Abstract
Practical assessment of subgrade settlement induced by train operation requires developing suitable models capable of describing permanent deformation characteristics of subgrade filling under repeated dynamic loading. In this paper, repeated load triaxial tests were performed on coarse-grained soil (CGS), and the axial permanent strain of CGS under different confining pressures and dynamic stress amplitudes was analysed. Permanent deformation behaviors of CGS were categorized based on the variation trend of permanent strain rate with accumulated permanent strain and the shakedown theory. A prediction model of permanent deformation considering stress state and number of load cycles was established, and the ranges of parameters for different types of dynamic behaviors were also divided. The results indicated that the variational trend of permanent strain rate with accumulated permanent strain can be used as a basis for classifying dynamic behaviors of CGS. The stress state (confining pressure and dynamic stress amplitude) has significant effects on the permanent strain rate. The accumulative characteristics of permanent deformation of CGS with the number of load cycles can be described by a power function, and the model parameters can reflect the influence of confining pressure and dynamic stress amplitude. The study’s results could help deepen understanding of the permanent deformation characteristics of CGS.
Highlights
Heavy haul railways have been internationally-recognized as the future direction of freight transportation because of their higher transport capacity and efficiency, lower energy consumption, and transport cost [1], and the development of heavy haul freight transportation has become a recent focus of China’s railway construction
Practical assessment of subgrade settlement induced by train operation requires developing suitable models capable of describing permanent deformation characteristics of subgrade filling under repeated dynamic loading
The results indicated that the variational trend of permanent strain rate with accumulated permanent strain can be used as a basis for classifying dynamic behaviors of coarse-grained soil (CGS)
Summary
Heavy haul railways have been internationally-recognized as the future direction of freight transportation because of their higher transport capacity and efficiency, lower energy consumption, and transport cost [1], and the development of heavy haul freight transportation has become a recent focus of China’s railway construction. The Code for Design of Heavy Haul Railway [2] issued by the State Railway Administration of China in 2017 is China’s first industry standard for heavyhaul railway. In order to avoid common issues in subgrade of heavy haul railways such as mud pumping, the code has recommended the use of coarse-grained soil (CGS) due to several reasons, including reducing deformation, controlling horizontal and vertical movement of railway foundations, providing better drainage and structural support for subgrade bed in the construction of heavy haul railway subgrade in China [3,4,5].
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