饱和细粒土固结过程中微观结构研究

饱和细粒土物质组成复杂且结构尺度跨度大，受压后微观结构的变化可反映宏观力学行为。借助室内试验（压汞试验、计算机断层扫描技术）及数值模拟方法（数据约束模型），建立饱和细粒土微观结构三维模型，实现土体物质组分和尺度的初步概化与分类。并尝试从微观结构和微宏观定量联系方面解释固结压力对饱和细粒土微观结构的影响，从而探讨饱和细粒土固结时的微宏观特征，确定固结压力过渡值。目前微纳米级小尺度团聚体的定量信息无法采用其他方法获取，但采用数据约束模型分析方法可以揭示孔隙和矿物团聚体的大小和数量随压力变化的敏感性。固结压力中400 kPa是压力过渡值，显示土体固结过程中孔隙收缩速度变慢，矿物团聚速度显著增加。饱和细粒土承受大于400 kPa以上的压力后，孔隙和矿物连通体的多尺度组合特征变得稳定。结合土体压缩变形特征，推测饱和细粒土蠕变界限在400 kPa左右，对应着土体结构破坏的临界压力。所采用的数据约束模型方法在突破微米级尺度后可实现微纳米尺度分析，可供其他工程材料研究参考。

Study on microstructure during consolidation process of saturated fine-grained soil

The composition and scale of saturated fine-grained soil are varied, and microscopic characteristics of saturated fine-grained soil in compression could reflect macroscopic mechanical property. Based on laboratory experiments (MIP and X-Ray μCT) and numerical simulation test (data constrained model, abbreviated as DCM), we built a 3D microstructure model of the saturated fine-grained soil. In addition, the multi-scale and compositions of soil samples were generalized and classified preliminarily. Considering microstructure and the quantitative relation between micro and macro, we studied the influence of consolidation pressure on microstructure of saturated fine-grained soil. The mechanical behavior in consolidation was discussed from the perspective of microstructure, and the transition value of consolidation pressure was determined. The DCM used in this study can reveal the variation sensitivity of size and number of pore clusters and mineral clusters to the pressure, which could not be realized by other methods. The results showed that 400kPa was the pressure transition value, indicating that the shrinkage rate of pore became slower and the rate of mineral agglomeration increased significantly. The multi-scale characteristics of pore and mineral clusters became stable when the pressure was greater than 400kPa. Combined with compression deformation characteristics, we deduced that critical pressure of soil structure failure was 400kPa, which was also the creep boundary of the saturated fine-grained soil. The DCM method can realize nano-scale analysis, providing reference for other engineering materials.