Discrete element modelling of ballasted track deformation behaviour

Discrete element modelling of lateral displacement of a granular assembly under cyclic loading

“…It gives a vertical settlement of 8.9 mm after 1000 cycles in comparison to 10.0 mm for the modified experimental results [11]. Compared with the experimental results, the vertical settlement always increases gradually the lack of variation in particle shape in the DEM simulation, which is similar to an earlier numerical study by Tutumluer et al [26]. It is noted that the behaviour of ballast under repeated loading (up to 1000 cycles) and dynamic loading (up to 10 6 cycles at 15 Hz frequency) is non-linear, and sudden settlement is shown at initial stages due to the dynamic compaction of aggregates (stabilisation phase).…”

Characterization of geogrid reinforced ballast behavior at different levels of degradation through triaxial shear strength test and discrete element modeling

“…This in turn results in higher peak deviator stress values achieved during shear strength testing. Note that a similar trend was reported by Tutumluer et al (2013) when ballast with lower angularity yielded less settlement in the field due to better packing.…”

“…Several recent research studies have reported successful applications of the Discrete Element Method (DEM) for simulating railroad ballast behavior (Indraratna et al, 2010;Lu and McDowell, 2010;Chen et al, 2012;Tutumluer et al, 2013). The DEM simulation approach developed at the University of Illinois (Ghaboussi and Barbosa, 1990;Zhao et al, 2006;Nezami et al, 2007) adopts real polyhedral particles and has the capability to create actual ballast aggregate particle shapes as 3D polyhedron elements having the same particle size distributions and imaging-quantified average shapes and angularities.…”

Behavior of Geogrid Reinforced Ballast at Different Levels of Degradation

“…Accordingly, the degraded ballast particles created an improved packing and a wellgraded and higher density specimen, which led to higher peak strengths during shearing. This was a similar trend to what was observed in the field when ballast with lower angularity yielded less settlement due to better packing (Tutumluer et al 2013). …”

“…The DEM simulation approach developed at the University of Illinois adopts real polyhedral particles and has the capability to create actual ballast aggregate particles as 3D polyhedron elements having the same particle size distributions and imaging quantified average shapes and angularities. This DEM approach was calibrated by the laboratory large scale direct shear test results (Tutumluer et al 2006), validated by field track settlement predictions (Tutumluer et al 2013), and has been successfully utilized to simulate complex ballast behavior, especially large scale triaxial tests with or without geogrid reinforcement. (Qian et al 2013a, b, c).…”