Centrifuge and theoretical study on tunnel-raft interaction in clay

Abstract

Tunnelling induced ground movement may affect adjacent raft foundations. A series of centrifuge model tests was performed to investigate the settlement and induced strain profiles of rafts of different rigidities due to tunnelling. The results reveal that the theoretical relationship between raft bending strain and deflection ratio derived from a simply supported centrally loaded Timoshenko beam is not able to predict the bending strain and raft settlement in certain situations. An elastic-continuum-based simplified method considering raft weight and soil-raft separation is then presented and first verified against the results of centrifuge tests. Parametric studies were further conducted to investigate the effect of the raft-soil relative location on the relationship between deflection ratio and bending strain. The results reveal the original deflection ratio cannot fully capture the deflection characteristic of the raft settlement due to tunnelling. A modified deflection ratio is proposed to better characterize different raft settlement profiles.