Experimental quantification of 3D deformations in sensitive clay during stress-probing

Unique 4D deformation data are collected during drained triaxial tests on intact specimens of a natural sensitive clay. This required the development of a miniature triaxial cell for advanced stress path testing, specifically designed for X-ray Computed Tomography (XCT). Salient features include the omission of membrane, and a mounting procedure that minimises disturbance from the experimenter. Three distinct drained stress ratios were studied for pseudo-isotropic, K_0, and highly deviatoric loading paths. The results indicate that the K₀ path shows the most uniform deformation mechanism, where the measured ratio of deviatoric and volumetric strain increments reaches the stress ratio applied at boundary value level for large magnitudes of total strain. The pseudo-isotropic test also reaches a strain ratio close to η at large total strain levels, however, the deformation field is less uniform. Furthermore, the highly deviatoric stress path shows the most heterogeneous deformation fields commensurate to the applied stress ratio, though the ratio of deviatoric and volumetric strain increments fell above the η applied. The mean value of the 3D spatial fields of strain corresponds well with the changes observed at boundary level, supporting prior research on drained stress-probing on clays for which there is no 4D deformation data available.