Influence of sleeper geometry on the lateral resistance of bamboo sleepers

This study investigates the effects of bamboo sleeper geometry on lateral track resistance in ballasted railway systems using the Discrete Element Method (DEM), where ballast is modeled as clumped spherical particles with Hertz-Mindlin contact model for non-linear stiffness. Four sleeper geometries, including traditional rectangular, dumbbell, rectangular-winged, and wedge-winged, were analyzed to evaluate their interaction with ballast under lateral loading. The Single Tie Push Test (STPT) procedure was used to measure lateral resistance, with lateral forces applied via a hydraulic jack. The results highlight that sleeper geometry significantly affects lateral resistance, with optimized designs (rectangular- and wedge-winged) achieving the highest resistance values. For the rectangular-winged sleeper, lateral resistance peaked at 6.85 kN, representing a 54% improvement over the traditional rectangular shape. The study also examines the contributions of ballast components (base, crib, and shoulder) to the overall lateral resistance. Base resistance dominated for all geometries but decreases as the crib and shoulder contributions increase with the non-traditional designs. Normal and tangential force distributions within the ballast were also analyzed, showing enhanced interparticle contact for the winged designs. Overall, the rectangular-winged sleeper was found to provide higher performance compared to the traditional prototype sleeper with respect to meeting track requirements for lateral stability.