高铁路基粗颗粒土非饱和水力学及微观特性研究

高铁路基粗颗粒土的水力学特性对路基内部水分运移及路基的长期累积变形有重要影响。采用了一种新型TDR与大直径渗透柱装置研究了不同压实度下高铁路基粗颗粒土的水力学特性,推导了考虑双层孔隙结构的不同干密度下的土水特征曲线模型。同时,由于土体的水力学特性与其微观结构密切相关,将水力学测试结果与扫描电镜实验以及压汞试验结果进行了对比分析。实验结果表明,随着压实度的增加,低吸力下,细粒含量为15%的路基填料的体积含水率降低,在高吸力下,体积含水率趋于一致。土体的微观特性结果显示,细粒含量为15%的路基填料中表现出双层孔隙结构,随着压实度的增加,大孔隙结构逐渐被压缩,而小孔隙结构则难以被压缩。微观测试结果与水力学测试结果一致,解释了不同压实度下路基填料的水分运移规律。

Microstructural and hydraulic properties of compacted high-speed rail subgrade coarse soils

The hydraulic characteristics of coarse-grained soils of high-speed railway subgrade profoundly affect the internal moisture migration and long-term accumulative deformation of the subgrade. A new TDR sensor and large-diameter preamble column testing devices are developed to study the hydraulic properties of the compacted coarse materials used in high-speed railways. In addition, the hydraulic properties is highly relate to the corresponding microstructure, and a new soil-water characteristic curve model which can consider the initial density of soils with dual-pore structure is proposed. The hydraulic properties are compared with those of the microscopic tests (scanning electron microscopy test and mercury injection test). The experimental results show that with the increase of compaction degree, the volumetric water content of subgrade filler with fine particle content of 15% decreases under low suction, however, it tends to be consistent under high suction. The microscopic characteristics of the soils show that the roadbed filler with a fine particle content of 15% exhibits a dual-pore structure. As the degree of compaction increases, the macroporous structure is gradually compressed, while the micropore structure is difficult to be compressed. The microscopic test results are found to be consistent with the hydraulic ones, indicating the water transport laws of the roadbed filler under different compaction degrees are still valid.