Response of clay soil to three-dimensional tunnelling simulation in centrifuge models

Tunnelling-induced ground movements are complicated and investigations into them normally require some simplifications. This paper provides a brief literature review which highlights the advantages of adopting simplifications in physical modelling and addresses some of the deficiencies in the assessment of soil deformation due to a simulated tunnel excavation. A set of centrifuge tests modelling a tunnel heading located at different depths in clay was carried out at 125g. The tunnel was modelled by a semi-circular cavity partly supported by a stiff lining. The unlined tunnel heading was supported by a thin rubber bag supplied with compressed air pressure. Tunnel excavation was simulated by reducing air pressure. The induced ground movements at the subsurface and surface were measured by a 2D image analysis and a new, novel 3D imaging system. The results show that the experiment successfully reproduced key aspects of tunnelling-induced soil deformation in practice. In addition, a new equation to predict horizontal displacements in the longitudinal direction is proposed.