Based on the methods of X-ray computerized tomography (X-CT ) , mercury intrusion porosimetry (MIP),scanning electron microscopy(SEM),nuclear magnetic resonance(NMR) and frost heaving tests on the coarse grained soil filling for the subgrade of high-speed railway in extremely cold areas , the micro struc-ture and frost heaving features of the coarse grained soil filling sample with different levels of fine-grain were studied . It is found that the distribution of fine-grain in the coarse grained soil filling showed obvious cluster characteristics and the water content mainly existed in the fine-grain cluster structure . The correlation among the fine-grain content , cluster ratio and frost heaving ratio was established . Results show that the fine-grain cluster ratio increases linearly with the increase of fine-grain content . When the fine-grain content is between 3% and 15% , the cluster ratio increases fastest . As the main water holding structure of pore water , the small and medium sized pores below 100μm are mainly distributed in the fine-grain clusters . The correlation between the frost heaving rate of the filling and the fine-grain cluster ratio is linear . When the cluster ratio is above 2% , the frost heaving ratio increases rapidly . When the cluster ratio is above 8% and the corresponding fine-grain content is above 15% , the frost heaving ratio will exceed 1% . This paper proposes for the first time the fine-grain cluster ,its distribution and the water holding features ,which can be used to explain the interaction mechanism of fine-grain in the frost heaving of coarse grained soil filling .%采用X-CT、压汞、扫描电镜、核磁共振、冻胀试验等方法,研究不同细颗粒含量下严寒地区高速铁路路基粗颗粒填料的微观结构及冻胀特性,发现填料中细颗粒分布具有明显的簇团特征,水分主要存在于簇团结构中,冻胀率、簇团率、细颗粒含量之间呈显著的线性关系.试验结果表明:簇团率随着细颗粒含量的增加线性增大,当细颗粒含量在3%~15%时,簇团率增长最快;100μm以下的中小孔隙作为孔隙水的主要持水结构主要分布于簇团中;填料的冻胀率与簇团率呈线性关系,簇团率超过2%后冻胀率快速增大,当簇团率超过8%、对应的细颗粒含量超过15%时,冻胀率将超过1%.本文提出细颗粒簇团及其分布与持水特征,可以用于解释细颗粒在粗颗粒填料冻胀中的作用机理.
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