Ballast plays a vital role in transmitting and distributing the train wheel loads to the underlying sub-ballast and subgrade. Bearing capacity of track, train speed, riding quality and passenger comfort all depend on the stability of ballast through mechanical interlocking of particles. Ballast attrition and breakage occur progressively under heavy cyclic loading, causing track deterioration and rail misalignment affecting safety, and also demanding frequent and costly track maintenance. In the absence of realistic constitutive models, the track substructure is traditionally designed using empirical approaches.
In this book, the authors present the detailed information on the strength, deformation and degradation aspects of fresh and recycled ballast under monotonic, cyclic and impact loading using innovative geotechnical testing devices. A new stress-strain constitutive model for ballast incorporating particle breakage is presented. The mathematical formulations and numerical models are validated using experimental evidence and field trials. The effectiveness of various commercially available geosynthetics for enhancing track drainage and stability is elucidated. Revised ballast gradations are presented for modern high speed trains capturing particle breakage. The book also provides extensive description of the use of geosynthetics in track design, and provides an insight to track design capturing particle degradation, fouling and drainage.
This book should prove most beneficial for final year civil engineering students and postgraduates. It is imperative for practicing railway engineers and researchers with the task of modernizing existing track designs for heavier and faster trains.
Dedication
Preface
Foreword
About the Author
Chapter 1 : Introduction
Chapter 2 : Track Structure and Rail Load
Chapter 3 : Factors Governing Ballast Behaviour
Chapter 4 : State-of-the-art Laboratory Testing and Degradation Assessment of Ballast
Chapter 5 : Behaviour of Ballast with and without Geosynthetics and Energy Absorbing Mats
Chapter 6 : Existing Track Deformation Models
Chapter 7 : A Constitutive Model for Ballast
Chapter 8 : Track Drainage and Use of Geosynthetics
Chapter 9 : Role of Sub-Ballast, its Drainage and Filtration Characteristics
Chapter 10 : Field Instrumentation for Track Performance Verification
Chapter 11 : DEM Modelling of Ballast Densification and Breakage
Chapter 12 : FEM Modelling of Tracks and Applications to Case Studies
Chapter 13 : Non-destructive testing and Track Condition Assessment
Chapter 14 : Track Maintenance
Chapter 15 : Recommended Ballast Gradations
Chapter 16 : Bio-Engineering for Track Stabilisation
Appendices
Subject Index
