Experimental study on dynamic properties of railway ballast mixed with tire derived aggregate by modal shaker test

Abstract

This article focuses on evaluating the dynamic behavior of ballast mixed with tire derived aggregate as an economic and environmental preserving method to obviate the rigidity problems in railway tracks. For this purpose, the ballast was mixed with 0, 11, 22, and 33 volume percentages of tire derived aggregate in a loading chamber and was examined under different types of dynamic loads such as Sweep sine imposed by a shaker on a rigid square plate. Considering the plate as rigid foundation resting on ballast mixed with tire derived aggregate as subgrade, frequency response functions of both foundation and subgrade were calculated by recorded accelerations and force using the installed accelerometers on loading plate and the wall of loading chamber and load transducer in shaker tip. The obtained results for pure ballast first proved that Sweep sine shaker test leads to more smooth spectra in comparison to other shaking methods. The obtained values for subgrade stiffness and damping ratio showed considerable decrease and increase with respect to increase in tire derived aggregate percentage in ballast mixture. As an optimum percentage of tire derived aggregate, values around 10 can be proposed for practical uses.