Investigating the effect of ballast contamination in vertical and shear interlocking stiffness: Experimental and numerical study

Abstract

The maintenance of railway tracks faces a significant challenge due to ballast contamination. This issue arises from the inevitable ingress of fine particles into the track structure through various means, such as fine sands, coal infiltration, aggregate breakage, and substructure pumping. Climate change exacerbates these conditions, leading to increased external debris contamination and the accelerated degradation of ballast aggregates. This contamination has major consequences, impacting track quality in terms of drainage capacity and dynamic behavior. As a response to this, the study focuses on assessing ballast contamination from sand infiltration, specifically evaluating vertical and shear interlocking stiffness through a dedicated experimental setup for ballast behavior analysis. Using materials from an actual track, contamination levels from clean to 30 % were simulated, and an empirical formulation of contaminated ballast stiffness was derived based on laboratory tests. Moreover, numerical sensitivity analyses were conducted to explore the impacts of ballast contamination on the dynamic behavior of track components. The findings indicate a significant increase in dynamic track responses up to a 30 % contamination level, based on gravimetric measurements, leading to substantial increases in maximum absolute accelerations of sleeper and ballast layer as well as exerted forces on the ballast layer by about 28 %, 21 %, and 46 %, respectively.