Quantitative analysis of deformation in hollow cylinder tests on anisotropic clay formations

A series of triaxial laboratory experiments are performed on thick-walled hollow cylindrical samples of boom clay. The aim of this testing program is to better understand the anisotropic deformation during the excavation. The testing conditions are similar to those to be experienced by host rocks around disposal galleries for radioactive waste. X-ray computed tomography is performed at different steps for each test with the samples remaining inside the loading cell. Initial analysis of the tomography images allows of the observation of the deformation of the central hole. In addition, particles manual tracking and 3D volumetric digital image correlation processing methods are considered being used to analyze the particles displacements and the boundary deformation of the sample quantitatively. An unsymmetrical damaged zone is induced around the hole, with a reverse deformation trend being found at the boundary after unloading, which indicates that the significant anisotropic deformation of boom clay can be induced by mechanical unloading.