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Author: Bo Wang Publisher: BoD – Books on Demand ISBN: 3734746663 Category : Technology & Engineering Languages : en Pages : 146
Book Description
As an essential component of the ballast track, the ballast layer provides functionali-ties such as drainage, load distribution, as well as strength and stability for the rail-way track. The mechanical behaviors of ballast track such as its permanent settle-ment, breakage, force propagation and void ratio are in a great extent influenced by the form distribution of ballast stones. Its reasonable design will greatly improve the mechanical behaviors, and thus prolong the maintenance cycle of ballast track, or reduce the number of ballast stones needed for construction. This dissertation focuses on proposing optimized ballast stones in the ballast aggre-gate in regard to their geometrical forms. As the first step, a ballast random form gen-erator, which is designed to generate ballast form databases with different form dis-tributions, is proposed. 15 databases are created for further usage. Afterwards, Dis-crete Element Method (DEM) based simulations are performed to investigate the mechanical behaviors of ballast aggregates. The simulation model is established based on a box test, whose result is presented firstly. Establishment and calibration process of the model are expatiated afterwards. A parameter study regarding to cru-cial modeling parameters is also performed. Using the validated parameters and the 15 generated form databases, DEM simulation models with different form distribu-tions of ballast stones in the ballast aggregate are proposed. Simulative methods to quantify the mechanical behaviors are elaborated. Based on the obtained results, the interrelation between mechanical behaviors of ballast aggregate and the form effect on mechanical behavior of the ballast aggregates are studied. The optimized ballast aggregate is proposed based on the findings stated above. The proposed optimized ballast aggregate is expected to be a reference for construc-tion of ballast track in real world. The modeling technic and the calibrated modeling parameters can be used for optimization for different railway operating programs.
Author: Bo Wang Publisher: BoD – Books on Demand ISBN: 3734746663 Category : Technology & Engineering Languages : en Pages : 146
Book Description
As an essential component of the ballast track, the ballast layer provides functionali-ties such as drainage, load distribution, as well as strength and stability for the rail-way track. The mechanical behaviors of ballast track such as its permanent settle-ment, breakage, force propagation and void ratio are in a great extent influenced by the form distribution of ballast stones. Its reasonable design will greatly improve the mechanical behaviors, and thus prolong the maintenance cycle of ballast track, or reduce the number of ballast stones needed for construction. This dissertation focuses on proposing optimized ballast stones in the ballast aggre-gate in regard to their geometrical forms. As the first step, a ballast random form gen-erator, which is designed to generate ballast form databases with different form dis-tributions, is proposed. 15 databases are created for further usage. Afterwards, Dis-crete Element Method (DEM) based simulations are performed to investigate the mechanical behaviors of ballast aggregates. The simulation model is established based on a box test, whose result is presented firstly. Establishment and calibration process of the model are expatiated afterwards. A parameter study regarding to cru-cial modeling parameters is also performed. Using the validated parameters and the 15 generated form databases, DEM simulation models with different form distribu-tions of ballast stones in the ballast aggregate are proposed. Simulative methods to quantify the mechanical behaviors are elaborated. Based on the obtained results, the interrelation between mechanical behaviors of ballast aggregate and the form effect on mechanical behavior of the ballast aggregates are studied. The optimized ballast aggregate is proposed based on the findings stated above. The proposed optimized ballast aggregate is expected to be a reference for construc-tion of ballast track in real world. The modeling technic and the calibrated modeling parameters can be used for optimization for different railway operating programs.
Author: Hai Huang Publisher: ISBN: Category : Languages : en Pages :
Book Description
Ballast is an essential layer of the railroad track structure, and provides primarily drainage and load distribution. In general, ballast aggregates are considered as uniformly graded, angular shaped with crushed faces. However, various ballast aggregate gradations and particle shapes are in use yet their effects on ballast performances remain unknown. In previous designs and modeling practices, railroad ballast has usually been treated as a homogeneous and continuous layer. This approach is not suitable to model the deformation behavior of the particulate nature railroad ballast aggregates under dynamic moving loads. Further, continuum solutions do not take into account realistically the morphological characteristics of aggregates such as particle size distribution and shapes. A combined digital image and Discrete Element Modeling (DEM) methodology has been developed in this PhD thesis to study effects of aggregate particle size and morphological characteristics on ballast performances. The approach has been calibrated using actual ballast aggregates through laboratory shear box texts and validated by further laboratory as well as field experiments. Using the DEM ballast model, individual effects of aggregate particle size distributions and shape properties on railroad ballast strength, lateral stability, and settlement potential were studied. From the DEM simulation results, it was found that aggregate particle size distribution and shape have significant impact on ballast performances. Ballast with broader size distribution was shown to yield less settlement potential than ballast with more uniformly graded aggregates. Also, ballast with angular aggregate particles were found from the DEM simulations to have higher strength as well as better lateral stability than ballast with rounded aggregate particles due to better stone on stone contact and aggregate interlock. In summary, the developed DEM ballast model has been proven in this PhD research to be a promising tool for studying railroad ballast load and deformation characteristics and could lead to the ultimate goal of designing better 0́−engineered ballast.0́+
Author: Bernard Cambou Publisher: Springer ISBN: 370912526X Category : Technology & Engineering Languages : en Pages : 403
Book Description
This book presents a complete and comprehensive analysis of the behaviour of granular materials including the description of experimental results, the different ways to define the global behaviour from local phenomena at the particle scale, the various modellings which can be used for a D.E.M. analysis to solve practical problems and finally the analysis of strain localisation. The concepts developed in this book are applicable to many kinds of granular materials considered in civil, mechanical or chemical engineering.
Author: Ernest Theodore Selig Publisher: Thomas Telford ISBN: 9780727720139 Category : Business & Economics Languages : en Pages : 468
Book Description
This comprehensive study provides practical advice and guidance on the important topics of rail transport and ground engineering, the use of which will result in optimum quality with the minimum maintenance effort and the most economical use of resources. The authors have synthesized all of their international knowledge and experience in this field, and produced, for the first time, a definitive guide for the design, construction, maintenance and renewal of railway track as they relate to geotechnology.
Author: Shunying Ji Publisher: Springer ISBN: 9789811533037 Category : Technology & Engineering Languages : en Pages : 387
Book Description
This book systematically introduces readers to computational granular mechanics and its relative engineering applications. Part I describes the fundamentals, such as the generation of irregular particle shapes, contact models, macro-micro theory, DEM-FEM coupling, and solid-fluid coupling of granular materials. It also discusses the theory behind various numerical methods developed in recent years. Further, it provides the GPU-based parallel algorithm to guide the programming of DEM and examines commercial and open-source codes and software for the analysis of granular materials. Part II focuses on engineering applications, including the latest advances in sea-ice engineering, railway ballast dynamics, and lunar landers. It also presents a rational method of parameter calibration and thorough analyses of DEM simulations, which illustrate the capabilities of DEM. The computational mechanics method for granular materials can be applied widely in various engineering fields, such as rock and soil mechanics, ocean engineering and chemical process engineering.
Author: Catherine O'Sullivan Publisher: CRC Press ISBN: 1482266490 Category : Technology & Engineering Languages : en Pages : 574
Book Description
The first single work on DEM providing the information to get started with this powerful numerical modelling approach. Provides the basic details of the numerical method and the approaches used to interpret the results of DEM simulations. It will be of use to professionals, researchers and higher level students, with a theoretical overview of DEM as well as practical guidance.Selected Contents: 1.Introduction 2.Use of DEM in Geomechanics 3.Calculation of Contact Forces 4.Particle Motion 5.Particle Types 6.Boundary Conditions 7.Initial Geometry and Specimen Generation 8.Time Integration and Discrete Element Modelling 9.DEM Interpretation: A Continuum Perspective 10.Postprocessing: Graphical Interpretation of DEM Simulations 11.Basic Statisti
Author: Kenichi Soga Publisher: CRC Press ISBN: 1315737329 Category : Technology & Engineering Languages : en Pages : 1668
Book Description
Geomechanics from Micro to Macro contains 268 papers presented at the International Symposium on Geomechanics from Micro and Macro (IS-Cambridge, UK, 1-3 September 2014). The symposium created a forum for the dissemination of new advances in the micro-macro relations of geomaterial behaviour and its modelling. The papers on experimental investigati
Author: Xikui Li Publisher: Springer ISBN: 9811019266 Category : Science Languages : en Pages : 1414
Book Description
This book presents the latest advances in Discrete Element Methods (DEM) and technology. It is the proceeding of 7th International Conference on DEM which was held at Dalian University of Technology on August 1 - 4, 2016. The subject of this book are the DEM and related computational techniques such as DDA, FEM/DEM, molecular dynamics, SPH, Meshless methods, etc., which are the main computational methods for modeling discontinua. In comparison to continua which have been already studied for a long time, the research of discontinua is relatively new, but increases dramatically in recent years and has already become an important field. This book will benefit researchers and scientists from the academic fields of physics, engineering and applied mathematics, as well as from industry and national laboratories who are interested in the DEM.
Author: Bo Wang
Author: Bo Wang
Author: Hai Huang
Author: Bernard Cambou
Author: Ernest Theodore Selig
Author: 
Author: Shunying Ji
Author: Catherine O'Sullivan
Author: Kenichi Soga
Author: 
Author: Xikui Li