Research on micro-influence mechanism of fine particles on dynamic characteristics of graded macadam materials in heavy-haul railway subgrade beds

Fine particle content is an important physical state parameter of graded macadam materials used in heavy-haul railway subgrade beds. Understanding the micro-influence mechanism of the fine particle content on the filler’s dynamical characteristics is of great significance. In this study, the granular system generation logic in PFC3D software was modified to enhance efficiency and quality, and the three-dimensional discrete element numerical model of graded macadam materials dynamic triaxial specimen was established. The servo program was used to simulate the dynamic triaxial numerical test confining pressure and dynamic loading conditions. A series of laboratory tests were performed using a GCTS large-scale cyclic triaxial test system to calibrate and verify the numerical model. Finally, dynamic triaxial numerical tests were conducted for graded macadam materials with different fine particle contents. These tests had the aim of determining the variation law for the contact force chain distribution, mechanical coordination number, average rotational angular velocity, and energy dissipation of the specimens under cyclic loading with the increase of fine particles and then revealing the influence mechanism of fine particles on the dynamic characteristics of graded macadam materials used in heavy-haul railway subgrade beds from a microscopic perspective. The study’s findings serve as a framework for describing the mechanism of subgrade bed disease occurrence and proposing effective remediation measures.