محمدحسين صيادي مانگ هلاتي

This study investigates the mechanical behavior of railway ballast under fouling conditions caused by the upward infiltration of a clay–water mixture from the subgrade, considering the effects of moisture content (time-dependent variation) an‎d fouling depth. Three key performance indicators—cumulative settlement, stiffness, an‎d damping ratio—were quantitatively eva‎luated. The experiments were conducted using a ballast box apparatus under cyclic loading conditions. For this purpose, clean ballast an‎d clay-contaminated (muddy) ballast specimens were prepared an‎d tested in three moisture states (dry, semi-fluid, an‎d fluid) an‎d two contamination depths (half-depth an‎d full-depth). The results showed that as the moisture content of the mud increased, the stiffness of the ballast decreased nonlinearly, while the settlement increased significantly. The damping ratio reached its minimum in the dry condition an‎d increased as the mud became more fluid; however, even in wet conditions, it remained lower than that of clean ballast. Comparison of different fouling depths revealed that in full-depth fouling, the reduction in stiffness an‎d the increase in settlement were more pronounced, indicating a substantial weakening of the load-bearing capacity of the ballast layer. In the most severe case—fully fluid mud throughout the ballast layer caused by the upward migration of clayey subgrade materials—the settlement was approximately three times greater, an‎d the stiffness was about half that of clean ballast. The findings of this research provide a quantitative framework for analyzing an‎d eva‎luating ballasted railway tracks under subgrade-induced fouling conditions an‎d demonstrate that clay infiltration an‎d mud accumulation in wet an‎d full-depth states lead to heterogeneous stiffness distribution, asymmetric settlements, an‎d geometric distortion of the track. Prolonged exposure to such conditions can result in increased maintenance frequency, degradation of ride quality, an‎d higher costs of track substructure an‎d superstructure maintenance.

بالاست راه‌آهن , گل‌زدگي ناشي از بستر , رس , بارگذاري چرخه‌اي , نشست , سختي , نسبت ميرايي , جعبه بالاست

Railway ballast , subgrade-induced fouling , clay , cyclic loading , settlement , stiffness , damping ratio , ballast box

Mohammad Hossein Sayyadi Manghelati

Morteza Esmaeili