Deformations caused by surface loading and tunnelling: the role of elastic anisotropy

Elastoplastic finite element analyses were performed to determine the effects of elastic anisotropy on surface settlements caused by a uniform surface loading and by tunnelling. For typical ranges of elastic cross-anisotropic parameters, the effect of anisotropy on settlement induced by surface loading is modest; however, for the case of tunnelling, the effect of elastic anisotropy, in particular the ratio of the independent shear modulus Gvh, to vertical modulus Ev, should be considered if reasonable predictions of settlement are to be obtained. The practical implications of these find- ings are shown by considering the centrifugal model tunnel tests conducted at Cambridge University. It is found that the anisotropy has a significant effect on the shape of the settlement trough and that reasonable agreement between observa-tion and theory is obtained for Gvh/Ev, of between 0·2 and O·25, which is smaller thanthe isotropic value of Gvh/Ev, = 0·33 (for the undrained condition). The reasons for this are disc...