非饱和Q<sub>3</sub>黄土微细观结构特征及对强度特性影响机制

韦雅之; 姚志华; 种小雷; 张建华

doi:10.11779/CJGE202111020

非饱和Q₃黄土微细观结构特征及对强度特性影响机制 English Version

1.
空军工程大学机场建筑工程教研室,陕西　西安　710038
2.
中国建筑西南勘察设计研究院有限公司,四川　成都　610052

基金项目:

国家自然科学基金项目 11972374

国家自然科学基金项目 51509257

详细信息

作者简介:
韦雅之(1994— ),女,博士研究生,主要从事机场规划及特殊土地基处理理论研究。E-mail：2651742406@qq.com

通讯作者:
姚志华, E-mail：lightbright@163.com

中图分类号: TU43
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- HTML全文浏览量: 24
- PDF下载量: 190
出版历程
- 收稿日期: 2020-12-15
- 网络出版日期: 2022-12-01
- 刊出日期: 2021-10-31

Microstructural properties of unsaturated Q₃ loess and their influence mechanisms on strength properties

1.
Dept. of Airdrome Construction Engineering, Air Force Engineering University, Xi’an 710038, China
2.
China Southwest Geotechnical Investigation & Design Institute Co., Ltd., Chengdu 610052, China

摘要

摘要: 结构性是影响非饱和原状黄土力学变形特征的重要因素,但鲜有从微细观与宏观相结合的角度分析原状与重塑黄土结构性差异的相关报道。以同一物理力学条件下的非饱和原状Q₃黄土及其重塑土为研究对象,进行控制吸力和净围压为常数的非饱和三轴剪切试验,并通过微细观扫描以揭示两者结构差异对强度特性的影响机制。试验表明原状和重塑Q₃黄土黏聚力c均随吸力增加呈线性增加趋势,且原状土黏聚力大于重塑土；内摩擦角受吸力影响较小,两者差异不大。原状黄土颗粒棱角明显,颗粒间为架空排列且具有良好胶结作用,结构性强并稳定；重塑黄土颗粒棱角浑圆,颗粒间为镶嵌接触且胶结作用破坏,土骨架作用不明显,结构性弱,形成的团粒结构易于压缩,团粒和颗粒联结不稳固,进而原状土具备更好的抵御外部剪切破坏的能力。同一物理条件下的原状和重塑黄土中孔径小于50 μm分别占试样总体积的22.7%和16.3%,50～200 μm孔径分别为71%和83.7%,大于200 μm分别为6.3%和0%。这表明支架大孔隙结构没有为原状土提供更大的变形空间,而良好的胶结作用和结构性保证了原状黄土具备较高的强度特征。
- 非饱和黄土 /
- 微细观 /
- 结构性 /
- 抗剪强度
Abstract: Structure is the important factor affecting the mechanical deformation characteristics of unsaturated undisturbed loess, but there are few reports on the structural differences between undisturbed and remolded loesses from the perspective of combining micro and macro-scopic views. Taking the unsaturated undisturbed Q₃ loess and its remolded soil under the same physical and mechanical conditions as the research objects, the unsaturated triaxial shear tests with the control suction and net confining pressure as constants are carried out, and the influence mechanism of the structural differences between the two on the strength characteristics is revealed by micro and meso-scopic scannings. The tests show that the cohesions of the undisturbed and remolded Q₃ loess increase linearly with the increase of matric suction, and the cohesion of the undisturbed soil is greater than that of the remolded soil. The angle of internal friction is basically constant and less affected by the matric suction, and the difference between the two is not significant. The undisturbed loess particles have obvious edges and corners, which are in bracket contact and have good cementation, and the structure of the undisturbed loess is strong. The remolded loess particles are close to round and in inlaid contact, and the cementation between them is destroyed. The soil skeleton function of the remolded loess is not obvious and the structure is weak, the formed aggregate structure is easy to compress, and the connection between aggregates and particles is not stable, thus forming the undisturbed soil with better resistance to the external shear failure. Under the same physical conditions, the pore sizes of undisturbed and remolded loesses less than 50 μm account for 22.7% and 16.3% of the total volume of the samples, respectively. The pore sizes between 50 μm and 200 μm are 71% and 83.7%, respectively, and those larger than 200 μm are 6.3% and 0%, respectively. The open structure composing of the bracket macro-void does not provide deformation space for the undisturbed soil, but the good cementation and structural properties ensure that the undisturbed loess has high strength characteristics.
- unsaturated loess /
- micro- and meso-scopic scale /
- structura property /
- shear strength

HTML全文

图 1 同一吸力不同净围压下非饱和Q₃原状和重塑黄土偏应力、体应变和轴应变关系曲线

Figure 1. Curves of deviatoric stress, volume strain and axial strain of unsaturated Q₃ undisturbed and remolded loesses under same suction and different net confining pressures

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图 2 非饱和Q₃黄土强度包线

Figure 2. Strength criteria of unsaturated Q₃ loess

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图 3 非饱和Q₃黄土c-s, $φ$ $φ$ -s关系曲线

Figure 3. Relationship curves of c-s, $φ$ $φ$ -s of unsaturated Q₃ loess

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图 4 原状土SEM图片

Figure 4. SEM image of undisturbed loess

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图 5 重塑土SEM图片

Figure 5. SEM images of remolded loess

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图 6 环刀试样三维重建及其三视图

Figure 6. Three-dimensional reconstruction of ring cutter specimen and its three views

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图 7 试样截取数据孔隙三维图

Figure 7. Three-dimensional diagram of interception data pores of specimen

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图 8 试样孔隙形状因子概率分布图

Figure 8. Probability distribution diagram of pore shape factor of specimen

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图 9 试样孔隙半径统计分布直方图

Figure 9. Statistical distribution histogram of pore radius of specimen

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