Dynamic response of stabilized cinder subgrade during train passage

Abstract Cinder (scoria) is a promising and low-cost fill material for ballasted track substructures with soil stabilization techniques. However, the comprehensive dynamic assessment of its suitability as railway aggregate is insufficient. In this paper, natural cinder and local fine-grained soil as its stabilizer were first tested for their basic properties. Permeability and consolidated drained dynamic triaxial tests were conducted on their mixtures at two blend ratios (2:1 and 3:1). Then, a field monitoring program was performed at two test sections in the Addis Ababa–Djibouti Railway, Ethiopia, using embedded pressure cells and integrated vibration sensors over the subgrade surface. Signals of dynamic stress, displacement, velocity, and acceleration were recorded during train passages at speeds between 5 and 100 km/h. A comparison was made between the dynamic responses of the earth structures constructed using stabilized cinders and traditional geomaterials. The longitudinal distribution of measured vertical stress was captured by an empirical formula incorporating normalized Gaussian functions, which was employed for a rough estimation of rail seat loads. Impact of train speed on subgrade vibrations in terms of four recorded signals was ultimately revealed with statistical analyses. Results from laboratory tests and field monitoring demonstrated that stabilized cinder generally outperforms the baseline fill due to better dynamic stability of the constructed facilities.