| 基于微结构量化的含渐变带黄土各向异性特征研究 |
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| 引用本文： | 包含,马扬帆,兰恒星,彭建兵,张科科,许江波,晏长根,孙强.基于微结构量化的含渐变带黄土各向异性特征研究[J].中国公路学报,2022,35(10):88-99. |
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| 作者姓名： | 包含 马扬帆 兰恒星 彭建兵 张科科 许江波 晏长根 孙强 |
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| 作者单位： | 1. 长安大学 公路学院, 陕西 西安 710064;2. 长安大学 地质工程与测绘学院, 陕西 西安 710054;3. 中国科学院地理科学与资源研究所资源与环境信息系统国家重点实验室, 北京 100101;4. 西安科技大学 地质与环境学院, 陕西 西安 710054 |
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| 基金项目： | 国家自然科学基金项目(41790443，41927806，42041006);西安市科协青年人才托举计划项目(095920201310)； 中央高校基本科研业务费专项资金项目(300102212213) |
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| 摘 要： | 黄土层间界面稳定性问题突出，天然黄土层之间的交界面呈现渐变过渡形式。为研究黄土渐变带及相邻两土层的各向异性特征，以含黄土层、古土壤层以及两者之间渐变带的早更新世(Q1)黄土为例，通过扫描电镜(SEM)获取各土层不同方向上的微观图像。对图像进行二值化处理，计算形状系数F、形态分维数D、概率熵Hm及定向频率Pi(α)等微观结构参数，分析3种典型土层在微观结构上的各向异性。此外，通过三轴压缩试验获得各土层不同方向上的抗剪强度参数，将微观结构参数和抗剪强度参数相结合，探究了两者之间的联系，揭示含渐变带Q1黄土的各向异性差异表现。结果表明：①各土层微观结构均具有显著的各向异性，当平行于沉积方向时，孔隙和颗粒排列的定向性最好，与沉积方向45°斜交及相垂直时次之，但受风化作用影响各向异性表现程度有所差别；②当加载方向与沉积方向平行时，各土层的强度表现最高，而垂直时则最低，这种各向异性主要源于黏聚力的差异，并且会随着围压和含水率的增大而减弱；③黄土层和古土壤层的力学各向异性与内部微观结构的各向异性关系紧密，但是在渐变带土层中，这种关联性却表现较弱；④渐变带土层的力学规律性和整体强度均明显弱于上下土层，是土体力学稳定需要关注的重要层位。
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| 关 键 词： | 道路工程 土层渐变带 Q1黄土 各向异性 微观结构 强度参数 |
| 收稿时间： | 2021-07-12 |
Anisotropic Characteristics of Loess with Gradation Zone Based on Microstructure Quantification |
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| BAO Han,MA Yang-fan,LAN Heng-xing,PENG Jian-bing,ZHANG Ke-ke,XU Jiang-bo,YAN Chang-gen,SUN Qiang.Anisotropic Characteristics of Loess with Gradation Zone Based on Microstructure Quantification[J].China Journal of Highway and Transport,2022,35(10):88-99. |
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| Authors: | BAO Han MA Yang-fan LAN Heng-xing PENG Jian-bing ZHANG Ke-ke XU Jiang-bo YAN Chang-gen SUN Qiang |
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| Affiliation: | 1. School of Highway, Chang'an University, Xi'an 710064, Shaanxi, China;2. School of Geological Engineering and Geomatics, Chang'an University, Xi'an 710054, Shaanxi, China;3. State Key Laboratory of Resources and Environmental Information System, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China;4. College of Geology and Environment, Xi'an University of Science and Technology, Xi'an 710054, Shaanxi, China |
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| Abstract: | The stability of the interface between loess layers is an important issue, and the interface between natural loess soil presents a gradual transition from loess layer to paleosol layer. To study the anisotropy of the loess gradation zone and its two adjacent soil layers, the early Pleistocene (Q1) loess, which includes a loess layer, a paleosol layer, and the gradation zone between them, was considered as an example, and the microscopic images of each soil layer in different directions were obtained by scanning electron microscope (SEM). The images were binarized, and the microstructure parameters such as shape coefficient F, shape fractal dimension D, probability entropy Hm, and orientation frequency Pi(α) were calculated and used to analyze the microstructure anisotropy of three typical soil layers. In addition, the shear strength parameters in different directions of each soil layer were obtained using a triaxial compression test. The relationship between the microstructure parameters and shear strength parameters was explored, and a difference in the anisotropy of Q1 loess with the gradation zone was observed. The following results were obtained: ① The microstructure of each soil layer has significant anisotropy, and the directionality of pores and particles with respect to the deposition direction is high in the following order: parallel > 45° oblique intersection > perpendicular. However, the degree of anisotropy affected by weathering differs. ② When the loading direction is parallel to the deposition direction, the strength of all three soil layers is the highest, whereas when it is vertical, it is the lowest. This anisotropy is mainly due to the difference in cohesion and decreases with an increase in the confining pressure and water content. ③ The mechanical anisotropy of the loess and paleosol layers is closely related to the anisotropy of the internal microstructure, but the correlation is weak in the gradation zone. ④ The mechanical regularity and overall strength of the soil in the gradation zone are weaker than those of the upper and lower soil layers. Addressing this issue is important for ensuring mechanical stability. |
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| Keywords: | road engineering gradation zone of soil layer Q1 loess anisotropy microstructure strength parameter |
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