2D Kinematic Effects of 3D Displacement Fields of Triaxial Sand Compression Specimens
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Understanding the development of localization effects, such as shear and compaction bands, observed in sand specimens under compression, has been of research interest to understand elemental soil failure mechanisms. Various experimental and numerical methods had been performed from micro (grain particle level) to macro-scale (soil specimen) level to understand this phenomenon. Recent studies had incorporated different imaging techniques to capture localization effects observed on sand compression specimens. Pictures and its associated displacement fields can be captured during the experiment to study the development of localization effects using digital image correlation technique. The following work aims at a better understanding of the development of localization effects by utilizing continuum mechanics kinematics operators of Three-Dimensional (3D) displacement fields. In addition, continuum kinematics operators are utilized to identify early indications of localization effects. The proposed methods will include the implementation of divergence, curl, and gradient of displacement fields as defined in MATLAB Calculus Toolbox. The results of the divergence and curl of displacement fields are presented in 2D and while 3D representation is presented for the gradient of displacement field. The use of continuum kinematics operators allows for the identification of compression/ expansion (divergence), rotation (curl), and the rate of compression/ expansion (gradient) in various directions along the surface of the specimens. The effects of varying confining pressure have also been proposed. The results of kinematics operators' implementation showed that it is possible to identify the development of localization effects as early as the beginning of strain softening or slightly after peak strength. In comparison, the localization effects observed visually by the human eye is found to develop at the end of strain softening towards the beginning of the critical volume. The effect of varying confining pressure affects the clarity, amount, rate, and location of localization observed.
Sand Triaxial Compression
Shear and Compaction Bands
Early signs of localization
Martogi, Debora Eliezer (2017). 2D Kinematic Effects of 3D Displacement Fields of Triaxial Sand Compression Specimens. Master's thesis, Texas A&M University. Available electronically from