Numerical study on tunnel final lining behaviour

Final lining made of cast-in-place concrete can be designed by using empirical, analytical or numerical methods, in order to approximate (with more or less precision) the real case study. For more general cases, moments and forces in circular and noncircular tunnel linings can be determined using structural finite element programs. This kind of approach allows to handle the most general cases, which can include variable properties of rock and lining elements, irregular boundaries and shapes. According to the adopted FEM modelling, more and more refined analyses can be performed in order to evaluate deformations and stability of the excavation face, loads and stresses in the lining as well as rock-lining interaction. 2D numerical models are more popular with respect to 3D ones, although a three-dimensional modelling allows to afford more complex problems and to evaluate the effects of the excavation process. In this paper 3D finite element analyses have been performed in order to properly simulate tunnel excavation and lining installation stages. The attention is focused on concrete final lining design, with the primary aim to determine the role of fibres with respect to traditional welded steel mesh on the structural behaviour of final lining.