Ballast Stabilization with Polyurethane for Use in Desert Areas

Sand dune accumulation in the railways passing through desert areas leads to ballast softening and settlement, which is one of the major challenges in the ballast maintenance operation. In this regard, ballast infilling with polyurethane could be mentioned as a novel solution that has been less attentional in previous studies. In this matter, in present study using a domestic cost-effective polyurethane, the ballast stabilization has been accomplished and the relevant shear strength parameters have been investigated via a series of large-scale direct shear tests. Since the utilized polyurethane has composed of two different components, in the first stage, the best weight ratios of components have been investigated via a series of compression tests. In this matter, the ratio of 1.5 units polyol to 1 unit isocyanate has been adopted as the best composition. Then, the resulting polyurethane was injected into the ballast to perform large-scale direct shear tests. According to the measurement results, the maximum shear stress, the internal friction angle, and the cohesion coefficient increased by 109%, 9.5%, and 162.5% with respect to the non-stabilized ballast (NSB), respectively. In addition, the dilation angle decreased by 66.4% with the injection of polyurethane into the ballast. Hence, the results indicate increased shear strength and lateral track resistance in the presence of polyurethane, which can prevent lateral deflection and improve track safety. In other words, the mentioned polyurethane has improved the shear parameters of the ballast more significantly than other polyurethanes and has shown its performance in increasing the bearing capacity.