Microscopic characteristics of partially saturated dense sand and their link to macroscopic responses under triaxial compression conditions
Microscopic characteristics of partially saturated dense sand and their link to macroscopic responses under triaxial compression conditions
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DOI：
10.1007/s11440-020-01049-w
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发表时间：
2020-08
期刊：
影响因子：
5.7
通讯作者：
Ryunosuke Kido;Y. Higo
中科院分区：
文献类型：
--
作者：
Ryunosuke Kido;Y. Higo
本文提出了一组对部分饱和致密砂进行的三轴压缩试验，以阐明微观特征及其与宏观响应的联系。在低围压下进行恒吸力试验（CS 试验）和恒含水量试验（CW 试验），以观察砂体与膨胀剪切带相关的微观和宏观行为。应用 X 射线显微断层扫描和图像分析技术来研究连续性，作为评估孔隙水形态、液桥数量和空气-水界面主曲率的定义指标。 CS 和 CW 测试中的液桥数量均减少，特别是在应变软化过程中，而 CW 测试中的液桥数量减少幅度大于 CS 测试。在CS测试下，空气-水界面的曲率几乎保持相同的值，而在CW测试下则趋于减小。曲率减小的趋势对应于CW测试中吸力减小的趋势。当孔隙水最初不连续时，CS 测试中的峰值偏应力高于 CW 测试中的峰值偏应力，而当孔隙水最初连续时，两个测试之间的峰值偏应力相同。 CW 测试中的残余应力低于 CS 测试中的残余应力，与初始保水状态无关。级配差的砂和级配好的砂在不同初始保水状态下的宏观响应在性质上是相同的。
This paper presents a set of triaxial compression tests on partially saturated dense sands to clarify the microscopic characteristics and their link to the macroscopic responses. Constant suction tests (CS tests) and constant water content tests (CW tests) are conducted under low confining pressure to observe microscopic and macroscopic behaviors of the sands associated with dilative shear bands. X-ray micro-tomography and image analysis techniques are applied to investigate the continuity as a defined index to evaluate the morphology of the pore water, the number of liquid bridges and the principal curvature of the air–water interface. The number of liquid bridges decreases for both the CS and CW tests, particularly during the strain softening process, while it decreases greater in the CW test than in the CS test. The curvature of the air–water interface remains at almost the same value under the CS test, while it tends to decrease under the CW test. The tendency of decreasing curvature corresponds to that of decreasing suction in the CW test. The peak deviator stress is higher in the CS test than in the CW test when the pore water is initially discontinuous, whereas it is identical between the two tests when the pore water is initially continuous. The residual stress is lower in the CW test than in the CS test, independent of the initial water retention states. The macroscopic responses at the different initial water retention states are qualitatively identical between poorly graded sand and well-graded sand.