Measuring Unsaturated Soil Deformations during Triaxial Testing using a Photogrammetry-Based Method
When characterizing an unsaturated soil using the triaxial test apparatus, it is required to measure the soil deformation during loading. Recently, a photogrammetry-based method has been developed for total and localized volume change measurements on unsaturated soils during triaxial testing. In this study, more in-depth discussions on the photogrammetry-based method are addressed, such as system setup, the measurement procedure, accuracy self-check, data post-processing, and differences from conventional image-based methods. Also, an application of the photogrammetry-based method on unsaturated soil deformation measurements is presented through a series of undrained triaxial tests with different loading paths. After testing, three-dimensional (3D) models of the tested soils at different loading steps were constructed based on the 3D coordinates of measurement targets on the soil surface. Clear barreling processes for soils during deviatoric loading were observed through the constructed 3D models at different axial strain levels. Soil volume changes and volumetric strain nonuniformities during isotropic and deviatoric loadings were extracted based upon detailed analyses of different soil layers. Through a full-field strain distribution analysis, a shear band evolution process was captured for the soil during deviatoric loading at a low confining stress. The photogrammetry-based method proved to be very powerful for in-depth soil deformation characteristics investigation.
L. Li et al., "Measuring Unsaturated Soil Deformations during Triaxial Testing using a Photogrammetry-Based Method," Canadian Geotechnical Journal, vol. 53, no. 3, pp. 472-489, Canadian Science Publishing, Sep 2015.
The definitive version is available at https://doi.org/10.1139/cgj-2015-0038
Civil, Architectural and Environmental Engineering
Keywords and Phrases
Data handling; Deformation; Photogrammetry; Ray tracing; Soil testing; Soils; Stress analysis; Optical ray tracing; Strain localizations; Three-dimensional (3D) model; Triaxial test apparatus; Undrained triaxial test; Unsaturated soil; Volume change; Volume change measurement; Soil surveys; Deformation mechanism; Loading test; Optical method; Photogrammetry; Strain analysis; Triaxial test; Unsaturated medium; Volume change; Photogrammetry-based method
International Standard Serial Number (ISSN)
Article - Journal
© 2015 Canadian Science Publishing, All rights reserved.