Experimental study on the permeability of railway ballast bed and its influencing factors

WANG Wei; LEI Sai; YANG Zhibang; ZHANG Tianshuang; XIAO Jian

doi:10.11860/j.issn.1673-0291.20250007

Abstract：To ensure the long-term safe and stable operation of railways,this study employs a self-designed permeameter to investigate the permeability of ballast aggregates under various service condi-tions,aiming to reveal the evolution patterns of ballast bed seepage performance.First,clean ballast aggregates meeting the premium crushed stone ballast standard are selected to analyze the effects of gradation non-uniformity coefficient and mean particle size on ballast aggregates permeability.Next,fly ash and fine sand are introduced as fouling agents and added to the upper,middle,and lower layers of clean ballast aggregates to simulate fouling distributions in existing ballast bed.The impacts of foul-ing degree,composition,and distribution on ballast aggregates permeability are systematically exam-ined.Finally,by varying initial densities and applying vertical loads,the effects of initial density and applied vertical load on ballast aggregates permeability are studied.Results indicate that,in the ab-sence of contamination within the ballast aggregates,a smaller non-uniformity coefficient and larger average particle size correspond to higher permeability and hydraulic conductivity.Conversely,the presence of contamination within the ballast aggregates,with higher contamination levels,smaller contaminant particle sizes,and more concentrated distribution,results in a smaller hydraulic conduc-tivity and weaker permeability.Moreover,clean ballast aggregates with lower initial density result in a greater hydraulic conductivity and gradually enhanced permeability,while contaminated aggre-gates with lower initial density show a reduced hydraulic conductivity and diminishing permeability.Additionally,the permeability of contaminated ballast aggregates decreases with higher vertical loads due to plastic deformation during loading,preventing permeability from fully recovering after unloading.