Effect of Flakiness-Elongation Index on Shear Behavior of Railway Ballast
JING Guoqing1, QIANG Weile2, CHANG Jinxiu1, LI Xu1
1. School of Civil Engineering, Beijing Jiaotong University, Beijing 100044, China; 2. Infrastructure Inspection Institute of China Academy of Railway Sciences, Beijing 100081, China
Abstract:In order to investigate the influences of flat and (or) elongated ballasts on direct shear mechanical properties considering the breakage effect,the direct shear tests with different test conditions were conducted to study the effect of the flat and/or elongated ballast content with the analysis of testing results from the ballast shear strength,deformation and breakage. The results show that: (1) With the increase of the flakiness and elongation index,the shear behavior of the ballast decreases,both the shear strength and internal friction angle (at 100 kPa,the shear strength respectively decreases by 10.9%,16.8% when the elongation index increases from 0 to 20%,40%; the shear strength respectively decreases by 14.7%,22.3% when the flakiness index increases from 0 to 20%,40%; the shear strength respectively decreases by 12.4%,18.9% when the flakiness-elongation index increases from 0 to 20%,40%). (2) The shear dilatation and shrinkage of samples decrease with the flat and/or elongated ballast content increasing. (3) The flat and elongated ballast particles are prone to break up during the direct shear test,and most of them are fractured with the sharp corner breakage,which significantly affects the ballast bed maintenance cycle.
RAYMOND G P. Research on railroad ballast specification and evaluation[J]. Transportation Research Record, 1985, 1006: 1-8
[4]
ANOCHIE-BOATENG J K, KOMBA J J, MVELASE G M. Three-dimensional laser scanning technique to quantify aggregate and ballast shape properties[J]. Construction and Building Materials, 2013, 43: 389-398
American Society of Testing and Materials. Standard test method for flat particles,elongated particles,or flat and elongated particles in coarse aggregate:D 4791—2010[S]. West Conshohocken:ASTM International,2010.
[7]
SELIG E T,WATERS J M. Track geotechnology and substructure management[M]. London:Thomas Telford,1994.
[8]
Australian Standard. Methods for sampling and testing aggregates-method 14:particle shape,by proportional caliper: AS 1141.14—2007[S]. Sydney:Standards Australia Ltd.,2007
[9]
Australian Standard Institution. Methods for sampling and testing aggregates-method 15:flakiness index:AS1141.15—1999[S]. Sydney: Standards Australia Ltd.,1999.
[10]
British Standards Institution. Tests for geometrical properties of aggregates—part 3:determination of particle shape—flakiness index:EN 933-3—2012[S]. London:BSI Standards Ltd.,2012.
[11]
British Standards Institution. Tests for geometrical properties of aggregates—part 4:determination of particle shape —shape index:EN 933-4 —2000[S]. London:BSI Standards Ltd.,2000.
[12]
American Railway Engineering and Maintenance-of-Way Association. Manual for railway engineering[M]. Lanham:American Railway Engineering Association,2012:5-10.
[13]
Australian Standard. Aggregates and rock for engineering purposes—part 7:railway ballast:AS 2758.7—2015[S]. Sydney: SAI Global Ltd.,2015
American Society of Testing and Materials. Standard test method for direct shear test of soils under consolidated drained conditions:D3080—2011[S]. West Conshohocken:ASTM International,2011.
[16]
MISHRA D,MAHMUD S M N. Effect of particle size and shape characteristics on ballast shear strength:a numerical study using the direct shear test[C]//Proceeding of the 2017 Joint Rail Conference. Philadelphia:American Society of Mechanical Engineers,2017: 1-10.
[17]
POTTICARY M,ZERVOS A,HARKNESS J. The effect of particle elongation on the strength of granular materials[C]//Proceedings of the 24th UK Conference of the Association for Computational Mechanics in Engineering. Cardiff:University of Southampton Institutional Repository,2016: 239-242.
[18]
井国庆,黄红梅,常锦秀,等. 清洗后的劣化道砟直剪力学特性分析[J]. 西南交通大学学报,2017,52(5): 1055-1060JING Guoqing, HUANG Hongmei, CHANG Jinxiu, et al. Analysis of mechanical characteristics of degradation railway ballast by direct shear test[J]. Journal of Southwest Jiaotong University, 2017, 52(5): 1055-1060
[19]
INDRARATNA B, IONESCU D, CHRISTIE H D. Shear behavior of railway ballast based on large-scale triaxial tests[J]. Journal of Geotechnical & Geoenvironmental Engineering, 1998, 124(5): 439-449
[20]
ASADZADEH M, SOROUSH A. Direct shear testing on a rockfill material[J]. Arabian Journal for Science and Engineering, 2009, 34(2): 379-396
[21]
王鹏程,刘建坤,李旭,等. 直剪条件下碎石集料力学特性研究[J]. 铁道学报,2014(2): 103-108WANG Pengcheng, LIU Jiankun, LI Xu, et al. Mechanical behavior of crushed stone aggregate subjected to direct shear conditions[J]. Journal of The China Railway Society, 2014(2): 103-108