The mechanism and effects of subgrade fluidisation under ballasted railway tracks

Abstract

The rapid growth in railway infrastructure and the construction of high-speed heavy-haul rail network, especially on ground that is basically unsuitable, poses challenges for geotechnical engineers because a large part of the money invested in the development of railway lines is often spent on track maintenance. In fact around the world, the mud pumping of subgrade fines is one of the common reasons why track performance deteriorates and track stability is hindered. This article presents a series of laboratory tests to examine following aspects of mud pumping: (1) the mechanisms of subgrade fluidisation under undrained condition, (2) the effects of mud pumping on the engineering characteristics of ballast, and (3) the use of vertical drains to stabilize subgrade under cyclic loads. The undrained cyclic triaxial testing on vulnerable soft subgrade was performed by varying the cyclic stress ratio (CSR) from 0.2 to 1.0 and the loading frequency f from 1.0 to 5.0 Hz. It is seen from the test results that for a specimen compacted at an initial dry density of 1790 kg/m³, the top portion of the specimen fluidises at CSR = 0.5, irrespective of the applied loading frequency. Under cyclic railway loading, the internal redistribution of water at the top of the subgrade layer softens the soil and also reduces its stiffness. In response to these problems, this paper explains how the inclusion of vertical drains in soft subgrade will help to prevent mud pumping by alleviating the build-up of excess pore pressures under moving train loads.

Keywords

Mud pumping / Ballasted track / Subgrade fluidisation / Fouled ballast / Prefabricated vertical drains

References

[1.] Hussaini SKK, Indraratna B, Vinod JS (2012) Performance of geosynthetically-reinforced rail ballast in direct shear conditions. In: Paper presented at the 11th Australia-New Zealand conference on geomechanics: ground engineering in a changing world, Australia, pp 1268–1273

[2.] Aw ES. Low cost monitoring system to diagnose problematic rail bed: case study at a mud pumping site, 2007 Cambridge Massachusetts Institute of Technology

[3.] Indraratna B Nimbalkar S Rujikiatkamjorn C. Future of Australian rail tracks capturing higher speeds with heavier freight. Int J Railw Technol, 2012 1 1 195-219

[4.] Trinh VN Tang AM Cui Y-J Dupla J-C Canou J Calon N Lambert L Robinet A Schoen O. Mechanical characterisation of the fouled ballast in ancient railway track substructure by large-scale triaxial tests. Soil Found Jpn Geotech Soc, 2012 52 3 511-523

[5.] Nguyen TT Indraratna B Kelly R Phan NM Haryono F. Mud pumping under railtracks: mechanisms, assessments and solutions. Aust Geomech J, 2019 54 4 59-80

[6.] Li D, Selig ET (1995) Evaluation of railway subgrade problems. Transportation Res Rec No 1489 Transportation Research Board, Washington, D.C., pp 17–25

[7.] Tennakoon N (2012) Geotechnical study of engineering behaviour of fouled ballast. Dissertation, University of Wollongong, Wollongong, NSW, Australia

[8.] Feldman F, Nissen D (2002) Alternative testing method for the measurement of ballast fouling: percentage void contamination. In; CORE: cost efficient railways through engineering, p 101

[9.] Huang H Tutumluer E Dombrow W. Laboratory characterization of fouled railroad ballast behavior. Transp Res Rec, 2009 2117 1 93-101

[10.] Tennakoon N Indraratna B. Behaviour of clay-fouled ballast under cyclic loading. Géotechnique, 2014 64 6 502-506

[11.] Knappett J Craig RF. Craig’s soil mechanics, 2012 London CRC Press LLC

[12.] Singh M Indraratna B Rujikiatkamjorn C. Sundaram R Shahu J Havanagi V. Use of geosynthetics in mitigating the effects of mud pumping: a railway perspective. Geotechnics for transportation infrastructure, 2019 Singapore Springer

[13.] Indraratna B Singh M Nguyen TT Leroueil S Abeywickrama A Kelly R Neville T. A laboratory study on subgrade fluidisation under undrained cyclic triaxial loading. Can Geotech J, 2020

[14.] Skempton A Brogan J. Experiments on piping in sandy gravels. Géotechnique, 1994 44 3 449-460

[15.] Locke M Indraratna B. Filtration of broadly graded soils: the reduced PSD method. Géotechnique, 2002 52 4 285-287

[16.] Kézdi Á. Soil physics: selected topics, 2013 Amsterdam Elsevier

[17.] Duong TV Cui Y-J Tang AM Dupla J-C Canou J Calon N Robinet A Chabot B De Laure E. Physical model for studying the migration of fine particles in the railway substructure. Geotech Test J, 2014 37 5 1-12

[18.] Chawla S Shahu JT. Reinforcement and mud-pumping benefits of geosynthetics in railway tracks: model tests. Geotext Geomembr, 2016 44 366-380

[19.] Kuo C, Hsu C, Wu C, Liu P, Chen D (2017) Study on the Piping Path and Mechanism of Mud-pumping in Railway Subgrade. In: The 19th international conference on soil mechanics and geotechnical engineering, Seoul, South Korea

[20.] Alobaidi I Hoare DJ. The development of pore water pressure at the subgrade–subbase interface of a highway pavement and its effect on pumping of fines. Geotext Geomembr, 1996 14 2 111-135

[21.] Jiang MJ Konrad JM Leroueil S. An efficient technique for generating homogeneous specimens for DEM studies. Comput Geotech, 2003 30 579-597

[22.] ASTM D2487–17. Standard practice for classification of soils for engineering purposes (unified soil classification system), 2017 West Conshohocken ASTM International

[23.] Larew HG Leonards GA. A strength criterion for repeated loads. Highw Res Board Proc, 1962 41 529-556

[24.] Sangrey DA Henkel DJ Esrig MI. The effective response of a saturated clay soil to repeated loading. Can Geotech J, 1969 6 3 241-252

[25.] Ansal AM Erken A. Undrained behaviour of clay under cyclic shear stresses. J Geotech Eng, 1989 115 7 968-983

[26.] Zhou J Gong X. Strain degradation of saturated clay under cyclic loading. Can Geotech J, 2001 38 208-212

[27.] Dash HK Sitharam TG. Effect of frequency of cyclic loading on liquefaction and dynamic properties of saturated sand. Int J Geotech Eng, 2016 10 5 487-492

[28.] ASTM D698-12e2 (2012) Standard test methods for laboratory compaction characteristics of soil using standard effort (12 400 ft-lbf/ft3 (600 kN-m/m3)), ASTM International, West Conshohocken, PA. https://www.astm.org

[29.] Indraratna B Korkitsuntornsan W Nguyen TT. Influence of kaolin content on the cyclic loading response of railway subgrade. Transp Geotech, 2020 22 100319

[30.] Tennakoon N Indraratna B Rujikiatkamjorn C Nimbalkar S Neville T. The role of ballast-fouling characteristics on the drainage capacity of rail substructure. Geotech Test J, 2012 35 4 629-640

[31.] Pilgrim DH. Australian rainfall and runoff: a guide to flood estimation, 1997 Australia Institution of Engineers

[32.] Indraratna B Tennakoon N Nimbalkar S Rujikiatkamjorn C. Behaviour of clay-fouled ballast under drained triaxial testing. Géotechnique, 2013 63 5 410-419

[33.] Indraratna B Rujikiatkamjorn C Sathananthan I. Analytical and numerical solutions for a single vertical drain including the effects of vacuum preloading. Can Geotech J, 2005 42 4 994-1014

[34.] Indraratna B Attya A Rujikiatkamjorn C. Experimental investigation on effectiveness of a vertical drain under cyclic loads. J Geotech Geoenviron Eng, 2009 135 6 835-839

[35.] Indraratna B Rujikiatkamjorn C Ewers B Adams M. Class A prediction of the behaviour of soft estuarine soil foundation stabilized by short vertical drains beneath a rail track. J Geotech Geoenviron Eng, 2010 136 5 686-696

[36.] Lambe T. Predictions in soil engineering. Géotechnique, 1973 23 2 151-202

Funding

Australian Research Council and ITTC-Rail(LP160101254)