Behaviour of coal-fouled elastomeric polyurethane-stabilized ballast under cyclic loading

The current study assesses the deformation and degradation behaviour of geogrid and elastomer-stabilized coal fouled ballast under cyclic loading with frequencies ( f) ranging from 15 to 35 Hz. Different percentages of coal were added to ballast to have void contamination index (VCI) in the range of 0–45%. Test results confirmed that the deformation and degradation behaviour of ballast was highly affected by the presence of coal fines. The elastomer-stabilized ballast (ESB) exhibited lower deformations and degradation when compared to geogrid-stabilized (GSB) and unstabilized ballast (USB). The effectiveness of geogrid/elastomer in arresting the spread of ballast along its depth is evaluated in terms of the stabilization efficiency factor ( S ef, cyc ). The S ef, cyc of clean GSB is computed to be 0.107, whereas the S ef, cyc of clean ESB is 0.811. The S ef, cyc of GSB decreased significantly with the increase in VCI but in case of ESB the reduction is only marginal. Further, the resilient modulus ( M r ) and damping ratio ( D) of ballast reduced due to coal fouling. The elastomer has significantly improved resilient modulus ( M r ) and damping ratio ( D) of ballast when compared to GSB. Moreover, the extent of lateral and vertical deformations was found to be influenced by the interface shear strength as obtained under direct shear conditions. In addition, empirical models were developed to predict deformation, breakage and resilient modulus of ballast as functions of loading frequencies and VCI.