The structural (un)safety of tunnels explained by analytical approach

From soft soil tunnelling practice it has been observed that the segmental thickness of the tunnel lining has a constant ratio to the tunnel diameter. Nevertheless many engineering models are published in literature and used in practice, which describe the structural behaviour of the tunnel lining. These models are used to analyse the structural safety of the tunnels. In this paper a new analytical approach is described which clearly reveals the influence on structural behaviour of longitudinal joints and lateral interaction between adjoining rings of the lining. Furthermore it is explained that a common missing parameter in today's models is the influence of the construction of the tunnel, and especially the influence of grouting. In this paper the influence of the grouting is assessed. It turns out that the observed lining thickness can be dominated by the influence of grouting.