the materials were tested and the optimum was determined. For the water gushing area, polyurethane material was the common option, whereas for the shield area, a new high-expansion grouting material with low-strength was chosen. For the cutter head area, cement silicate grout modified by adding bentonite and quick-setting additives was tested, with the resulting material showing low strength and a quick-setting property. For the tunnel vault area, cement silicate grout and polymer-modified material were deemed suitable. After testing its viscosity change, we found that the polymer-modified material had a viscosity stabilization period. Thus, it was subsequently used at the key area. The selection of materials could reduce the consolidation risk of cutter disc and shield shell in the TBM. The research findings provide useful reference for similar projects.

Tool path active design for tooth modification of face-hobbed spiral bevel gears

An advanced design and manufacturing method called tool path active design for face-hobbed spiral bevel gears is mainly discussed in this paper. The method bases on the forming mechanism of extended epicycloids and utilizes an integrated cutter head without tilting, meanwhile, all its controlled parameters can be directly calculated according to the given meshing performances and modified conditions. Starting with the cutting principle of face-hobbing method, a tooth flank mending plan of altering tool path is developed, which detailed expressions are also given in functions. Then, the meshing performances which are used to determine the modification parameters are introduced and their formulas are also derived. Finally, the proposed method is validated by a numerical example of tooth contact analysis for a face-bobbed hypoid gear pair. As a further explanation, a numerical example of tooth contact analysis is done to validate the feasibility of the proposed method.

Clogging Potential of Earth-Pressure Balance Shield Driven Tunnels

Background: Nowadays, the construction of urban tunnels for rapid transportation in metropolises is necessary. Since these tunnels are excavated at low depths, they are often associated with different problems and hazards. Some of them can reduce the efficiency of the tunnel boring machines and sometimes will stop the project. Among these problems the clogging can cause problems at the cutter head, in the chamber, and in other sections where the material transference occurs. Objective: The main purpose of this paper is to evaluate and determine the risk of clogging in the tunneling boring machine in Line 6 of the Tehran Metro. It includes stations: Amirkabir, Shohada Square, Emam Hossein Square and Sayyadeh Shirazi. This phenomenon induces an adhesion of the shield with the soil, increasing the necessary shear forces and it can eventually leads to the project interruption. Methods: Due to the fact that the criterion for the behavior of fine soils against moisture is Atterberg Limits, therefore, Atterberg Limits and the water content were utilized. For this purpose, the new method proposed by Hollman and Thewes (2013) was used. In this study, in addition to the Atterberg limits, the amount of free water resulting from the machine and from the underground water inflow was included in the calculations. Results: It was found that the water content should be increased carefully as the soil is very sensitive to this parameter. An increase of 15% of the water content permits to reduce the risk of clogging. If the added free water amount 15%, the probability of clogging becomes high. Whereas, in case where the added free water amount reaches 20%, the risk of clogging decreases significantly. Conclusion: According to the performed assessments, it was found that critical areas for the clogging aspect are both the cutter head and the chamber. The sensitivity of the soil is very important to the free water amount. Therefore, due to the behavior of sticky and plastic of clay soils against increasing water, it is necessary to determine the percentage of allowable water used in mechanized excavation projects.

Analytical Calculation of the Tooth Surface Contact Stress of Cylindrical Gear with Variable Hyperbolic Circular-Arc-Tooth-Trace

In order to theoretically research the tooth surface maximum contact stress of a Cylindrical Gear with Variable Hyperbolic Circular-Arc-Tooth-Trace (VH-CATT), the computing formula of maximum contact stress of VH-CATT cylindrical gear is investigated according to Hertz formula in this paper. Insufficient contact fatigue strength will lead to pitting corrosion, plastic deformation of tooth surface and other damages. Therefore, the maximum contact stress of tooth surface must be carried out. The contact stress calculation formula is particularly considering the effect of normal force, total carrying length, synthetical curvature radius, and position angle. The present work establishes analytical solutions to research the effect of different parameters for the contact stress of VH-CATT cylindrical gear incorporating elastic deformation on the tooth surface, and which have shown that the different module, transmission ratio, pressure angle, tooth width, and the cutter head radius have a crucial effect on the contact stress and contact ellipse of VH-CATT cylindrical gear along the tooth width direction. Moreover, a finite element analysis is carried out to verify the correctness of the theoretical computing formula of contact stress of VH-CATT cylindrical gear. By contrast with the theoretical calculated value and the stress value of finite element analysis, its error is very small. It is indicated that the derived formula of contact fatigue strength of VH-CATT cylindrical gear has high accuracy and can accurately reflect the real contact stress value of tooth surface, which is beneficial for research on tooth break reduction, pitting, wear resistance and fatigue life improvement of the VH-CATT cylindrical gear. The study results also have a certain reference value for the design and check calculation of the VH-CATT cylindrical gear.

Effect of Spatial Variability on Disc Cutters Failure During TBM Tunneling in Hard Rock

This study examines the effect of variations of the rock property and TBM parameters on the cutter failure. A new disc cutter wear model is developed by coupling Archard’s model and TBM cutter kinematics. The rock property and the TBM parameters are modelled as anisotropic cross-correlated log-normal random fields. The proposed model with a discretized algorithm allows a quantitative evaluation of the possible cutter failure during the TBM tunneling. The failure of the cutter head system is characterized by a random failure pattern and its failure can be evaluated using a probability method. With this technique, it can be a useful tool in providing an indication for the cutters replacement. Both the cutter and its mechanical system life are determined based on their allowed working distance of the TBM at the targeted safety level. The obtained results indicate that the life of the cutters and its cutter head system decreases with the presence of rock spatial heterogeneity. Finally, the obtained attenuation factors incorporating different randomness levels is practically useful for the evaluation of the cutter life.

Ants as prey for the endemic and endangered Spanish tiger beetle Cephalota dulcinea (Coleoptera: Carabidae)

Summary Among the insects inhabiting endorheic, temporary and highly saline small lakes of central Spain during dry periods, tiger beetles (Coleoptera: Carabidae: Cicindelinae) form particularly rich assemblages including unique endemic species. Cephalota dulcinea López, De la Rosa & Baena, 2006 is an endemic, regionally protected species that occurs only in saline marshes in Castilla-La Mancha (Central Spain). Here, we report that C. dulcinea suffers potential risks associated with counter-attacks by ants (Hymenoptera: Formicidae), while using them as prey at one of these marshes. Through mark–recapture methods, we estimated the population size of C. dulcinea at the study marsh as of 1352 individuals, with a sex ratio slightly biased towards males. Evident signs of ant defensive attack by the seed-harvesting ant Messor barbarus (Forel, 1905) were detected in 14% of marked individuals, sometimes with cut ant heads still grasped with their mandibles to the beetle body parts. Ant injuries have been more frequently recorded at the end of adult C. dulcinea yearly activity, and in similar proportions in males and females, perhaps because the similar body mass of the two sexes makes the output of interactions similar. Because antennae and tarsi were particularly involved in such injuries, consequences on both chemosensory and locomotion abilities may be expected. Future studies may discover if ants are effectively a costly prey for this endangered tiger beetle.

A new short-time high-overload BLDC driving system based on electronic flywheel and time-division switching control

Most of the existing (BLDCM) brushless dc motor drive systems are designed with the traditional drive scheme for long-time operation. For short-time and heavy-duty applications, there are problems of energy consumption, large volume, heavyweight and high-cost. In this paper, a new short-time high-overload BLDCM drive system based on "electronic flywheel" and time-division switching control is proposed, which includes three core contents: a crushing chamber based on combined cutter head, an energy storage device based on an "electronic flywheel" and high overload factor BLDC using a new calculation method of capacitance and a speed control system based on time-division switching control of the speed loop and the current loop. To prove the effectiveness of the proposed scheme, a kitchen garbage processor is developed and tested. The results show that the "electronic flywheel" energy storage driving device designed in this paper is able to provide most of the energy required in the heavy-duty driving process. The designed time-division switching control scheme can well meet the control requirements for the short-time heavy load drive of the kitchen waste processor. Compared with the traditional long-time rated load drive scheme, the proposed system has the advantages of energy-saving, small volume, lightweight and low-cost.

Free vibration analysis of shield cutter head using element-free method

Free vibration of cutter head is very important to the shield tunneling machine in design, manufacture and construction. It is a free vibration problem of simply-connected circular plates with clamped supported boundary. In this paper, a element-free key to solve the problems of cutter head vibration by the Radial Basis Function is put forward. In order to save the computational time, the real-part MFS is used to carry out the mathematical analysis which is different from the previous complex value calculation. For the cutter head, the eigenequations were obtained by analytic deduction using the discrete element-free model. It is found that the spurious eigenequation relies on the equations employed, but the true eigenequation is related to the boundary conditions. By using Burton & Miller methods, the true eigenequation was extracted. A numerical case of clamped cutter head was adopted to valid the effectiveness of the present method.

Research on Application of Environmental Protection Dredging Construction Technology in Environmentally Sensitive Areas

At present, there are few cases about the implementation of environmental protection dredging project in China’s environmentally sensitive areas, and there is a serious lack of relevant project implementation experience. This paper combines the basic characteristics of environmental dredging in environmentally sensitive areas, and takes Xiangyang City’s moat dredging project as an example to analyze the difficulties in the implementation of the project, mainly including the control of construction impact, compliance with schedule, prevention of secondary pollution, and sludge. In order to solve these problems, the project mainly adopts targeted measures to minimize the impact of project construction; in order to realize the scheduled implementation of the sludge disposal mode using 6000m3 of daily dredging and dredging combined with the industrialization mode; The project successfully prevented potential secondary pollution risks during construction through the use of environmentally friendly cutter heads, integrated ultra-magnetic separation equipment and specialized sludge conditioning agents; finally, the combined use of soil improvement soil outside the mud cake and landfill for external transportation successfully solved the silt digestion problem of the project. At the same time, through the pilot test of sludge resource utilization, two major soils for mud cake production engineering and landscaping were developed Process products lay a solid foundation for the multi-channel comprehensive utilization of sludge.

A DEM-based study of the disturbance in dry sandy ground caused by EPB shield tunneling

A discrete element method simulation was used to evaluate tunneling-induced ground movement and the parameters of tunnel boring machines. The process of excavation by an Earth Pressure Balance (EPB) shield machine, including soil excavation with a cutter head, soil conditioning in the chamber, and removal of the excavated soil with a screw conveyor, is modeled using the Discrete Element Method (DEM). Deformation of the surface and subsurface of the ground in a sandy soil were studied for different tunnel burial depths and different screw conveyor rotation speeds with a constant advance rate. In addition, machine parameters, such as the cutter head torque, the normal pressure on the cutter head, the screw conveyor torque, and the chamber pressure also were analyzed. The results of the DEM model were found to be in good agreement with results reported in the literature. The method showed great potential for the analysis of both tunneling-induced ground movement and ground-machine interactions. It was determined that the distribution of the pressure of the soil in the chamber was non-linear, especially near the screw conveyor. The pressure of the soil in the chamber, the torque of the machine, and the normal pressure on the cutter head increased with the depth of excavation until a depth was reached at which stress arching occurred in the soil. Changes in the depth of excavation had little effect on the torque of the screw conveyor.

Earth pressure balance control for shield tunneling machine based on adaptive dynamic programming

In order to avoid the safety accidents caused by earth pressure imbalance during shield machine tunneling process, the earth pressure between excavation face and that in chamber must be maintained balance, but it is difficult for practical engineering. Therefore, a data-driven multi-variable optimization method based on dual heuristic programming (DHP) is proposed. First, a cost function with respect to the chamber’s earth pressure is given in light of Bellman’s principle. Then, based on back propagation neural networks (BPNN), the action network, model network and critic network are established that compose the DHP controller. The networks’ weights are updated through the gradient descent algorithm. By minimizing the cost function, the action network utilizes the critic network’s error to optimize the control variables, so that the optimal advance speed, cutter head torque, cutter head speed, total thrust and screw conveyor speed are obtained. Finally, the simulation experiments are carried out, and the results indicate that the method can effectively control the earth pressure balance in chamber and has strong anti-interference ability.

Study of Rock-Cutting Process by Disc Cutters in Mixed Ground based on Three-dimensional Particle Flow Model

With the increasing number of long tunnelling and urban subway constructions, mixed-face ground conditions are frequently encountered. Rock fragmentation mechanism under disc cutter cutting in TBM tunneling through the mixed-face ground is complex and can lead to engineering difficulties. During TBM tunneling in mixed-face ground with soft rock in upper layer and hard rock in the lower layer, reduction of the advance rate and reduced rotational speed of cutter head occur compared with homogeneous ground. As a result, the muck in the working chamber cannot be replaced timely, leading to the formation of mud cake. Additionally, the disc cutters cannot rotate normally and are worn eccentrically and severely. Finally, the cutters collide with hard rock periodically at the interface between soft and hard rock, thus being subject to a huge impact load, even overload on some cutters, resulting in chipping of the cutter ring and damage to the cutter holder. This paper presents numerical analysis of the disc cutter cutting process considering the difference of rock-cutting behaviors of disc cutters in the mixed-face ground with the aid of PFC3D code. Based on the forces imposed on the disc cutter and rock crack propagation, TBM tunneling in the mixed-face ground is investigated. The decrease of the mean rolling force of the disc cutter causes rotation hindering in the disc cutter in soft rock stratum leading to flat cutter wear. The gap of the normal force between the soft rock and hard rock generates the overturning moment of the cutter head, which causes the eccentricity and vibration of the cutter head.

Design and Simulation Analysis of Cutter in New Sewer Dredging Device

The existing sewer dredging method can not meet the needs of high-speed operation of the city. Through the research and analysis of the cutterhead of the shield tunneling machine, combined with the requirements of the sewer environment and dredging work, three-dimensional model, Ansys simulation analysis and physical experiments are adopted. In this way, a new type of spoke panel cutter head was designed. The cutter head adopts a new type of scraper. The structure is exquisite and the assembly is simple. It can effectively clear the sediment in the sewer environment and complete the initial recovery of the silt.

Numerical simulation of freezing effect and tool change of shield machine with a frozen cutterhead

A shield machine with freezing function is proposed in order to realize tool change operation at atmospheric pressure. Furthermore, the transformation project of freezing cutterhead and tool change maintenance method are put forward. Taking the shield construction of Huanxi Power Tunnel as an example, a numerical analysis of the freezing cutter head of the project was carried out. The results show that when the brine temperature is −25 °C, after 30 d of freezing, the thickness of the frozen wall can reach 0.67 m and the average temperature drops to −9.9 °C. When the brine temperature is −30 °C, after 50 d of freezing, the thickness of the frozen wall can reach 1.01 m and the average temperature drops to −12.4 °C. If the thickness of the frozen wall is 0.5 m and the average temperature is −10 °C, as the design index of the frozen wall, the brine temperature should be lower than −28 °C to meet the excavation requirements in 30 d. Analyzing the frozen wall stress under 0.5 m thickness and −10 °C average temperature condition, the tensile safety factor and compressive safety factor are both greater than 2 at the most dangerous position, which can meet the tool change requirements for shield construction.

Prediction model of wear rate of inner disc cutter of engineering in Yinsong, Jilin

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.

Optimal control of a novel cutter head driving system for tunnel boring machine

The cutter head of a tunnel boring machine may be trapped in extremely adverse geological environments, which requires a large enough driving torque to get rid of the trapped condition. In this paper, a novel driving scheme is proposed to improve the driving performance of the tunnel boring machine cutter head without increasing the installation power. First, the hydro-viscous clutch is introduced to achieve the soft start of the cutter head by the flexible effect of viscous oil film. Then, the flywheel is employed as the energy storage element to provide sufficient torque during the hydro-viscous clutch engagement, which assists the cutter head to get rid of the trapped condition. Moreover, an optimal state feedback control law based on a linear quadratic regulator is designed by compromising system impact and hydro-viscous clutch friction loss to optimize the hydro-viscous clutch engagement process and achieve favorable driving performance of the cutter head. Finally, numerical simulations are conducted to validate the effectiveness of the proposed driving technology.

HİNT MİTOLOJİSİNDE ÖLÜM VE ÖLÜM SONRASI

In Indian mythology, the issue of death was very important and many gods and goddesses were associated with death. The first ones that come to mind are Yama, Rudra-Shiva, Kālī, Durgā, Agni, Pūshan, Savitṛi, Nirṛitī, Mṛityu and Varuṇa. One of the first writings on this subject is located in Ṛigveda (X, 14-18). When the issue of death is examined in Indian mythology, the first notions that we will encounter are; death, immortality, immortality drink, after death, gods and goddesses related to death, descriptions of heaven and hell, reincarnation, ātman, karma, nirvāna, samsāra. It is also necessary to examine these issues by dividing them into two separate periods: the Vedic Period in which Saṃhitās, Brāhmaṇas, Ᾱraṇyakas and Upanishads were written; and the Epic Period in which the epics of Rāmāyaṇa, Mahābhārata and Harivaṃsha were written. As it is seen, Indian mythology and religious belief are so rich that it is very difficult to classify a subject according to its examples in other geographies / societies. On the other hand, the goddess named Chinnamastā occupies a very important place among death-related imaginations. According to this, Chinnamastā is standing or sitting on the bodies of Kāma (God of Love) and his wife Rati (this pair is sometimes replaced by Kṛishṇa and Radhā ve) and is shown in his own blood with a cut head. She also feeds two more women with her own blood. In this form of the goddess; birth, life and death are shown in a single frame. This is extremely important in terms of explaining the beginning, continuing and ending of life completely independently from concepts such as karma, samsāra and nirvāna. Although the description is shown as belonging to the later periods, it can be taken back to early times in terms of the expression it emphasizes.

Research on Water Inrush Disaster Control Technology in Double Shield TBM Excavation Process

Taking the TBM water inrush accident in An-Xue section of Qingdao Metro Line 1 as the engineering background, the research is carried out from two aspects of TBM water inrush emergency measures and grouting reinforcement treatment technology, which can ensure the strength of stratum reinforcement and water shutoff, and at the same time prevent the slurry from damaging the cutter head. For different areas, the grouting construction technology is proposed. After the reinforcement, the water stopping effect is obvious, the water inrush point has no water flow out, the hole drilling effect is good, the core removal rate is 75%∼85%, and the strength meets TBM excavation requirements.

Structural Design of Tool Head of Pipe Dredging Device

In the cold season, pipelines are prone to icing-induced clogging, causing great inconvenience to people’s production and life. To solve the icing-induced clogging of the pipeline, analysis was made on the reason why the original device fails to break the ice, to provide some guidance for conducting an innovative design of the cutter head of the device. Based on the actual needs for the cutter heads in the course of ice-breaking, a parallel inclined spherical rotary cutter head was proposed, and its 3D model created with the help of a modelling software. Through the operational and arc-traversing performance analyses of the cutter head, the relationship between the radial direction and the axial direction of the cutter head was constructed. The pressure relationship of the device was analysed. The conclusion was drawn as follows: the designed cutter head can improve the effectiveness of the device on ice-breaking and reduce the requirement for the structural intensity, providing a significant basis for the development of its physical prototype.