Visualization of non-uniform soil deformation during triaxial testing

Triaxial test on both saturated and unsaturated soils is associated with non-uniform deformation, especially during shearing. This non-uniform deformation plays an important role in the soil strength and constitutive behavior. In the past, several image-based methods have been proposed to measure non-uniform soil deformation. However, accurate non-uniform soil deformation measurement during triaxial testing is still a great challenge for researchers. This study documented a new technique for the visualization of a deforming specimen during triaxial testing based on a full-field deformation measurement system with help of a self-developed software package GeoTri3D. A dot matrix (i.e., 13,320 dots in 90 rows × 148 columns) at a density of 57 dots/cm2 is directly printed to a latex membrane which covers a 61.8 × 123.2 mm specimen during triaxial testing. With the deformation measurement system, three-dimensional (3D) coordinates of each dot on membrane surface are accurately measured at different axial displacements during loading. Point clouds, which represent the specimen surface at these displacement levels, are then generated and further utilized for the generation of triangular meshes and reconstruction of specimen 3D surfaces. The full-field deformations (i.e., axial displacement, radial and axial strain) during testing are then derived based on the triangular meshes. These 3D surfaces and full-field deformations facilitated a 3D visualization of the specimen deforming process at an unprecedented high resolution. Accurate reconstruction of specimen surface and the associated 3D visualization of the deforming process offer a great potential for advanced soil behavior characterization.