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Geomechanics and Engineering
  Volume 35, Number 5, Dcember10 2023 , pages 475-486

Effects of normal stress, shearing rate, PSD and sample size on behavior of ballast in direct shear tests using DEM simulation
Md Hussain and Syed Khaja Karimullah Hussaini

    Ballast particles have an irregular shape and are discrete in nature. Due to the discrete nature of ballast, it exhibits complex mechanical behaviour under loading conditions. The discrete element method (DEM) can model the behaviour of discrete particles under a multitude of loading conditions. DEM is used in this paper to simulate a series of three-dimensional direct shear tests in order to investigate the shear behaviour of railway ballast and its interaction at the microscopic level. Particle flow code in three dimension (PFC3D) models the irregular shape of ballast particles as clump particles. To investigate the influence of particle size distribution (PSD), real PSD of Indian railway ballast specification IRS:GE:1:2004, China high-speed rail (HSR) and French rail specifications are generated. PFC3D built-in linear contact model is used to simulate the interaction of ballast particles under various normal stresses, shearing rate and shear box sizes. The results indicate how shear resistance and volumetric changes in ballast assembly are affected by normal stress, shearing rate, PSD and shear box size. In addition to macroscopic behaviour, DEM represents the microscopic behaviour of ballast particles in the form of particle displacement at different stages of the shearing process.
Key Words
    dilation angle; direct shear test; normal stress; particle displacement; particle size distribution; shear box
Md Hussain: Department of Civil and Environmental Engineering, Indian Institute of Technology Patna, Bihar-801106, India;
Department of Civil Engineering, Saharsa College of Engineering, Saharsa, Bihar-852201, India
Syed Khaja Karimullah Hussaini: Department of Civil and Environmental Engineering, Indian Institute of Technology Patna, Bihar-801106, India

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