Application of bounding surface plasticity concept for clay-fouled ballast under drained loading

Tennakoon, Nayoma; Indraratna, Buddhima; Nimbalkar, Sanjay; Sloan, Scott W.

doi:10.1016/j.compgeo.2015.07.010

Cited by 20 publications

(5 citation statements)

References 20 publications

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“…When the current stress point is on the BS, hence coinciding with its image stress point, the combination of the Eqs. (21), (23), (24) and (26) leads to the following expression of the plastic modulus:…”

Section: Plastic Potential Non-associative Flow Rule and Plastic Modmentioning

confidence: 99%

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Modelling the poroplastic damageable behaviour of earthen materials

Wong

Fabbri

et al. 2018

Mater Struct

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This paper presents a new constitutive model on the poroplastic behaviour of earthen materials accounting for stiffness degradation, using the approach of continuum damage mechanics. The poroplastic behaviour is modelled based on the bounding surface plasticity (BSP) theory and the concept of effective stress while isotropic damage is modelled using a scalar variable. Plastic flow and damage evolution occur simultaneously in a coupled process which take into account the impact of suction. The model was successfully validated against results of triaxial compression tests performed at different relative humidities and confining pressures. Despite the relatively small number of material parameters, this model can reproduce the essential features of earthen materials behaviour observed experimentally: suctioninduced hardening and stiffening, post-peak softening, as well as the progressive transition from contractant to dilatant volumetric behaviour. Use of the BSP theory allows to reproduce a smooth stress-strain relation as experimentally observed, instead of an abrupt change upon plastic yielding predicted by classic elastoplastic models. Furthermore, the present model also furnishes a quantitative description on the degradation of elastic properties hitherto not accounted for, thanks to the additional scalar damage variable. Keywords Unsaturated rammed earth Á Bounding surface plasticity Á Suction Á Damage Á Degradation The original version of this article was revised due to a retrospective Open Access order.

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Section: Plastic Potential Non-associative Flow Rule and Plastic Modmentioning

confidence: 99%

“…BSP theory was later extended to partially saturated materials in order to describe suction effects [14][15][16][17][18][19]. In addition, BSP theory is also applied on geomaterials other than soils due to its versatility, such as rockfills and clay-fouled ballast [20,21].…”

Section: Introductionmentioning

confidence: 99%

Modelling the poroplastic damageable behaviour of earthen materials

Wong

Fabbri

et al. 2018

Mater Struct

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“…Consequently, triggering the rapid fragmentation of the sub-structure's ballast aggregates, and thereby reducing the mechanical and drainage performance of the rail track. Likewise, the ballast may be subjected to fouling via cyclic loadings Wang et al, 2018;Wang et al, 2018a), upward movement of clayey fines from the subgrade and the migration of coal trickling down wagon trains (Ebrahimi et al, 2012;Giannakos, 2010;Huang et al, 2009;Indraratna, Navaratnarajah et al, 2014b;Tennakoon et al, 2015). All of these can adversely impact track drainage capacity.…”

Section: Introductionmentioning

confidence: 99%

Experimental characterization of track ballast under triple-fouling condition: Evidence from selected Nigerian Railways

et al. 2021

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This study assessed the aggregate properties that influence track ballast performance along selected Nigerian railway lines. Ballast materials from five selected rail tracks (RT1, RT2, RT3, RT4, and RT5) in Nigeria were collected and assessed in present conditions and after triple-fouling (subjected to degradation, clay, and diesel intrusion). Tests performed include gradation, strength, soundness, and drain-ability tests. Results obtained were compared with the requirements established in five recognized railway ballast standards,where applicable. Initial gradation results indicate that presently, ballast materials from the selected study locations can all be classified as "uniformly graded gravel". However, upon triplefouling, a gradation shift towards the "well graded" classification was observed. Based on EN 13,450, the gradations of RT1, RT2, and RT3 ballast materials were more satisfactory than gradations of RT4 and RT5. Strength test results show that ballast materials from tracks RT1, RT2, and RT3 performed satisfactorily based on the five ballast standards considered. RT4 and RT5 on the other hand, only performed suitably based on the AREMA No. 4 ballast standard. The least resistance to weathering was observed in the RT4 and RT5 samples. Initial drain-ability test

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“…This in turn, leads to a rapid fragmentation of ballast aggregates which affects the strength and drainage of track. Moreover, the ballast layer is also fouled by an upward migration of subgrade clay fines and a downward migration of coal spilling from wagons Tennakoon et al 2015), all of which seriously affects the drainage capacity of track.…”

Section: Introductionmentioning

confidence: 99%

Current research into ballasted rail tracks: model tests and their practical implications

Indraratna

Sun

Ngo

et al. 2017

Australian Journal of Structural Engineering

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Ballasted rail tracks are the most important mode of transportation in terms of traffic tonnage serving the needs of bulk freight and passenger movement, but under train loads, the particles degrade due to breakage and the progressive accumulation of external fines or mud-pumping under the subgrade, all of which reduce its shear strength and increase track instability. These actions adversely affect the safety, passenger comfort and efficiency of tracks, as well as enforcing speed restrictions and more frequent track maintenance. In spite of advances in rail track geotechnology, the optimum choice of ballast for track design is still considered critical because ballast degradation is influenced by the amplitude and number of load cycles, particle gradation, track confining pressure and the angularity and fracture strength of individual grains. One of the most effective methods of enhancing track stability and reducing the stresses transmitted to a soft subgrade layer is to increase the stiffness of the overlying granular media. This paper presents our current knowledge of rail track geomechanics, including important concepts/topics related to laboratory testing and computational modelling approaches used to study the load-deformation behaviour of ballast improved with waste tyres, synthetic geogrids and geocells.Abstract: Transport infrastructure must now perform over the long term because heavy haul transport networks are expected to withstand higher speeds and heavier axle loads. Ballasted rail tracks are the most important mode of transportation in terms of traffic tonnage serving the needs of bulk freight and passenger movement, but under train loads the particles degrade due to breakage and the progressive accumulation of external fines or mud-pumping under the subgrade, all of which reduces its shear strength and increases track instability. These actions adversely affect the safety, passenger comfort and efficiency of tracks, as well as enforcing speed restrictions and more frequent track maintenance. In spite of advances in rail track geotechnology, the optimum choice of ballast for track design is still considered critical because ballast degradation is influenced by the amplitude and number of load cycles, particle gradation, track confining pressure, and the angularity and fracture strength of individual grains. One of the most effective methods of enhancing track stability and reducing the stresses transmitted to a soft subgrade layer is to increase the stiffness of the overlying granular media. The Centre for Geomechanics and Railway Engineering (CGRE) has developed new design and construction concepts for track upgrading by applying theory to practice to enhance track longevity and minimise the maintenance costs. Research conducted at CGRE has shown that understanding the load transfer mechanisms and their effect on ballast breakage are important pre-requisites for decreasing track maintenance costs. This paper presents our current knowledge of rail track geomechanics, including important concepts/t...

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Application of bounding surface plasticity concept for clay-fouled ballast under drained loading

Cited by 20 publications

References 20 publications

Modelling the poroplastic damageable behaviour of earthen materials

Modelling the poroplastic damageable behaviour of earthen materials

Experimental characterization of track ballast under triple-fouling condition: Evidence from selected Nigerian Railways

Current research into ballasted rail tracks: model tests and their practical implications

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