Degradation mechanism of vibratory compaction of high-speed railway graded gravel fillers

It is of great significance to reveal the mechanism of compaction deterioration of graded gravel fillers in high-speed railway subgrade under vibratory loading for enhancing the service performance of the subgrade. Firstly, vibratory compaction experiments on graded gravel fillers were conducted using an intelligent vibratory compactor, which explored the correlation between the physical parameter-dry density ρd and the mechanical parameter-dynamic stiffness K of graded gravel fillers, and the compaction deterioration. Secondly, X-ray Computed Tomography (X-CT) scanning experiments were conducted on graded gravel fillers at different stages of vibratory compaction, revealing the key controlling factors of vibratory compaction deterioration. Finally, a high-precision three-dimensional discrete element model of vibratory compaction with varying degrees of deterioration was established, which based on the key controlling factors of vibratory compaction deterioration. This model was used to explore the intrinsic relationship between the compaction deterioration of graded gravel fillers and the key controlling factors, further revealing the micro-mechanism of vibratory compaction deterioration of graded gravel fillers. The research results indicate that the “inflection point” on the K curve can characterize the compaction deterioration state of graded gravel fillers during vibratory compaction. The X-CT experiments can reveal that the key controlling factors of vibratory compaction deterioration of graded gravel fillers is the abrasion crushing of coarse particles. Furthermore, the abrasion degrees DF is proposed to quantify the degree of compaction deterioration of graded gravel fillers. The evolution characteristics of the microstructure of graded gravel fillers in the model of vibratory compaction can indicate that with the DF increasing, the anisotropy, mechanical coordination number, and contact force of coarse particles gradually decrease, which further reduces the internal structural stability and K of the graded gravel. Moreover, when DF ≥0.68, the reduction rates of anisotropy, mechanical coordination number, contact force chain of coarse particles, and K all decrease. The research results have great guiding significance for the compaction quality control of graded gravel fillers in high-speed railway subgrade. © 2024, Central South University Press. All rights reserved.