Improved Performance of Railway Ballast under Impact Loads Using Shock Mats

Impact loads generated because of wheel and rail defects cause accelerated ballast breakage leading to adverse performance of ballasted rail tracks. In the present study, experimental and numerical investigations have been carried out to develop an understanding of the performance of shock mats in the attenuation of dynamic impact loads and subsequent mitigation of ballast degradation. The investigations include different locations of shock mats considering stiff and weak subgrade conditions. With the provision of shock mats, the magnitude of impact forces decreases, and the time duration of impact ges prolonged. In the case of stiff subgrade, the efficiency of the shock mat in reducing the impact forces is greater when it is located at the bottom of ballast rather than at the top, whereas the reverse is true for weak subgrade. However, the provision of shock mats both at the top and bottom of the ballast bed, irrespective of the subgrade condition, is the best solution for minimising the impact force. The shock mats can bring down the impact-induced strains in the ballast bed by as much as 50%, apart from substantially reducing the ballast breakage. DOI: 10.1061/(ASCE)GT.1943-5606.0000598. (C) 2012 American Society of Civil Engineers.