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Geomechanics and Engineering
  Volume 10, Number 4, April 2016, pages 455-470

Importance of particle shape on stress-strain behaviour of crushed stone-sand mixtures
Janaka J. Kumara and Kimitoshi Hayano

    In ballasted railway tracks, ballast fouling due to finer material intrusion has been identified as a challenging issue in track maintenance works. In this research, deformation characteristics of crushed stone-sand mixtures, simulating fresh and fouled ballasts were studied from laboratory and a 3-D discrete element method (DEM) triaxial compression tests. The DEM simulation was performed using a recently developed DEM approach, named, Yet Another Dynamic Engine (YADE). First, void ratio characteristics of crushed stone-sand mixtures were studied. Then, triaxial compression tests were conducted on specimens with 80 and 50% of relative densities simulating dense and loose states respectively. Initial DEM simulations were conducted using sphere particles. As stress-strain behaviour of crushed stone-sand mixtures evaluated by sphere particles were different from laboratory specimens, in next DEM simulations, the particles were modeled by a clump particle. The clump shape was selected using shape indexes of the actual particles evaluated by an image analysis. It was observed that the packing behaviour of laboratory crushed stone-sand mixtures were matched well with the DEM simulation with clump particles. The results also showed that the strength properties of crushed stone deteriorate when they are mixed by 30% or more of sand, specially under dense state. The results also showed that clump particles give closer stress-strain behaviour to laboratory specimens than sphere particles.
Key Words
    discrete element method; fouled ballast; railway track; stress-strain behaviour; triaxial test
(1) Janaka J. Kumara:
Department of Civil Engineering, Tokyo University of Science, 2641, Yamazaki, Noda, Chiba 278-8510, Japan;
(2) Kimitoshi Hayano:
Department of Urban Innovation, Yokohama National University, 79-5, Tokiwadai, Hodogaya-ku, Yokohama, Kanagawa 240-8501, Japan.

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