An analysis of microstructure changes in sand grain mucky soil of Dongting Lake during consolidation
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摘要: 砂纹淤泥质土是一种特殊的夹有微薄层粉细砂的洞庭湖湖相沉积软土，具有独特的薄砂层构造。该软土固结过程中的微观结构变化，对解释宏观的工程现象、揭示土体变形的本质和采取合理的地基处理措施具有重要意义。本文利用X射线微区衍射试验和扫描电子显微镜试验，研究洞庭湖砂纹淤泥质土的矿物成分和微观结构，同时结合固结试验探讨砂纹淤泥质土微观孔隙与结构单元体参数变化特征。研究结果表明：洞庭湖砂纹淤泥质土主要矿物成分为绿泥石、白云母和石英，微观结构为片状或板状聚体结构；随着固结压力增加，等效粒径增长呈先快速后放缓的规律，结构单元体形态参数则先增大后减小；砂纹淤泥质土压缩系数与竖直切面结构单元体定向概率熵呈明显负相关关系。Abstract: Sand grain mucky soil is a special type of lacustrine sedimentary soft soil in the Dongting Lake area with a modest layer of fine silty sand. Analysis of the microstructure changes in the soil during consolidation can explain the engineering phenomenon on a macro level, and sheds light on the nature of soil deformation. In this study, X ray diffraction test and scanning electron microscope test are conducted to observe the mineral compositions and the microstructure of the sand grain mucky soil, and the change in microstructure parameters of the sand grain mucky soil during consolidation. The results show that (a) the sand grain mucky soil is primarily composed of chlorite, muscovite and quartz, and its microstructure is flake and tabular; (b) as the consolidation pressure increases, the increasing rate of the equivalent particle size is higher in the early stage than that in the later stage, and the morphological parameter of structural units increases first, and decreases later; and (c) there is negative correlation between the compressibility and probability entropy of structural units of the sand grain mucky soil.
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