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Frontiers of Structural and Civil Engineering >> 2020, Volume 14, Issue 2 doi: 10.1007/s11709-019-0599-2

A miniature triaxial apparatus for investigating the micromechanics of granular soils with

. Department of Architecture and Civil Engineering, City University of Hong Kong, Hong Kong 999077, China.. Shenzhen Research Institute of City University of Hong Kong, Shenzhen 518057, China.. Department of Civil, Environmental and Geomatic Engineering, University College London, London WC1E 6BT, UK.. Department of Civil Engineering, Shanghai Jiaotong University, Shanghai 200240, China

Accepted: 2020-03-11 Available online: 2020-03-11

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The development of a miniature triaxial apparatus is presented. In conjunction with an X-ray micro-tomography (termed as X-ray μCT hereafter) facility and advanced image processing techniques, this apparatus can be used for investigation of the micro-scale mechanical behavior of granular soils under shear. The apparatus allows for triaxial testing of a miniature dry sample with a size of (diameter height). triaxial testing of a 0.4–0.8 mm Leighton Buzzard sand (LBS) under a constant confining pressure of 500 kPa is presented. The evolutions of local porosities (i.e., the porosities of regions associated with individual particles), particle kinematics (i.e., particle translation and particle rotation) of the sample during the shear are quantitatively studied using image processing and analysis techniques. Meanwhile, a novel method is presented to quantify the volumetric strain distribution of the sample based on the results of local porosities and particle tracking. It is found that the sample, with nearly homogenous initial local porosities, starts to exhibit obvious inhomogeneity of local porosities and localization of particle kinematics and volumetric strain around the peak of deviatoric stress. In the post-peak shear stage, large local porosities and volumetric dilation mainly occur in a localized band. The developed triaxial apparatus, in its combined use of X-ray μCT imaging techniques, is a powerful tool to investigate the micro-scale mechanical behavior of granular soils.

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