Investigation of the deformation and strength properties of fouled graded macadam materials in heavy-haul railway subgrade beds. (1st March 2021)

• Record Type: Journal Article
• Authors: Yang, Zhihao; Yue, Zurun; Tai, Bowen
• Is Part Of: Construction & building materials. Volume 273(2021)
• Publication Date: 2021-03-01
• Subjects: Heavy-haul railway subgrade bed -- Fouled graded macadam materials -- Critical dynamic stress -- Accumulative plastic strain -- Dynamic stress-strain relationship; Building materials -- Periodicals; 624.18
• DOI: 10.1016/j.conbuildmat.2020.121778
• Languages: English
• ISSNs: 0950-0618

Abstract

Highlights: Deformation and strength characteristics for FGM were investigated. The influence laws of F c on the hysteretic curve of FGM were revealed. An accumulative plastic strain prediction model of FGM was established. A dynamic stress-strain relationship calculation model of FGM was established. Abstract: Over the course of long-term operation, the graded macadam materials used in heavy-haul railway subgrade bed surfaces become polluted to different degrees. This fouling is due to its own breakage, the intrusion of external coal debris, sand blasting, dust, and other foreign materials that accumulate on the ballast along with rainwater seepage, and the internal-structure mud-pumping. This study had the goal of determining the variation law for the deformation and strength characteristics of fouled graded macadam materials under cyclic loading. First, graded macadam materials with different fine particle contents were prepared, and a series of dynamic triaxial tests were carried out using a GCTS large-scale cyclic triaxial test system. These initial tests were conducted to determine the mechanism for the coupled effect of the fine particle content, confining pressure, and dynamic stress amplitude on a specimen's accumulative plastic strain under cyclic loading. Using the plastic stability theory as a guideline, the dynamic deformation behaviours of specimens under different stress levels were determined, and a critical dynamic stress calculation model for specimens in the plastic creep state was established by considering the parameters of the confining pressure and fine particle content. Then, an accumulative plastic strain prediction model was established for specimens in the plastic creep state considering the stress level and fine particle content parameters, and a hardening index calculation model under cyclic loading was also established. At the same time, the physical significance of each parameter was clarified. Finally, a dynamic stress-strain relationship calculation model for fouled, graded macadam materials, which took into account the stiffness hardening under cyclic loading and stiffness degradation after fine particle intrusion, was constructed on the basis of a modified version of Iwan's series–parallel model. The research results provide a reference for evaluating the health of existing heavy-haul railway subgrades and will be useful for designing new subgrade structures that take into account the comprehensive control principle of strength and deformation.