Tunnelling-induced ground movements in clay

A series of plane strain centrifuge model tests of single tunnels in modera tely stiff clay has been conducted at City University, London. Ground movem ents were measured using conventional displacement transducers at the groun d surface and by digital image-processing techniques below ground level. Th e relatively simple tests are shown to result in ground movements which are consistent with field measurements, but the tests produced considerably mo re high-quality data, which have been analysed to improve predictions of bo th surface and subsurface movements in the plane transverse to a tunnel in clay. The measured data are assessed against commonly used empirical predic tive techniques, indicating some deviations from current practice. A proced ure for predicting horizontal movements as a function of the vertical settl ement profile is suggested.