Macro- and micro- deterioration mechanism of high-speed railway graded gravel filler during vibratory compaction

Abstract

This study aims to explore the impact mechanism of the vibratory compaction deterioration in high-speed railway graded gravel (HRGG) fillers, which can contribute to the control compaction quality and enhance the service performance of subgrade. Firstly, vibratory compaction experiments were conducted with HRGG fillers using the intelligent vibratory compactor to reveal the vibratory compaction deterioration from the evolution of the dry density ρd, dynamic stiffness Krd. Secondly, X-ray computed tomography (X-CT) scan tests were conducted with the fillers of different compaction stages. Then, the evolution of coarse particle shape characteristics was obtained to reveal the key controlling factor of compaction deterioration. Finally, the high-precision 3D vibratory compaction discrete element method (DEM) models were established for different deterioration degrees. The micro-indicators, such as the coordination number, contact force chains, and fabric anisotropy were investigated to explore the inherent relationship between the compaction deterioration and the key controlling factor. The results showed that the Krd gradually decreased at the compaction deterioration. Additionally, it was found that the key controlling factor for compaction deterioration was the abrasion of coarse particles. From the DEM simulations with different compaction deterioration degrees (CDDS), the dynamic stiffness Krd decreased with increasing CDDS, which was consistent with the results of the vibratory compaction experiments. Moreover, it was observed that the micro-indicators exhibited a decreasing trend with increasing CDDS, indicating a decrease in the ability of coarse particles to wrap fine particles and particles interlocking, which disrupts the ability of the particle skeleton to withstand external loads. This study not only provides a novel approach to investigate the deterioration mechanism during vibratory compaction but also establishes a new theoretical basis for the controlling compaction quality of HRGG fillers.