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Keywords: granular filter, filter porosity, subballast, seepage, cyclic loads, filter permeability.

Summary

Occurrences of inadequacies of subballast as a filtration layer of the ballasted rail tracks would become persistent if inappropriate criteria were still being used in the design. Traditionally, the subballast is considered mainly to act as a stress dissipation layer, more commonly known as a capping layer. Attention towards its function as a granular filter is proven by the fact that common design practice uses design criteria that are primarily based on steady seepage loading that is common in embankment dams. The seepage hydraulics through porous media is influenced by the cyclic mechanical loading generated by passing trains. Under the influence of cyclic train loading, subballast particles rearrange and attempt to attain a more stable configuration through the process of vertical compression, lateral spreading, and particle degradation. The deformability of the pore medium itself would then affect the filter condition due to the changes in porosity and its subsequent impact on hydraulic conductivity. This paper presents a procedure that combines a family of formulations and configuration charts that considers the effectiveness of the subballast as a granular filter being dependent on the reduction of its porosity and hydraulic conductivity over time.

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Front Page Browse CCP CSETS CTR IJRT Other Authors Search Purchase Guide FAQ Contact us	Civil-Comp Proceedings ISSN 1759-3433 CCP: 104 PROCEEDINGS OF THE SECOND INTERNATIONAL CONFERENCE ON RAILWAY TECHNOLOGY: RESEARCH, DEVELOPMENT AND MAINTENANCE Edited by: J. Pombo Paper 127 A Procedure to Assess Subballast Filtration under Cyclic Loading L.D. Trani^1,2 and B. Indraratna² ¹Coffey Geotechnics Pty Ltd, Wollongong, Australia ²Civil, Mining and Environmental Engineering, University of Wollongong, Australia doi:10.4203/ccp.104.127 purchase the full-text of this paper Full Bibliographic Reference for this paper L.D. Trani, B. Indraratna, "A Procedure to Assess Subballast Filtration under Cyclic Loading", in J. Pombo, (Editor), "Proceedings of the Second International Conference on Railway Technology: Research, Development and Maintenance", Civil-Comp Press, Stirlingshire, UK, Paper 127, 2014. doi:10.4203/ccp.104.127 Keywords: granular filter, filter porosity, subballast, seepage, cyclic loads, filter permeability. Summary Occurrences of inadequacies of subballast as a filtration layer of the ballasted rail tracks would become persistent if inappropriate criteria were still being used in the design. Traditionally, the subballast is considered mainly to act as a stress dissipation layer, more commonly known as a capping layer. Attention towards its function as a granular filter is proven by the fact that common design practice uses design criteria that are primarily based on steady seepage loading that is common in embankment dams. The seepage hydraulics through porous media is influenced by the cyclic mechanical loading generated by passing trains. Under the influence of cyclic train loading, subballast particles rearrange and attempt to attain a more stable configuration through the process of vertical compression, lateral spreading, and particle degradation. The deformability of the pore medium itself would then affect the filter condition due to the changes in porosity and its subsequent impact on hydraulic conductivity. This paper presents a procedure that combines a family of formulations and configuration charts that considers the effectiveness of the subballast as a granular filter being dependent on the reduction of its porosity and hydraulic conductivity over time. purchase the full-text of this paper (price £20) go to the previous paper go to the next paper return to the table of contents return to the book description purchase this book (price £65 +P&P)
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