高速铁路级配碎石填料振动压实劣化机制研究

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

揭示振动荷载下高速铁路路基级配碎石填料压实劣化的影响机制对提高路基服役性能具有重要意义。首先,采用智能振动压实仪开展级配碎石填料振动压实试验,探究级配碎石填料物理指标干密度ρd、力学指标动刚度K与振动压实劣化的相关性;其次,对不同振动压实阶段的级配碎石填料进行X-CT(X-ray Computed Tomography)扫描试验,揭示级配碎石填料振动压实劣化的主控因素;最后,基于劣化主控因素建立不同劣化程度的高精度三维振动压实离散元模型,探究级配碎石填料压实劣化与主控因素的内在联系,进而深入揭示级配碎石填料振动压实劣化的细观机制。研究结果表明:振动压实过程中,可通过动刚度K曲线的“拐点”表征级配碎石填料振动压实劣化状态;通过X-CT试验明确级配碎石填料振动压实劣化的主控因素为粗颗粒研磨破碎,进一步提出研磨度DF指标量化级配碎石填料的压实劣化程度;振动压实离散元模型中级配碎石填料的细观结构演化特征表明,随着DF的增加,填料各向异性、力学配位数、粗颗粒接触力均逐渐减小,从而使级配碎石填料的内部结构稳定性和动刚度K减小,且当DF≥0.68时,各向异性、力学配位数、粗颗粒接触力链与动刚度K减小速率均降低。研究结果对高速铁路路基级配碎石填料的振动压实质量控制具有重要指导意义。

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.