Laboratory Modelling and Assessment of Internal Instability Potential of Subballast Filter under Cyclic Loading

Jahanzaib Israr, Jehangir Israr

Abstract


Internal instability occurs when the filtrates under the influence of seepage forces washout the finer fraction from granular soils, resulting in the deterioration of the mechanical and geotechnical properties, e.g. change in soil gradation, large volumetric strains and increased permeability etc. In railway substructures, filters are installed as drainage or subballast layers to arrest the eroding subgrade fines into superstructure that could otherwise endanger the stability of tracks due to ballast fouling and clay pumping. Notably, the design and assessments for internal instability potential for subballast are currently emphasized through existing filtration criteria which neglect the effects of cyclic loading. This paper reports an investigation of the internal stability assessment of saturated subballast filters subjected to cyclic loading. Experimental results conducted on selected soil gradations in specially designed cyclic loading permeameter revealed that repeated loading promotes substantial and premature suffusion failure, the intensity of which increases with the loading frequency. An existing criterion for assessing the internal instability potential is modified to capture the effects of cyclic loading that is subsequently validated through extensive laboratory data. Comparisons between static and cyclic response of test samples revealed that the suffusion could occur at unique hydro-mechanical boundaries, which would have implications in practical design of internally stable subballast filters under unfavorable hydro-mechanical and cyclic loading conditions.

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References


Christie, D. Bulli field trial: Vertical and lateral pressure measurement. Rail CRC Seminar, seminar conducted at the University of Wollongong, (2007), Wollongong, NSW.

Chung Ip, M., Haque, A. and Bouazza, A. Influence of cyclic stress pulse shapes on filtration behaviour of railway subballast. Journal of Geotechnical and Geoenvironmental Engineering 138-2(2012), 230-235.

Haque, A., Kabir, E. and Bouazza, A. Cyclic filtration apparatus for testing subballast under rail track. Journal of Geotechnical and Geoenvironmental Engineering 133-3(2007), 338-341.

Indraratna, B., Israr, J., and Rujikiatkamjorn, C. Geometrical method for evaluating the internal instability of granular filters based on constriction size distribution. Journal of Geotechnical and Geoenvironmental Engineering 141-10(2015), 1-14. (DOI: 10.1061/(ASCE)GT.1943-5606.0001343).

Kamruzzaman, A. H. M., Haque, A. and Bouazza, A. Filtration behaviour of granular soils under cyclic load. Geotechnique 58-6(2008), 517–522.

Kenney, T. C., and Lau, D. Internal stability of granular filters. Canadian Geotechnical Journal 22(1985), 215–225.

Kezdi, A. Soil physics, Elsevier Scientific, (1979) Amsterdam, The Netherlands.

Li, M., and Fannin, R. J. Comparison of two criteria for internal stability of granular soil. Canadian Geotechnical Journal 45-9(2008), 1303–1309.

Locke, M., Indraratna, B., and Adikari, G. Time-dependent particle transport through granular filters. Journal of Geotechnical and Geoenvironmental Engineering 6-521(2001), 521-529.

Selig, E. T. and Waters, J. M. Track technology and substructure management. Thomas Telford, (1994), London.

Sherard, J. L. Sinkholes in dams of coarse broadly graded soils. In Proceeding of the 13th Congress on Large Dams, Paris, France, 1-2(1979), 25–35.

Skempton, A. W., and Brogan, J. M. Experiments on piping in sandy gravels. Geotechnique 44-3(1994), 449–460.

Terzaghi, K. Soil mechanics—A new chapter in engineering science. Institute of Civil Engineers 12-7(1939), 106–142.

Trani, L. D. O. and Indraratna, B. Assessment of Subballast Filtration under Cyclic Loading. Journal of Geotechnical and Geoenvironmental Engineering 136-11(2009), 1519-1528.

Zou, Y., Chen, Q., Chen, X. and Cui, P. Discrete numerical modelling of particle transport in granular filters. Computers and Geotechnics 32-5(2013), 340–57.






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