Abstract
This study aims to explore the compaction deterioration micro-mechanism of high-speed railway graded aggregate (HRGA) fillers and further improve the compaction quality of HRGA fillers, contributing to improving subgrade service performance. Firstly, based on the vibratory compaction experiments, the compaction deterioration macro-characteristics of HRGA fillers with different gradations were revealed from the mechanical properties (i.e., dynamic stiffness Kd and subgrade reaction modulus K20). Secondly, X-ray Computed Tomography (X-CT) testing was conducted based on the multiple typical compaction stages selected from the Kd curve. The internal microstructure (i.e., particles and voids) characteristics within HRGA fillers with different gradations were measured by high-precision image processing approaches. Finally, the evolution characteristics of Kd, K20, and microstructure were used to reveal the compaction deterioration micro-mechanism of HRGA fillers with different gradations, and further explore the relationship between filler gradation and compaction deterioration. The results indicated that compaction deterioration characteristics of HRGA fillers with different gradations could be characterized by the inflection points of Kd and K20 curves. Besides, during compaction deterioration, particle abrasion crushing and the increase in surface edges and corners of the void reduced the stability of the skeleton structure within HRGA fillers with different gradations, resulting in a gradual decrease of Kd and K20. Furthermore, the relationship between Kd, K20, and microstructure with gradation could be quantitatively characterized by quadratic functions. Hence, based on X-CT measurement, it was feasible to reveal the compaction deterioration mechanism of HRGA fillers from macro- and micro-perspectives. This study contributes to establishing a theoretical framework for revealing the compaction deterioration of high-speed railway subgrade fillers and improving the quality of vibratory compaction for on-site subgrade construction.
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