Interface Behavior of Geogrid-Reinforced Sub-ballast: Laboratory and Discrete Element Modeling
This paper shows a study on the interface behavior of biaxial geogrids and sub-ballast using a direct shear box and computational modeling. A series of large-scale direct shear tests are performed on sub-ballast (capping layer) with and without geogrid inclusions. The laboratory test data indicate that the interface shear strength is mainly decided by applied normal stresses and types of geosynthetics tested. Discrete element modeling approach is used to investigate the interface shear behavior of the sub-ballast subjected to direct shear loads. Irregular-shaped sub-ballast particles are modeled by clumping of many spheres together in pre-determined sizes and positions. Biaxial geogrids are simulated in the DEM by bonding small balls together to build desired geogrid shapes and opening apertures. The numerical results reasonably match with the measured test data, showing that the introduced DEM model can simulate the interface behavior of sub-ballast stabilized by the geogrids. In addition, the triaxial geogrid presents the highest interface shear strength compared to the biaxial geogrids; and this can be associated with the symmetric geometry of grids’ apertures that can distribute load in all directions. Evolutions of contact forces of unreinforced/reinforced sub-ballast specimens and contour strain distributions during shear tests are also investigated.
KeywordsTransport geotechnics Geogrid Sub-ballast Interface behavior Discrete element method
The authors greatly appreciate the financial support from the Rail Manufacturing Cooperative Research Centre (funded jointly by participating rail organizations and the Australian Federal Government’s Business Cooperative Research Centres Program) through Project R2.5.1—Performance of recycled rubber inclusions for improved stability of railways. The Authors would like to thank the Australasian Centre for Rail Innovation (ACRI) Limited, and Tyre Stewardship Australia Limited for providing the financial support needed to undertake this research. Some research outcome is reproduced in this paper with kind permission from the Granular Matter. The Authors are thankful to Mr. Alan Grant, Duncan Best, and Mr. Ritchie McLean for their help in the laboratory.
- AS 2758.7 (1996) Aggragates and rocks for engineering purposes; Part 7: Railway ballast, Sydney, NSW, AustraliaGoogle Scholar
- Huang H, Tutumluer E, Hashash YMA, Ghaboussi J (2009b) Discrete element modelling of aggregate behaviour in fouled railroad ballast. In: Geotechnical Special Publication, 192, pp 33–41Google Scholar
- Itasca (2016) Particle flow code in three dimensions (PFC3D). Itasca Consulting Group Inc, MinnesotaGoogle Scholar
- Ngo NT, Indraratna B, Rujikiatkamjorn C (2015) A study of the behaviour of fresh and coal fouled ballast reinforced by geogrid using the discrete element method. In: Geomechanics from micro to macro - proceedings of the TC105 ISSMGE international symposium on geomechanics from micro to macro, IS-Cambridge 2014Google Scholar
- Ngo NT, Indraratna B, Rujikiatkamjorn C (2017a) Micromechanics-based investigation of fouled ballast using large-scale triaxial tests and discrete element modeling. J Geotech Geoenviron Eng 134 (2): pp 04016089Google Scholar
- Ngo NT, Indraratna B, Rujikiatkamjorn C (2017c) A study of the geogrid–subballast interface via experimental evaluation and discrete element modelling. Granular Matter 19 (3): 54, 51–16Google Scholar
- Rujikiatkamjorn C, Indraratna B, Ngo NT, Coop M (2012) A laboratory study of railway ballast behaviour under various fouling degree. In: The 5th Asian regional conference on geosynthetics, pp 507–514Google Scholar
- Rujikiatkamjorn C, Ngo NT, Indraratna B, Vinod J, Coop M (2013) Simulation of fresh and fouled ballast behavior using discrete element method. In: Proceedings of the international conference on ground improvement and ground control, pp 1585–1592. Singapore, Research PublishingGoogle Scholar
- Tutumluer E, Dombrow W, Huang H (2008) Laboratory characterization of coal dust fouled ballast behaviour. In: AREMA 2008 annual conference and exposition, Salt Lake City, UT, USAGoogle Scholar