E3S Web Conf.
Volume 92, 20197th International Symposium on Deformation Characteristics of Geomaterials (IS-Glasgow 2019)
|Number of page(s)||6|
|Section||Behaviour of Unsaturated Geomaterials|
|Published online||25 June 2019|
Mechanical behaviour of unsaturated undisturbed black volcanic ash soil under static and cyclic loading
Department of Civil and Structural Engineering, Kyushu University, 744 Motooka, Nishi-ku, Fukuoka 819-0395, Japan
2 West Nippon Expressway Company Limited, 1-6-20 Dojima, Kita-ku, Osaka City, Japan
* Corresponding author: firstname.lastname@example.org
The mechanical behaviour of unsaturated undisturbed black volcanic ash soils was investigated using a constant volume direct shear apparatus. A series of static and cyclic tests were conducted under unsaturated and saturated samples. The cyclic test under two patterns were adopted. First type of pattern, cyclic one-sided shearing was applied. For the second type, two-sided shearing was conducted. For further understanding of the chemical content and microstructure, X-Ray Fluorescence analysis (XRF) and Scanning Electron Microscope (SEM) were evaluated. It was found that, under static shearing, the unsaturated sample exhibits a higher apparent cohesion and friction angle in comparison to the saturated sample. The normalized vertical stress under one-sided cyclic shearing in both overconsolidated and normally consolidated samples rapidly reduced at the beginning of shearing. This might be attributed to increase of the pore water pressure during shearing. Furthermore, there is a significant difference between the normalized shear stress under cyclic one-sided and two-sided shearing. For the two-sided cyclic shearing test, the normalized shear stress value is higher than the one-sided cyclic shearing test. In addition, the normalized shear stress under unsaturated condition is significantly larger. This can be related to the suction forces to the total strength of soils. The main chemical content of the black volcanic ash soil is allophane. Further, the microstructure of the black volcanic ash changes due to shearing. For the overconsolidated sample, particles of soil more severe damage than normally consolidated sample.
© The Authors, published by EDP Sciences, 2019
This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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