A numerical method for the calculation of the distribution of displacements for tunnelling in clays has been developed. The method employs an orthotropic elastic – perfectly plastic soil model that takes into account various sources of ground loss and soil–lining interaction. Both undrained and drained analyses have been carried out and the results are compared with the measured soil displacements of two instrumented arrays at the Thunder Bay tunnel. It is shown that the range of maximum settlements, the shape of the settlement troughs, and the pore pressure change, as well as the magnitude and direction of spatial displacements obtained from the analyses, compare reasonably well with the results of field measurements for both short- and long-term conditions.Key words: tunnelling, clays, anisotropy, elastic–plastic displacements, settlement trough, Thunder Bay tunnel.