scholarly journals Discrete-Element Analysis of the Excavation Performance of an EPB Shield TBM under Different Operating Conditions

2021 ◽  
Vol 11 (11) ◽  
pp. 5119
Author(s):  
Byungkwan Park ◽  
Chulho Lee ◽  
Soon-Wook Choi ◽  
Tae-Ho Kang ◽  
Soo-Ho Chang
Keyword(s):  
Rotation Speed ◽  
Compressive Force ◽  
Discrete Element ◽  
Operating Conditions ◽  
Screw Conveyor ◽  
Pressure Balance ◽  
Element Analysis ◽  
Disc Cutters ◽  
Excavation Performance ◽  
Epb Shield

This study used a discrete-element analysis to predict the excavation performance of a 7.73 m-diameter earth pressure balance (EPB) shield tunnel boring machine (TBM). The simulation mainly predicted several excavation performance indicators for the machine, under different operating conditions. The number of particles in the chamber and the chamber pressure varied, as the operating conditions changed during the simulated TBM excavation. The results showed that the compressive force, torque, and driving power acting on the TBM cutterhead varied with its rotation speed, increasing as the cutterhead rotation speed rose. The overall compressive force acting on all of the disc cutters and their impact wear increased linearly as the cutterhead rotation accelerated. The position of a disc cutter on the cutterhead had a particularly strong influence, with higher compressive forces experienced by the cutters closer to the center. In contrast, the gauge disc cutters at the transition zone of the cutterhead showed more wear than those elsewhere. The muck discharge rate and the driving power of the screw conveyor rose with increasing screw conveyor and cutterhead rotation speeds. Finally, this study suggests optimal operation conditions, based on pressure balance and operational management of the TBM.

scholarly journals Numerical Simulation of EPB Shield Tunnelling with TBM Operational Condition Control Using Coupled DEM–FDM

2021 ◽  
Vol 11 (6) ◽  
pp. 2551
Author(s):  
Hyobum Lee ◽  
Hangseok Choi ◽  
Soon-Wook Choi ◽  
Soo-Ho Chang ◽  
Tae-Ho Kang ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Large Scale ◽  
Tunnel Boring Machine ◽  
Chamber Pressure ◽  
Screw Conveyor ◽  
Shield Tunnel ◽  
Pressure Balance ◽  
Operational Conditions ◽  
Shield Tunnelling ◽  
Epb Shield

This study demonstrates a three-dimensional numerical simulation of earth pressure balance (EPB) shield tunnelling using a coupled discrete element method (DEM) and a finite difference method (FDM). The analysis adopted the actual size of a spoke-type EPB shield tunnel boring machine (TBM) consisting of a cutter head with cutting tools, working chamber, screw conveyor, and shield. For the coupled model to reproduce the in situ ground condition, the ground formation was generated partially using the DEM (for the limited domain influenced by excavation), with the rest of the domain being composed of FDM grids. In the DEM domain, contact parameters of particles were calibrated via a series of large-scale triaxial test analyses. The model simulated tunnelling as the TBM operational conditions were controlled. The penetration rate and the rotational speed of the screw conveyor were automatically adjusted as the TBM advanced to prevent the generation of excessive or insufficient torque, thrust force, or chamber pressure. Accordingly, these parameters were maintained consistently around their set operational ranges during excavation. The simulation results show that the proposed numerical model based on DEM–FDM coupling could reasonably simulate EPB driving while considering the TBM operational conditions.

scholarly journals Discrete element modelling of screw conveyor-mixers

2015 ◽  
Vol 69 (1) ◽  
pp. 95-101 ◽  
Author(s):  
Aca Jovanovic ◽  
Lato Pezo ◽  
Sanja Stanojlovic ◽  
Nenad Kosanic ◽  
Ljubinko Levic
Keyword(s):  
Discrete Element ◽  
Operating Conditions ◽  
Discrete Element Modelling ◽  
Screw Conveyor ◽  
Bulk Materials ◽  
Particle Path ◽  
Element Modelling ◽  
Straight Line ◽  
Empirical Performance ◽  
Fill Level

Screw conveyors are used extensively in food, plastics, mineral processing, agriculture and processing industries for elevating and/or transporting bulk materials over short to medium distances. Despite their apparent simplicity in design, the transportation action is very complex for design and constructors have tended to rely heavily on empirical performance data. Screw conveyor performance is affected by its operating conditions (such as: the rotational speed of the screw, the inclination of the screw conveyor, and its volumetric fill level). In this paper, horizontal, several single-pitch screw conveyors with some geometry variations in screw blade was investigated for mixing action during transport, using Discrete Element Method (DEM). The influence of geometry modifications on the performance of screw conveyor was examined, different screw designs were compared, and the effects of geometrical variations on mixing performances during transport were explored. During the transport, the particle tumbles down from the top of the helix to the next free surface and that segment of the path was used for auxiliary mixing action. The particle path is dramatically increased with the addition of three complementary helices oriented in the same direction as screw blades (1458.2 mm compared to 397.6 mm in case of single flight screw conveyor) Transport route enlarges to 1764.4 mm, when installing helices oriented in the opposite direction from screw blades. By addition of straight line blade to single flight screw conveyor, the longest particle path is being reached: 2061.6 mm

scholarly journals Stress Analysis and Design Validation of Chute using DEM Software

2020 ◽  
pp. 68-72
Author(s):  
Sadige Akhil Prasad
Keyword(s):  
Bulk Material ◽  
Low Cost ◽  
Research Work ◽  
Discrete Element ◽  
Conveyor Belt ◽  
Screw Conveyor ◽  
Element Analysis ◽  
Analysis And Design ◽  
Individual Record ◽  
The Individual

The discrete element method (DEM) is attracting growing attention for the simulation of industrial Bulk solid flow; much of the earlier DEM modelling has considered two-dimensional (2D) flows and used circular particles. The DEM maintains the individual record (velocities, forces, etc.) of particles in flow and stress on equipment. This will enable the designer to know the problems in the design. Transfer chute is used in many industries to facilitate bulk material from one conveyor belt to another or for guide flow from a delivery point (feeder, screw conveyor) into a process or equipment (centrifuge, screener, etc.). Although the transfer chute itself may appear to be a low-cost part of the equipment train, it can easily become costly in maintenance due to plugging, abrasive wear, segregation, etc. The objective of this study is to analyse the stress distribution in a transfer chute when it is in use and to validate design is free from plugging. The modelling was done using the CREO PARAMETRIC software as per Industry standards. The Chute was modelled and simulated using the ROCKY DEM software. In the present research work, a discrete element analysis procedure is used in the ROCKY DEM simulation to predict the level of stress and velocities of particles.

scholarly journals Risk Mitigation and Construction Control for Effective Underwater Recovery of an EPB Shield: A Case Study of the First Metro Tunnel in Tel Aviv

2020 ◽  
Vol 2020 ◽  
pp. 1-15
Author(s):  
Weiqiang Qi ◽  
Zhiyong Yang ◽  
Yusheng Jiang ◽  
Zhiyong Liu ◽  
Yinxin Guo ◽  
...  
Keyword(s):  
Risk Mitigation ◽  
Fine Sand ◽  
Diaphragm Wall ◽  
Screw Conveyor ◽  
Shield Tunnel ◽  
Pressure Balance ◽  
Shield Tunneling ◽  
Tel Aviv ◽  
Metro Tunnel ◽  
Epb Shield

Shield recovery in water-rich sand strata is a challenging issue in the field of shield tunnel engineering, especially when the end of the shaft cannot be reinforced by jet grouting or freezing or when the shield cannot be supported with a steel sleeve. Therefore, it is important to develop an effective recovery approach and adopt suitable techniques to control the risks. In this study, a new method based on filling the receiving shaft with water is proposed for the underwater recovery of an earth pressure balance (EPB) shield with zero end reinforcement from a metro tunnel in Tel Aviv, Israel. Several additional techniques are used to ensure safe recovery of the shield, including the design of a concrete cradle, drilling of pressure relief holes, control of excavation parameters, screw conveyor sealing, portal sealing, tail sealing, and grouting. Furthermore, according to the actual situation on site, filling the shaft with water to 1 m above the water level in the strata can prevent the fine sand from percolating into the shaft. Before the cutterhead approaches the underground diaphragm wall, the driving attitude should be strictly controlled, and the edge hob should be inspected for wear. The necessary thrust of shield tunneling in the underground diaphragm wall and shaft is calculated theoretically. In order to ensure the deformation control of the underground diaphragm wall and the smooth tunneling of the shield, the thrust of the shield excavating the underground diaphragm wall will not be larger than 12 000 kN, and the penetration degree will be limited to 3 mm/r. Qualitative observations and measurements of surface subsidence in the metro tunnel indicate that these risk mitigation techniques are effective and suitable for the underwater recovery of EPB shields in water-rich sand strata.

Screw Conveyor Design and Discrete Element Simulation Analysis of the Rice Mill

2014 ◽  
Vol 644-650 ◽  
pp. 689-692
Author(s):  
Yan Hua Shi ◽  
Guo Quan Zhang ◽  
Ning Zhang ◽  
Zhi Ping Huang
Keyword(s):  
Structural Design ◽  
Simulation Analysis ◽  
Discrete Element ◽  
Screw Conveyor ◽  
Discrete Element Simulation ◽  
Element Analysis ◽  
Element Simulation ◽  
Overall Stability ◽  
Important Field ◽  
Important Basis

During the rice mill structural design process, static analysis is an extremely important field, not only decide to what the structure size is, but also for the subsequent fatigue analysis, providing the basis for the overall stability analysis. In this paper, vertical screw conveyor vertical rice mill, rice discrete element analysis simulation under different speed, the internal movement of materials to simulate the process for improving the productivity of the vertical screw conveyor has a certain significance. Providing an important basis for further design optimization of the rice mill structure.

scholarly journals Discrete Element Analysis of High-Pressure Zones of Sea Ice on Vertical Structures

2021 ◽  
Vol 9 (3) ◽  
pp. 348
Author(s):  
Xue Long ◽  
Lu Liu ◽  
Shewen Liu ◽  
Shunying Ji
Keyword(s):  
High Pressure ◽  
Sea Ice ◽  
Failure Mode ◽  
Contact Area ◽  
Loading Rate ◽  
Discrete Element ◽  
Offshore Platforms ◽  
Marine Structures ◽  
Element Analysis ◽  
Ice Pressure

In cold regions, ice pressure poses a serious threat to the safe operation of ship hulls and fixed offshore platforms. In this study, a discrete element method (DEM) with bonded particles was adapted to simulate the generation and distribution of local ice pressures during the interaction between level ice and vertical structures. The strength and failure mode of simulated sea ice under uniaxial compression were consistent with the experimental results, which verifies the accuracy of the discrete element parameters. The crushing process of sea ice acting on the vertical structure simulated by the DEM was compared with the field test. The distribution of ice pressure on the contact surface was calculated, and it was found that the local ice pressure was much greater than the global ice pressure. The high-pressure zones in sea ice are mainly caused by its simultaneous destruction, and these zones are primarily distributed near the midline of the contact area of sea ice and the structure. The contact area and loading rate are the two main factors affecting the high-pressure zones. The maximum local and global ice pressures decrease with an increase in the contact area. The influence of the loading rate on the local ice pressure is caused by the change in the sea ice failure mode. When the loading rate is low, ductile failure of sea ice occurs, and the ice pressure increases with the increase in the loading rate. When the loading rate is high, brittle failure of sea ice occurs, and the ice pressure decreases with an increase in the loading rate. This DEM study of sea ice can reasonably predict the distribution of high-pressure zones on marine structures and provide a reference for the anti-ice performance design of marine structures.

scholarly journals Application Ranges of EPB Shield TBM in Weathered Granite Soil: A Laboratory Scale Study

2021 ◽  
Vol 11 (7) ◽  
pp. 2995
Author(s):  
Tae-Hwan Kim ◽  
In-Mo Lee ◽  
Hee-Young Chung ◽  
Jeong-Jun Park ◽  
Young-Moo Ryu
Keyword(s):  
Water Content ◽  
Upper And Lower Bounds ◽  
Shield Tunnel ◽  
Particle Crushing ◽  
Pressure Balance ◽  
Soil Conditioning ◽  
Weathered Granite ◽  
Weathered Granite Soil ◽  
Granite Soil ◽  
Epb Shield

Soil conditioning is a key factor in increasing tunnel face stability and extraction efficiency of excavated soil when excavating tunnels using an earth pressure balance (EPB) shield tunnel boring machine (TBM). Weathered granite soil, which is abundant in the Korean Peninsula (also in Japan, Hong Kong, and Singapore), has different characteristics than sand and clay; it also has particle-crushing characteristics. Conditioning agents were mixed with weathered granite soils of different individual particle-size gradations, and three characteristics (workability, permeability, and compressibility) were evaluated to find an optimal conditioning method. The lower and upper bounds of the water content that are needed for a well-functioning EPB shield TBM were also proposed. Through a trial-and-error experimental analysis, it was confirmed that soil conditioning using foam only was possible when the water content was controlled within the allowable range, that is, between the upper and lower bounds; when water content exceeded the upper bound, soil conditioning with solidification agents was needed along with foam. By taking advantage of the particle-crushing characteristics of the weathered granite soil, it was feasible to adopt the EPB shield TBM even when the soil was extremely coarse and cohesionless by conditioning with polymer slurries along with foam. Finally, the application ranges of EPB shield TBM in weathered granite soil were proposed; the newly proposed ranges are wider and expanded to coarser zones compared with those proposed so far.

scholarly journals Discrete element analysis of the punching behaviour of a secured drapery system: from laboratory characterization to idealized in situ conditions

2021 ◽  
Author(s):  
Antonio Pol ◽  
Fabio Gabrieli ◽  
Lorenzo Brezzi
Keyword(s):  
Mechanical Response ◽  
Steel Wire ◽  
Discrete Element ◽  
Wire Mesh ◽  
Steel Plates ◽  
Loading Conditions ◽  
Element Analysis ◽  
In Situ Conditions ◽  
Wire Meshes

AbstractIn this work, the mechanical response of a steel wire mesh panel against a punching load is studied starting from laboratory test conditions and extending the results to field applications. Wire meshes anchored with bolts and steel plates are extensively used in rockfall protection and slope stabilization. Their performances are evaluated through laboratory tests, but the mechanical constraints, the geometry and the loading conditions may strongly differ from the in situ conditions leading to incorrect estimations of the strength of the mesh. In this work, the discrete element method is used to simulate a wire mesh. After validation of the numerical mesh model against experimental data, the punching behaviour of an anchored mesh panel is investigated in order to obtain a more realistic characterization of the mesh mechanical response in field conditions. The dimension of the punching element, its position, the anchor plate size and the anchor spacing are varied, providing analytical relationships able to predict the panel response in different loading conditions. Furthermore, the mesh panel aspect ratio is analysed showing the existence of an optimal value. The results of this study can provide useful information to practitioners for designing secured drapery systems, as well as for the assessment of their safety conditions.

Discrete element analysis of stone cantilever stairs

Meccanica ◽  
2017 ◽  
Vol 53 (7) ◽  
pp. 1571-1589 ◽  
Author(s):  
Balázs Rigó ◽  
Katalin Bagi
Keyword(s):  
Discrete Element ◽  
Element Analysis
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