Three-dimensional modelling of NATM tunnelling in decomposed granite soil

Three-dimensional analyses of tunnel excavation and lining construction are rarely performed in practice, because it is difficult to reproduce the exact boundary conditions involved in this process, and because such analyses require considerable computing resources if realistic non-linear soil behaviour is to be reproduced. This paper presents a pseudo-three-dimensional analysis of tunnel construction by utilising the Fourier series aided finite element method (FSAFEM). The theory behind this approach, and its validation when applied to a tunnelling problem, are described. The method is then used to predict the behaviour of tunnels forming part of the Seoul Subway system in Korea. The results are compared with field measurements.