Mechanical behaviors of the geocell reinforced graded aggregates under train loading: Based on Indoor tests and DEM

Usually, a graded-aggregates layer with a given thickness is laid between a rigid subgrade (box subgrade, pile-plank subgrade) and a ballastless track structure. Such a configuration is realized to achieve features such as dynamic buffering, vibration reduction, energy dissipation, and limitation of uneven settlement. Geocells are typically used to reinforce the graded aggregates layer by enhancing its strength and stiffness. A dynamic test device was independently developed to investigate the mechanical behavior of geocell-reinforced graded aggregates under train loading. The test device can simulate the cyclic train loading and lateral confining pressure on graded aggregates. Subsequently, a comparative test of graded aggregates with geocell and without geocell was carried out by using the device. The above said experiments were simulated by a 3D discrete-element approach that considered the actual shape of the graded aggregate particles. The macroscopic mechanical property changes of graded aggregate under train loads were analyzed from microscopic behaviors such as particle contact and particle migration. This study is intended to provide a basis for optimizing and improving the dynamic performance and evaluation of the ballastless track sandwich subgrade with an upper rigid layer, a middle flexible layer, and a lower rigid layer during long-term service.