Deformation Analysis of Sand Specimens using 3D Digital Image Correlation for the Calibration of an Elasto-Plastic Model

Abstract

The use of Digital Image Correlation (DIC) technique has become increasingly popular for displacement measurements and for characterizing localized material deformation. In this study, a three-dimensional digital image correlation analysis (3D-DIC) was performed to investigate the displacements on the surface of isotropically consolidated and drained sand specimens during triaxial compression tests.

The deformation of a representative volume of the material captured by 3D-DIC is used for the estimation of the kinematic and volumetric conditions of the specimen at different stages of deformation, combined with the readings of the global axial compression of the specimen. This allowed for the characterization of a Mohr-Coulomb plasticity model with hardening and softening laws.

In addition, a two-dimensional axisymmetric finite element model was built to simulate the actual experimental conditions, including both the global and local kinematics effects captured by 3D digital image correlation analysis on the boundary of the specimen.

A comparison between the axisymmetic model predictions and the experimental observations showed good agreement, for both the global and local behavior, in the case of different sand specimen configuration, including loose, dense and half-loose half-dense specimens.