Discrete element modelling of geogrid-reinforced aggregates

Abstract

A discrete element model has been developed for geogrid-reinforced ballast. A model for unreinforced ballast has first been developed and evaluated using simulations of large-scale triaxial experiments and comparing with available data. A model for the geogrid has also been developed by bonding many small balls together to form the desired geometry and evaluated by simulating standard tests. The discrete element method (DEM) has then been used to model the interaction between ballast and geogrid by simulating pull-out tests and comparing with experimental data. The DEM simulations have been shown to predict well the peak mobilised resistance and the displacement necessary to mobilise peak pull-out force. The effect of the ratio of the geogrid aperture size to ballast particle diameter on pull-out resistance has also been investigated. The zone of influence of the geogrid has also been examined by simulating larger-scale pull-out tests in addition to cyclic triaxial tests. The method holds much promise as a tool for investigating aggregate–geogrid composite systems with a view to choosing appropriate geometries to optimise performance.

A study of geogrid-reinforced ballast using laboratory pull-out tests and discrete element modelling

“…These figures display the strong contact forces in the vicinity of the geogrid area, which clearly shows the interlocking effect. This is in agreement with the simulation modelled by McDowell et al (2006). It can be seen that, the clump ballast particles arch around each transverse rib during pull-out.…”

“…The use of PFC 3D to model ballast particles and introduce interlock using clumps have also been described (Lim andMcDowell 2005, Lu andMcDowell 2007). McDowell et al (2006) involved application of DEM for modelling of both ballast and the biaxial geogrid, together with small box pull-out experiments to validate the simulation results. They found that the optimum ratio between geogrid aperture size and aggregate size should be around 1.4.…”

“…The discrete element method has been used for simulating complex soil/aggregate geogrid interaction (Konietzky et al 2004, McDowell et al 2006, Zhang et al 2007, 2008. This numerical simulation approach is fully capable of modelling the interaction of ballast particle and the geogrid by accounting for the aggregate particle shape, reproducing the actual geometry of geogrid and assigning properly particles and geogrids properties.…”

“…Recent work by Konietzky et al (2004) and McDowell et al (2006) focused on aggregate and geogrid interactions and modelling confinement effects. The findings of DEM studies covered interaction between geogrids and surrounding soil/aggregate in both triaxial and small box pull-out tests, contact force distributions, deformations and particle rearrangements.…”

Micromechanics-Based Investigation of Fouled Ballast Using Large-Scale Triaxial Tests and Discrete Element Modeling

“…McDowell et al (2006) used the discrete element method to model largescale triaxial experiments of ballast aggregates reinforced with geogrids, and concluded that the DEM approach holds much promise as a tool for investigating granular aggregate assemblies. Bolton et al (2008) used the DEM to simulate triaxial compression shearing tests for both breakable and unbreakable agglomerate assemblies, capturing the influence of confining pressure on the stress-strain and volumetric response.…”