Abstract
Based on Biot's theory, a 2.5-dimensional finite element analysis model for the coupled track–subgrade–multilayer saturated soil foundation system was established, a calculation method for subgrade cumulative settlement considering actual cyclic train loading was proposed, and the influences of water level rise, train speed, and train axle load on the dynamic response and long-term settlement of the subgrade were analyzed. The research results indicate that: the amplification effect of water level rise on soil vibration intensity is not limited to the depth range of water level change, but leads to enhanced vibration throughout the entire subgrade and foundation cross-section; and this full-section vibration amplification effect intensifies with increasing train speed; when the water level rises into the subgrade, significant excess pore water pressure appears in the subgrade, reaching a maximum value of 27.52 kPa, causing a substantial decrease in effective stress and bringing the stress path of subgrade soil elements closer to the failure line; when the water level is located within the foundation, the cumulative deformation of the subgrade under cyclic train loading is relatively small, and the track settlement mainly originates from the foundation; when the water level rises into the subgrade, the subgrade cumulative deformation develops rapidly with increasing number of load cycles, reaching approximately 54 mm after 1 million loading cycles, far exceeding the allowable value, indicating that subgrade waterproofing has a restraining effect on the long-term evolution process of "failure"; furthermore, this paper also discusses the influence of train speed and train axle load on cumulative deformation, which increases significantly with increasing train axle load, and the effect of axle load increase on subgrade cumulative deformation is more pronounced compared to that on the foundation, requiring strict attention in design.
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Title: Influences of Water Level Rise on Dynamic Response and Long-Term Settlement of High-Speed Railway Subgrade
Authors: HU Jing¹, TANG Yue¹, ZHANG Jia-kang¹, JIANG Hong-guang², BIAN Xue-cheng³, DENG Tao¹
Affiliations:
¹ College of Civil Engineering, Fuzhou University, Fuzhou 350108, Fujian, China
² School of Qilu Transportation, Shandong University, Jinan 250002, Shandong, China
³ College of Civil Engineering and Architecture, Zhejiang University, Hangzhou 310058, Zhejiang, China
Abstract
Based on Biot's theory, this study establishes a 2.5-dimensional finite element analysis model for a coupled track-subgrade-multi-layer saturated soil foundation system and proposes a calculation method for subgrade cumulative settlement under actual train cyclic loading. The influences of water level rise, train speed, and train axle load on subgrade dynamic response and long-term settlement are systematically investigated. The results reveal that the amplifying effect of water level rise on soil vibration intensity is not confined to the depth range of water level variation, but rather enhances vibration throughout the entire subgrade and foundation cross-section. This full-section vibration amplification effect becomes more pronounced with increasing train speed.
When the water level rises into the subgrade, significant excess pore water pressure develops, reaching a maximum of 27.52 kPa, which causes a substantial reduction in effective stress and drives the stress path of subgrade soil elements toward the failure line. In cases where the water level remains within the foundation, the cumulative deformation of the subgrade under train cyclic loading is relatively small, and track settlement primarily originates from the foundation. However, when the water level rises into the subgrade, the cumulative deformation of the subgrade develops rapidly with increasing load cycles, reaching approximately 54 mm after one million loading cycles—far exceeding allowable limits. This demonstrates that subgrade waterproofing plays a critical role in constraining the long-term evolution of failure. Furthermore, cumulative deformation increases significantly with train axle load, and the effect of axle load increase on subgrade cumulative deformation is more pronounced than that on the foundation, warranting careful consideration in design.
Keywords: subgrade engineering, dynamic response, 2.5-dimensional finite element, water level rise, saturated foundation, long-term settlement