While considerable effort has been spent investigating the behaviour of the ground during tunnelling, comparatively little work has been done on sprayed concrete tunnel linings. Discrepancies have often been noted between field data of stresses and strains- in sprayed concrete linings and design predictions using "closed-form" analytical or numerical methods. Experimental data suggests that sprayed concrete behaves in a more complex way than is normally assumed in design. These discrepancies can lead to uneconomic or unsafe designs because the factor of safety in the lining cannot be determined with the normal certainty. The goal of this research was to examine the effect of the constitutive model for sprayed concrete in numerical analyses of tunnel linings. An extensive literature search has been undertaken to examine the state of knowledge of sprayed concrete behaviour. There is considerable experience of SCL tunnelling throughout the world but much of this information is slow to reach countries where SCL tunnelling is relatively new. Problems of increasing complexity have been analysed using the FLAC finite difference program, starting with uniaxial laboratory tests performed on a sample of sprayed concrete, then the large-scale load tests performed on sprayed concrete rings as part of an earlier research project and culminating with the 3D analysis of a single tunnel face as it advances. The results of these analyses have been compared with the results from the original experiments and field data from the Heathrow Express project. This research has found that the constitutive modelling of sprayed concrete can have a large influence on design predictions of SCL tunnel behaviour. Variations in the construction sequence for the tunnel can also have a significant influence on the loads in the lining.