Dynamic mechanical performance of geogrid–waste tyre-reinforced railway ballast under cyclic loading

Abstract

The accumulation of permanent deformation under cyclic loading in the granular bed is the main source of ballast track settlement. Therefore, studying the dynamic mechanical behaviour of reinforced railway track beds under cyclic loading is crucial. To reduce the accumulated of permanent deformation of railway track bed, geogrids–waste-tyre reinforced railway track bed was used to study in order to effectively control the permanent deformation of ballasted railway track bed. The test was conducted to investigate the mechanism of permanent deformation of geogrid–waste tyre-reinforced railway track bed through the evolution of cumulative plastic strain, permanent strain rate and dynamic elastic modulus of railway track bed under different confining pressures, dynamic stress amplitude, and amount of reinforcement. Results show that geogrid and waste tyre reinforcement have significant effects on the accumulated permanent deformation of the railway ballast. Geogrid reinforcement is better than waste tyres in improving the performance of the ballast fill. Reinforcement with geogrid significantly reduces the permanent strain rate, although the impact on this rate varies depending on the position and amount of reinforcement used. Notably, reinforcing the middle three layers of the track bed sample with waste tyres substantially decreases the permanent deformation rate. In contrast, the application of reinforcement across all five layers with waste tyres increases the permanent deformation rate. The dynamic elastic modulus of the track bed sample not only increases significantly but also rises with the dynamic stress amplitude due to the reinforcement of the geogrid and the waste tyre. The dynamic elastic modulus gradually stabilises with the increase in cyclic loading, indicating a stable accumulated deformation in the railway track bed.