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  2024, Vol. 43 Issue (8): 2027-2041    DOI: 10.13722/j.cnki.jrme.2023.0269
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Analysis of macroscopic strength and meso-scale particle rotation characteristics of railroad ballasts fouled by different levels of coal dust
WANG Meng1,XIAO Yuanjie1,2,ZHANG Chongchong1,YANG Tao1,TAN Pan1,LU Mingjiao3
(1. School of Civil Engineering,Central South University,Changsha,Hunan 410075,China;2. MOE Key Laboratory of Engineering Structures of Heavy Haul Railway,Central South University,Changsha,Hunan 410075,China;
3. School of Civil Engineering,Tongji University,Shanghai 200092,China)
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Abstract  Fouled ballast can commonly cause severe defects of ballasted trackbed including mud pumping and differential settlement,thus further endangering stable and safe operations of trains. To address this engineering challenge,ballast specimens with different fouling levels were prepared in the laboratory by adopting the classic fouling index(FI),and subsequently subjected to monotonic triaxial compression tests. The newly-invented wireless,self-powered and smart sensors(SmartRock) were placed at different positions inside ballast specimens to measure real-time particle rotation data. The macroscopic shear strength behaviors of ballast specimens with different fouling levels were analyzed comparatively and linked to meso-scale ballast particle movement. The results show that increasing coal dust fouling level could cause gradual transition of macroscopic behavior from strain hardening to strain softening. When the fouling index(FI) value ranges from 10% to 15%,both peak deviator stress at failure and apparent cohesion reach their minimums,respectively. The rotation of ballast particles inside the triaxial specimens mainly occurrs in the vertical planes,whereas the vertical-plane rotations of ballast particles located closer to the bottom of clean ballast triaxial specimens increasingly attenuate due to the increasing restraint of lateral boundaries on particle movement. When the FI value reaches 15%,no discernible rotation pattern is observed for ballast particles inside triaxial specimens,which may be attributable to the loss of inter-particle force-transferring skeleton. When the FI value further exceeds beyond 15%,ballast particle rotations exhibite significantly increasing differences,probably resulting in macroscopic mechanical instability. The uniformity of ballast particle rotations determines macroscopic shear strength behavior to a certain extent and thus can be employed to estimate the actual fouling level of ballast beds. The findings are expected to provide theoretical basis and technical reference for Non-destructive evaluation of fouling degree,ballast-cleaning schedule optimization,and intelligent maintenance of ballasted trackbeds.
Key wordssubgrade engineering      ballasted trackbed      ballast fouling      monotonic triaxial compression test      SmartRock sensor      shear strength      particle rotation
     
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Articles by authors
WANG Meng1
XIAO Yuanjie1
2
ZHANG Chongchong1
YANG Tao1
TAN Pan1
LU Mingjiao3
Cite this article:   
WANG Meng1,XIAO Yuanjie1,2, et al. Analysis of macroscopic strength and meso-scale particle rotation characteristics of railroad ballasts fouled by different levels of coal dust[J]. , 2024, 43(8): 2027-2041.
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