STUDY OF NATURAL SOIL ANISOTROPY USING HOLLOW CYLINDER TESTS

Predicting soil response to tunnelling using a TBM remains challenging due to multiple influencing factors, with the choice of the constitutive model playing a critical role. While natural soils often exhibit anisotropic behaviour, most models are based on isotropic constitutive models due to the experimental complexity of characterising anisotropy. However, incorporating anisotropy can significantly enhance the accuracy of ground displacement predictions. This study demonstrates that the Hollow Cylinder Apparatus (HCA) is an effective tool for investigating the elastic anisotropic parameters, defining a transversely isotropic soil model. The proposed approach requires a single specimen and does not need horizontal, vertical and/ or inclined tests, which are not easy to perform experimentally. An analytical study of the HCA test is presented, followed by a methodology for experimentally determining these parameters. A detailed application on a natural soil sample is provided, illustrating the possibilities of the proposed approach.