【摘要】 中低压缩性黏土作为高速铁路的天然地基，呈现出较好的沉降控制效果，但该类土在压缩变形过程中的变形特性难以用传统排水固结理论解释，限制了其在工程实践中应用。为系统揭示其液-固-气三相演化机制，以合肥地区该类土质为研究对象，开展高精度压缩排水、强弱结合水含量、土-水特性及微观孔隙结构试验。结果表明：中低压缩性黏土在加载初期变形迅速、收敛速度快，加载后0.5 h内变形比例达80%，孔隙水排出极少，呈现出明显的非典型排水变形特征；结合水占天然含水率的74.4%，其中强结合水为32.7%、弱结合水为41.7%，自由水比例虽达6.0%（占天然含水率的25.6%），但因毛细吸力主导、水力梯度不足及孔隙结构受限等原因，难以从孔隙中有效排出；颗粒破碎细化导致粒径小于2μm的颗粒含量从8.1%上升至15.3%，大孔隙压缩转化为小孔隙，0.2μm以下的小孔隙比例提升至25.4%，形成颗粒细化、孔隙压缩、结构致密的微观重构特征。中低压缩性黏土在外荷载作用下的压缩变形过程，是固相重组、液相吸附与孔隙压缩三者协同演化的结果，为该类土地基在高速铁路中的变形控制提供了微观依据与理论支撑。更多还原

【Abstract】 Medium-low compressible clays are used as natural foundations for high-speed railways(HSR), demonstrating favorable settlement control. However, their deformation characteristics during compression are difficult to explain by conventional drainage-consolidation theory, limiting their engineering application. This study focuses on such soils in the Hefei area, conducting high-precision compression drainage tests, measurements of strongly and weakly bound water content, soil-water characteristic curve(SWCC) tests, and microstructural pore analyses. The research systematically reveals their liquid-solid-gas phase evolution mechanism. The results indicate that: Medium-low compressible clay exhibits rapid deformation and fast convergence during initial loading, with approximately 80% of the total deformation occurring within 0. 5 hour after loading and minimal pore-water drainage, showing distinct atypical drainage deformation behavior; Bound water accounts for 74. 4% of the natural water content(strongly bound: 32. 7%; weakly bound: 41. 7%). Although free water constitutes 25. 6% of the natural water content(6. 0% of total water), its effective drainage is impeded due to dominant capillary suction forces, insufficient hydraulic gradient, and the constraints of the pore structure. Particle fragmentation and refinement increase the content of particles smaller than 2 μm from 8. 1% to 15. 3%. Compression leads to the conversion of larger pores into smaller ones, increasing the proportion of pores smaller than 0. 2 μm to 25. 4%. Results signify a microstructural restructuring characterized by particle refinement, pore compression, and structural densification. The compression deformation process of medium-low compressible clays under external loading results from the co-evolution of solid-phase reorganization, liquid-phase adsorption/retention, and pore compression, providing a micro-scale basis and theoretical support for deformation control of such soil foundations in high-speed railways.更多还原