Numerical investigation of the behavior of stone ballast mixed by steel slag in ballasted railway track

Recently, implementing steel slag ballast has been proposed as an appropriate material to substitute stone ballast. In this regard, one of the technical concerns is the behavior of steel slag ballast in both time and frequency domains that needs to be assessed, properly. Furthermore, the combination of stone ballast and steel slag is unavoidable in steel slag ballasted tracks during track maintenance concerning the limitation of steel slag resources. Therefore, this paper suggests an optimal stone ballast-steel slag (SB-SS) combination regarding the dynamic behavior of five SB-SS combinations as 0%SS, 25%SS, 50%SS, 75%SS and 100%SS by weight of ballast using a finite element method (FEM) model of a 50-meter test track. Moreover, using elasticity modulus and Moher-coulomb parameters obtained via a series of plate load and shear strength tests for each SB-SS combination turns FEM model to be more close to the real test track results. Experimental results show that adding steel slag particles to stone ballast increases elasticity modulus and friction angle of ballast layer resulting in the improvement of mechanical behavior of railway track. Consequently, the maximum deflections and root mean square (RMS) of accelerations decrease by increasing steel slag content. Analyzing free vibration of ballast layer combinations reveals that damping ratios of 100%SS ballast layer is the maximum value as 0.25 followed by 75%SS, 50%SS, 25%SS and 0%SS combinations. Moreover, the dominant frequencies of each ballast layer combinations determine that 0%SS, 25%SS and 50%SS coincides within the track excitation frequency range made by wheel sets, while 75%SS and 100%SS are out of which. Finally, according to all results, 75%SS ballast layer is proposed as the optimal SB-SS combination.